Small rider TT bike: to 650c or to 700c ? That's the question.

Discuss light weight issues concerning road bikes & parts.
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LouisN
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Joined: Mon Feb 19, 2007 3:44 am
Location: Canada

by LouisN

Seems like 650c wheels dissapeared from the road cycling scene 8 years ago (sine Emma Pooley's World TT title)...
There must be many factors, one should suspect the bike industry in the first place.
The cycling teams looking to limit the amount of material and compatibility, etc...
But,
Technically, and based on facts and science, if you have a rider measuring 162cm and 63cm saddle to BB height (short legs!!):
What's the best TT bike option ?
A 700c XS or XXS (Argon 18 E-117 or Liv Avow for example) bike ?
Or a 650c TT bike ?

Let's discuss advantages, drawbacks, etc... in an open way :) .


Louis :)

by Weenie


IchDien
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Joined: Mon Nov 05, 2012 12:23 am
Location: Veneto

by IchDien

Surely an investment in 700c wheels is more logical. Also the fact you'll be able to source wheels easier, and swap them out easier; in my squad some swap/borrow wheels with friends when doing an ITT or if we have two teams in the TTT (that won't be on the course at the same time).

Measurements seem roughly equal to Pozzovivo - his saddle is 2cm higher, albeit. I know he had issues with some manufacturers but he seems to do alright now.

mattr
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Joined: Fri May 25, 2007 6:43 pm
Location: The Grim North.

by mattr

Biggest issue with 650 is the woeful shortage of parts at multiple price points. Mate of mines wife is shorter than that (5 foot 2, so about 158) and her first road bike was a 650c. The only stuff available was either absolute top end carbon tri weenie wet dream stuff.

Or utter crap for (essentially) box shifter bikes.

She managed to get sensibly fitted to a XS giant road bike and a couple of years later a XS TT frame from (i think) planet-x, or maybe direct from china. Not 100% sure.

But they can easily share wheels, and tyres are widely available. So it's even practical to stick road wheels on for training etc.

I had read somewhere that the UCI were looking to restrict wheel size to 700 only for all road events, but not sure if they ever got it all the way to the rule book.

FWIW, as long as the rider can get the right reach, fairly narrow/flat back, there's not a huge amount in it. Even the medium frame i have downstairs would probably do a mid 60s cm saddle height without looking too odd. (the owner has nearer 75cm, but ~6cm of stack/spacers under the extensions and 4 cm on the steerer.)

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LouisN
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by LouisN

I can understand the industry being more dominant and powerful than just common sense and science.
here an article about Pooley, PhD Engineer :
https://cyclingtips.com/2017/03/bespoke ... new-bikes/

I can't find her Bond TT (650c) bike anywhere on the net...

I'm also trying to find Coryn Rivera's (Sunweb) Giant TT bike, but no success either...

Louis :)

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silvalis
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Location: Aus

by silvalis

LouisN wrote: ↑
Sat Dec 08, 2018 10:25 pm

I can't find her Bond TT (650c) bike anywhere on the net...
Maybe you could ask gcn to do a feature on her 650c tt bike
Chasse patate

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LouisN
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Location: Canada

by LouisN

Found this on her Facebook page:

https://www.facebook.com/emmapooleyoffi ... =3&theater

Louis :)
Attachments
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alcatraz
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Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

Cervelo p2 with the new geometry in a 48 is quite good. I'm tempted.

It's got an 8cm bb drop suitable for short cranks and decent head tube length. Still 700c wheels. 71 degree head tube angle.

I have a short torso and short arms and I'm tempted to buy this geometry. The only thing that I'm not very pleased with is the 97cm wheelbase. It's not very long. I could be wrong with that measurement though. It's the price of running a short reach. It's annying at speeds over 45km/h when in the aero bars. Not the most stable cruising feel.

/a

spdntrxi
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Joined: Sat Jul 20, 2013 6:11 pm

by spdntrxi

depends on the geo... you might not be able to get really low on 700c... that's where a 650 TT bike is handy.

mattr
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Joined: Fri May 25, 2007 6:43 pm
Location: The Grim North.

by mattr

LouisN wrote: ↑
Sat Dec 08, 2018 10:25 pm
here an article about Pooley, PhD Engineer :
https://cyclingtips.com/2017/03/bespoke ... new-bikes/
I'd take a lot more interest in her experience as a pro than her PhD in Geotechnical Engineering....... ;)

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kman
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Location: Sydney, Australia

by kman

I'm 170cm and ride a 52cm TT bike with 700c wheels. My position is pretty aggressive/low at the front and if I tried to go much lower I'd struggle to get the bars down (and bend my neck enough to see!). For someone smaller than me, with a similar position, I think 650c wheels would have to be a better option.
Custom frame (Taiwanese Ti?) and some aero wheels and you'd be sorted. I see pairs of Zipp 404s etc in 650c coming up for sale every so often - and usually very cheap.
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2lo8
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by 2lo8

If you can get away with 700c, its probably a good idea to get 700c, the lower limits of which are probably closer to 160cm.

Yes, geometry is compromised. Short of scoring great deals on ancient carbon 650c wheels, parts selection for 650c will probably be compromised too. Generally speaking, if money is no object, there are better parts available for 700c. If cost is an issue, you can usually get better 700c stuff for the same price or the same thing cheaper unless you're getting deals on closeout 650c stuff no one wants. You don't have to worry about compatibility issues or not being able to walk into a shop and buy stuff off the shelf either.

What's more important than getting a tiny frame with tiny wheels is getting tiny (150-155mm) cranks. Cranks are part of fit coordinates. Unless the frame/wheel size is impairing fit coordinates, always go for the stuff that actually impacts fit first.
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benjieb
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Joined: Mon Nov 19, 2018 5:16 am

by benjieb

You might be able to fit on a 700c TT bike, but you won't be in a good position. There's just too much stack for smaller riders to get a good aero position. Enve, HED and Zipp all make 650c wheels so why compromise? Check out premier tactical. They make a highly regarded 650c TT bike that comes with a disc wheel!

audiojan
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Location: New Hampshire

by audiojan

My wife is 158cm and rides a Ventum with 700 wheels (and a Cervelo P3 before that). No issue at all with fit (and a pretty aggressive one at at that, she's a triathlete so not limited by UCI regulations). I would say the biggest argument for 700 wheels would be the choices available for wheels and tires. When her Felt DA1 (which was 650's), we just didn't have great options for wheels, and if you get a flat, forget finding anyone with a tube for you...
"Suddenly the thought struck me; my floor is someone elses ceiling" - Nils Ferlin

by Weenie


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