Don’t tri bikes have to have both wheels the same size?

it would most likely lead to an unstable, twitchy front end due to the sharp increase in head tube angle.

On a modern tri bike with disc brakes, possibly, you'd have more luck trying with a 650b instead: the size difference is minimal (584mm vs 571mm), and you'll find plenty of modern features availability (disc brake, carbon rim, tubeless tires...); with 650c it's a challenge even finding a 23mm wide clincher

They do under UCI and ITU rules
̶T̶h̶e̶y̶ ̶d̶o̶ ̶n̶o̶t̶ ̶u̶n̶d̶e̶r̶ ̶U̶S̶A̶T̶ ̶r̶u̶l̶e̶s̶
I stand corrected, it must have changed in 2023

https://teamusa-org-migration.s3.amazonaws.com/...petition%20Rules.pdf

5.9 Bicycle Specifications

a.) In general, UCI rules, as of January 1st of the current year, will apply during competition and
also during familiarization sessions and official training:
(i) CI road race rules for draft-legal triathlon and duathlon competitions;
(ii) UCI time trial rules for non-draft legal triathlon and duathlon competitions;
(iii) UCI Mountain Bike (MTB) rules for winter triathlon, cross triathlon and cross duathlon
competitions. World Triathlon Competition Rules 28 January 2022

b.) The bicycle is a human powered vehicle with two wheels of equal diameter. The front wheel
shall be steerable; the rear wheel shall be driven through a system consisting of pedals and
a chain. Bicycles are referred to as bikes and will have the following characteristics in the
following sections:
page 18

While I have not done this, I've read that you can turn the fork around backwards and the front end geometry will be very close to correct.

The other issue would be pedal clearance.

The fastest 650c clincher (Conti 4000s II) is no where close to the fastest clincher or tubeless tire in 650b or 700c.

The Bontrager Aero TT is a faster Clincher than the 4000SII measured on a 2002 HED3 and a 2009 Jet 60 by a wide margin.

As was the Vittoria Corsa 19mm

nowadays, all you can find, even with some difficulty, in 650c, are cheap training tires

Didn't know the Bontrager Aero TT was available in 650c. I have never seen it for sale in 650c.

I'm not saying anyone should switch to 650C wheels but you can buy these all day long from Germany
https://www.bike24.com/p2361383.html

You can buy Gatorskins for training tires from many places.

I have such a big stock of tires I could race for the next 10 years. Personally I have at least four sets of 23mm Bontrager Aero TT's and three 25mm Aero TT's

I only wish somebody would make a bike that actually fits me. If anyone knows of a stock bike that you can get the pad stack down under 500, please let me know.

Preferably without a huge amount of pedal overlap.

Remind me: Aero TTs have the rubber lip around the rim interface?

Yes, those little wings that fit next to the rim so well and they were fairly thin and flexible.

I'll take the toe overlap, I have in on every bike I own right now.

The best fitting 700C bike I have is my track bike. It has a low stack (480mm) because the bottom bracket is an inch higher than most other bikes.

Any manufacturer can do that with their smaller bikes, I don't know why they don't. An example is the Trek Superfly. There is no need to get the bottom bracket as low as others, the people riding that size are frickin' tiny. Instead they just got rid of the bikes that fit and said F to 15% of the people that needed it.

Sorry, rant over. (You'll probably hear it again out of me)

In fact, those are cheap training tires, unless you have a different definition for a $25 67TPI clincher.
I have a couple of old steel 650c bikes and run some of those Schwalbe's on a few wheels: they're not bad at all, but not a racing tire by any means, at least for my standards

That's why I have a stock of other tires as well

Our XS can get you to 500.

---

Dan Kennison

facebook: @triPremierBike
http://www.PremierBike.com
http://www.PositionOneSports.com

This nixes my idle speculation (as well as scuppering my aero-penny-farthing idea). Thanks.

Interestingly it also states that power shall be transmitted by a chain. Is this new?? If not, it raises a question of why CeramicSpeed bothered with their complicated drive system a couple years back.

Yeah, no.

On forks with any significant offset at all, you'd go from a reasonable trail figure to one akin to using a caster where the axle trails the head tube axis. You sometimes see this done on track bikes used in derny races to allow the rider to get as close as possible to the derny. The increase in the trail value isn't a problem on the track as you're never really turning the wheel to make it 'round the banking. Plus, the typical track fork has very little offset, so turning it around doesn't put it as far behind the steerer axis as a road fork turned around would.

Have you actually done this or are you speculating?

I don't know what you mean by track bikes have very little offset, these are just the ones I researched when I was looking to purchase

Fork offsets for some track bikes
Dolan 35mm
BXT 45mm
Planetx 44
Holdsworth 43
Veloflyer 32
Fuji 42