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Triathletes and the 650 wheels... what is the reason? nm(13 posts)

Triathletes and the 650 wheels... what is the reason? nmfunknuggets
Nov 8, 2002 9:21 AM
i think . . .bm
Nov 8, 2002 10:27 AM
smaller wheels are for quicker acceleration and since they're lighter you theoretically climb hills easier.

those are some reasons i've heard so far. i am only a beginning triathlete, but i like the classic 700s. not everything is made in the 650 size, and i think 650s are only on TT frame bikes. but if i had enough $$, i'd probably get a TT frame with 650s and a touring roadie with 700s.
re: Triathletes and the 650 wheels... what is the reason?brider
Nov 8, 2002 10:33 AM
While the 650s DO have a slight edge on acceleration and climbing, that's not the reason that they're used for triathlon bikes (for most triathlons, you have a minimum of accelerations). I have 650s on my track bike for the acceleration characteristics, and (to me at least) the difference is noticeable. But the real reason they're used on tri bikes is to allow a lower front end on small frames. There's a trend in the industry to go with 700s on frames 55cm and up, and stay with 650s on smaller frames. The jury is still out on the aero benefits of 650s (the wheel itself may be more aero, but that is generally negated by the differences in the frame).
re: Triathletes and the 650 wheels... what is the reason?timfire
Nov 8, 2002 1:55 PM
A study I read (don't remember where, one of those Tri-sites, I think), stated that a 650 wheel had a slight aero advantage on smaller frames (under 55cm, I think). But on larger frames, the 700's had the (slight) advantage, mainly because of longer headtubes on the 650's.

-Tim Kleinert
Frame geometry issuesjoekm
Nov 8, 2002 10:38 AM
The seat tube is more vertical on triathlon/ time-trial bikes. This permits a more aerodynamic position on the bike while still maintaining handling and keeping your thighs from running into your stomach. The 650 wheels are used so the rear triangle is not too long as a result.

....I believe that is it anyways.....
Why not use 650 wheels on road frames for men?niteschaos
Nov 8, 2002 11:08 AM
I've seen them on road frames for women because it allows frames to be scaled to fit more accurately in the smaller sizes. Would that same flexibility carry over to larger frames? Like Crit frames with smaller and stiffer rear ends?

And the easiest way to lighten something is to make it smaller, why aren't there road bike in conventional sizes that make use of lighter 650 wheels (like for climbing and Crit where acceleration around turns is greatly appreciated)?
Ride quality, Aero, Tire Wear, Fred Factor:-), Cost....nmSpunout
Nov 8, 2002 2:47 PM
My thoughts...Anaerobic_Nut
Nov 8, 2002 11:33 AM
My wife is a triathlete and I know a few others as well. The 650 wheel was a trend which started a few years ago to keep the overall bike weight down. Yes, they are quicker under acceleration, but overall the benefits (lower weight and such) are negated with higher revolutions and the momentum of the wheel. It will take you longer on a 650 wheel versus a 700 in say a 40k TT and will deplete your energy faster. There have been studies (John Cobb??) which revealed that a 700 wheel is the most efficient size for cycling and as such you rarely see 650's used by the top triathletes. Look at MTB, they're experimenting with a 29 inch size wheel and those who have ridden (winner of XTERRA series name?) say they are faster as well.

Yes, in smaller frame sizes, a 650 wheel will be in more proportion, but overall it appears 700 is the way to go.
My thoughts...brider
Nov 8, 2002 12:44 PM
Actaully, the lesser wheel weight is offset by the longer frame tubes it takes to accomodate them. As for the top triathletes, many are being forced to ride road geometry due to the now-draft-legal ITU races (for pros). That then puts them on 700 wheels.

The reason that the larger wheels on MTBs roll better is due to the effects of obstacles. A larger wheel will roll over an obstacle better with less energy depletion due to deflection.
The Real Reason isclimber1
Nov 8, 2002 3:39 PM
650 wheels accelerate faster than 700 wheels,
since pro triathletes
The Real Reason isjjohnson05
Nov 8, 2002 6:50 PM
Sorry to disagree with climber1, but he is dead wrong. Bikes with 650c wheels are not closer to the ground, the bottom brackets are essentially the same height as bikes with 700c wheels. "Pro" triathletes and duathletes who compete in ITU world cup races and world championships are competing in "draft-legal" races. 650c wheels are most often used in non-drafting races (like Ironman) where acceleration is of far less importance than it is in draft-legal races. As for steeep seat angles benefiting a triathlete's running performance, you should know that the vast majority of the top pro triathletes ride what would generally be called "traditional road geomerty". Very few use seat angles steeper than 74 degrees. The only exception is in Ironman distances, which are so extreme as to be irrelevant. Ironman is not a speed sport, it is a survival sport, it is for the "if you can't go fast go long" crowd.

The real reason for the popularity of 650c wheels on tri bikes is that years back some triathletes thought they were of superior intelligence and would reinventing cycling in their own image and arbitrarilly decided that a wheel with a lesser height (650c) presented a smaller profile to the wind than larger whels (700c)and therefore was more aero. It took some real hard data compiled by John Cobb in the wind tunnel to demonstrate that the drag generated by larger head tubes required by small wheeled bikes more than offset any percieved reduction in drag from smaller wheels. John also demonstrated, with scientific data, that bottles in cages mounted on the down tube and seat tube are more areo than bottles mounted behind the saddle, but amature triathletes overwhelmingly use behind-the-seat-bottle-cages because they percieve a benefit that does not exist.

Except in the case of small frame size bikes, 52-53 cm and smaller, 650c wheels serve no beneficial purpose. Unless you're a short-ass, stay away from those little wheels.
The Real Reason isflying
Nov 9, 2002 5:48 PM
Ironman is not a speed sport, it is a survival sport, it is for the "if you can't go fast go long" crowd.

You call 4:34:52 for 112 miles with very decent wind & heat slow huh? You must be pretty quick.
re: Triathletes and the 650 wheels... what is the reason? nmSteve Bailey
Nov 8, 2002 6:44 PM
Many of the other posts comment about aero advantage, acceleration, etc... but the most common reason I've seen is to allow balance of the rider on the bike with a 78-80 degree seat tube.

The forward position allowed by a steeper seat tube, in theory, allows an easier transition into the run, as well as positioning the riding comfortably on the aero bars.

Using 700c wheels on a steep seat tube frame tends to push more of the riders weight forward onto the front of the frame. Using a 650c rear wheel allows the frame designer to get the balance point towards the rear, improving the handling.

No other real advantage that I've read about.

Steve B.