Rear axel build on, ahem, gravel bike

larkim

Seeking advice here as I suspect 12mm through axles and 12x142mm hubs are more common than in the roadie section (where to be fair some roadies have provided some help and guidance).

Bottom line is that my son's Cannondale Topstone had a failing freehub, took it to LBS for replacement / repair and it came back all working fine for a few days. Then he had to remove the rear wheel for some reason and when he put it back on, without changing anything, he noticed a lot of rubbing on the rear caliper. Down the phone I advised him to check it was all properly seated and if so then have a fiddle with backing off the bolts for the caliper, gripping up the brake, retightnening etc etc. Standard brake alignment stuff. But he reported back that it was making no difference, even at the extremes he couldn't stop the rubbing.

So he brought it home this weekend for me to have a look. Bear in mind I've not owned a gravel bike, nor a 142mm hub rear with a 12mm axle before so I didn't know what to expect entirely.

After a couple of failed attempts to get the caliper aligned, what struck me was how close the rotor was to the frame of the bike where the brake mounting points were. I can barely get two pieces of paper in there. Which made / makes me wonder if there's some spacing missing somehow on the axle or similar?

Am I barking up the wrong tree thinking the rotor is very close? There don't seem to be too many other Topstone riders around to compare with, so just after general pointers, but any help gratefully received!

reaperactual

To my eye the pads look too tight with no clearance. The inboard piston/cam especially looks over extended so the rotor isn't centred in the caliper's rotor groove as it should be.

Looks like a cable operated Spyre caliper or similar so I assume both pads/pistons compress. Maybe something needs to be adjusted or eased off and then the caliper would realign properly slightly further outwards?

larkim

If you can, ignore the caliper issue. It's the hub position and the rotor position in relation to the frame that is the issue.
It is a Spyre caliper, yes, and we're OK with the caliper adjustments, but even at the furthest outboard position we can get the caliper the caliper body is rubbing on the rotor a little. And bear in mind this was a rotor / caliper that was perfect prior to going into the LBS :-)
If the bike was with me and the shop was local to me I'd have no issues taking it in and having a chat with the mechanic, but sadly it's away with my son up in his Uni town and he's not as confident about that sort of conversation (nor does he have the time!)

reaperactual

Okay I'll ignore the caliper.

So the issue is this gap which was fine after getting it back from the lbs but has now decreased since the rear wheel was removed and then replaced as normal:-

reaperactual

Most thru axle hubs (which I guess it must be) generally just have push on end caps with a rubber sealed sleeve which slots inside the hub axle to keep it from falling out during removal.

Not come across any that have extra spacers or washers that might have fallen out to cause the frame to squeeze in further than usual.

Maybe some more pics of the set up on each side of the hub out of the frame could help.

alwaystimetotorque

Have the drive side and non drive side end caps been mixed up when the hub was serviced?
Pop them both off and see if they are similar but different lengths. That could be the issue.

larkim

When you say "end caps" are you talking about the "bolt" that is the outside part of that axle?

I've circled both the NDS and DS on the photos below, it looks to me like the DS one is actually narrower than the NDS one, so that wouldn't make sense.

Is it allowable to stick some form of washer / spacer in between that end cap (if I've got the terminology correct) to add a MM or 2 to the width?

larkim

reaperactual said:

Okay I'll ignore the caliper.

So the issue is this gap which was fine after getting it back from the lbs but has now decreased since the rear wheel was removed and then replaced as normal:-

Yep, exactly that.

larkim

alwaystimetotorque said:

Have the drive side and non drive side end caps been mixed up when the hub was serviced?
Pop them both off and see if they are similar but different lengths. That could be the issue.

You'd have to help me out appreciate what the "end cap" might be in this context! As there didn't appear to be anything which could be "popped off" on either side (which may be the issue!)

reaperactual

Thru axle end caps are something resembling this:-

larkim

Nothing like that on this hub. At least, not on the outside.

Think this is what the actual axle is

https://www.westbrookcycles.co.uk/formula_rxc-400_rear_hub_repair_kit_(2020)-1869

alwaystimetotorque

OP - you have correctly circled the end caps in your post above. The length of the NDS does look longer on the pic but it's not easy to tell where the inner part of the DS ends as it's hidden by the cassette.

It's quite difficult to diagnose like this though. It would be very unusual for there to be a spacer between the end cap and the bearings.

Have you taken the wheel out and measured the spacing of the hub? is it 142mm? If it is then I'd still take off the end caps to check as it would rule this out. They should just pull off on the rear wheel.

larkim

Will they just pull off? Sadly I don't have the bike with me but I'll get the Uni lad to try that out! (No bearings will fall out will they?)

reaperactual

Plucked this image off the Internet to show what spacers, washers, etc should be included in the assembly. A Bergamont/Formula hub:-



I did have a similar (Kore re-branded) Formula 148x12 Boost thru axle hub.

No pop off end caps and will require cone spanners to remove, (although I did just manage to take mine apart, re-assemble and pre load using a normal spanner and a big Allen key in the end of the hub axle). These hubs are more similar to a pre loading cone and locking nut found on typical loose bearing type hubs. Except these have cartridge bearings as you can see so no balls are going to fall out.

It's possible there could be a spacer/washer missing (or maybe one could be added) but nothing that would have fallen out when your lad took the wheel off.

larkim

Thanks, at least I'm not being dense with missing something obvious! Doubly confused now about the issues. Maybe it's the facing in the caliper bolt mounting points. Will get another look at the bike in a few weeks so will experiment more then if he's not got it sorted.

alwaystimetotorque

larkim said:

Will they just pull off? Sadly I don't have the bike with me but I'll get the Uni lad to try that out! (No bearings will fall out will they?)

Quite often yes - but that diagram shows that the axle ends are threaded so if that is the correct hub then you'll need a cone spanner in each end to take end nuts off as Reaper states above.
Starter for ten is check that you have that hub and then check that you have the parts shown by taking apart. You could still check you have 142mm spacing across the end caps - if you can measure that accurately it should show whether or not there could be a washer missing. It does look from your photo though that the washer is present between the two nuts on the NDS. Part number 8 on the diagram. I can't see the DS clearly enough.

If all of the parts are present then it could be that if that is your hub, that the axle isn't central in the hub shell. It's just a straight axle with no stop anywhere for a guide. The position of the axle relative to the shell is set by the inner lock nuts which pre-load the bearings. It's the hub shell which dictates where the rotor sits.

It could be that the whole axle needs loosening and re-centering. A check would be to take the wheel out and check how if the threads on the nuts from the end of the caps are the same on both sides. It looks from your photo that the wheel is offset to the NDS therefore there should be more thread on the nut on the DS compared to the NDS.
To re-centre you would need to back off the outer nuts (part 9) on each side and then reset the inner nuts (part 12 and 7) to move the axle relative to the hub shell one way or the other.

Have you moved the caliper during any of the attempt to reset? If you haven't and it all worked before the hub was stripped then it looks like the rotor centre line needs to move a couple of mm towards the DS possibly.

reaperactual

No worries. Yes a weird and unusual one for sure.

A good look in person will help if needed then hopefully find the issue and fix. Good luck. 🤞

larkim

alwaystimetotorque said:

larkim said:

Will they just pull off? Sadly I don't have the bike with me but I'll get the Uni lad to try that out! (No bearings will fall out will they?)

Quite often yes - but that diagram shows that the axle ends are threaded so if that is the correct hub then you'll need a cone spanner in each end to take end nuts off as Reaper states above.
Starter for ten is check that you have that hub and then check that you have the parts shown by taking apart. You could still check you have 142mm spacing across the end caps - if you can measure that accurately it should show whether or not there could be a washer missing. It does look from your photo though that the washer is present between the two nuts on the NDS. Part number 8 on the diagram. I can't see the DS clearly enough.

If all of the parts are present then it could be that if that is your hub, that the axle isn't central in the hub shell. It's just a straight axle with no stop anywhere for a guide. The position of the axle relative to the shell is set by the inner lock nuts which pre-load the bearings. It's the hub shell which dictates where the rotor sits.

It could be that the whole axle needs loosening and re-centering. A check would be to take the wheel out and check how if the threads on the nuts from the end of the caps are the same on both sides. It looks from your photo that the wheel is offset to the NDS therefore there should be more thread on the nut on the DS compared to the NDS.
To re-centre you would need to back off the outer nuts (part 9) on each side and then reset the inner nuts (part 12 and 7) to move the axle relative to the hub shell one way or the other.

Have you moved the caliper during any of the attempt to reset? If you haven't and it all worked before the hub was stripped then it looks like the rotor centre line needs to move a couple of mm towards the DS possibly.

Thanks for this. All makes sense. I can't see why, when the bike went in for a freehub replacement, that they'd have touched the basics of the axle, but maybe they did. If it was my bike I'd have no issues with doing a strip down and maybe seeing if the axle body threaded ends were different lengths too (that looks a possibility from the exploded diagram).

reaperactual

Yes, good call! 👏Axle being off centre is a viable possibility. 😎

alwaystimetotorque

They would have had to remove at least on of the outer nuts completely to change the freehub bearing but both would likely have moved in the process of loosening. I would expect that most LBS would have checked all bearings in the hub and they would have removed the axle completely to do this.

larkim

Oh, good insight thanks. I'll suggest to eldest he gets it back to the shop with some helpful narrative. Though as doctors throughout the land would probably attest, no-one likes a customer coming in and saying "I've read on the internet that you might have stuffed this up"!

reaperactual

Been pondering on the off centre axle theory. Honesty the last thing I want to do is muddy the waters as such.

Anything outboard of the nds bearing (providing nothing is missing and fitted in the correct order) would still come out to the same distance. An off centre axle would just protrude past the end cap/over lock nut lengthening the overall 142mm dimension.

On my similar hub the very outer edges of the end caps/over lock nut was the point of contact with the inner dropouts and the hub axle was just inside those outer edges.

Sorry, something to think about or maybe I'm having a brain fart! 😬

larkim

If the centre axle was threaded 5mm on one side and 10mm on the the other, then that would shift the position of the hub body if it was flipped around, surely? Assuming the inner nuts (12 and 7) rest against the non-threaded part of the axle body? There's 127mm (142-10-5 say) of unthreaded bar there, it could either go NDS - 10 - 127 - 5 - DS or NDS - 5 - 127 - 10 - DS which would surely shift the centre point of the hub body?

reaperactual

To my surprise my hub had a floating bearing arrangement much like an external bb and crankset (minus the 'inside nut' #3). The inner end cap/lock nut (#7) was pressed up against the inner bearing race for preload.

I imagine there will be a little threading left over on both sides as not to bottom out on the non threaded section first.

I took it mine apart to investigate play assuming it had to be a worn bearing (even though it was on a new bike) so didn't touch the driveside at all.

larkim

Just to wrap this up, after a long hiatus finally got the bike into a different lbs who sorted it in 24 hours. I wasn't there in person but the word that came back was that "the freehub cones were on backwards". I.e. the original lbs had stuffed up slightly.

Good to finally get sorted and know that the calipers weren't doing something odd.

alwaystimetotorque

Glad you've got it sorted and sounds like the original diagnosis then. Quite an easy mistake to make but very poor from the original LBS really.

larkim

Everyone makes mistakes from time to time. Would have been easier if the fault had been picked up by my son earlier so he could have nipped back into the same shop and get it sorted, but various factors got in the way.

Anyway, on a positive he had a great weekend on the fixed bike touring up the gravel roads of Northumberland via Kielder, Innerleithen, Glentress to Edinbugh and the bike worked like a charm!