Post Mount Facing, Bristol Area

Sparky6911

Hey guys

Bit of a strange one this, I'm having real problems centering my calipers on my post mount forks. I can center the caliper perfectly when the brake isn't on but as soon as the brake is applied hard the disc is twisted, returning when the brake is released.

I'm convinced it is the facing as when the mounting bolts are slackened off and the brake applied the caliper is also square the the disc buy as I torque up the mounting bolts against the mounts the caliper is pulled out of true relative to the disc.

So does anyone have any ideas if this can be sorted to home or know of a shop in the Bristol area that can do post Mount facing.

Thanks

David

nicklouse

what brakes?

badhopper

Do the caliper bolts have washers?

Sparky6911

Trp spYres going on a Volagi Liscio, technically this is a road set up but as disc brakes are such a new thing on road bikes I thought the Mtb section would have more people in the know about disc brake set ups as I've never had to deal with this on my Cannondale Prophet as I've only ever used avids with it

nicklouse

Sparky6911 wrote:

Trp spYres going on a Volagi Liscio, technically this is a road set up but as disc brakes are such a new thing on road bikes I thought the Mtb section would have more people in the know about disc brake set ups as I've never had to deal with this on my Cannondale Prophet as I've only ever used avids with it

Give me a moment but the way you are saying you are setting it up is wrong.

Sparky6911

The caliper bolts have washers but not the tri-alignment kind

nicklouse

Have a read http://www.trpbrakes.com/userfiles/file ... l_053113(1).pdf

Section D.

badhopper

Sorry after re-reading it does sound like it might need facing.

If you screw the caliper bolts into the posts without the caliper fitted, does the face of the post mount look 90degrees to the bolt?

Sparky6911

Hi Nicklouse

Yeh done that, when the brake is pulled before the caliper is torqued down the caliper is centered and true but soon as it is torqued up you can see it change angle relative to the disc and then twist the disc until the brake is released

nicklouse

right got you. just checking that you are doing it correctly as some align by eye and then wonder why things change.

i would be temped you just get out on it and let them bed in.

post mount facing is out there but never had to do it on any fork. have you tried the other caliper just thinking about the finish on the caliper mating surface.

i would call Bike Dock or some other big independent in the area.

Horton

No idea if any of these guys will be able to do it, but Mud Dock in town are pretty good. You've also got psyclewerx on Cotham hill who have a small shop but some pretty exclusive stuff and do a lot of custom builds. Then just outside Bristol you've got Bad Ass Bikes - about 20 mins south of bristol, not too far off the A38 - really good shop and workshop.

Sparky6911

Thanks for all of your help and suggestions guys, I'm just waiting to hear back from the manufacturer to find out if there are any specific idiosyncrasies with these than I'll be taking them to muddoc, my local shop offered to get the tool in and have a go, I politely declined as they have never done it before.

Cheers All

stubs

Is there a thick layer of paint of the face of the post mount. On a set of Fox Forks I had this was a problem it made the caliper twist as I tightened the bolts down no matter how hard I gripped the caliper or how carefully I torqued the bolts. Got a new 10A swann Morton scalpel and sat there and carefully peeled the paint away till I got to solid metal being extra careful I didnt shave any metal off. Solved the problem I probably could have left it and the paint would have squashed down eventually.