I’m debating going to a smaller frame with a 650 wheelset. I’ve been told that 650’s handle differently than 700’s but I’m not sure how. In addition to that, are there any other considerations (other than handling) that I should consider in making this decision.
Thanks.
650 - pros: less weight, less surface area of wheel, fork, bike
650 cons: more rolling resistance, wheel has to turn faster for a given bike speed, less moment of inertia on the wheel at a given weight. (this would be a pro in a sprint, or twisty course perhaps, but not a time trial)
I think the only practical considerations are that tire and tube selection are difficult. No latex tubes for 650c wheels for instance.
Will it be a tribike or roadie? i just switched from a 650c tri frame(titanium) to a 700c road frame(aluminum)…been on a 650c wheels since 1996, same set up with my roadie with regard to tires, maybe it was the shallower seat angle but it felt a lot better than my old frameset…but downside, i joined our team for a 20k TTT and i was dropped…did not have the power but not riding your bike regularly does that LOL…the ride on the 700c wheels will take some getting used to, specially when the road goes up, the 650cs accelerated quicker
LOL whilst everything you said is correct, not a single one of those facts answers the OP’s question.
one of the more obvious differences is that the turning radius of the 650c bike is smaller, so it corners better.
He had two questions:
"are there any other considerations (other than handling) that I should consider in making this decision.
"
LOL whilst everything you said is correct, not a single one of those facts answers the OP’s question.
one of the more obvious differences is that the turning radius of the 650c bike is smaller, so it corners better.
oops! my bad. my apologies!
oops! my bad. my apologies!
hugs
I couldn’t comment on the handling other than my GF’s 650c tri bike feels the same as my 700c tri bike…
but in Houston everything is flat haha
Just curious as to where you found that there is higher rolling resistance with 650’s?
If lowering the moment of interia is bad then why do people keep buying lighter wheels?
jaretj
I have not seen the actual CRR data on 650s, but i have heard it is the case, and with the lower circumference, this makes sense. Just like the 23s have a lower CRR than the 19s.
Also you can’t get latex tubes, so there is a crr penalty there.
As to why do people keep getting lighter wheels.
Because people are stupid. I include myself in this, I used to think reducing a tri bikes wheel weight would be a good thing to focus on until I saw someone do the math.
A lighter wheel is better, but to reduce the moment of inertia at the same weight is worse, in most time trials, even up steep hills.
search “wheel math” posted by me for a copy/paste of the math
Just curious as to where you found that there is higher rolling resistance with 650’s?
If lowering the moment of interia is bad then why do people keep buying lighter wheels?
jaretj
23mm tyres have lower Crr because they have a smaller contact patch than 19mm tyres. 19mm tyres are taller than 23mm tyres.
as for the math behind why 650c wheels have higher Crr, it is rather tedious but it’s somewhere in the archives. a long hard search ought to dig it up.
Never make definitive statements about friction as to why things are happening, its rarely that simple. I would wager its got more to do with tire carcas deformation, ideal pressures, and such rather than just the size of the contact patch.
Like why do wide tires lead to better corner grip for cars?
they do not have a bigger contact patch
or maybe they do if you set each to optimal tire pressures =)
23mm tyres have lower Crr because they have a smaller contact patch than 19mm tyres. 19mm tyres are taller than 23mm tyres.
as for the math behind why 650c wheels have higher Crr, it is rather tedious but it’s somewhere in the archives. a long hard search ought to dig it up.
Well, all the experts notwithstanding, I’ve been TTing on both a 700c bike and a 650c bike for the last four years.
My fastest TT ever produced a track record for my age group at the Lowes Motor Speedway series (29.7 mph) and that was on 650c wheels with butyl tubes. That’s not a flat course, but it’s pretty smooth and, on a smooth course, 650c wheels can be damned fast.
I’ve won my state TT (age group) each of the last three years. The course is very rough chip and seal (we call it Carolina Pave) and, though there aren’t any large hills, it’s never really flat, either. In '08 I ran my 700c bike and took nearly a minute off of my best previous time. Could be all kinds of variables, but the larger wheels seem to roll better on the rougher surface (plus I was using a Hed C2 wheel with only 90 psi … smoooooooooooth).
Generally, a 650c bike will have a shorter wheel base and this will make for a rougher ride if the pavement is bad. (Think about how bouncy a jeep is … short wheel base.) It will also make for quicker handling. I do a few races that have very tight turnarounds. They’re much easier to handle on the 650c bike. Cut your wheel hard on a small bike with 700c wheels and you’re likely to hit your foot on your front wheel. That won’t happen on a 650c bike unless you have circus feet.
The business about 650c wheels climbing better seems to be true in my experience … but you have to be talking about a genuine climb for there to be any difference. Otherwise, the 700c wheels seem to carry more momentum into small hills and, if you’re geared right, you can get up and over rather quickly.
If you have two bikes set up identically except one has 650c wheels, you’re effectively turning your drivetrain into a compact. When you go to 650c wheels, you may want to go to larger chainrings. I run 56/44 on mine.
As for latex tubes, I buy Vredestein latex tubes and I cut them down and glue them back together to make my own 650c tubes. It’s very easy and works just fine. PM me for details if you’re interested.
Selections of wheels and tires are more limited in 650c, but there’s some very good stuff that’s readily available.
FWIW … I’m selling a P3sl 51cm/650c frameset and also a set of 650c Zipp tubular race wheels (404 and disc). PM me if interested. (I just built up an '09 P2 48cm/650c and I’ll race a HED Jet on the front and Renn 575 rear. SAWEEEEET!)
.
Why race the Renn when we could just bribe Steve to make us some Jet Discs in 650c? Get enough people together and you never know…
There is also the HED Jet 90 rear which can easily be made into a Jet Disk with another 100 grams of CF.
I think I will make that my early season project since it would be super fast and the GF would have a disc without having to purchase another Clincher race wheel that I’m never going to use myself. Kind of makes it a waste of weight to have bladed spokes that way, but I can probably get past that issue if I really focus 
Chris
step 1: hed jet 90 in 650
step 2: rebuilt with super light non bladed spokes
step 3:wheelbuilder cover
step 4:victory!
Why race the Renn when we could just bribe Steve to make us some Jet Discs in 650c? Get enough people together and you never know…
There is also the HED Jet 90 rear which can easily be made into a Jet Disk with another 100 grams of CF.
I think I will make that my early season project since it would be super fast and the GF would have a disc without having to purchase another Clincher race wheel that I’m never going to use myself. Kind of makes it a waste of weight to have bladed spokes that way, but I can probably get past that issue if I really focus
Chris
Why race the Renn when we could just bribe Steve to make us some Jet Discs in 650c? Get enough people together and you never know…
I have called HED about it. Didn’t get to talk to Steve, though. (Was it Tim?) I did some whining when they said they didn’t (and wouldn’t) make 'em. If you need me for some arm-twisting, I’m all in!
I’ve used a 404 with a Wheelbuilder cover. It hasn’t been as fast as the Renn disc.
Bob:
What are selling the P3 and Zipps for.
No offense to those who use Wheelbuilder covers, but I consider them junk. The old Lightning covers that were carbon were totally acceptable, and additionally the UNI covers which were a stretch material that connected to the spokes was very nice as well.
I’m going to spend some time developing up a way to hold the conical shape of the spokes and then do it out of CF. I have several yards just waiting for a project like that. Pretty sure it can be done on a 90mm wheel at around 100 grams or so.
I have a Jet clincher 90 and also a CX 90 in tubular, so the cover would probably work perfectly on either one. Love that now that I think of it. I suppose that would make having TWO other tubular discs pretty superfluous, but such is the nature of creation.
Chris
If you get a set of Jets instead of just the front, I will make you a cover for the rear out of CF. I’m going to build one anyway, so once the mold is working making one more will be a quick job.
Chris
If the road is bumpy, 650c gives a rougher less stable ride. This adds to fatigue which does rob you of some energy. Smaller diameter wheels have more rolling resistance due to the sharper angle of the contact patch. Dont buy 650 unless you have a very small frame that can’t properly use 700c.