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Old 01-27-13, 09:20 PM   #1
snowscaper
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650c on 700

I have a 48cm frame that I would like to use for my daughter's bike. Problem is the standover height is about and inch or so to high. Does anyone know if it is possible to put 650c wheels on the 700c frame? Long reach brakes a possibility?

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My fault for not explaining myself fully. Both my children, ages 14 and 9, race road and track. As you can imagine, this has become quite expensive for me. My son recently outgrew his last bike "Jamis Xenith Comp". 48cm carbon fiber race bike and my daughter is about to outgrow her 24" trek KDR 1000 34.5 cm. I am hoping to avoid buying a 650c complete bike and put her rite into the 700c Jamis, but as I said in my original post the stand over height is a bit to high. Hence my question regarding wheel size. Drum brakes, disk brakes, and skidding are not options.

Last edited by snowscaper; 01-28-13 at 08:03 AM. Reason: Bad explanation
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Old 01-27-13, 09:53 PM   #2
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You can use long reach brakes (sometimes), or make a drop bolt to use more standard (eg, better) brakes.
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Old 01-28-13, 12:23 AM   #3
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Yes, everything that 400trix said. You can also use coaster brakes, disc brakes, or skidding if your bike allows it.
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Old 01-28-13, 01:16 AM   #4
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i've gone to the trouble to try out mtb wheels (559mm) on an old steel frame built for 27 (630mm) wheels. i put a coaster brake rear hub on it to solve the braking problem. no front brake. so going from 622mm to 571, as you mentioned, will involve a smaller discrepancy (about 20mms) LESS than the one i tried. then i rode it around for a while.

the BB is low, but not unreasonable so. the killer for me was that the smaller front wheel induced a terrible front wheel wobble at anything above 10MPH. i was surprised.

i'm pretty sure a long reach caliper brake won't cut it. maybe a drop bolt...

i think there are front drum brake hubs too. that may be a possibility.

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Old 01-28-13, 09:28 AM   #5
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I presume the kids are both still growing? I ask because I'm curious if you're shooting for 1-2" of standover clearance, or if your littlest can't clear the top tube at all.

I would sooner convert to 650A or 650B:

1) Skinny tires are available for both (25-590 and 32-584) that would drop the TT by 1/2" and 3/8" respectively
2) Brakes are just a matter of installing long-reach calipers like Tektro 556/559
3) You'll have plenty of buyers for a 650B wheelset if/when you convert back to 700C
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Old 01-28-13, 02:37 PM   #6
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Sell it and get a bike that fits.
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Old 01-28-13, 02:43 PM   #7
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My daughter rides a bike that size. It is made for 27" wheels but I put 26" (mountain bike size, so smaller than 650c) on it, with drum brakes. And short crank arms.

The problem with 650c is that the tire selection is pretty limited. You can get some very nice tires, but they are mostly very narrow. The widest I have found are 28 mm Terry tires. I know this because my wife rides a 650c bike. My daughter's bike, with the 26" wheels, has 32 mm tires.
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Old 01-29-13, 12:19 AM   #8
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Grant Petersen at Rivendell is a 650 fan. They have everything you need. Www.rivbike.com.
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Old 01-29-13, 09:08 AM   #9
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Grant Petersen at Rivendell is a 650 fan. They have everything you need. Www.rivbike.com.

Rivendell promotes 650B, not 650C. 650B is likely a better choice as a set of regular long-reach brakes (also available from Rivendell) will probably work for the conversion. Going to 650C may make it more difficult to get brakes to work. They won't drop the bike down a whole inch, though.
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Old 01-29-13, 10:37 AM   #10
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Besides the brake issue, dropping the standover height by an inch or more is going to have a major effect on the pedal clearance unless you also shorten the cranks that much. If she's going to be racing then she'll want to be able to pedal through moderate turns and could easily crash as a result of a pedal strike. If you really can't get her a bike that fits then I'd think it would be better to make some changes to her current KDR 1000 (longer stem and seatpost) that would let her use that bike a little longer until the Jamis is a better fit.
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Old 01-29-13, 11:32 AM   #11
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650A and 650B will lower the bike such a negligible distance that it would basically do nothing to solve the problem.

A small rider should have shorter crank arms anyway. And by 'short' I mean 140 or 150.

For a road bike, the only issue will be brake reach. If you can't find a good brake with enough reach, you may have to get drop bolts. Even if you have to employ more cumbersome workarounds than that, it is still worth pursuing.

For a track bike, obviously the brake issue is not an issue.
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