How light are disc brake bikes?

[fogrider]

I know that by spending a boat load of money, crazy lightweight bikes are possible. but lets say using Sram AXS, tubeless carbon wheels and tires, okay this is not cheap already, but is it reasonable to get close to the UCI weight limit of 6.8 kg?

[R3awak3n]

I know that by spending a boat load of money, crazy lightweight bikes are possible. but lets say using Sram AXS, tubeless carbon wheels and tires, okay this is not cheap already, but is it reasonable to get close to the UCI weight limit of 6.8 kg?

My Open is 17lbs and its a grave bike with 48mm tires. I think if you get a decently nice frame and a wheel set that is sub 1500g (not hard now a days), a 15lb bike is not that hard to do.

[SPOKE]

I’m thinking that a bit less than 17lbs is pretty easy to achieve for a disc brake bike including pedals and bottle cages. I‘ll bet that you can even hit this weight with a nicely built Ti frame.

[oldpotatoe]

I know that by spending a boat load of money, crazy lightweight bikes are possible. but lets say using Sram AXS, tubeless carbon wheels and tires, okay this is not cheap already, but is it reasonable to get close to the UCI weight limit of 6.8 kg?

Sure, pretty easy. As they say, with enough money, you can do anything.

[lookout2015]

I know that by spending a boat load of money, crazy lightweight bikes are possible. but lets say using Sram AXS, tubeless carbon wheels and tires, okay this is not cheap already, but is it reasonable to get close to the UCI weight limit of 6.8 kg?


You might find browsing through Canyon’s site interesting, because they’re not particularly thought of as a “weight weenie” brand but they post clear weight claims for each build and offer the same models with lots of drivetrains and in rim or brake variants

https://www.canyon.com/en-us/road-bikes-us/race-bikes/ultimate/ultimate-cf-evo-10.0-ltd/2172.html - AXS Rim, 6.00 kg claimed

https://www.canyon.com/en-us/road-bikes-us/race-bikes/ultimate/ultimate-cf-evo-disc-10.0-ltd/2313.html - AXS Disc, 5.99 kg claimed

https://www.canyon.com/en-us/road-bikes-us/race-bikes/ultimate/ultimate-cf-sl-disc-8.0-di2/2159.html - Ultegra Di2 Disc, 7.5 kg claimed, much more reasonable price :banana:

(Not meant to be a Canyon ad, just picked them as an example because they show their builds and weights clearly. But point is that somewhere around 6.8 isn’t totally hard to hit if that’s your goal. Also fun that their AXS Rim and AXS Disc builds are the same weight)

[Clancy]

I’m thinking that a bit less than 17lbs is pretty easy to achieve for a disc brake bike including pedals and bottle cages. I‘ll bet that you can even hit this weight with a nicely built Ti frame.

Anyone like to take on the challenge? Hypothetically spec out a Ti frame disc bike to hit under let’s say 16 pounds. Possible to do with a budget of $4,000?

Which groupset? Red 22 mechanical would be the least expensive and lightest I believe. But from there I wouldn’t know what to pick for wheels, cockpit, etc.

[fa63]

16 lbs with a Ti frame disc bike and a budget of $4K MAY be possible, but I am not sure. Most carbon bikes in that price range are in the 7.5-8 kg (16.5-17.5 lbs) range.

For example, my Felt FR Disc with Ultegra 8000 and Reynolds AR41 carbon wheels weighs 8 kg with pedals and cages. That is with a ~1,500 g frameset (frame, fork, headset). Plus it came with a Praxis Zayante Carbon crankset, which is much lighter than an Ultegra one.

Edit: for fun I went to Wrench Science's website and built a bike using a Litespeed T1SL Disc frame (the lightest disc TI frame that I know of) and SRAM Red mechanical. With a carbon cockpit (Zipp) and carbon wheels (Fulcrum 40 DB), the estimated weight was 17.5 lbs at a price of $10K...

Anyone like to take on the challenge? Hypothetically spec out a Ti frame disc bike to hit under let’s say 16 pounds. Possible to do with a budget of $4,000?

[NHAero]

There must be a fairly tight range people have measured about the real increment from rim to disc. Heavier brakes; hubs, fork. What else? I'd be surprised if it exceeds 1-1.5 lbs.

[fa63]

It is about 0.5 kg / 1 lbs.

There must be a fairly tight range people have measured about the real increment from rim to disc. Heavier brakes; hubs, fork. What else? I'd be surprised if it exceeds 1-1.5 lbs.

[Dave]

Force AXS is particularly heavy, so you'll need at least another thousand to get Red AXS.
Force also costs about twice as much as Chorus 12 and weighs more.

The component by component weight comparisons I've done with Campy parts shows a weight increase in the 300-400 gram range, with disc brakes. The shifters, brakes with calipers and same model wheelsets all weigh more.

It's necessary to spend about twice as much for a Trek Emonda SLR frame, instead of an SL model, to get the same weight as a rim brake bike.

On the weight weenies forum, it's not popular to ask about excess body weight, but it is relevant. What's the point in building a 6kg bike if you're carrying 2-10kg of excess body fat? At my lightest, up to age 57, I weighed 134 or 61kg, but 10 years later, I'll be surprised if I get that low again. It takes a lot of money to buy a 2kg lighter bike.

I'm satisfied with my modern rim brake colnago with chorus 12 that only cost about 3K with all new parts. It weighs in at 7.6kg, ready to ride. The listed weights for complete bikes on manufacturer's websites omit about 300gm that will be added for pedals, bottle cages and computer.

FWIW, Trek has the Emonda SLR 9 with DA Di2 that weighs 6.42kg. The Red AXS version weighs slightly more at 6.68kg. The Force AXS SLR 7 version weighs 7.18kg. Both without pedals, cages or computer.

https://www.trekbikes.com/us/en_US/bikes/road-bikes/performance-road-bikes/%C3%A9monda/%C3%A9monda-slr/%C3%A9monda-slr-9-disc/p/31047/?colorCode=red_white

https://www.trekbikes.com/us/en_US/bikes/road-bikes/performance-road-bikes/%C3%A9monda/%C3%A9monda-slr/%C3%A9monda-slr-9-disc-etap/p/28489/?colorCode=white_blue

https://www.trekbikes.com/us/en_US/bikes/road-bikes/performance-road-bikes/%C3%A9monda/%C3%A9monda-slr/%C3%A9monda-slr-7-disc-etap/p/31052/?colorCode=red_white

[oldpotatoe]

Anyone like to take on the challenge? Hypothetically spec out a Ti frame disc bike to hit under let’s say 16 pounds. Possible to do with a budget of $4,000?

Which groupset? Red 22 mechanical would be the least expensive and lightest I believe. But from there I wouldn’t know what to pick for wheels, cockpit, etc.

Doubt you could do it for only $4k..Ti frame and carbon wheels, cockpit, etc...

[StephenCL]

It’s pretty tough to do with a ti frame however. My firefly is as top of the line as they come, and in road form it is just under18lbs and that is with Bora carbon wheels, and some pretty light bits including super record 12 speed.

When I put on my gravel kings and shamal alloys, it balloons to 19lbs.

After I first built it, I kept looking for the lead weights???? Didn’t make any sense.

Discs are just that much heavier. They have their place, but there is a pretty significant weight penalty.

You have to use a crazy light carbon frame to get down to the 15 lbs range.

[Tony]

Anyone like to take on the challenge? Hypothetically spec out a Ti frame disc bike to hit under let’s say 16 pounds. Possible to do with a budget of $4,000?

Which groupset? Red 22 mechanical would be the least expensive and lightest I believe. But from there I wouldn’t know what to pick for wheels, cockpit, etc.

No way possible. Need more money.

[Mark McM]

There must be a fairly tight range people have measured about the real increment from rim to disc. Heavier brakes; hubs, fork. What else? I'd be surprised if it exceeds 1-1.5 lbs.

Disc brake levers can also be heavier, plus there is the weight of the rotor which is absent for rim brakes. As you say, the weight differential is usually considered to be 1 - 1.5 lb between otherwise similar rim and disk brake bikes.

I just went to the Shimano web site and looked up the weights of rim a and disc Dura-Ace 9100 mechanical shift group components. For wheels, I looked at the C40 clinchers. Here are the published numbers for the components (Levers, calipers, rotors, wheels, and total):

Rim: 365g, 298g, - ,1504g, 2167g
Disc: 538g, 256g, 236g, 1622g, 2652g

In total, the disc brake components are 485g (1.1 lb) heavier. This isn't accounting for frame and fork, which are also likely to be a little bit heavier for disc brakes. (There's likely also a difference in cable/hose weight, but this is probably a wash - hydraulic hose can be lighter per foot, but disc brake hose is longer than rim brake cables.) The weight differences in lower level groups are probably slight more.

The only Dura-Ace disc brake component that is lighter are the calipers. Not surprisingly the biggest weight difference is the rotors (which rim brakes don't need), but there are also significant differences in lever and wheel weights.

[NHAero]

Thanks for the research!
When I included brakes as bits that are heavier, the brake calipers plus the discs and levers would be compared to the rim brake equivalents.

My rim brake Firefly is about 8 kg with pedals. Not much carbon - fork and SRAM Red cranks. My old CAAD10 was 0.5 kg lighter. I've been amazed at some of the weights shown here for the modern steel frames, I wonder if they are building up lighter than any Ti frames?

So maybe re-phrase the question to, can a metal framed disc bike hit the UCI limit? Especially without super $$$ weight weenie parts.

I gotta say I was tempted by the blue EE brakes for sale here recently, given that the Firefly is blue. But the price, even used, to save 150g or whatever over the Dura Ace - I'm too old and slow, even though I'm not fat :)

Disc brake levers can also be heavier, plus there is the weight of the rotor which is absent for rim brakes. As you say, the weight differential is usually considered to be 1 - 1.5 lb between otherwise similar rim and disk brake bikes.

I just went to the Shimano web site and looked up the weights of rim a and disc Dura-Ace 9100 mechanical shift group components. For wheels, I looked at the C40 clinchers. Here are the published numbers for the components (Levers, calipers, rotors, wheels, and total):

Rim: 365g, 298g, - ,1504g, 2167g
Disc: 538g, 256g, 236g, 1622g, 2652g

In total, the disc brake components are 485g (1.1 lb) heavier. This isn't accounting for frame and fork, which are also likely to be a little bit heavier for disc brakes. (There's likely also a difference in cable/hose weight, but this is probably a wash - hydraulic hose can be lighter per foot, but disc brake hose is longer than rim brake cables.) The weight differences in lower level groups are probably slight more.

The only Dura-Ace disc brake component that is lighter are the calipers. Not surprisingly the biggest weight difference is the rotors (which rim brakes don't need), but there are also significant differences in lever and wheel weights.

[PaMtbRider]

A 15 lb Ti disc frame is not going to happen without a boatload of money. The big questions are what are you including? pedals, bottle cages? Are you talking about a 48cm frame? For reference my, Ti Zanconato with cages and pedals is just over 19 lbs. Although not top of the line, none of the components were chosen to save money. It is roughly a 61 cm frame, so it is on the larger side. I would love someone to show me how to drop 4 pounds off this build, remain dirt road capable, without spending several thousand more on what was not a budget bike to begin with.
https://uploads.tapatalk-cdn.com/20191122/6063aa9a1fbd49d9df222a48a1e86d42.jpg

[kppolich]

Less than 3k spent (built used), 16.77lbs including tubeless wheels, cages, 28mm tires, ultegra pedals, garmin mount, rear light mount, and heavy classic Arione saddle.
eTap 11sp hydro disc, Roval CL50 wheels, 2019 tarmac pro carbon 56cm frame.

https://live.staticflickr.com/65535/49155049566_550d71e61b_b.jpg

[AngryScientist]

well to be fair, i think the OP was talking about a road bike and i have always thought the biggest weight penalty for gravel bikes is the meaty tires that you need to run, but that has nothing to do with brake type.

i agree that without spending a lot of money, it would be hard to get to the limit.

wrench science website is pretty good at putting together bikes and seeing what they will weigh.

this 13k dollar pina for example, is still >15#

https://www.wrenchscience.com/DBImages/800H/Pinarello-Dogma-F12-Disk-430-BoB.jpg

[crownjewelwl]

Don't think you could get there with a ti frame...

My spectrum is 1500g or so....everything else is pretty light and I'm just over 17lb

You could shave 600g with a carbon frame

[yinzerniner]

So maybe re-phrase the question to, can a metal framed disc bike hit the UCI limit? Especially without super $$$ weight weenie parts.

It’s possible but it won’t be with ti, but with aluminum.

You’d have to spec out carbon tubulars and get creative with used items that are very light but with a previous gen CAAD 12 disc frameset I bet you can get to UCI as it’s roughly 1150g for the frame and 375g for the fork.

Some items that would help a lot in the hunt for cheap gram shaving :
-red bb30 exogram crankset ~520g $125
-carbon tubular wheels ~1300g ~$600
-ritchey cockpit -bars stem seatpost ~440g ~$170
-speedplay pedals ti ~155g $100

Given that a used caad12 frameset goes for around $550-700 you’re well on your way to getting a UCI bike for less than $3k

[PaMtbRider]

well to be fair, i think the OP was talking about a road bike and i have always thought the biggest weight penalty for gravel bikes is the meaty tires that you need to run, but that has nothing to do with brake type.




Good point. Changing from 700x38 gravelkings to 700x25 gp5000 would save me a pound.

[mtechnica]

A lot of them are heavy, people on weight weenies are saying stock caad 13 with Ultegra are 20+lbs

[fogrider]

Thanks for the responses...I have a Santa Cruz Stig comes in around 18 pounds... I'm running carbon rims and 38mm Maxxis Rambler tires and Di2 1x. While I like Ti and have a Legend Ti, I was not thinking of going Ti for a road disc. I'm not a weight weenie, but I have a Time VXRS that is setup at 6.8 kg and rides great! And if I were to build a new bike, it would have to measure up to the Time. Note that I'm running ee brakes, and aero tubulars to get to 6.8 kgs.

[Kyle h]

We are building up an R5 Disc for my wife and will have ~4K in it and be less that 15#. Granted she runs a 49cm bike but we’re building with 9170, pro vibe stem, cervelo aero bars, and ENVE 5.6.

Excel Sports in Boulder has R5 frames for $1500-2000.

[Clancy]

My T-Lab with Red 22 mechanical/hydro disc brakes, Hunt carbon wheels with Vittoria 25c Open Corsas, Ritchey bars, stem, seatpost, Ultegra pedals and King cages comes in at 17.1 lbs.

I’ll gladly take a pound of weight penalty to ride this Ti frame. Absolutely no question. My last carbon bike was a Sarto - rim brakes - and it came in at 15.3 pounds and was easily the finest riding carbon bike I’ve ever ridden, but my T-Lab titanium frames rides just that much better.

A pound or a pound and a half is a big weight penalty but disappears once the bike is rolling and for me the ride quality more than makes up for it.

[lookout2015]

It’s possible but it won’t be with ti, but with aluminum.

You’d have to spec out carbon tubulars and get creative with used items that are very light but with a previous gen CAAD 12 disc frameset I bet you can get to UCI as it’s roughly 1150g for the frame and 375g for the fork.

Some items that would help a lot in the hunt for cheap gram shaving :
-red bb30 exogram crankset ~520g $125
-carbon tubular wheels ~1300g ~$600
-ritchey cockpit -bars stem seatpost ~440g ~$170
-speedplay pedals ti ~155g $100

Given that a used caad12 frameset goes for around $550-700 you’re well on your way to getting a UCI bike for less than $3k

You can get a production Ti frame at the same weight point: https://litespeed.com/collections/titanium-road-bikes/products/t1sl-disc-frame

So around $4k new / $2k used for a frame alone

[PaMtbRider]

We are building up an R5 Disc for my wife and will have ~4K in it and be less that 15#. Granted she runs a 49cm bike but we’re building with 9170, pro vibe stem, cervelo aero bars, and ENVE 5.6.

Excel Sports in Boulder has R5 frames for $1500-2000.

You must be buying used components. 9170 group new is $2400 from merlincycles, most places are selling Enve 5.6 for over $2000. If you get the frame for $1600 you are at $6000 before adding bar, stem, saddle, pedals...

[R3awak3n]

It comes down to 2 things, just like rim brake bikes. Frame/fork weight and wheelset weight. If those 2 are light enough you will be under 15. There are now a few 1350g and under disc clincher wheelsets out there. That paired with a decently light frame, a lightish seatpost and saddle (ritchey superlogic, fabric carbon railed saddle), lightish handlebars (200g) and stem (100g). The disc bike will be at 15lbs or very close

[mdeth1313]

Also depends on some of the build. Most people will go for standard name brands which tend to be heavier - there's plenty of lighter pieces you can go for.

My farsport disc wheels (clincher) came in around 1350-1390. On a previous bike I used ashima rotors. You trade off some braking performance, but on a disc bike, I never had an issue, especially on the road.

I'm using a hylix seatpost that comes in around 110 g and if you go for bikehard carbon bars they come in under 200 g. Kalloy uno stem w/ ti bolts will keep you in the 100-110 g range (or less) for <$50.

The main parts will still be the frame/fork and drivetrain.

[fignon's barber]

I've been contemplating the whole rim/disc thing for a couple months now. In my mind, for a road bike, if you will ride 30mm or smaller tires, go rim. If you ride over 30mm tires, do disc. A good steel frame with rim brakes is within a couple hundred grams (basically not noticeable) of a disc carbon bike.

[Kyle h]

You must be buying used components. 9170 group new is $2400 from merlincycles, most places are selling Enve 5.6 for over $2000. If you get the frame for $1600 you are at $6000 before adding bar, stem, saddle, pedals...

Oops, I forgot we had the 9170 shifters/brakes and crank already. $1500 for frame, $1500 for wheels (Competitive Cyclist has them on clearance since they’re no longer ya DT240), $150 for bar, $80 for stem, $500 for derailleurs, $400 for battery, wires, handlebar junction.

[John H.]

I see almost 2 lb. in wheels, pedals and cranks without even digging deep into your build.

A 15 lb Ti disc frame is not going to happen without a boatload of money. The big questions are what are you including? pedals, bottle cages? Are you talking about a 48cm frame? For reference my, Ti Zanconato with cages and pedals is just over 19 lbs. Although not top of the line, none of the components were chosen to save money. It is roughly a 61 cm frame, so it is on the larger side. I would love someone to show me how to drop 4 pounds off this build, remain dirt road capable, without spending several thousand more on what was not a budget bike to begin with.
https://uploads.tapatalk-cdn.com/20191122/6063aa9a1fbd49d9df222a48a1e86d42.jpg

[John H.]

15 lb. is possible, but it takes a light frame and light build.
4k would need to buy something used that was already light.

Reference points-
My Open Upper weighs about 17 even with a 2x 9170 build, sub 1400 gram carbon wheels and Maxxis Ramble 700x40mm tires.
My Scott Addict disc (no longer have) was low 15 lb. range with 9170 build and Roval CLX 32 wheeleset.
Mt titanium Evergreen XV is almost 2 lb. Heavier than the Open with same build.

[PaMtbRider]

I see almost 2 lb. in wheels, pedals and cranks without even digging deep into your build.

Maybe if you are building it as a road and not gravel bike. Tires would be the biggest savings. XTR pedals, praxis carbon crank, Chris King hubs, cx-ray spokes, to carbon rims. None of these are heavy weight parts. Lighter parts are available but not without spending a lot of money or making other sacrifices I was not willing to make. I wasn't going for a weight weenie build, and I guess that is what this thread is about so it doesn't really matter.

[Tony]

A 15 lb Ti disc frame is not going to happen without a boatload of money. The big questions are what are you including? pedals, bottle cages? Are you talking about a 48cm frame? For reference my, Ti Zanconato with cages and pedals is just over 19 lbs. Although not top of the line, none of the components were chosen to save money. It is roughly a 61 cm frame, so it is on the larger side. I would love someone to show me how to drop 4 pounds off this build, remain dirt road capable, without spending several thousand more on what was not a budget bike to begin with.
https://uploads.tapatalk-cdn.com/20191122/6063aa9a1fbd49d9df222a48a1e86d42.jpg

Beautiful bike!

[fogrider]

I completely agree...frame and wheels are critical! I'm looking at these at 1350 https://fse.bike/products/g40-30x-aero-gravel


It comes down to 2 things, just like rim brake bikes. Frame/fork weight and wheelset weight. If those 2 are light enough you will be under 15. There are now a few 1350g and under disc clincher wheelsets out there. That paired with a decently light frame, a lightish seatpost and saddle (ritchey superlogic, fabric carbon railed saddle), lightish handlebars (200g) and stem (100g). The disc bike will be at 15lbs or very close

[fogrider]

I ride in the Marin County a fair amount and there's a fair amount of climbing... I'm either going up or I'm going down. I have 2 steel bikes in rotation and one of them has the 2nd most miles on it...if I lived in Florida, I'm not sure I would even consider a disc brake road bike.

I've been contemplating the whole rim/disc thing for a couple months now. In my mind, for a road bike, if you will ride 30mm or smaller tires, go rim. If you ride over 30mm tires, do disc. A good steel frame with rim brakes is within a couple hundred grams (basically not noticeable) of a disc carbon bike.

[Ken Robb]

My Open is 17lbs and its a grave bike with 48mm tires. I think if you get a decently nice frame and a wheel set that is sub 1500g (not hard now a days), a 15lb bike is not that hard to do.

I hope I won't need a "grave" bike for a few more years.:)

[Clancy]

It comes down to 2 things, just like rim brake bikes. Frame/fork weight and wheelset weight. If those 2 are light enough you will be under 15. There are now a few 1350g and under disc clincher wheelsets out there. That paired with a decently light frame, a lightish seatpost and saddle (ritchey superlogic, fabric carbon railed saddle), lightish handlebars (200g) and stem (100g). The disc bike will be at 15lbs or very close

This I am assuming is a carbon frame.

I’d still like to see someone spec’ out a Ti frame that would come in at 15 lbs. I’d like to see one spec’d at 16 lbs. at a “reasonable” cost.

I don’t believe it’s possible but also believe the weight penalty for a Ti frame is more than worth it.

[cgates66]

I just built up a titanium disc frame - not a weight-weenie build, but not cheap, either, and it came in at 19 pounds more or less on the button (Ultegra 8020, Vanquish 6 GP wheels due to support for higher spoke counts are the parts highlights, and an EC90 aero bar, with alloy seat post, saddle rails and stem, Lynskey R480 58cm frame).

The issue with Ti is that the shear modulus (the "twisting" resistance) is I think ~45GPa, while the elastic modulus is ~115GPa (the "bending" resistance). T700 has a tensile modulus of ~115GPa. What that means is that the T700 is essentially 3x as resistant to twisting and the same in bending, if laid up properly, at a much lower density - and T700 is an intermediate modulus fiber. T1100 I think is 150 or 175 - I don't remember.

Anyway, for equivalent bending/twisting resistance, a titanium frame needs more of a denser material, so heavier. The upside is that it'll be strong in all directions (assuming the welds are good...).

I would imagine a $4K disc titanium frame build <16 is possible, but it'd be more flexible than a well-built carbon fiber frame with a similar weight.

It just depends on what you want to ride. I don't think any of this stuff affects speed much, unless the frame is really, really flexible or way too stiff for a given rider, but it does affect ride quality.

[ltwtsculler91]

Double post

[ltwtsculler91]

Carbon is possible with enough cash and a lightweight top line frame like an Emonda SLR or HiMod SuperSix with Dura Ace or Red. A "stock" Dura Ace or Red Emonda SLR comes in around 14.5 lbs depending on size.

I'd think you could get a Ti bike at 15 with the right weight weenie parts (ie super light Crank or bars) or tubulars. My No22 Reactor sits at 15lbs with SRAM Red, a relatively heavy Parlee bar/stem, and 1500g Bontrager Aeolus wheels. Swap the crank for a THM, or the wheels and bar/stem for lighter parts to offset the about 1 lb for disc and an Aurora can easily get to 15..

As for light disc bikes, my girlfriend's father cruises around on a 13.2 lb disc Crumpton so it's possible. Although his rim bike is around 11.5 lbs..

[Mark McM]

The issue with Ti is that the shear modulus (the "twisting" resistance) is I think ~45GPa, while the elastic modulus is ~115GPa (the "bending" resistance). T700 has a tensile modulus of ~115GPa. What that means is that the T700 is essentially 3x as resistant to twisting and the same in bending, if laid up properly, at a much lower density - and T700 is an intermediate modulus fiber. T1100 I think is 150 or 175 - I don't remember.

Anyway, for equivalent bending/twisting resistance, a titanium frame needs more of a denser material, so heavier. The upside is that it'll be strong in all directions (assuming the welds are good...).

It's not quite as simple as this. Carbon fibers themselves only have virtual no shear strength/stiffness. The angle of the layup is what gives them strength/stiffness in shear. While isotropic materials (most metals) have a constant ratio of shear modulus to longitudinal modulus (referred to as Poisson's ratio), the ratio of shear/longitudinal modulus of carbon fiber can be varied by varying the layup angle.

The reason carbon fiber frames are often lighter than titanium (or other metals) has more to do with the stiffness/weight and stiffness/strength of the materials than it does to ratio of shear/longitudinal stiffness.

I would imagine a $4K disc titanium frame build <16 is possible, but it'd be more flexible than a well-built carbon fiber frame with a similar weight.

The question isn't so much can you build a sub-15 lb. titanium frame bike with disc brakes, but rather should you. My 2012 Litespeed Ghisallo titanium frame weighs just 865 grams, and is build into a bike that weighs about 13 lb. - and that's with clincher tires, aluminum rims and all metal componentry, save for the fork blades (the steerer is titanium). Carbon tubular rims and a full carbon fork would put it well under 13 lb. Adding disc brakes would keep it under 15 lb. But this bike is very, very flexy, and not confidence inspiring at speed at all. I doubt many people would enjoy riding this bike, regardless of what type of brakes it used.

[Heisenberg]

light metal disc bikes are tricky.

most of the materials and component choices (headtubes, forks, headsets, dropouts) when it comes to disc brakes for metal builders (save large manufacturers) are pretty porky. oversized everything is the norm, and oversized is heavy.

building durable complete disc bikes below 17lbs with ti or steel is doable. but not easy. if you have oem fork and droupout systems it's easier.

[yinzerniner]

You can get a production Ti frame at the same weight point: https://litespeed.com/collections/titanium-road-bikes/products/t1sl-disc-frame

So around $4k new / $2k used for a frame alone

Was trying to stay with the quoted max price of $3k in a previous post. Obviously a T1SL will be about the same weight, but the price of the frameset is prohibitive for doing a lower budget weight weenie build.

building durable complete disc bikes below 17lbs with ti or steel is doable. but not easy. if you have oem fork and droupout systems it's easier.
One somewhat easy way to do it (albeit with lots of cash on hand) is to look at some of the lightest weight disc builds out there and try to mimic the spec.

As previously mentioned Canyon was able to make a 6kg disc brake bike with clinchers with a roughly 640g frame and 285g fork. If you do tubulars you can have roughly 1100g to add back into the frame and fork weights which is possible with titanium and possibly even some very lightweight steel.

Another great repository is the Fairwheel Bikes Blog. They have parts lists and weights for all the custom rigs they put together.
http://blog.fairwheelbikes.com/

[Heisenberg]

One somewhat easy way to do it (albeit with lots of cash on hand) is to look at some of the lightest weight disc builds out there and try to mimic the spec.

As previously mentioned Canyon was able to make a 6kg disc brake bike with clinchers with a roughly 640g frame and 285g fork. If you do tubulars you can have roughly 1100g to add back into the frame and fork weights which is possible with titanium and possibly even some very lightweight steel.

Another great repository is the Fairwheel Bikes Blog. They have parts lists and weights for all the custom rigs they put together.
http://blog.fairwheelbikes.com/

most aftermarket disc road forks are ~420-600g.

most metal handbuilt (daily driver) steel and ti frames setup for discs in a 54-56cm size range from 1300g-2000g. a king i8 headset is 140g (integrated OEM OS hs in that canyon is probably around 50-60g). so let's be generous and say that a VERY LIGHT metal disc frameset (frame/fork/hs/clamp) is 1900g.

against a 950g OEM big-box frameset.

you're only going to save 200-300g with the tubular version of a wheelset (also depending on tire choice and tubeless or not).

supply chain is where it falls short. if you (as a metal builder) can afford to cut your own mold and test the fork/frame as a unit you'll be better off, but it's still going to be an uphill battle with some creative solutions involved.

[nmrt]

I have a size 56 No. 22 Great Divide Disc (Titanium frame) at 16.5 lb. This weight includes pedals, garmin mount, bottle cage, and a Sram Red Dzero powermeter.

How was this build possible?
With 1170 g disc wheelset with DT Swiss 180 EXP hubs! :-)
BTW, Old Potatoe built those wheels. :)

[fogrider]

I have a size 56 No. 22 Great Divide Disc (Titanium frame) at 16.5 lb. This weight includes pedals, garmin mount, bottle cage, and a Sram Red Dzero powermeter.

How was this build possible?
With 1170 g disc wheelset with DT Swiss 180 EXP hubs! :-)
BTW, Old Potatoe built those wheels. :)

Wow, that's pretty great! so that's with Sram Red AXS with the Dzero?

[huck*this]

I have a size 56 No. 22 Great Divide Disc (Titanium frame) at 16.5 lb. This weight includes pedals, garmin mount, bottle cage, and a Sram Red Dzero powermeter.

How was this build possible?
With 1170 g disc wheelset with DT Swiss 180 EXP hubs! :-)
BTW, Old Potatoe built those wheels. :)

What rims were used to build up that light? Very nice numbers

[Heisenberg]

What rims were used to build up that light? Very nice numbers

i have some stan’s grail c (300g rims) laced to rotor hubs that tip the scales at 1050 disc/tubeless, but if you weigh more than 130lbs they’re absolute noodles.

[Clancy]

I have a size 56 No. 22 Great Divide Disc (Titanium frame) at 16.5 lb. This weight includes pedals, garmin mount, bottle cage, and a Sram Red Dzero powermeter.

How was this build possible?
With 1170 g disc wheelset with DT Swiss 180 EXP hubs! :-)
BTW, Old Potatoe built those wheels. :)

Detail the build please, inquiring minds want to know.

[oldpotatoe]

Detail the build please, inquiring minds want to know.

Spokes were CX-Sprint drive side rear and disc side front. Rest were CX-Rays. Alloy Squorx nipples(the only alloy nipps I'll use). BTLOS Asian carbon rims....

DT180 straight pull disc hubs..Both sourced by NMRT...

[David in Maine]

Just listened to the Cyclingtips Nerd Alert podcast which included an interview with an engineer from, I believe, Hayes brakes about the current attempts to improve road disc and the inherent challenges in disc brake systems. I have to say, I'm really glad I went with long reach calipers on my new Seven! Sorry, not really on topic, although they talked about how making disc bikes lighter increases the possibility of flex = noisy brakes.

David

[ikecycke]

Spokes were CX-Sprint drive side rear and disc side front. Rest were CX-Rays. Alloy Squorx nipples(the only alloy nipps I'll use). BTLOS Asian carbon rims....

DT180 straight pull disc hubs..Both sourced by NMRT...

A bit OT, but what did you think of those rims? I've used Light Bicycle and Nextie before with good luck, but never know which China carbon rims are trustworthy. Disc rims seem to be a bit more forgiving, but don't want to throw caution to the wind too much.

[oldpotatoe]

A bit OT, but what did you think of those rims? I've used Light Bicycle and Nextie before with good luck, but never know which China carbon rims are trustworthy. Disc rims seem to be a bit more forgiving, but don't want to throw caution to the wind too much.

They built just fine and seem to be reliable. Haven't heard from NMRT..he's local, if there was a problem, pretty sure I would have heard about it.

[ikecycke]

They built just fine and seem to be reliable. Haven't heard from NMRT..he's local, if there was a problem, pretty sure I would have heard about it.

Thanks for the response. The prices are a little better than the others, and they have free shipping during Chinese New Year, so may be worth a little experimenting.

[Gummee]

I've been contemplating the whole rim/disc thing for a couple months now. In my mind, for a road bike, if you will ride 30mm or smaller tires, go rim. If you ride over 30mm tires, do disc. A good steel frame with rim brakes is within a couple hundred grams (basically not noticeable) of a disc carbon bike.

...unless you want all your wheels to be cross compatible (get it?!) across the garage...

That's where I am at the moment. 4 bikes have gone TA disc that mix n match, there's a boost bike that needs to move as well as a 650b bike that needs to move.

M

[nmrt]

These were the rims -- the extralight versions at 270 g! https://btlos.com/mountain-bike/m-carbon-rims/asymmetric-mountain-bike-xc-trail-carbon-rim

These were the hubs -- at 280 g for the hubset! https://www.dtswiss.com/en/ratchetexp

Spokes were mostly CX Rays with a few CX Sprints on the drive side.

And how are the wheels at 1170 g? Absolutely fantastic. They feel so smooth and dare I say stiff (!) at their measly weight. I am no shill for the Old P. But all the wheels that he has built for me have been perfect. I do not think it is in my imagination when I say the the same bike feels so much better when I put on Old P built wheels and remove the local "LBS" built wheels. :)

Lastly, I have had Old P build me wheels from BTLOS before. And some wheels are going on in the second year. And they have been perfect. I would not think twice from buying from them.
Detail the build please, inquiring minds want to know.

[nmrt]

My bike at 16.5 lbs is with the 1170 g disc wheelset and Sram Red 11-speed mechanical with Sram Red Dzero crankset (heavy crankset!). If I were to get rid of this powermeter and crankset, I am sure I could have the bike at 15.XX lb.

Wow, that's pretty great! so that's with Sram Red AXS with the Dzero?

[Heisenberg]

These were the rims -- the extralight versions at 270 g! https://btlos.com/mountain-bike/m-carbon-rims/asymmetric-mountain-bike-xc-trail-carbon-rim

These were the hubs -- at 280 g for the hubset! https://www.dtswiss.com/en/ratchetexp

Spokes were mostly CX Rays with a few CX Sprints on the drive side.

And how are the wheels at 1170 g? Absolutely fantastic. They feel so smooth and dare I say stiff (!) at their measly weight. I am no shill for the Old P. But all the wheels that he has built for me have been perfect. I do not think it is in my imagination when I say the the same bike feels so much better when I put on Old P built wheels and remove the local "LBS" built wheels. :)

Lastly, I have had Old P build me wheels from BTLOS before. And some wheels are going on in the second year. And they have been perfect. I would not think twice from buying from them.

huh - max pressure is a little worrisome with a roadish build, but for gravel they look neat.

can i ask how much you weigh and what kind of rider you are?

the squishiness of the stans grail C i have may not be entirely the rim's fault, the rotor hub is pretty terrible. 2:1 24h lacing, really narrow ds flange spacing because of the extrawide fhub body.

[vincenz]

Just listened to the Cyclingtips Nerd Alert podcast which included an interview with an engineer from, I believe, Hayes brakes about the current attempts to improve road disc and the inherent challenges in disc brake systems. I have to say, I'm really glad I went with long reach calipers on my new Seven! Sorry, not really on topic, although they talked about how making disc bikes lighter increases the possibility of flex = noisy brakes.



David


I would believe that as you can’t fight physics. Unless they are able to make disc as light as rim, I will not touch them. I don’t believe they will be able to though. A comparative rim setup should always be lighter. The 1 to 1.5 lbs difference is not much, but in the performance bike world, it’s a lot. For road, I don’t believe disc is needed nor worth the weight penalty. For off-road, the trade-off makes more sense.

My No22 Great Divide rim comes in at 15.5 lbs with SR 11, bora clinchers, and zero weight weenie parts. No compromises with durability, performance, and aesthetics in my book. I would not trade it for any disc equivalent.

[nmrt]

I weigh between 143-148 lb.
I am not sure what you mean by what kind of rider...but I will try to answer.
I do not race ever. Just ride solo in the Boulder foothills and the Colorado mountains as hard as I can. Being in Boulder with all the elite and semi-elite and heck just grandma's on their evening ride, I get beat by most. But that is ok by me. This is Boulder. :-)

I have been riding those BTLOS rims I linked at 80-85 psi and they seem fine. I had asked BTLOS about this before I purchased and they said it should be okay. So I took a risk and bought them. I knew that even if they did not work with a road setup, I would have used them on my gravel bike.

huh - max pressure is a little worrisome with a roadish build, but for gravel they look neat.

can i ask how much you weigh and what kind of rider you are?

the squishiness of the stans grail C i have may not be entirely the rim's fault, the rotor hub is pretty terrible. 2:1 24h lacing, really narrow ds flange spacing because of the extrawide fhub body.

[Mikej]

Hmm, i'm wondering what the calibration is on some of these scales.

[nmrt]

The last I checked and calibrated my scale, it was calibrated at 6.022 X 10^-23 femtograms. ;)

Hmm, i'm wondering what the calibration is on some of these scales.

[Mark McM]

The last I checked and calibrated my scale, it was calibrated at 6.022 X 10^-23 femtograms. ;)

Do I detect a mole?

Avogadro strikes again!

[CAAD]

My 54cm Trek Checkpoint comes in at 16.06lbs with pedals, cages, K-edge mount. This is with 25c tires riding on 35 deep x 28 wide farsports wheels 24/24spokes 1387g. Absolutely solid wheels. Full SRAM Red 10 speed group including cassette, spyre calipers. Nothing exotic.

With a lighter frame/fork and a few other choice parts, a 14lb disc bike is doable.

[nmrt]

almost! the power i used was to a negative 23. mole is to a power of positive 23. But good catch! :)

Do I detect a mole?

Avogadro strikes again!

[unterhausen]

These were the rims -- the extralight versions at 270 g! https://btlos.com/mountain-bike/m-carbon-rims/asymmetric-mountain-bike-xc-trail-carbon-rim
Are you buying direct from their alibaba store?

[oldpotatoe]

These were the rims -- the extralight versions at 270 g! https://btlos.com/mountain-bike/m-carbon-rims/asymmetric-mountain-bike-xc-trail-carbon-rim

These were the hubs -- at 280 g for the hubset! https://www.dtswiss.com/en/ratchetexp

Spokes were mostly CX Rays with a few CX Sprints on the drive side.

And how are the wheels at 1170 g? Absolutely fantastic. They feel so smooth and dare I say stiff (!) at their measly weight. I am no shill for the Old P. But all the wheels that he has built for me have been perfect. I do not think it is in my imagination when I say the the same bike feels so much better when I put on Old P built wheels and remove the local "LBS" built wheels. :)

Lastly, I have had Old P build me wheels from BTLOS before. And some wheels are going on in the second year. And they have been perfect. I would not think twice from buying from them.

Thank you sir..been a pleasure to build these..:)

[fogrider]

Thank you sir..been a pleasure to build these..:)

OP, 'just sent you a DM.

[rollinslow]

Just listened to the Cyclingtips Nerd Alert podcast which included an interview with an engineer from, I believe, Hayes brakes about the current attempts to improve road disc and the inherent challenges in disc brake systems. I have to say, I'm really glad I went with long reach calipers on my new Seven! Sorry, not really on topic, although they talked about how making disc bikes lighter increases the possibility of flex = noisy brakes.

David

I really enjoyed this Nerd Alert podcast. I think if you have multiple experts who have been very pro-disc come-out and detail exactly what the current issues with discs are it made it crystal clear that early adoption of an engineering mess is not for me anytime soon. The mechanic at the Grupetto knows what he is talking about as well. I think the biggest issue to me is the poor manufacturing tolerances not being able to be overcome for most carbon consumer disc frames as well as resonance issues inherent to frames.

[NHAero]

I need to listen to this podcast, sounds very interesting. I have mechanical discs (Avid BB7) on my Big Dummy, and hydro discs on my Anderson, dropbar conversion Litespeed, and Pivot FS 29er. The first two are steel forks and steel frames, the Pivot is a carbon frame with a suspension fork, and the Litespeed is a Ti frame with a suspension fork.

None of these brakesets have given me a lick of trouble. Two of the hydros are Shimano, the other is SRAM. The BB7s are 10 years old, the Pivot's SRAM brakes are 6 years old (replaced pads), and the Shimano brakesets are 2-3 years old. Only the Pivot has through axles. I'll be interested to hear what others' issues have been.

I really enjoyed this Nerd Alert podcast. I think if you have multiple experts who have been very pro-disc come-out and detail exactly what the current issues with discs are it made it crystal clear that early adoption of an engineering mess is not for me anytime soon. The mechanic at the Grupetto knows what he is talking about as well. I think the biggest issue to me is the poor manufacturing tolerances not being able to be overcome for most carbon consumer disc frames.

[Gummee]

I need to listen to this podcast, sounds very interesting. I have mechanical discs (Avid BB7) on my Big Dummy, and hydro discs on my Anderson, dropbar conversion Litespeed, and Pivot FS 29er. The first two are steel forks and steel frames, the Pivot is a carbon frame with a suspension fork, and the Litespeed is a Ti frame with a suspension fork.

None of these brakesets have given me a lick of trouble. Two of the hydros are Shimano, the other is SRAM. The BB7s are 10 years old, the Pivot's SRAM brakes are 6 years old (replaced pads), and the Shimano brakesets are 2-3 years old. Only the Pivot has through axles. I'll be interested to hear what others' issues have been.
I've got Shimano, Shimano, Shimano and well.... more Shimano brakes on my bikes.

4 mtn bikes with primarily XT brakes that have been fantastic, 2 CX bikes with Ultegra or D/A calipers and 1 road disc bike with Ultegra calipers.

I haven't seen any significant 'manufacturing flaws' on the CX or road bike and they're Chinesium. The place you'd think that 'manufacturing flaws' would manifest first.

The only issue I've had is a squealing at 'almost stopped' speeds on the road disc bike. ...and that's likely user error in assembly (contamination)

M

[Heisenberg]

I really enjoyed this Nerd Alert podcast. I think if you have multiple experts who have been very pro-disc come-out and detail exactly what the current issues with discs are it made it crystal clear that early adoption of an engineering mess is not for me anytime soon. The mechanic at the Grupetto knows what he is talking about as well. I think the biggest issue to me is the poor manufacturing tolerances not being able to be overcome for most carbon consumer disc frames as well as resonance issues inherent to frames.

flatmount exacerbates the issue. tolerances need to be dead on...it can be a nightmare at times. milled or printed one-piece dropouts/brake mounts can help.

[Davist]

Surprised to read about flatmount making things worse, my sample size of 3 (Aluminum Scott speedster gravel, Carbon Canyon ultimate roadie and Carbon Vitus substance gravel) one of which was "mid range" the other two are definitely budget have been flawless. Shimano ultegra, rs 485 and sram apex brakes. I'm typically not that lucky...

[rollinslow]

Surprised to read about flatmount making things worse, my sample size of 3 (Aluminum Scott speedster gravel, Carbon Canyon ultimate roadie and Carbon Vitus substance gravel) one of which was "mid range" the other two are definitely budget have been flawless. Shimano ultegra, rs 485 and sram apex brakes. I'm typically not that lucky...

I would just give this a listen from a few days ago on Cycling Tips. I think it makes a lot of sense why some people have no issues and other have massive problems.

https://cyclingtips.com/2020/02/nerd-alert-podcast-how-to-make-the-perfect-disc-brake/

[tomato coupe]

Surprised to read about flatmount making things worse, my sample size of 3 (Aluminum Scott speedster gravel, Carbon Canyon ultimate roadie and Carbon Vitus substance gravel) one of which was "mid range" the other two are definitely budget have been flawless. Shimano ultegra, rs 485 and sram apex brakes. I'm typically not that lucky...

Same experience here. The flat mounts on three bikes (Factor O2, Cervelo Aspero, Alchemy Atlas) built this year were all fine, no re-facing required.