Hello, having some big stress with my new Shimano XT rear brake. It’s on a On One Inbred with Hope Ti-Glide rear hub – which means the disc is slightly thicker than modern ones.

I fitted and set the brakes up Friday and there was zero rub – I was amazed as my old Juicys always had a wee bit of drag. Went the Quantocks yesterday, and there was a tiny bit of rub (wheel removed while in car) and it was fine. Put the wheel back in when I got home yesterday, and the wheel only turns with a lot of force. I have loosened the bolts to realign the calliper, but it always drags. I have also pushed the pistons out, and set it from that. Removed pads and there’s nothing obviously wrong. Pistons appear to move equally when the brake is applied. I have also checked the wheel is in the dropouts properly, and that too us fine.

So, oh wizened hive, what can I do? Thanks!

Are you running the same disk/setup on the front and are you having issues with that, if not then you can rule the actual disk out?

As far as setup is concerned don’t just pull the lever and rely on the pistons to line things up, it’s an unreliable way of doing it IME. Align caliper to disk by eye, only then make sure pistons are aligned evenly left and right and contacting the disk at the same time.

Front is same brake but shimano 6bolt disc, on a Shimano hub. No rubbing at all. Rear disc does have a very slight warp, but the brake drags throughout the rotation. Even at the stiffest point in the rotation, a squeeze of the brakes shows both pistons moving.

Front is same brake but shimano 6bolt disc, on a Shimano hub. No rubbing at all. Rear disc does have a very slight warp, but the brake drags throughout the rotation. Even at the stiffest point in the rotation, a squeeze of the brakes shows both pistons moving.

Can you swap the disks around to rule it out?

Nope, front is 6 bolt Shimano, rear is 5 bolt Hope.

Bollox!

Got another wheel you could try, you need to rule the disk out?

No other disc wheel I can think of. I have had two disc wheels in my life – the other was a Hop Big Un, with shortened axle, from the days before disc mounts on frames!

Having had a look, the rubbing is against the calliper – it looks like I need to put a washer between calliper and disc mount. How on earth did I get this so dialled without any washers?!

Seriously, that wasn’t a rhetorical question. I would like to know if this sounds reasonable, or whether there’s something else that needs addressed? Cheers folks

Ah, so I assume the caliper cannot be aligned over rotor, no reason not to add a washer as that’s how they used to do it.

I’ve have had to do the same on one of my bikes and that runs a full Shimano setup, discs hubs and all, I have put it down to a tolerance issue with rear frame mount, as per your post front is fine.

They’re post mount – so the washer is to put the calliper further away from the hub (as in, vertically, toward the tyre, not left or right, if you see what I mean).

Just odd it was fine first time round. Seem to recall Hope rotors (or at least the old ones) are 5mm bigger diameter than standard, so these will be 165mm I guess. Fingers crossed this has sorted it!

Seem to recall Hope rotors (or at least the old ones) are 5mm bigger diameter than standard, so these will be 165mm I guess. Fingers crossed this has sorted it!

Think I have my lines crossed here, from your new description it’s the very outer edge rubbing due to the increased diameter of the Hope 165mm rotors over Shimanos 160mm ie not lateral rubbing as I previously thought, if it is then I still see no reason why 5mm of washers or a 5mm spacer wouldn’t be fine, Avid design theirs to use washers (Tri Align).

Yes, outer edge rubbing. At first I thought it was side to side, but I can see where the black coat has worn away on the calliper where the outer edge has rubbed. Thanks for your thoughts, helped me get to the bottom of it!

I had this with Clarkes brakes on the rear. Had to put a 1.5mm washers under the calliper even when using an IS to Post mount adapter. Later fitted BB7, and now XT using the same mount (and disc) but no washers needed.

Strange, but there you go.

Yes, that all makes sense. Just odd it was fine for the first ride. And lucky I had a piles of washers that I found on a table in a pub once!