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Lol_Drater 07-14-13 09:15 PM

Best place to mount rear disc brakes?
I've got an older aluminum frame i'm looking to weld a disc brake mount onto the rear for. I figured you frame builders would know the answer to my question about it.

I've seen rear mounted disc brake in several different spots, but for a frame never ment to have them, where would the best spot to put the tabs be? Or because it's aluminum does it not even matter?

Thanks guys!

Andrew R Stewart 07-14-13 09:29 PM

Above and behind the seat stays is the most common place to mount a caliper. The least interference with the rest of the frame. There is a concern about the SS taking the loads a disk will show it, bracing tube from the SS to the chain stays helps.

Between the stays and attached to the CS is the next likely location. The CS is usually beefier so long term tube failure is less. But fit and interference may be a problem. If a rack/fender are part of the package this location has pluses.

Really the only way to figure this out is to try to locate the caliper with a disked wheel in place. See where the problems are and what the solutions might be.

But before you even do this, are you up to speed with the welding issues of the grade of Alu used on this bike? You can do all the right design and machining and the frame will crack soon enough if the welding and post joining treatment is wrong. Andy.

unterhausen 07-14-13 09:59 PM

annealed aluminum can be very weak in fatigue, as Andy says, check to see if the series of aluminum the bike is made from requires post-weld heat treatment

you should also make sure that the frame has clearance for the disc

Dave Kirk 07-16-13 08:09 AM

Realistically you probably don't have an option as i doubt you will have room to mount the caliper on the c-stay. In most cases you will not be able to get it rearward enough to be in the proper position without it bumping into the all depends on the rear dropout design. If you have any option I think the c-stay mount gives better strength and performance but the cable routing can be awkward.

You got some measuring to do to see where the caliper will fit and if the disc will clear the c-stay.


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