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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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