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650b Conversion

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650b Conversion

Old 12-08-23, 09:36 AM
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650b Conversion

Hi,

I would like to know whether is possible to fit 650B wheels on my 700c road frame.

The reason is trying to fit a wider/winter/commuting tyre as now I can mount max 28mm and no clearence at all.

Frame and fork are chinese made carbon road, rim carbon caliper brakes, Koozer RS1400 700C wheels, 28mm commuter tyres.

I'm supposing I cannot use my brakes due to diameter difference (there are any 'extensions' out there?) so looking for a disk brake conversion too.

Basically I wonder whether is possible to put a 650B, 35-40mm tyres, and use some adapter to fit disk brakes.

Thanks for any thought about that.

Cheers
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Old 12-08-23, 11:42 AM
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We don't have enough information to answer your question. If you upload pictures to an album in your gallery, someone can rescue them for you and post here. Would need to see the tire in the chainstays.

On many frames, the clearance spreads further back on the chainstays. As far as brakes go, there are long reach brakes. It really depends on what the reach on your current brakes is.
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Old 12-08-23, 12:03 PM
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I'I've uploaded a couple of pics on my profile, can you see them?

Cheers
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Old 12-08-23, 12:24 PM
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I don't see any roadblocks yet. New long reach brakes, wheelset and rubber. If I was doing a 650b conversion now, I'd make the rims tubeless because there's more choice in tires.
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Old 12-08-23, 02:03 PM
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I converted a Bianchi road frame and was able to fit 40's on with sufficient clearance. I had to go to long reach caliper brakes and also had to press dimples into the inner chainstays for it to work. Obviously you won't be able to modify the chainstays on a carbon bike. Also be careful about going to disk brakes if your frame is not already set up structurally for them. The braking forces could lead to frame damage unless specifically reinforced.
Whenever I wonder whether a particular frame can fit a particular tire, I use a 'story stick'. In this case, this device is a short piece of wood with a hole drilled in one end. Into this hole is fitted an axle diameter dowel or rod. from the center line of this 'axle' measure outward and mark the specific locations for rim braking surface width, tire bead, point of max tire width, and outside diameter of tire. You can then mount this device into with the dowel/rod into the drop out and then swing the stick to see where things will be positioned at the stays and bridges. For instance, you can measure the width between the stays at the line of max tire width to gauge your clearance.
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Old 12-08-23, 04:54 PM
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I think you should be able to get at least a 35mm tire in there.
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Old 12-09-23, 06:42 AM
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Thanks for all the answers.

Currently I'm fitting a Schwalbe CX comp 700c 30mm and it's absolutely spot on 0 clearance.

0 clearance on the seat tube and I had to sandpaper a little bit of the carbon break caliper that was slightly touching the tyre.

I still have some doubt about the brakes.

The bike is supposed to be 'light' (it weights 6.5kg).

Now I have these carbon brakes who perform just 'good enough' but in rain it's not the safest thing. But it's the lightest.

I can, maybe:

-Use an extension for my current caliper? I'v seen a metal plate to add between the brake and the frame. (not a lot o choice on wheelset 650b with rim brakes)
-Buy a new and heavy long reach brake but still not a lot o choice on wheelset 650b with rim brakes.
-Convert to disk brakes, adding weight but safety. I've seen some conversion kit, don't know whether they can work on my bike, especially if the disk+wheel fit into the frame.

Thanks, sorry I'm still thinking what would be a proper fitting.

Sergej

Last edited by Sergej; 12-09-23 at 06:48 AM. Reason: Gramma
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Old 12-09-23, 08:33 AM
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I don't think the disc brake conversion should be on your list of possibilities.
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Old 12-10-23, 12:17 PM
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Originally Posted by BTinNYC
I don't think the disc brake conversion should be on your list of possibilities.
One possibility would be to replace the fork with one designed for disc brake loads, and use a rim brake caliper on the rear wheel. It's likely that the original caliper will need to be replaced with a longer reach caliper to reach the smaller radius brake track on a 650B rim.
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