Brake disc location standards

[foz]

Have brake discs always been in the same place (distance from hub centreline)? I hadn't though otherwise, but I have found a nice condition Magura front hub for sale locally, and not knowning anything about them I started to google. I have seen some references that the older ones at least aren't compatible with modern disc setups, as the disc is further from the centreline (closer to the dropout) than in more modern (post 2000-ish) disc brakes. I know there were different mounting standards (3, 4, 5 then 6 hole, Hope spline, etc.) but had never given any thought to the disc position along the spindle... can anyone enlighten me?

 

[mdvineng]

There will be some variance from brands. Hope used to sell disc shims in various thicknesses for 6 bolt pattern. I have no documents on what variances to expect though but manufacturing tolerances will be in play too.

 

[foz]

Yes I would expect some differences between brands, but nowadays all should be within the international standard dimensions and tolerances. I am more concerned that this particular hub is quite old, and may be from a time before standardisation so while it will take a modern 6 bolt disc, the disc will be too far out and not work with a modern fork and caliper, at least not without some modification which I would prefer to avoid. If the disc is too far in then that's easy to correct, but too far out means either machining the hub or modifying the caliper

 

[Lacuna]

I know some frames and forks with IS mounts needed a lot of shims to space the caliper far enough in. I guess Magura were compensating?

 

[foz]

That is a possibility. I don't actually know if this hub is different to "normal" or not, am trying to find out so that I don't buy it to then find it won't work... I think they were made by Sachs, at least some of the magura hubs were, not sure if all of them. But there is very little info on them...

 

[mdvineng]

Best thing to do is measure the distance from axle inner fork face to disc mount face and compare to other hubs that you have.

 

[novocaine]

27.25+-0.1 has been the standard for as long as I can remember (think 96 ish). if it's older than that it could be anything. newer and you'll most likely be fine.

ISO 4210-6 was released in 96. centre lock followed the same principals and dimensions.

 

[sam_white]

Yes there were variations. Personally I've only come across a single hub with issues, that being a Coyote branded disc hub from around 2000. I believe they were standardised post 2000 with the 'International Standard 2000' mount.

On my hub, the disc was too far inboard, so easily adjusted by adding around 3/4mm of shims between the disc caliper and the fork.