I think its a matter of frame size fit. With new bikes, only the very smallest frames use 650s. Find a fram that fits and accept whatever wheel size that works! By the way, I have an older bike that is a 56 and it uses 650s. I like them but can't say they make much of a difference either way.

I can't point you to any solid evidence beyond the stated opinions of frame builders and people in the know. Once the frame size gets down under 51 or so it's beneficial.
FWIW, I personally believe that 650 wheels are faster (most likely due to aerodynamics). They probably climb better too.

Less toe overlap, which is great for all the times you track stand in a triathlon. Actually, for training rides, the toe overlap issue is noticeable. I love my 650's.

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Tri Me.
Work Me.

For tech reasons what is your height?

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http://www.truckeecyclocross.com
California

Sorry, meant to post that. I am 5'7". Short legs, pretty regular torso. I ride a 51cm Cervelo One.

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Tri Me.
Work Me.

I've also scratched my head around that question too. I think one consideration is what appearsto be a general migration away from 650 wheeled bikes. I see fewer and fewer available as well as more limitied availability of tires and tubes. Kinda wonder if it was a fad that had its day?

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Swim - ( x ) All good ( ) In the shop
Bike - ( x ) All good ( ) In the shop
Run - ( ) All good ( x ) In the shop

Sorry, meant to post that. I am 5'7". Short legs, pretty regular torso. I ride a 51cm Cervelo One.[/reply] I've wondered about this, too. I am 5'5" with short legs and a long torso. I ride a 49cm with 700 wheels and I can BARELY stand over it, but my torso feels cramped in the aerobars. I've considered going with a bigger frame and smaller wheels, but idk...

I'm 5' 6". I've been racing TTs for a few years now and I've gone back and forth between a 51cm Cervelo P3sl with 650c wheels and a 51cm Cervelo P3C with 700c wheels. Hands down, the fastest race I ever did was on 650c wheels ... but that was one of those nights. Everything clicked. I might have done a PR on a donkey. Setting that aside, I've determined over the years that there are horses for courses and courses for horses. If it's a shorter, more technical course with turns (accelerations out of turns) and hills, I opt for the 650c bike. If it's a long-course triathlon relay on a pretty flat course, I bring out the 700c bike.

Over the winter I bought a 48cm P3C off of ebay and built it up. 650c. It's gorgeous. I posted some photos and I've been told that those photos were discussed at one of the Fistapalooza gatherings by none other than the legendary John Cobb who allegedly gave me props for my 48cm/650c experiment. This is heresay to me. Someone else told me about the dialog with John Cobb and, since he posts here regularly, he might say I'm full of it. Even if he does, I'd LOVE to hear his thoughts on 650c. (I won the first race I did on the bike. Race #2 is tomorrow!)

There's no doubt that 650c stuff is getting harder to find. But there's still some very good stuff out there. I recently scored a disc wheel made by a company called Fast Forward and it's VERY nice. Vittoria still makes wonderful tires in 650c. You can still get Hed Jet wheels, Zipp wheels, etc. Lots of 650c stuff for sale on the Slowtwitch classifieds and ebay. The big problem is latex tubes. They don't exist in 650c. I've been making my own (cutting down 700c tubes), but results have been frustratingly inconsistent.

OH ... lots of Trek/Bontrager stuff in 650c thanks to their WSD (women specific design) program.
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Bob C.

The "science" on any matter can never be settled until every possible variable is taken into account.

I've wondered about this, too. I am 5'5" with short legs and a long torso. I ride a 49cm with 700 wheels and I can BARELY stand over it, but my torso feels cramped in the aerobars. I've considered going with a bigger frame and smaller wheels, but idk...


This is a classic. Many bike shops will tell you to determine your frame size based on "stand-over height." I'm like you. I have a long torso and short legs. Stand-over height results in a very small bike for me ... and a completely wrong bike when it comes to a TT/Tri frame. You need to determine what your reach or top tube requirements are and size your frame based on that. Every bike I ride would rack me royally if my feet came out of the pedals and I had to do an emergency "stand-over" of the frame. That's never happened in 15 years of riding 12,000+ miles per year. Stand-over is meaningless. Don't give it a second thought.
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Bob C.

The "science" on any matter can never be settled until every possible variable is taken into account.

For frames under 51 cm 650 makes sense, as previously mentioned. I had 650 on my older 54 cm QR Kilo and Cervelo P2K, but would only ride 700 now. It's a wash, any technical advantages of one size cancels the other so there is no difference between 650 or 700 performance wise. I've been faster on 700, but more than the wheel size are involved I'm sure.

650 is becoming less popular except on small frames, in fact I'm not sure if any new bikes above a 48 cm use them any more and tires are harder to find. The only real advantage I can think of is that used 650 aero wheels on ebay are cheaper than the comparable 700 versions.