650c wheels vs 700c wheels

[watchman]

Can someone tell me what is the difference in performance between 650c wheels and 700c wheels?

Is there a difference? Why would someone switch from one to the other?

Would you notice a difference when riding?

mike

[philjolliff]

I don't have a lot of knowledge on the subject but I believe I can answer this intelligently.

The answer to "switching" from one to the other is you wouldn't - this is generally a decision made during the bike's purchase/design.

650c wheels are mostly meant for smaller bikes. Someone 5'6" or under ideally but it isn't mandatory. There are 2 main reasons.
Reason number 1 is toe overlap. If a short person is on a 49 or 50cm frame and is using 700c wheels there is a chance that their toes actually would hit the larger front wheel when making sharp turns because of how small their frame is. This is obviously dangerous.
Reason number 2 is handling/control. A large bike using smaller wheels is going to see a large reduction in handling. A large bike using 700c wheels is going to handle very similarly to a small bike using 650c wheels.
There used to be a geometric problem of not being able to get a short person low enough in the aerobars because of the 700c wheels so they had to use smaller wheels. That isn't as much of a problem anymore with how bike design has changed. See the "slowtwitch" article below for a further explanation of that.

As far as speed is concerned: If the gearing is appropriate, there really shouldn't be a difference. There have been plenty of triathlon bike split records set on 650c wheels.

Here are a few links if you desire some extra reading with some very valuable arguments/information:
www.slowtwitch.com/mainheadings/techctr/650ctoday.html
amandalovato.com/blog/sponsors/kestrels-ask-a-pro-my-thoughts-on-650c-vs-700c/

[jimdehner]

Mike - I have 650's on my tri bike and 700's on my road bike - Phil is right - when I bought my tri bike the goal was to cut the wind resistance by getting me closer to the ground - that said - if I were to buy again today I would definitely buy a 700 - couple of reasons - bike design has changed alot as Phil said - additionally - finding wheels, tires and tubes for a 650 is not all that easy - where you have a choice of many brands and models for a 700 there just aren't that many choices for a 650 - also if I every decide to get race wheels - i have to decide between the 650's for the tri bike or the 700's for the road bike -

[Eric]

One reason for a 650 wheel was not mentioned in the articles Phil posted. As tri bikes were being developed the seat tube angle was made more aggressive, made steeper, to get into the aero position. As the seat moved forward some adjustments needed to be made in the rear triangle, primarily a longer seatstay and sometimes chainstay. This often lead to more flex in the rear triangle, longer chain lengths needed between the cranks and cassette and less power delivered to the rear wheel.

So in came the 650 wheel which would held reduce the size of the rear triangle.

I have also read where a 650 wheel can get up to speed faster than a 700 wheel simply due to it's diameter, but with carbon fiber wheels I think that is a moot point now. Besides you want a larger wheel for a faster speed.

My wife has a Cervelo with 650's and it fits her great. Her road bike with 700's never fit her right and she never felt comfortable on it. Last years womens world time trial champion rode a 650 wheel.

www.velonation.com/News/ID/5825/Emma-Pooley-wins-womens-World-Time-Trial.aspx

[Tim Edwards]

I rode a TT bike with 650's to 2nd at the National Time Trial Championships. They provide a lower position for improved aerodynamics, get up to speed faster which is great for courses with lots of corners, hills, or other changes in speed. The smaller wheels are usually ligher because they are smaller. The weight in a rotating mass is increased so any gram saved in wheels is better than saving a gram on the frame.

I rode them for years and loved them. It was not that hard to get spares. I just got a bunch and set them on the shelf in the workshop.

I have a frame fork and wheelset (52 cm) if anybody is interested in buying it from me ;D

[watchman]

Once again great info from the infamous CTC forum

I was wondering it there was an areo advantage to the smaller wheels

If I have a bike with 700c wheels can i put the 650c's on?

I like the idea of getting lower in the wind

mike

[jimdehner]

sorry Mike - doesn't work that way - the bike and the wheels are a pair

[watchman]

Thanks Jim for info

this is a great forum

there is not a week that goes by that I do not tell someone about it or the club

Great forum great club

mike

[mrzymek]

The bike and the wheels are just along for the ride. Its the engine that makes the real difference.

[lessthanmike]

Here's another article on 650's and 700's I found on FB
lavamagazine.com/content/ConWebDoc/877#axzz1IKQ0guon

[philjolliff]

Thanks Mike! That was a great article - easy to understand as well.