non scientist re: differences in wheel bearings

[eddief]

Was talking to a friend about wheels and bearings. He has a Roubaix with decent wheels, nothing special. He weighs around 200. He said a much more svelte rider smoked him coasting down a hill and that guy had really high end wheels.

1. Have you experienced noticeable difference related to the quality of bearings in the wheels you ride?

2. If it is true that better bearings make a noticeable difference, is the advantage somehow the same when coasting as when pedaling up a climb?

????

[yinzerniner]

Was talking to a friend about wheels and bearings. He has a Roubaix with decent wheels, nothing special. He weighs around 200. He said a much more svelte rider smoked him coasting down a hill and that guy had really high end wheels.

1. Have you experienced noticeable difference related to the quality of bearing in the wheels your ride?

2. If it is true that better bearings make a noticeable difference, is the advantage somehow the same when coasting as when pedaling up a climb?

????

Bearings had nothing to do with your larger friend getting smoked. A full ceramic upgrade (pulleys, BB, Wheels) only saves 5-10w of drag.

On the bike there will be a small difference between rough and smooth bearings, but no difference between "average" and "top shelf" bearings on the bike if they're both in good shape.

[Mark McM]

Here's a simple test:

Lift your rear wheel off the ground, put the bike in its largest gear, and spin the cranks by hand until the rear wheel is spinning the equivalent of 30 mph. After reaching that speed, feel how much force you have to apply on the cranks to maintain that wheel speed.

Cut out a piece of plywood sheet (or other flat stiff material) with the same surface area as a rider on a bicycle. Get in a car with a friend in the driver's seat, and have the friend drive at a constant 30 mph. Open the sun roof, and hold the plywood sheet out through the roof of the car, in the wind. Feel how much force you have to apply to the plywood sheet to keep it from being pulled out of your hands.

If you do this, you will come to the conclusion that the wind drag force on a rider while descending is much larger than the wheel bearing drag force. So much so, that differences in bearing drag, from the very best bearings to the very worst, will make scant difference in speed.

(And just in case you're interested in numbers, you'll find that the power to propel a bike at 25 mph is in the range of 250 - 300 Watts. At that speed, the wheel bearings are consuming about 1 Watt.)

[woodworker]

[QUOTE=Mark McM;2447449]Here's a simple test:

Cut out a piece of plywood sheet (or other flat stiff material) with the same surface area as a rider on a bicycle. Get in a car with a friend in the driver's seat, and have the friend drive at a constant 30 mph. Open the sun roof, and hold the plywood sheet out through the roof of the car, in the wind. Feel how much force you have to apply to the plywood sheet to keep it from being pulled out of your hands.

Ummm... I wouldn't recommend this. :eek::)

[soulspinner]

Here's a simple test:

Lift your rear wheel off the ground, put the bike in its largest gear, and spin the cranks by hand until the rear wheel is spinning the equivalent of 30 mph. After reaching that speed, feel how much force you have to apply on the cranks to maintain that wheel speed.

Cut out a piece of plywood sheet (or other flat stiff material) with the same surface area as a rider on a bicycle. Get in a car with a friend in the driver's seat, and have the friend drive at a constant 30 mph. Open the sun roof, and hold the plywood sheet out through the roof of the car, in the wind. Feel how much force you have to apply to the plywood sheet to keep it from being pulled out of your hands.

If you do this, you will come to the conclusion that the wind drag force on a rider while descending is much larger than the wheel bearing drag force. So much so, that differences in bearing drag, from the very best bearings to the very worst, will make scant difference in speed.

(And just in case you're interested in numbers, you'll find that the power to propel a bike at 25 mph is in the range of 250 - 300 Watts. At that speed, the wheel bearings are consuming about 1 Watt.)

What he said. My father( works with pretty cool stuff) says a good application for those bearings is 40000 RPM where regular bearings give up. Then they make a big difference...

[Mark McM]

Was talking to a friend about wheels and bearings. He has a Roubaix with decent wheels, nothing special. He weighs around 200. He said a much more svelte rider smoked him coasting down a hill and that guy had really high end wheels.

To more directly get at possible reasons: As you've implied, normally a heavier rider will descend faster than a lighter rider, if all else is the same - but if the lighter rider descends faster, than all else is not the same.

Consider this: Drop a one pound hammer and 2 lb beach ball simultaneously from the same height. Which one hits the ground first? Almost certainly the hammer, even though it is lighter. The difference is that beach ball has a much larger volume and surface area, so it has much more air drag slowing it down.

When descending (or at high speeds in general), the largest drag force is air resistance. And the largest portion of the air resistance on a bike is the rider's body (a rider typically contributes 85 - 90% of the air resistance, and the bike contributes about 10 - 15%). A rider can change their air resistance dramatically by changing their position on the bike. A rider in a tight tuck will descent faster than a rider that is sitting up high (all else being the same). If a lighter rider was descending faster than your 200 lb. friend, I'd be willing to bet that the lighter rider was in a more aerodynamic position on the bike.

[yinzerniner]

Ummm... I wouldn't recommend this. :eek::)

Seriously, one man's "simple" is every other man's terrifying and complicated.

How would one know that the rear wheel is spinning at 30mph? And pedaling while lifting a wheel off the ground at such a high speed must be difficult as eff. How can one easily calculate the total frontal surface area of a rider, and in what position? And what vehicle has a sunroof that is large enough to prop up the said plywood rider cutout through it while moving? And who has strong enough wrists to hold anything up at any speed through a sunroof without breaking something?

Please, please tell us that you have video of this particular scientific demonstration available.

[Mark McM]

Seriously, one man's "simple" is every other man's terrifying and complicated.

How would one know that the rear wheel is spinning at 30mph? And pedaling while lifting a wheel off the ground at such a high speed must be difficult as eff. How can one easily calculate the total frontal surface area of a rider, and in what position? And what vehicle has a sunroof that is large enough to prop up the said plywood rider cutout through it while moving? And who has strong enough wrists to hold anything up at any speed through a sunroof without breaking something?

Please, please tell us that you have video of this particular scientific demonstration available.

It was a thought experiment. (Or at least the plywood sheet part was - I can easily do the spin the pedals with the wheel off the ground part, as I have a workstand to hold the bike, and my bike computer uses a rear wheel sensor so I know how fast the wheel is spinning.) In any case, most of us can relate these two "tests" to similar experiences. Many people have flipped their bike upside (standing it up on the saddle and handlebar) and spun the cranks by hand, and have learned that it really doesn't take much force to spin the rear wheel, even at high speed. And many of us have ridden in a car with the window rolled down, and held a hand out of the window and felt the air pushing against it. One doesn't have to have a strong imagination to know that if our whole body was out in the wind there would be a much greater wind force.

[verbs4us]

Some quasi-scientific data that suggest bearings might sometimes make a difference. I ride with a guy who is about 200 pounds, 6'3" and lean. When I was on the steel Masi with sew-ups and Phil Wood hubs, he would always coast faster. On the new Ti bike, with T11 hubs on 25 mm clinchers, I have to hit the brakes, even when coasting next to him. Tire pressure the same. My weight the same. Masi was 10 pounds heavier than the Ti bike. When I unship the chain and spin the Phil wheel, its spin for about half the time as the White Industries. Ditto for the front wheel. The Phils are known for a lot of seal drag (even, or perhaps esp., with fresh bearings). Wheels on both bikes feel buttery smooth and both bikes "feel" fast, but the Ti is clearly the faster coaster.

[John H.]

Could be anything or could be many things.
Weight does help downhill but it could also be:
1.) Bearings as you mentioned- but not likely bearings by themselves.
2.) Wheel profile, depth, and other wheel related aero qualities.
3.) Tires- model, pressure, width, type of tube
4.) Rider position
5.) aero clothing and helmet- tightly fitting.
Or any combination of these on the side of the faster rider, and any combination of the slower version for the 200 lb. rider.

Fastest being: Fast bearings, very aero wheels, fast tires at fast pressures, aero clothing that fits tightly, and aero helmet with an aero position.

Slowest being: cheap and/or worn bearings, box section wheels with many spokes, slow tires with butyl tubes at incorrect pressure, loose and flappy clothing, basic helmet, and block of wood position.

Lastly- Comfort at speed. Some feel safe freewheeling at 50 mph, some touch their brakes.

Was talking to a friend about wheels and bearings. He has a Roubaix with decent wheels, nothing special. He weighs around 200. He said a much more svelte rider smoked him coasting down a hill and that guy had really high end wheels.

1. Have you experienced noticeable difference related to the quality of bearings in the wheels you ride?

2. If it is true that better bearings make a noticeable difference, is the advantage somehow the same when coasting as when pedaling up a climb?

????

[Mark McM]

Some quasi-scientific data that suggest bearings might sometimes make a difference. I ride with a guy who is about 200 pounds, 6'3" and lean. When I was on the steel Masi with sew-ups and Phil Wood hubs, he would always coast faster. On the new Ti bike, with T11 hubs on 25 mm clinchers, I have to hit the brakes, even when coasting next to him. Tire pressure the same. My weight the same. Masi was 10 pounds heavier than the Ti bike. When I unship the chain and spin the Phil wheel, its spin for about half the time as the White Industries. Ditto for the front wheel. The Phils are known for a lot of seal drag (even, or perhaps esp., with fresh bearings). Wheels on both bikes feel buttery smooth and both bikes "feel" fast, but the Ti is clearly the faster coaster.

There are far too many variables here to draw any conclusions that the difference in speed was due the wheel bearings. But based on previous test measurements, the difference in wheel bearings was probably one of the smaller factors in speed difference. For example only looking at the wheels, the measured differences in tubular tire drag vs. clincher tire rolling resistance drag is much larger than the measured differences in wheel bearing drag.

[Seramount]

Some quasi-scientific data that suggest bearings might sometimes make a difference.

um, no...that doesn't even qualify as 'quasi'...

it's just anecdotal.

[Mark McM]

Could be anything or could be many things.
Weight does help downhill but it could also be:
1.) Bearings as you mentioned- but not likely bearings by themselves.
2.) Wheel profile, depth, and other wheel related aero qualities.
3.) Tires- model, pressure, width, type of tube
4.) Rider position
5.) aero clothing and helmet- tightly fitting.
Or any combination of these on the side of the faster rider, and any combination of the slower version for the 200 lb. rider.

Yes, it could be any of these things. But if these items were put in order of relative importance (based on previous test measurements), I think the list would look more like this:

1.) Rider position
2.) aero clothing and helmet- tightly fitting.
3.) Tires- model, pressure, width, type of tube
4.) Wheel profile, depth, and other wheel related aero qualities.
5.) Bearings

[yinzerniner]

Yes, it could be any of these things. But if these items were put in order of relative importance (based on previous test measurements), I think the list would look more like this:

1.) Rider position
2.) aero clothing and helmet- tightly fitting.
3.) Tires- model, pressure, width, type of tube
4.) Wheel profile, depth, and other wheel related aero qualities.
5.) Bearings

Would probably be more like:

1.) Rider position
2.) Aero clothing and helmet- tightly fitting.
3.) Tires- model, pressure, width, type of tube
4.) Frame/Fork/Handlebar/Cable Profile
5.) Wheel profile, depth, and other wheel related aero qualities.
6.) Barometric Pressure and/or Atmospheric Disturbances
7.) Whether Mercury is in Retrograde
8.) Bearings

It's honestly foolish for ANYONE who's not a pro to think that they're noticeably slower because they don't have "fast" bearings. As long as the bearings are smooth they'll operate fine. End of story.

[pasadena]

lowering the resistance in one part of the system is like lubricating one-fourth of your chain.

[eddief]

and you guys are supporting that idea. i will keep my normal wheels until the proof suggests otherwise.

[Mikej]

The problem is we don’t know the condition of each riders bearings. More expensive bearings tend to be manufactured to tighter tolerances and utilize better materials and processes. This can yield a more robust product that can last longer. They are also more spherical- Higher quality bearings could last longer and perform to a higher level than less expensive bearings. Of course the devil is in the details on a subject such as this, bearings is quite a broad term.

[choke]

I'll go against the grain here and say that yes, they can make a difference - either that or the hubs themselves do. I have a couple of sets of wheels built in the 90s with Bullseye hubs and they roll smoother and coast longer than any other wheels that I've ever owned....Campy, Mavic, WI, it doesn't matter.

[oldpotatoe]

Some quasi-scientific data that suggest bearings might sometimes make a difference. I ride with a guy who is about 200 pounds, 6'3" and lean. When I was on the steel Masi with sew-ups and Phil Wood hubs, he would always coast faster. On the new Ti bike, with T11 hubs on 25 mm clinchers, I have to hit the brakes, even when coasting next to him. Tire pressure the same. My weight the same. Masi was 10 pounds heavier than the Ti bike. When I unship the chain and spin the Phil wheel, its spin for about half the time as the White Industries. Ditto for the front wheel. The Phils are known for a lot of seal drag (even, or perhaps esp., with fresh bearings). Wheels on both bikes feel buttery smooth and both bikes "feel" fast, but the Ti is clearly the faster coaster.

'Might' but probably not..too many variables, as has been mentioned.:)

I'm just glad somebody who $pent big $ on ceramic didn't yell about it being a 'game changer'...yikes.

[cmg]

too many variables to blame the bearings. Was the slower rider short, fat, wide 200lbs or taller, not as wide, not riding in tuck 200lbs. Was svelte rider the same 200lbs? riding into a headwind, more effect on short and wide then tall and not as wide. while it's amusing on the possibilities of the why, i'll blame the color purple as having an effect, seems possible. it's a slower color. :)

[eddief]

according to the story I was told, slower guy is 200 and not in top shape at all. The other guy was probably in great shape and 165. Not sure about riding position but got the impression they were probably simply on the tops of their bars and coasting down hill. My 200 lb friend was taken aback at how fast skinny was going.

too many variables to blame the bearings. Was the slower rider short, fat, wide 200lbs or taller, not as wide, not riding in tuck 200lbs. Was svelte rider the same 200lbs? riding into a headwind, more effect on short and wide then tall and not as wide. while it's amusing on the possibilities of the why, i'll blame the color purple as having an effect, seems possible. it's a slower color. :)

[Mark McM]

Here's a little more potential evidence to determine if bearing drag causes speed differences:

Energy lost to friction drag doesn't just "disappear". Friction drag converts kinetic energy (energy of motion) into heat energy. A very obvious case of this is when brakes heat up when stopping. Even if you just drag the brakes for some distance (to limit speed), there will be some noticeable temperature rise. If there is any significant energy lost in bearing drag, the bearings should heat up. Has anybody every noticed an temperature rise in the wheel bearings after use? Or any indication that that there has been a temperature rise (such as lubricant getting thinner and leaking out? I know I sure haven't noticed any indications that the wheel bearings (or BB bearings, or pedal bearings) have any meaningful temperature rise.

[Mark McM]

according to the story I was told, slower guy is 200 and not in top shape at all. The other guy was probably in great shape and 165. Not sure about riding position but got the impression they were probably simply on the tops of their bars and coasting down hill. My 200 lb friend was taken aback at how fast skinny was going.

I'm not a big guy (150 lb.), but I often surprise bigger riders by passing them on downhills - especially when I am coasting and they are pedaling! I can get into a very tight tuck, resulting in a drag savings larger than the power people may generate by pedaling. When riding with others on downhills. I often make small speed adjustments to match the speeds of other riders by varying my position on the bike; a tighter tuck will increase my speed, and sitting up will slow me down.

[93KgBike]

Wind Resistance = Surface Area x Fluid Pressure x Drag Coefficient

I'm guessing your 200lb friend has more surface area.

[Dave B]

Wind Resistance = Surface Area x Fluid Pressure x Drag Coefficient

I'm guessing your 200lb friend has more surface area.

This. Remember when you were a kid...or my age and stuck your arm out of the window and you could have your hand and arm act like a wing and manipulate the friction to lift or lower your arm. Turn your palm and all of a sudden the air brake comes on and your arms moves quickly backward. Nothing but surface area.

It is why a Ferrari doesn't look like a semi up front. Aerodynamics

Didn't Sagan coast downhill in a superman position and pass a ton of riders who were in normal cycling position. Thought is was him, but i am sure that video is on the interweb somewhere.

From some of the sciency stuff I have read that if the bearings are ceramic the "cups" also need to be ceramic for you to get the true effect.

[yinzerniner]

This. Remember when you were a kid...or my age and stuck your arm out of the window and you could have your hand and arm act like a wing and manipulate the friction to lift or lower your arm. Turn your palm and all of a sudden the air brake comes on and your arms moves quickly backward. Nothing but surface area.

It is why a Ferrari doesn't look like a semi up front. Aerodynamics

Didn't Sagan coast downhill in a superman position and pass a ton of riders who were in normal cycling position. Thought is was him, but i am sure that video is on the interweb somewhere.

From some of the sciency stuff I have read that if the bearings are ceramic the "cups" also need to be ceramic for you to get the true effect.

Repeated a lot of stuff already posited earlier, but also added some misinformation to boot.

Sagan and Froome are probably most famous for the top-tube riding position which theoretically reduces frontal surface area vs a normal tuck position, but it's not the only reason they pass people going downhill. Handling, power application, braking, etc. all have a hand in the passing, and GCN did a pretty decent video explaining that while top-tube can be faster there are other factors that are also in play.
https://www.youtube.com/watch?v=AJvV03hqKBE

And ceramic bearings usually do need to be fully ceramic (ie balls and races) to get the full benefit, but even then the performance increase is negligible to non-existant in most biking applications. See video below for detailed explanation, but basically at the relatively low RPM numbers of cycling the hardness of ceramic doesn't have that much of an advantage over steel, and the other factors for bearings such as sealing and grease for weather resistance also hinder whatever benefits ceramic might have.
https://www.youtube.com/watch?v=o7iZVfSDbiA

And everyone knows that sloping front-ends of Ferraris are STRICTLY for looks.

[El Chaba]

It's actually downright disappointing how small the effect of bearing quality is on total resistance. The quality of a bearing does show up with respect to longevity. In addition to the small advantage a quality bearing has over a cheap one WRT rolling resistance, it has a rather large advantage in longevity. Cheap Chinese bearings don't last nearly as long as -for example- a quality bearing from SKF, FAG or NSK. Additionally, the cheap bearings are often shielded or sealed poorly allowing the ingress of dirt that further hastens their demise....

[Dave B]

Repeated a lot of stuff already posited earlier, but also added some misinformation to boot.

Sagan and Froome are probably most famous for the top-tube riding position which theoretically reduces frontal surface area vs a normal tuck position, but it's not the only reason they pass people going downhill. Handling, power application, braking, etc. all have a hand in the passing, and GCN did a pretty decent video explaining that while top-tube can be faster there are other factors that are also in play.
https://www.youtube.com/watch?v=AJvV03hqKBE

And ceramic bearings usually do need to be fully ceramic (ie balls and races) to get the full benefit, but even then the performance increase is negligible to non-existant in most biking applications. See video below for detailed explanation, but basically at the relatively low RPM numbers of cycling the hardness of ceramic doesn't have that much of an advantage over steel, and the other factors for bearings such as sealing and grease for weather resistance also hinder whatever benefits ceramic might have.
https://www.youtube.com/watch?v=o7iZVfSDbiA

And everyone knows that sloping front-ends of Ferraris are STRICTLY for looks.


I was thinking of this...wasn't Sagan.

https://www.youtube.com/watch?v=I_1Mo6gRsGo

[verbs4us]

the measured differences in tubular tire drag vs. clincher tire rolling resistance drag is much larger than the measured differences in wheel bearing drag.

Are you saying that clinchers have lower rolling resistance than tubulars?

[cmg]

Are you saying that clinchers have lower rolling resistance than tubulars? the measured differences in tubular tire drag vs. clincher tire rolling resistance drag is much larger than the measured differences in wheel bearing drag.


this one deserves another thread. i'm sure it's been discussed. were the tires the same weight, same size? please post a link.

[Bob Ross]

And what vehicle has a sunroof that is large enough to prop up the said plywood rider cutout through it while moving? And who has strong enough wrists to hold anything up at any speed through a sunroof without breaking something?

True story: When I was 17 years old my friend Pat -- whose father owned the only Citroen dealer in a 200 mile radius of NYC -- and my buddy Bob and I ...and now that I think of it, I'm pretty sure the Guardiano sisters were with us this night...went for a drive in one of Pat's dad's swanky sporty Citroens.

Which Pat insisted could easily exceed 125 miles an hour.

To which the rest of us said "Bull****!"

So Pat demonstrated. On the Palisades Interstate Parkway.

And when Pat pointed to the speedometer and said "Okay, there we are, 125, check it out!" my first reaction was to roll down the passenger side window and stick my head out of the car.



I couldn't move my neck for two weeks.
My head got slammed into the pillar so hard it was like stepping into the ring with Joe Frazier. That wasn't air outside the car window, that was an invisible brick wall. Moving in the opposite direction we were travelling. Yeah, it hurt.

A sheet of plywood wouldn't fit in a Citroen. But at 30mph it might be a bit less self-destructive. I suspect it wouldn't be any less irresponsible.

[yinzerniner]

the measured differences in tubular tire drag vs. clincher tire rolling resistance drag is much larger than the measured differences in wheel bearing drag.


this one deserves another thread. i'm sure it's been discussed. were the tires the same weight, same size? please post a link.

https://www.youtube.com/watch?v=0ovYHQ35-5o

[bikinchris]

Was talking to a friend about wheels and bearings. He has a Roubaix with decent wheels, nothing special. He weighs around 200. He said a much more svelte rider smoked him coasting down a hill and that guy had really high end wheels.

1. Have you experienced noticeable difference related to the quality of bearings in the wheels you ride?

2. If it is true that better bearings make a noticeable difference, is the advantage somehow the same when coasting as when pedaling up a climb?

????

Your heavy friend's brakes are dragging.

[eddief]

you were rewarded with a dog biscuit for doing the experiment.

True story: When I was 17 years old my friend Pat -- whose father owned the only Citroen dealer in a 200 mile radius of NYC -- and my buddy Bob and I ...and now that I think of it, I'm pretty sure the Guardiano sisters were with us this night...went for a drive in one of Pat's dad's swanky sporty Citroens.

Which Pat insisted could easily exceed 125 miles an hour.

To which the rest of us said "Bull****!"

So Pat demonstrated. On the Palisades Interstate Parkway.

And when Pat pointed to the speedometer and said "Okay, there we are, 125, check it out!" my first reaction was to roll down the passenger side window and stick my head out of the car.



I couldn't move my neck for two weeks.
My head got slammed into the pillar so hard it was like stepping into the ring with Joe Frazier. That wasn't air outside the car window, that was an invisible brick wall. Moving in the opposite direction we were travelling. Yeah, it hurt.

A sheet of plywood wouldn't fit in a Citroen. But at 30mph it might be a bit less self-destructive. I suspect it wouldn't be any less irresponsible.

[Mark McM]

Are you saying that clinchers have lower rolling resistance than tubulars?

All else being the same*, yes. This has been demonstrated in rolling resistance tests for several decades. This is why time trialists (and triathlon riders) largely now use clinchers.


*Sure, there are some low rolling resistance tubulars and some high rolling resistance clinchers, because there are far more variables than just how the tire is attached to the rim. But if you compare tubular tires of similar size and construction, the clincher will have the lower rolling resistance.

[Dave B]

All else being the same*, yes. This has been demonstrated in rolling resistance tests for several decades. This is why time trialists (and triathlon riders) largely now use clinchers.


*Sure, there are some low rolling resistance tubulars and some high rolling resistance clinchers, because there are far more variables than just how the tire is attached to the rim. But if you compare tubular tires of similar size and construction, the clincher will have the lower rolling resistance.


No antagonism here in my question, but if what you say is in fact accurate, then why aren't the pros using clinchers more than they do tubulars? If clinchers of the same tire ( I would assume same size, psi, etc) are faster, then why not use them in the pro ranks?

Flats?

[yinzerniner]

No antagonism here in my question, but if what you say is in fact accurate, then why aren't the pros using clinchers more than they do tubulars? If clinchers of the same tire ( I would assume same size, psi, etc) are faster, then why not use them in the pro ranks?

Flats?

Same reason all pros don't always use aero-specific bikes, or 28mm tires, or 90mm deep wheels.

Personal Preference

As stated over and over again, the pros are usually very nitpicky and resistant to change as they need the comfort incredibly dialed in to ride hundreds of hours a week. But you do see change as the evidence starts to pile up, and also as the manufacturers begin adjusting to the pro's comfort and other needs, and vice versa.

Another thing is tubulars due to their significant rim weight savings are much easier to spin up to speed, which is key when overtaking, making a move, sprinting, etc. And their aero benefits are probably lessened a bit due to most riders being in the peleton.

All else being equal yes, clinchers are faster. But at no point in a race are things exactly equal, other than a TT.

[oldpotatoe]

No antagonism here in my question, but if what you say is in fact accurate, then why aren't the pros using clinchers more than they do tubulars? If clinchers of the same tire ( I would assume same size, psi, etc) are faster, then why not use them in the pro ranks?

Flats?

PelOton

Tubulars have some real advantages.
-more comfy-no pinch flats at low pressures
-corner better, not as stiff sidewalls, generally, rounder tire, less light bulb shape, more tread on road when cornering
-safer-assuming they are glued on correctly, they won't come off if ya flat, like more than a few clinchers, do
-lighter rims altho bikes already at UCI minimum..BUT a lighter rim by 100 grams or so, that 'flywheel effect', when accelerating is also teeny, tiny and lost in the noise.

RR differences are teeny tiny, but I think the above means something to pros.
Since they have team and neutral wheel support, I don't see any compelling reason to use clinchers, IMHO, of course. I don't either for me..and I don't have neutral or team support. own no clinchers.

[djdj]

True story: When I was 17 years old my friend Pat -- whose father owned the only Citroen dealer in a 200 mile radius of NYC -- and my buddy Bob and I ...and now that I think of it, I'm pretty sure the Guardiano sisters were with us this night...went for a drive in one of Pat's dad's swanky sporty Citroens.

Which Pat insisted could easily exceed 125 miles an hour.

To which the rest of us said "Bull****!"

So Pat demonstrated. On the Palisades Interstate Parkway.

And when Pat pointed to the speedometer and said "Okay, there we are, 125, check it out!" my first reaction was to roll down the passenger side window and stick my head out of the car.



I couldn't move my neck for two weeks.
My head got slammed into the pillar so hard it was like stepping into the ring with Joe Frazier. That wasn't air outside the car window, that was an invisible brick wall. Moving in the opposite direction we were travelling. Yeah, it hurt.

A sheet of plywood wouldn't fit in a Citroen. But at 30mph it might be a bit less self-destructive. I suspect it wouldn't be any less irresponsible.

Great story!

[Mark McM]

Another thing is tubulars due to their significant rim weight savings are much easier to spin up to speed, which is key when overtaking, making a move, sprinting, etc. And their aero benefits are probably lessened a bit due to most riders being in the peleton.

If you work out the numbers, I think you'll find that this particular reasoning may not work out the way you might think it does, and may be based on a common mis-application of newton's 2nd law of motion (F = mA). Everybody knows that for the same force, a lighter mass accelerates faster, right? But the force that accelerates a bicycle is not the gross force applied by the rider (through the drive train to the wheel), but is actually the net force (rider applied force minus drag force). That means that only the portion of the rider's force that is greater than the aero drag, plus rolling resistance drag, plus drivetrain losses, etc., actually accelerates a bike. If, for example, rolling resistance decreases, than the net force increases, and acceleration rate increases. So, while the clincher may increase inertia, their reduced drag also increases the acceleration force. The net result may be that in many cases, heavier clincher wheels will actually accelerate faster than lighter tubular wheels.

[Mark McM]

No antagonism here in my question, but if what you say is in fact accurate, then why aren't the pros using clinchers more than they do tubulars? If clinchers of the same tire ( I would assume same size, psi, etc) are faster, then why not use them in the pro ranks?

As noted, there is more to tire selection than rolling resistance. For example, very lightweight tires, with very thin casings and treads, typically have the lowest rolling resistance than standard weight tires. But these tires are very delicate, and puncture easily, so most riders will accept some extra rolling resistance for a tire which is more guaranteed to go the distance.

In regard to tubulars vs. clinchers, tubular tires are far more immune to pinch flats than clinchers, plus you can more safely ride a flatted tubular than a flatted clincher. For a pro road racers, the danger of loosing time due to a flat tire is usually of greater concern than the small decrease in rolling resistance of clincher tires*, so by and large the top ranks of pro racers use tubulars. (I suspect if you looked at the bottom ranks of pro racers, for practical/financial reasons you might find that clinchers were more common). But even the top professional racers don't exclusively use tubulars - for time trials, most racers have switched to clinchers. As an example, Tony Martin has won the World Professional Time Trial Championship 4 times - every time with clincher tires.

*This is also one of the main reasons that many pro riders haven't switched to disc brakes. There are more complications in wheel changes with disc brakes, so the danger of losing time due wheel problem (such as a flat tire) is greater than any minor braking advantage disc brakes may give.

[verbs4us]

the measured differences in tubular tire drag vs. clincher tire rolling resistance drag is much larger than the measured differences in wheel bearing drag.


this one deserves another thread. i'm sure it's been discussed. were the tires the same weight, same size? please post a link.

Both sew-ups and clinchers were Contis, same size and width (25 mm) and same tread pattern. The sew-ups are much lighter, but I don't know the weight differences. I ride both at 90 psi.

[mattsurf]

I think that clothing could well be the reason. On my weekly club ride, there is a downhill section where the club etiquet is to for the lead group to coast downhill to see who goes fastest without pedalling (and gives the slower riders a chance to catch up). Normally I get to 60kph (40mph), however, last week, in damp conditions, while wearing a light, reasonably tight waterproof, I could feel it really tugging at the arms, as a result my max speed was ony just over 50kph (damp road surface may also have been a factor)

There is also 2 other possibilities: the lighter rider may have built up a higher speed before starting to coast. Secondly, when the lighter rider was behind the heavier rider, the lead bike was punching a pretty big hole in the air, leading to lower air resistance for the following bike - I think that you get a benefit from at least 10m back

[paredown]

Great story!

Yes--a true knuckle-headed decision. I made a few of those myself,:)

[Road Fan]

Could be anything or could be many things.
Weight does help downhill but it could also be:
1.) Bearings as you mentioned- but not likely bearings by themselves.
2.) Wheel profile, depth, and other wheel related aero qualities.
3.) Tires- model, pressure, width, type of tube
4.) Rider position
5.) aero clothing and helmet- tightly fitting.
Or any combination of these on the side of the faster rider, and any combination of the slower version for the 200 lb. rider.

Fastest being: Fast bearings, very aero wheels, fast tires at fast pressures, aero clothing that fits tightly, and aero helmet with an aero position.

Slowest being: cheap and/or worn bearings, box section wheels with many spokes, slow tires with butyl tubes at incorrect pressure, loose and flappy clothing, basic helmet, and block of wood position.

Lastly- Comfort at speed. Some feel safe freewheeling at 50 mph, some touch their brakes.

Another much simpler cause or two for being passed is that the other rider started his downhill run at a higher speed than the OP did, or added a few pedal strokes (ohhhh the sneak!!!) before he passed.

Another simple one: OP said he is bigger and heavier than the other "more svelte" rider. Neglecting shape factors (aero of the two bodies), the smaller rider probably punched a smaller hole in the air than the OP, and actually had less air resistance than the OP did at that moment.

It would not take a big difference for one rider to overtake, while coasting, nor with adding a little energy or braking off a little energy.

[Road Fan]

If you work out the numbers, I think you'll find that this particular reasoning may not work out the way you might think it does, and may be based on a common mis-application of newton's 2nd law of motion (F = mA). Everybody knows that for the same force, a lighter mass accelerates faster, right? But the force that accelerates a bicycle is not the gross force applied by the rider (through the drive train to the wheel), but is actually the net force (rider applied force minus drag force). That means that only the portion of the rider's force that is greater than the aero drag, plus rolling resistance drag, plus drivetrain losses, etc., actually accelerates a bike. If, for example, rolling resistance decreases, than the net force increases, and acceleration rate increases. So, while the clincher may increase inertia, their reduced drag also increases the acceleration force. The net result may be that in many cases, heavier clincher wheels will actually accelerate faster than lighter tubular wheels.

Another force factor to add to the equation is force applied by the rear wheel to maintain speed while climbing, or its negative, a contribution to net force added by gravity if the road is pitched downward.

Plus, the effect of road surface is related to drag and small variations in surface, so choice of line could be significant.

[martl]

2. If it is true that better bearings make a noticeable difference, is the advantage somehow the same when coasting as when pedaling up a climb?

????
nope. They don't make a difference, and there certainly is no advantage at climbing.

martl, german engineer

(Explanation: the forces act at the R(dyn), which is about 331mm on a 28" racing bike. The radius of the bearing is 5mm. The lever is so huge that any resistance differences the bearing may have will less than any measuring failure).

Shimano lower-ish type gear, like 105 or Acera, will have bearings with noticeable "roughness" when new. Doesn't change a thing. A Sky rider equipped with those wheels would still win the TdF. The story that a wheel equipped with, say, super-smooth Super Record hubs, will actually make you faster, is one of the many myths of the classic era. They *will* have a longer life, though.

(note: removing grease from bearings and replacing it with oil, as documented in the Joergen Leth movies -which i love- also has no effect other than bolstering the riders morale)