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Old 11-15-10, 09:00 PM   #1
RobE30 
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Reasons to convert to 650b

There may be a 61cm touring frame/fork coming my way for a trade of a much smaller frame. I plan on riding it and seeing how it feels before I do anything to it, but if the reach (top tube) feels good but if standover is TOO much, I might consider swapping to 650b.

Is there a benefit to going to 650b wheels? What downsides am I going run into if I do the swap? One more question, what are some reasons that someone would want to convert to 650b?

I think that's it. My current "fleet" runs from a 22" to a 23 1/2 (a bit tall for me, but the reach feels good). This bike comes in at 24".
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Old 11-15-10, 09:07 PM   #2
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Converting to 650b basically lets you run big, cushy tires on a tight-clearance bike. I don't know that a touring bike would be the best candidate because it will have a low bottom bracket, it already has room for big tires, and it would be hard (if not impossible) to find compatible brakes if we're talking cantis. Going to 650b will drop the standover some, but usually not all that much. Then again, with the bike being only slightly too big, maybe it would be enought to make a difference.
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Old 11-15-10, 09:45 PM   #3
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In my case, it was because I wanted to put my 26 inch wheel set with 7 spd IGH on my wife's bike, and VO was (is) running a special on a 650b rim with 8 spd IGH for less than the price of the hub alone. The result is great--the larger wheel set fits my frame perfectly (it always looked a bit out of proportion with 26 inch wheels) and my brakes even reach. The change raised the bike about one cm--still plenty of stand over clearance. Going the other direction, from 700c to 650b, could require new brakes with more reach.
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Old 11-16-10, 09:29 AM   #4
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i've done all the math on this, as i'm currently converting a large touring frame to 650B. in terms of lowering the standover height, you have to take into account not only the change in wheel diameter, but also tire size.

the way i've calculated the change in standover height for my project is as follows:

27" -> 650B rims = height decrease of 23mm (half of 46mm)
27 x 1-1/4" tires -> 650 x 38C = height increase of 6mm (32mm versus 38mm)

net height change = 23mm - 6mm = 17mm.

if you are converting from 700c to 650B rims and not from 27" as i am, then instead of a 23mm height decrease, you will have a 19mm height decrease, before factoring in the tire thickness.

oh, and PM sent!
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Old 11-16-10, 10:58 AM   #5
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The frame I'm looking at needs a ton of cosmetic help so if swapping to a smaller wheelset will give me the standover needed (assuming it doesn't lower the BB height too much causing pedal strike) perhaps I could get the canti mounts moved down to fit 650b wheels. I need to get the frame and see how it fits first. I hate waiting!!!!!
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Old 11-16-10, 03:40 PM   #6
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IMO, a 650b conversion done right will have very nearly the same standover height as the original. The whole point is to fit big ol' tires—the outer diameter should remain more or less the same. Otherwise, it's just an ill-fitting bike with tiny wheels.
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Old 11-16-10, 05:00 PM   #7
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Quote:
Originally Posted by RobE30 View Post
There may be a 61cm touring frame/fork coming my way ..., but if the reach (top tube) feels good but if standover is TOO much, I might consider swapping to 650b.

Get a frame that fits.


That's it. It's as simple as that.
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Old 11-16-10, 07:34 PM   #8
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Quote:
Originally Posted by jtgotsjets View Post
IMO, a 650b conversion done right will have very nearly the same standover height as the original. The whole point is to fit big ol' tires—the outer diameter should remain more or less the same. Otherwise, it's just an ill-fitting bike with tiny wheels.
Answers that question, thanks
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