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undersized road bike frame trend in professional ranks

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undersized road bike frame trend in professional ranks

14 Jun 2018 20:24

Been watching a lot of racing and what I am seeing is that most of the pros are running what appears to be at least 1 frame size too small with tall seat posts and long stems (>110).
I am perplexed by this. Am I imagining this?

Back in the day riders would often get the size smaller to save frame weight. But now weight is no longer an issue as it is easy to make a modern bike meet the UCI limit.

I always thought running an excessively long stem like 120+ would hurt bike handling characteristics.
Does anyone have insight on this trend?
offbyone
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14 Jun 2018 20:31

Small frames are stiffer. Long seatposts=comfort
(Warning: Posts may contain traces of irony)
User avatar macbindle
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Re:

14 Jun 2018 22:48

macbindle wrote:Small frames are stiffer. Long seatposts=comfort

----------------
Or, full-sized carbon frame with moderate seatpost length would be too stiff / uncomfortable.
Small carbon frame is plenty stiff for power application, and long stem & seatpost enable desired position & comfort.

Jay
JayKosta
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Re:

15 Jun 2018 02:51

macbindle wrote:Small frames are stiffer. Long seatposts=comfort


You are telling me there is a significant stiffness difference between say a 54 and 56 or 54 and 58 modern carbon frame?
offbyone
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15 Jun 2018 06:44

Yes
(Warning: Posts may contain traces of irony)
User avatar macbindle
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22 Jun 2018 23:06

Smaller carbon frames are not stiffer than larger ones. The carbon layup determines stiffness and you can bet that the size run is either identical in every measure of stiffness and ride comfort, or if anything, stiffer on larger frames within a model.

As to why pros ride a certain size: preference, superstition, recommendation, tradition...
jmdirt
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23 Jun 2018 07:27

Assuming that designers account for this (which some do to a greater or lesser extent), yes. All other things being equal smaller frames with same diameter tubes will be stiffer. Also depends on their starting point size for design.
(Warning: Posts may contain traces of irony)
User avatar macbindle
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23 Jun 2018 15:26

I'm not trying to bust your chops here mac, but you are talking about old school steel frames. Carbon manufacturing is a different beast. The manufacturers who have the money to be in the protour either know how to control factors/charactoristics like stiffness, or have "sub contract engineers" who do.

Note: even steel (by the '80s), Ti, and AL frame manufacturing accounted for frame size with tube wall thickness, size (ID/OD), shape, butting, etc.
jmdirt
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23 Jun 2018 15:43

:D No chops busted
(Warning: Posts may contain traces of irony)
User avatar macbindle
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24 Jun 2018 01:24

The deflection at the handlebars and seat will be greater for small frames running long stems and seat-posts compared to more conventional sizing, although the actual frame deflections at the BB relative to the hubs may be smaller. But that's not why they run small frames. They do so to get a short head-tube so they can get their bars low. Modern bikes have increasingly tall head-tubes to suit the MAMIL crowd. Custom sizing is rare in carbon (but not unknown). Trek's H1/H2 fit options are a solution.

It is my observation that head-tubes for many riders are still not nearly tall enough. Riders run stacks of spacers, upside-down, priapic stems and STILL never get into the drops.
winkybiker
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27 Aug 2018 00:27

They been riding one size smaller frames for as long as I've been alive and I'm 65, so that probably means they've riding smaller frames for a lot longer than I've been alive. It's always been about frame flex, and smaller frames flex less, which that thing is odd since the most flexy bike ever raced was the Vitus 979 ridden by Sean Kelly and it didn't seem to cause him to lose...in fact he won the TDF.
froze
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Re:

28 Aug 2018 00:32

froze wrote:They been riding one size smaller frames for as long as I've been alive and I'm 65, so that probably means they've riding smaller frames for a lot longer than I've been alive. It's always been about frame flex, and smaller frames flex less, which that thing is odd since the most flexy bike ever raced was the Vitus 979 ridden by Sean Kelly and it didn't seem to cause him to lose...in fact he won the TDF.


Of course there comes a point where rider and machine have a divergence to where you could put said rider on any relevant bike of the time and will win. Kelly would have won on any bike of his era. However, we're dealing with carbon instead of steel or alu now. But even in the metal era tubing mixes and shapes made properly sized frames stiffer. For example, in the early 80's the Colnago Master came to because Giuseppe Saronni wanted a stiffer bike than the Super he was riding, not a smaller size. So Ernesto had Columbus produce that famous diamond shaped Columbus Gilco main triangle tube set. I've had both models and still have my Master, the ride between them is starkly different in terms of stiffness! Similar tubing and lug experimentation was happening across all manufacturers.

So with carbon manufacturing there is far more control with layup to keep ride quality and stiffness relatively consistent through the fat part of the size range. Going from a 56 to a 54 isn't done to achieve stiffness or lighter weight even. winkybiker and jmdirt got it right here earlier in the conversation, the main reason pros are sizing down in the carbon frame era is stack height, not stiffness.
User avatar Giuseppe Magnetico
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28 Aug 2018 08:06

I'd also guess that a longer seatpost, whether integrated or not, gives a little bit of cushion. It may not translate into loss of efficiency if the bb area is laterally and vertically stiff. Also, all things being equal it's a bit easier to control a smaller frame, and if the hard points are to a rider's preference, then frame size probably doesn't matter +/- 2 cm. Stack height...hmmm, I'd think we're talking only a few mms either way between, say, 54/56 cm. but maybe enough to matter.

If between frame sizes I always go down, assume the pros are the same way. It could also be the belief that a lighter frame is better and any weight needed to reach UCI minimum is best apportioned among various components.
Bolder
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04 Sep 2018 11:13

I’ve always thought that it was about 2 things - stack height and increased seat post for comfort.
User avatar 42x16ss
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Re:

10 Sep 2018 20:50

froze wrote:They been riding one size smaller frames for as long as I've been alive and I'm 65, so that probably means they've riding smaller frames for a lot longer than I've been alive. It's always been about frame flex, and smaller frames flex less, which that thing is odd since the most flexy bike ever raced was the Vitus 979 ridden by Sean Kelly and it didn't seem to cause him to lose...in fact he won the TDF.


Just for the sake of accuracy, Kelly won the Vuelta, never a TDF. He won the points classification at the Tour but not the general classification.
User avatar Angliru
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Re: undersized road bike frame trend in professional ranks

10 Sep 2018 21:54

offbyone wrote:Been watching a lot of racing and what I am seeing is that most of the pros are running what appears to be at least 1 frame size too small with tall seat posts and long stems (>110).
I am perplexed by this. Am I imagining this?

Back in the day riders would often get the size smaller to save frame weight. But now weight is no longer an issue as it is easy to make a modern bike meet the UCI limit.

I always thought running an excessively long stem like 120+ would hurt bike handling characteristics.
Does anyone have insight on this trend?


Yes I've noticed that too. But a few teams (ie Sky, EF drapac and Astana) are not running high seat posts with their Pinarello F10's. I was watching Kwiatowski last Vuelta stage, and he's riding a pretty fair to low saddle height.
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