Can't get Topstone rear caliper properly aligned / hub width?

larkim

My son's Topstone 3 has aftermarket Spyre calipers fitted front and rear, and all was working fine. However, the rear hub failed recently so the hub was replaced by a LBS and when the bike came back all was good.
However, he then had to remove the rear wheel (can't remember why) and every since then the disc has been very poorly located in the caliper to the extent that it is rubbing. And no amount of loosening off the nuts and moving the caliper around seems to sort it.
The bike normally lives away with him at Uni but he brought it home this weekend for me to take a look at.
My immediate thought was that a 140mm hub (if such exists) had been fitted, or a spacer missed as the rotor spins incredibly close to the frame when the wheel is bolted in place. Like less than 0.5mm or so.
But measuring the hub as best we could it came out as 142mm which I believe is the spec.
The caliper feels like it pulls inboard slightly at the final tightening too, but again checking the brak spec it doesn't look like there should be any bolts which allow for anything other than a straight mount.
https://photos.app.goo.gl/VQH8wtnNSXcCDQyi7
This photo was taken when we'd got the caliper positioned outboard as far as we could, but it wouldn't stay there. But the photo is really mean to illustrate how close the rotor is to the frame, and perhaps wonder if there is a spacer missing / wrong side on the hub?

me-109

If the caliper mounting bolt holes are not slotted then your only choice is to change the position of the disc. You may be able to do this on the axle, which runs the risk of offsetting the rim relative to the frame, or you could shim the disc - easiest to achieve by a slim washer over each bolt between the back face of the disc and the hub.

Wheelspinner

Hmm, pic looks unusual. Is it a through-axle hub?? Should be, if it's a 142 mm spacing.

larkim

Yep, spec is a 12x142mm hub. The freehub seized recently so it went into the LBS. Came back OK, but first time the wheel was taken off and put back on again son noticed rubbing on the caliper, so he brought it home this weekend and I'm baffled.

Could there be a spacer or something missing / wrong side (i.e. on drive side, should be on rotor side)? That's all I can think if it was outboard of the rotor which would keep the distance from the rotor to the frame more "sensible" at 2mm or so.

larkim

me-109 said:

If the caliper mounting bolt holes are not slotted then your only choice is to change the position of the disc. You may be able to do this on the axle, which runs the risk of offsetting the rim relative to the frame, or you could shim the disc - easiest to achieve by a slim washer over each bolt between the back face of the disc and the hub.

There's a normal amount of slotting on the mounting positions to allow a bit of left / right movement of the caliper, and if the rotor was further away from the frame I'm pretty sure it would all be nice and easily solvable.

I've only rarely got involved with hubs / freehubs though so I'm a long way out of my comfort zone (though I'm reasonably competent!) in knowing exactly how a thru axel etc should be spaced.

i.bhamra

If it was OK before the wheel was taken out I'd be thinking along the lines of a spacer misplaced when the wheel was removed? is the axle end-cap/spacer or similar missing from the drive-side? Sounds silly but I missed a spacer that got stuck in a cassette tool before.

larkim

Not knowing what should be on the end of the axle, that's difficult to answer! Any suggestions for any measurements I could take, or photos of similar hubs that might give a pointer in the right direction?

whyamihere

It looks fine. As long as the rotor isn't rubbing on the frame, this is about getting the caliper in the right position. In the picture, there's clear light between the outer pad and the rotor, so if the caliper is tightened in that position it will work. Get something to prevent the caliper from moving inboard as it's tightened. It may also be worth getting a good bike shop to check if the mount needs facing, as a mount with an angled face would pull the caliper off its location as it's tightened.

trevor.hall12

Is the dish on the wheel OK?

larkim

Dishing looks fine, wheel centered as I'd expect.

I can't get two pieces of paper between the mounts and the disc, are you sure @whyamihere that's standard? If it is, will check out the facing, though when the problem first arose the caliper hadn't been moved off the bike.

Bear in mind the caliper positions in the photos are just loose positions whilst it was a work in progress so that side of things in the photos is meaningless.

trevor.hall12

When you set the caliper by using the pad adjusters to centre it does it rub or not stay in position ?

larkim

It sits quite off centre as much as we try to encourage it, via pad adjustments or otherwise.

me-109

I'd back off the pad adjusters, centre the caliper over the disc and just nip up the bolts enough to stop it moving. Set the pad adjusters to move the pads in then give the lever a god squeeze to hold the caliper firm before tightening up the caliper bolts. That should stop it moving. Also, make sure the caliper bolts have washers underneath the heads so the bolt is not bearing directly against the frame which should reduce the creeping as you tighten the bolts.

itboffin

Topstone model are 6mm offset at the rear sounds like your wheel is not correctly dished

trevor.hall12

itboffin said:

Topstone model are 6mm offset at the rear sounds like your wheel is not correctly dished

This was my first thought too ,OP says it looks fine ,might be an idea to check it properly .

larkim

How / why would wheel dish impact the position of the rotor in relation to the frame though? Even if there were no spokes and no rim on the wheel, the alignment / positioning issue we've got would be the same.
Happy to learn though, I appreciate the help so far!

me-109

Just a thought ... Does the hub have a spacer on either end? The sort of hub I'm thinking of is Fulcrum, where there a different end caps depending on the axle you're using. If so, check if both caps are the same depth (width, height, however you're measuring) - if different try swapping them over.
Some t/a hubs have a complete axle - maybe try reversing that and see what you get.

larkim

Thanks, I'll see if I can get a look or a photo!

photonic69

That rotor looks super close to frame! Is that a locknut on the axle? A washer between the locknut and cone nut would give you an extra 1.5mm. Just a thought.

larkim

Difficult for me to comment as I don't know precisely what *should* be there! Don't want to just stick a washer in there if I'm barking up the wrong tree.
Here's both the drive and NDS and whilst I can't be precise about this (the bike has now gone back to Uni with son) it does look like the final nut, whatever it is, is smaller on the drive side so swapping around wouldn't make sense as it would put the rotor and the frame in contact.
I was hoping someone with a Topstone might have a close up photo of their rear config to compare / contrast with!

larkim

Just for completeness, eventually my son got round to getting it into a different LBS who diagnosed that the first one had put the "freehub cones" on the wrong way round. They sorted it quickly and cheaply and it now rides like a dream again :-)