# Fit 650 wheels on a 700 bike



## ansetou (Jul 17, 2009)

i'm curious to find out if a bike that's designed to use 700 cm wheel will be able to work with 650 wheels. one problem I can see is the brake pads may not be able to reach as low to find the proper part of the 650 wheel. Is it true that the brake track on the 650 wheel will be 25 mm lower than the 700 wheel? 

what if I swap out the fork to one that's designed for 650 wheels? does that solve all the the problems? Thanks,


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## zriggle (Apr 16, 2008)

…why?


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## ansetou (Jul 17, 2009)

my wife is a new rider and she likes to be able to have her toes reaching the ground without getting off from the saddle. I thought this would be a way of accomplishing this while save some weight on the bike, lower her center of gravity, make it easier for her to climb hills.


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## natethomas2000 (Aug 2, 2009)

I'd think if you swapped out for a shorter fork the bike would be angled a bit down. I'm not an expert, but I think that would effect some things like handling and comfort.


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## zriggle (Apr 16, 2008)

ansetou said:


> my wife is a new rider and she likes to be able to have her toes reaching the ground without getting off from the saddle. I thought this would be a way of accomplishing this while save some weight on the bike, lower her center of gravity, make it easier for her to climb hills.


Laws of fit say that this shouldn’t be possible, since a (nearly) extended knee should occur at the bottom of a pedal stroke. Either she’s going to be uncomfortable (knees bent the whole time, by dropping the saddle), or she’s going to have other comfort and potential pedal-strike issues (funny wheels). If you think getting off the saddle is a problem, just wait till she flips the bike because her pedal hit the ground going around a corner. That, and the wheel will be too short anything but long-reach calipers to reach, and that’s a maybe at best.

The reason that I’ve found that new riders like to be able to touch the ground is because that’s what they did when they were 6 years old and had balance issues, and were only going 15-60 feet at a time before putting their feet down — it was out of necessity, not convenience. As children, we were afraid to lose our training wheels. Time for her to lose hers! I disconnected the rear brake on my girlfriend’s bike because she was afraid to use the front, and nearly had an incident where she couldn’t stop fast enough because she was relying on the rear brake in wet weather.

I’m all for getting your wife on the bike more, but I don’t think that it’s the right way to go about it.


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## Trek2.3 (Sep 13, 2009)

I actually asked my LBS about this last Summer. This is their answer. If she has a WSD bike, she's already got a short 165mm crank so she'll have plenty of ground clearance.

"The 43cm or 47cm is the length of the seat tube, the measurement is taken from the center of the crank to the top of the seat tube. We could put 650c wheels on basically any bike. There may be an issue with the reach of the brakes, but those could be replaced as well. My only concern doing this would be that bike geometries are relational, that is as the bike gets taller (43cm to 47cm) it also get longer. It doesn't get much longer, but it does get longer. As long as your reach on the 47cm frame is OK then I wouldn't have any problem just putting 650c wheels on the larger frame."


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## ultimobici (Jul 16, 2005)

Trek2.3 said:


> I actually asked my LBS about this last Summer. This is their answer. If she has a WSD bike, she's already got a short 165mm crank so she'll have plenty of ground clearance.
> 
> "The 43cm or 47cm is the length of the seat tube, the measurement is taken from the center of the crank to the top of the seat tube. We could put 650c wheels on basically any bike. There may be an issue with the reach of the brakes, but those could be replaced as well. My only concern doing this would be that bike geometries are relational, that is as the bike gets taller (43cm to 47cm) it also get longer. It doesn't get much longer, but it does get longer. As long as your reach on the 47cm frame is OK then I wouldn't have any problem just putting 650c wheels on the larger frame."


The ETRO designation for a 700C tyre is 622 whereas the 650 will be 571. So there's 51mm difference in diameter at the rim. The brakes would need to be 25mm deeper to begin with. The BB shell would be a smilar 25mm lower, so 5-10mm shorter cranks would still drag in corners. A 650C bike is designed as a 650C bike, so the BB will be at the same height. Your LBS have'nt thought it through properly.


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## spade2you (May 12, 2009)

Learn how to ride and the problem will fix it self. $0.


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## wim (Feb 28, 2005)

ansetou said:


> my wife is a new rider and she likes to be able to have her toes reaching the ground without getting off from the saddle.


Her not getting off the saddle is the root of the problem. Stopping a road bike means getting off the saddle and unclipping one foot just before the moment of the stop. If she doesn't know or believe that, you could teach and convince her by way of demonstrations and practice sessions. The 650 wheel approach is nonsense. Among other questionable notions, it assumes that she can't or doesn't want to become a good bike handler.

/w


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## il sogno (Jul 15, 2002)

wim said:


> Her not getting off the saddle is the root of the problem. Stopping a road bike means getting off the saddle and unclipping one foot just before the moment of the stop. If she doesn't know or believe that, you could teach and convince her by way of demonstrations and practice sessions. The 650 wheel approach is nonsense. Among other questionable notions, it assumes that she can't or doesn't want to become a good bike handler.
> 
> /w


Agreed. She should get off the saddle when stopping.


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