Disc rotor fouling brake post mount....

rolf_f

Hello folks

Building up a new frame (Orange Crush - parts swap from a P7). On fitting the rear wheel (Deore hub), I found that the brake disc (Shimano XT) fouls the post mount - not a lot but even not a lot isn't right!

This seems to mean that I need a deeper retaining nut for the cones on the non drive side (and vice versa) or an extra washer and a tighter fit for the wheel in the dropouts. This seems a bit odd though - I'd assume that the placement of the post mounts would always allow clearance for the discs as these are surely fixed standards. Is this just something that occasionally happens (and if so, how is it normally dealt with?) or is it a frame problem. I can't see that it is a problem with the wheel. The P7 used an adaptor on the rear and it worked perfectly well.

Advice appreciated!

The Rookie

First measure where the wheel rim sits between seat and chain stays, if it's in the middle as I expect then it sounds like you need to look for a thinner PM mount, some can be a bit fat!

Dirtydog11

It may have been serviced and put back together incorrectly, Id have a look at the exploded view on the Shimano site and check washers/spacers against yours.


iirc the spacers/washers are drive side and non drive side specific (different thickness to each other) and may have been fitted the wrong way around, I can vaguely remember having a similar issue.

stubs

If they are the new Shimano discs with the steel rotor riveted to an aluminium spider they can catch post mounts. Both the post mounts front and rear on my Canyon have lost the paint, the clearance is minimal and the rivets catch slightly when cornering. Clearances are tight with the post mount standard but I would check with Orange the tolerances might be out.

BigStu2

I had a similar problem with my Avids, I just used a thicker cone washer fom a set of V brakes to space the caliper further out.

The Rookie

Erm....it's fouling the adaptor, moving the caliper aint't goint to do much!

stubs

The Beginner wrote:

Erm....it's fouling the adaptor, moving the caliper aint't goint to do much!

If its a post mount frame and an XT caliper there wont be an adaptor will there.

The Rookie

stubs wrote:

If its a post mount frame

It's an Orange crush, check the Orange website, all are IS mount.....

stubs

crush_frame-182 by http://www.flickr.com/people/[email protected]/, on Flickr

Looks post mount to me

The Rookie

Not this sucker

http://www.orangebikes.co.uk/bikes/2011/crush/

stubs

He says its a new frame and thats a 2 year old frame you have linked to.

The Rookie

Indeed, until he comes back, we won't know, the orange website doesn't show that frame and the photo of the 2012 is inconclusive.

Chunkers1980

Pretty sure the op say rear brake and fouling the post mount.

stubs

The photo I posted is the 2013 Orange Crush frame it has post mounts as did the 2012 frame. The 2011 frame has IS mounts till we know what the OP has we are just going round in circles.

rolf_f

Apologies - I think I got my terms confused - I thought they were post mounts because they look like posts. I should know better given other confusing terms like clipless pedals etc..... :oops:

And just to make sure I don't get them wrong again, rather than say what it isn't, I will say that the frame is as per the pic Stubs posted. I can post a pic of the actual frame when I get back to it in a couple of days but it probably isn't needed. On the pic, it is the upper of the two mounts which the disc rubs on.

The caliper is the sort with the separate spider.

I promise to try to go back to the Road Forums where I'm hopefully less of a liability when I've got this bike back on the road

stubs

Hi Rolf it can be confusing the pic here shows the 2 standards. It shows fork legs but frames are the same


Post a pic of your bike showing the damage then we might be able to shed some light on the problem.

rolf_f

Keeping it tech...... it's the one on the right!

Tuesday hopefully for a pic but at the moment it might not show much - it's only scraped a sliver of paint off as I've only had the wheel briefly mounted with the frame on the stand. I could probably let it finish scraping the paint off but even then I'd worry at what might happen if the disc developed a slight warp. The clearance just seems stupidly non existent.

rolf_f

A couple of pics. You can see in the first a sort of step in the metal of the post which, if it wasn't there, would give a bit more clearance. The second shows more clearly how tight it is there. I think I need to ring Orange again....

stubs

That is very tight clearance. Have you got access to another disc brake wheel to try and see if it is the wheel.

allthegearnoidea

i'd certainly go for trying another disc as it looks like the disc spider is moving the over tight to the mount, i'd pop a 'normal disc' on there and check with that.

rolf_f

I can certainly try the old plain Avid disc (no other complete wheel to try) - but I don't think it will make a difference. The spider is dished towards the hub to allow the disc itself to remain in the same alignment as a single piece disc.

supersonic

Migth be able to repsace the hub slightly, and redish the rim.

The Rookie

+1 not unusual for discs with an ally spider to have clearance issues while (the lighter and more reliable) plain discs are fine.

rolf_f

Possibly solved!

Took the disc off - filed away at the disc mount on the hub to make sure no censored of flash was getting in the way. Filed away at the paint on the post and repolished it (thick powder coat so plenty of potential for thining it!) and then polished the slightly protruding heads of the rivets that hold the disc to the spider. Result below. Seems an almost improbably effective result but the answers speak for themselves.

Thanks for the input folks. I now need to wait for my decent BB cup tool and a new cassette lockring tool so replace the one I knackered trying to get this cassette off and I might almost be ready to finish the build!