Is there a "new normal" for bike geometry?

[XXtwindad]

Prompted by some of the discussion around Joosttx's lovely Bingham Built All-Road, I'm really curious about some facets of bike geometry. The crucial caveat is that I'm no expert, and I'm interested in being educated further on the subject.

It does seem to me, however, that there is a trend toward lower BBs and slightly longer chain stays, which lends more stability, or a feeling of being "in" the bike rather than "on" the bike.

Here are four recent examples of "road race " bikes I found that would seem to indicate the trend. The first is the geo for Clean39's ti/carbon Firefly I lusted after. 70mm BB drop with 420 chain stays. The Speedvagen stock OG has a 75mm BB drop with 413 chain stays. And Erik's race day road Alliance has a 80mm BB drop with 417 chain stays. The Breadwinner Lolo has a 72 BB drop with 415 chain stays.

Again, I make no claims about being an expert on bike geometry. Far from it. However, I recently was interested in a cross bike, and I talked with a frame builder I have a lot of respect for, and he said the high BB drop (610) would make it very "twitchy" on fast road descents. That has always been an area of concern for me, so I passed.

From where I stand, this is a great trend. I like the increased stability. But if anyone has differing viewpoints, I'd be happy to learn more.

[tuscanyswe]

I dont think custom bikes are a good way to determine trends but even so it would be suprising if bb drops were not slightly increased overall since tires size have increased overall on roadbikes.

Most now fit 28s or more.

How do u fit a larger tire in the "same" frame?

Well u make the chainstays longer.

How do u make your frame low enough to not hit the toptube when standing over it or negate the feel of beeing to high up when mounted on the same saddleheight but with now larger volume tires making the bike effectively taller?

Well u lower the bb to negate that effect.

In this sense it would seem logical that your observation could hold true. Personally i havent thought about it b4.

[thirdgenbird]

I’ve had my cross frame with 61mm drop over 40mph and it felt fine. The hill was a gradual sweeper so i certainly didn’t push things to the limit, but it seems to work fine for daily riding. I like it enough it’s transitioned to my main road bike.

[tomato coupe]

Is there a new normal? I wouldn’t look at a handful of niche bikes to answer that question.

[XXtwindad]

Is there a new normal? I wouldn’t look at a handful of niche bikes to answer that question.

You might have a point. I don’t know. The Spec Tarmac has a 72BB drop with 410 stays, so that seems in the ballpark.

Is Mark McM in the building?

[dddd]

I thought that this thread might have been more about frame angles, but apparently not.

I had checked all of my newer carbon road bike's geometry not too long ago, and discovered that in my ~56cm size (52cm sloping) that all (except for my more-twitchy Koppenberg) have near-identical 55.5-56cm toptube, roughly 73.5-degree seattube angle and roughly 72.5-degree headtube angle.

I consider this the (relatively) new normal, though my bikes aren't made for the newer tire sizes over 25mm.

[Velocipede]

No such thing as a "Normal" now. I do a bunch of custom frames. Just sent over the geometry from a stock frame(someone else's design) to someone, and they refused to do it. They don't feel it's a good geometry even though it's a really popular frame and well handling/riding frame. It comes down to the builder and what they feel is best for them and their bikes.

[FlashUNC]

To crib from Richard Sachs, there's no new normal, it's the same it's always been -- putting the wheels in the right position in relation to the rider's contact points.

[Kirk007]

Hard to say with the current interest in gravel bikes, disc brakes and increasing efforts to make one bike fit every application I think the new normal today is endless variability. But for all around road bikes I think builders like De Rosa, Colnago, Pegoretti, Merckx had this generally figured out awhile ago, with personal variations around general ideas (not to mention our builder luminaries like Richard Sachs, Tom Kellogg, Della Santa, Weigle and the newer generation - Dave Kirk, etc. etc.

As someone who rides. large frames I have a strong preference for at least 75mm and ideally 80mm of bottom bracket drop (which is a main reason that I think the do it all - 700c and 650b wheels - 25mm to 52mm tire bikes are too much of a compromise for me; 60-65mm of bottom bracket drop and 700c wheels for road ridings feels yucky to me.

[robt57]

(except for my more-twitchy Koppenberg)

How are you BTW?

Is it twitchy, or just comparatively? My classics is a Limo, there ain't a twitch to be found. ;)

Robt57/Sparky

[John H.]

1st off. None of this is new. Serotta was offering stock geometry frames with 80mm of drop at least 16 years ago- Maybe more.
I think Richard Sachs wrote something like "I set my jig at 80mm of bb drop in the 70's and never moved it" (Maybe I am paraphrasing- I don't mean to speak for Richard. But you get the idea).

Angles and fork rakes- Depends on the brand. If custom, depends on the rider fit, how aggressive, overall setup, etc..

I personally have found that a variety of geometries can work great in practice. It is important not to get too caught up in the minutia unless you really know what you are after and what works best for you.

Personally I have ridden higher bb bikes like Scott Addict (road and gravel), shorter stays, longer stays, slack head angles, etc.
One guy on VS said that he thought an Open with 71 degree head angle and 50mm rake handled poorly as a road setup.
I thought mine rode great-

I have found that regardless of angles, drops, and rakes- The thing that works best for me is a bike with a long front center.
A longer front center gets the front wheel out there, and to me it feels better especially offroad.
No stock gravel bike in my size has as long of front center as I like. I can still make the bikes work fine, but if they had another 15-20mm of front end length they would be even better for me.
But I bet this does not apply to all riders.

[cinema]

if the industry is any clue at all, they just updated the the long haul trucker geometry with a sloping TT. yes, you read that right. Surly. modernized. their geo. not in any of the ways noted here but they added things like sloping tube for standover and thru axles for rigidity.

i've noticed a lot of manufacturers elongating the chianstays on race models for a better part of the last decade, for a good reason. more clearance for worse road conditions and no matter what someone believes a bike with a slightly longer wheelbase will climb 'better' (stable) than a crit bike. (but you might not like it). physics. it will also be more stable feeling when descending technical terrain.

Kirk is right about the italian masters. had a good idea of how to make a frame stable and comfortable. they often slacked out the head tube to what a parlee rider might find absurd. if you look at the catalogs, they don't even list headtube angles. they were around 71 on a 54-56 frame on a colnago tecnos/master de rosa primato professional etc.

[Velocipede]

if the industry is any clue at all, they just updated the the long haul trucker geometry with a sloping TT. yes, you read that right. Surly. modernized. their geo. not in any of the ways noted here but they added things like sloping tube for standover and thru axles for rigidity.

i've noticed a lot of manufacturers elongating the chianstays on race models for a better part of the last decade, for a good reason. more clearance for worse road conditions and no matter what someone believes a bike with a slightly longer wheelbase will climb 'better' (stable) than a crit bike. (but you might not like it). physics. it will also be more stable feeling when descending technical terrain.

Kirk is right about the italian masters. they often slacked out the head tube to what a parlee rider might find absurd. if you look at the catalogs, they don't even list headtube angles. they were around 71 on a 54-56 frame on a colnago tecnos/master de rosa primato professional etc.

Erik did an amazing job with Surly. It's hard to believe how they treated him and what he's accomplished since he left.

[unterhausen]

I am not sure the designers of production bikes will ever adopt lower bb because they are afraid of pedal strike. But low bb are definitely in style among custom builders. Not sure I believe it does anything special, but my travel bike has 85mm of drop.

People seem to be experimenting with slacker head tubes. Which would be fine, but it's still difficult to find a fork that doesn't have 45mm of rake. That just seems wrong to me. I think they are following the MTB trend of slack head tubes, but there it makes a lot more sense since a compressed suspension fork can lead to crit bike-like head tube angles. Not that great when you are going down something steep with rocks 'n' roots.

[colker]

The major "new" is the looong front center on gravel bikes.There is nothing unusual on a 75mm even 80mm bb drop nor a 420mm chainstay on a road bike. A 575mm effective top tube otoh coupled w/ a shallow head angle... now that´s new.

[jwin]

I think the long front center is very interesting. In my mind what it does is creates stability by lengthening the wheelbase while retaining ~60mm trail for quick handling and maintaining a ~71 deg HA (not too slack, but not too steep). I'm curious what others think of this trend.

If I'm not racing (I don't) then I want stability, but quick feeling handling, but I don't need to feel like it's on rails or that it's twitchy.

I think BB height is very much personal preference.

[vincenz]

If you’re talking about road race geo, trends should be analyzed with mass market production bikes, not custom bikes because custom deviates from production.

Race geo has been “settled” for decades now. Deviations from a 70mm bb drop and 405mm chainstays are usually within ~ 5-10mm for the best road race bikes.

[David Tollefson]

All mine are custom, so maybe outside of the scope of what you call "normal", but the comments about maximizing front center on gravel rigs sit well with me. I also go with pretty high trail when left to my own devices, and love big-volume tires.

[Davist]

Interesting, I went from a Cannondale Supersix Evo to a Canyon Ultimate, longer chainstays 405 to 415, definitely like the longer Canyon chainstays (drop not published though), and sized my gravel bike for a longer front center vs road as I didn't want as long a stem or reach. I guess I'm on trend, both work well by me.

[Hellgate]

To crib from Richard Sachs, there's no new normal, it's the same it's always been -- putting the wheels in the right position in relation to the rider's contact points.You can substitute Max Kullaway in that statement too.

[Clancy]

Erik did an amazing job with Surly. It's hard to believe how they treated him and what he's accomplished since he left.

Point me in the direction of that story please, if you can.
Curious

[joosttx]

For me gravel bikes are the old “club racer” bike. I haven’t compared geo between early 2000 “club racer” bikes to modern day gravel bikes but I would guess they are similar. What is different is disc brakes and the wider tires, head tubes, thruaxles and boost. As others have said it’s about the position of the wheels relative to the contact points.

[dddd]

How are you BTW?

Is it twitchy, or just comparatively? My classics is a Limo, there ain't a twitch to be found. ;)

Robt57/Sparky

Good year for health and fitness so far. :)

My perception of "twitchy" is indeed relative, though quite a bit outside of what I consider median steering behavior. It's pretty hard-core to the extent that I really ain't fully up to exploiting it's cornering prowess (like an old man riding a 125 GP bike maybe).
But it gets better each consecutive day that I ride it. Problem is that I do like to ride other bikes, usually there are 3-4 in rotation at any particular time.

You have a Domane Classics, which I believe is one of two non-Koppenberg variants. The Koppenberg geo is Emonda-based so is shorter in wheelbase, there even are reverse-bend fork dropouts. Trek published geo shows 42cm chainstays, but mine measures 41cm there so I don't consider any of their published geometry reliable.

I was running a 115mm stem with good results, and with adequate knee clearance. Then with the big six-oh approaching I switched to a slightly taller (angle) 110mm WCS stem. This shorter/taller stem is definitely taking things to the limit WRT my ability to relax and focus on a longer-sightline up the road when over 40mph. The handling is fine below that speed however.

It supposedly has 7.8cm bb drop, which seems like a lot for a bike still wearing 23mm tires. I will be trying 25mm tires when these GP4K tires are done.

[Velocipede]

Point me in the direction of that story please, if you can.
Curious

It's not an external story. But people in the industry know it, especially people in the Twin Cities area. Erik Noren of Peacock Groove really made Surly what it is. He did a ton of design, sales and marketing for the bikes. He was the boss of Surly at one point. He even made some of the prototypes and first frames. And if you think about his bikes and bike names and what Surly has, you see where it all came from. There's a lot to the story.

[Peter P.]

I personally like the handling of my 6.5cm BB drop bike better than my 8.0cm BB drop bike. Going into a lean or changing from left to right, seems easier yet the bike doesn't feel top heavy.

There's a range of dimensions that will work with road frames and while one dimension may affect another, they're mostly "mixable". There's no secret combination which works better than others.

And when comparing geometries, you must compare road-road, 'cross-'cross, etc.

Manufacturers and framebuilders have figured out what works, long ago. Some merely offer highly specific numbers to differentiate themselves in the market. I mean, is there really a difference between 415 and 413mm chainstays that will make you crave one brand over another?

I don't see "a new normal" in frame geometries. I just see geometries.

[cinema]

^^ have to agree with this. for some reason i feel better descending on my 6.5 drop bike. i am no pro and i think the bike fits a lot better than my smaller racier frames.

[thwart]

I’ve had my cross frame with 61mm drop over 40mph and it felt fine. The hill was a gradual sweeper so i certainly didn’t push things to the limit, but it seems to work fine for daily riding. I like it enough it’s transitioned to my main road bike.

Same experience here. So many facets of what makes a 'good handling bike'...

[buddybikes]

My FF has 80, my own frame built in 1981 had 80.

[colker]

^^ have to agree with this. for some reason i feel better descending on my 6.5 drop bike. i am no pro and i think the bike fits a lot better than my smaller racier frames.

700 or 650B?

[cinema]

700 but its a longer/slacker cross bike not a tight road bike

[Andy340]

Is geometry change a byproduct of squeezing in bigger and bigger 700c tires - for example, if the frame / fork needs to move front axle further out to avoid toe overlap with bigger tires will that functional change lead to increased front center?

[Germany_chris]

if the industry is any clue at all, they just updated the the long haul trucker geometry with a sloping TT. yes, you read that right. Surly. modernized. their geo. not in any of the ways noted here but they added things like sloping tube for standover and thru axles for rigidity.

i've noticed a lot of manufacturers elongating the chianstays on race models for a better part of the last decade, for a good reason. more clearance for worse road conditions and no matter what someone believes a bike with a slightly longer wheelbase will climb 'better' (stable) than a crit bike. (but you might not like it). physics. it will also be more stable feeling when descending technical terrain.

Kirk is right about the italian masters. had a good idea of how to make a frame stable and comfortable. they often slacked out the head tube to what a parlee rider might find absurd. if you look at the catalogs, they don't even list headtube angles. they were around 71 on a 54-56 frame on a colnago tecnos/master de rosa primato professional etc.


Surly just cut 20mm of chainstay length and brought it down to 430 which seems more reasonable to me than the 450 it used to be. With bike packing being a thing over racks and panniers there's just no need for the heel clearance that lang chainstays provide.

[weisan]

Once I descended on my Surly LHT with 60+ pounds of bikepacking gear at 50mph ....that was the only time I actually felt that I could (not that I would) go hands-free off the handlebar...while I comb my hair, cook an omelet, read a book -- not all at the same time of course, and yet feel perfectly safe and comfortable. No other bike I have has ever done that, nor give me that sense of confidence.

https://vimeo.com/126438520