Disc Rotor Sometimes Centered, Sometimes Not
 

Do you know why sometimes when I do up my rear thru axle the disc sometimes is perfectly centered and sometimes is more to one side? I can't seem to figure out what I need to do to get it centered again. I only touched the thru axle bolts.

I thought through-axles would help eliminate this kind of thing. I have conventional quick-releases, and this is a frequent occurrence. There seems to be quite a bit of potential slop when using drop-outs. The only suggestion I have is to use a torque-wrench and make sure you get the same (preferably recommended) torque setting each time you put the wheel on.

If it really bugs you, push the pistons all the way back into the calipers before mounting a wheel, and let them reset to the rotor after a few squeezes. If you make sure the slot of the caliper itself is centered on the rotor, I find it makes it more reproducible.

Yes, after some trial and error I found that most times it's perfect, sometimes not. I'm not sure what exactly happens in the case where it's sometimes out of whack and what is causing that. I'm now using a hex key like this: https://images-na.ssl-images-amazon....AC_SL1000_.jpg

I go as tight as it will go without getting aggressive. This is getting me a good result. I have a maxle thru axle with a low max torque specification, so basically if I can't undo it with a mini tool then it's over-torqued.

Why do you need a hex wrench to tighten a Maxle thru axle? I'm not seeing it in my mind.

https://cdn.shopify.com/s/files/1/03...4525_x1024.jpg

Your mind's eye needs glasses.

If yours is the axle pictured, I would use a torque wrench and tighten it to 13.5 Nxm every time (which is a fairly substantial torque, probably more than I could deliver reproducibly with a multi-tool, or possibly even those hex-keys -- I have the same ones).

My bet is that you're flipping your bicycle upside down to install your front wheel. When you do that, sometimes you don't get the axle bottomed on both sides.

It's a through-axle.

So you're ASSUMING that it's seated and I'm GUESSING that it's not. Neither one of us can see what's really going on. The bottom line is that the OP isn't satisfied with how it's working right now.

Getting the disc centered on what? The pads? How much off?

Don't the pads float and center themselves to where the disc is once you actuate the levers a few times?

It's the rear wheel. Why would the bike being upside down make it more difficult to install the wheel correctly?

There is slop in the fitment of the thru axle thru the hub. That's why.

Some people are horrified if you turn a bike upside down. Don't know why. There were a few early hydraulic brake systems that it maybe played heck with air bubbles getting in the lines, but only one or two early ones.

Otherwise, I think it was some people trying to sell bike stands that started the rumor.<grin>

If it is a (non-thru-axle) drop-out, Retro Grouch would be right, in my experience. The only way to reproducibly get a conventional quick-release absolutely positioned reproducibly every time is to weight the bike on the wheel. (The same issue can happen if you do it on a stand -- it isn't the upside-won part per se). With thru-axles, the round hole is symmetric, so it shouldn't matter at all. The only variable (unless you cross-thread it) is the torque.

Taking it in to a shop to see what they say. To the one who said the brake pads would adjust anyway, but then the gearing will be slightly out of whack if the wheel is mounted slightly different, and anyway I don't want to ride the bike if the wheel isn't perfectly mounted.

No my max nm is only 11, and that's probably with dry threads. That means about 7 nm with lubricated threads should be ideal.

So how come just undoing the thru axle and re-tightening it to proper torque, I'm getting rub sometimes?

I think the problem might be your pads, not the wheel, assuming you are replacing the wheel and torqueing the thru axle the same each time. If the caliper isn't centered about the disc, then the pads will retract asymmetrically, and less reproducibly.

To fix this, take the wheel off, pull out the brake pads, push the pistons all the way back into the caliper, put the wheel back on, tighten to exactly 11 Nxm with a torque wrench, then center the slot of the caliper, front and back, over the disc. Only then replace the pads, then pump the brakes to reset them.

When you next take the wheel off, just put it back in and torque it to 11. I think you will find the pads don't rub.

So what do you suggest?

OK. Another question: am I going to have to have the shifting cables and deraileur adjusted after doing that? It seems there's going to be different alignment. What symptoms will I notice if I need to have those adjusted? Noisy chain, or just poor shifting?

And you don't think the axle should be torqued less if the threads are well-lubricated?

Guys working on their cars had tissue with over torque after using anti-seize. The anti-seize they were using gave them 40% more torque at the same torque value.

This is the best plan. You seem to have had a multitude of issues with this part of your bike. Let the shop check it out. If all is well, ask them to demonstrate wheel removal/replacement and follow their lead in the future. :thumb:

Sometimes the manufacturer in their installation instructions or other maintenance doc's will state whether to grease, not grease or even use anti-sieze (which is another form of grease for non-moving parts)

Wipe off the excess grease and torque it to the torque spec. if a greased thread were likely an issue, how probable is it that you are the first person to discover this potential problem, and that your irreproducibility has nothing to do with your decision to deliberately under-torque the thru-axle. You don't tighten it to spec, and the wheel positioning is problematic. The paralysis is striking.

But I agree, maybe you should take it to a bike shop.

What I found is that the disc is too far to one side of the frame when I don't push on the part of the frame at the drive train side. Every time I do up the thru axle without pushing the frame in on that side, it's not centered. It's centered every time, however, when I make sure to push on that part of the frame when I am doing it up. Since the bike was initially set up by a good shop, I'm guessing I should do up the thru axle that way versus adjusting the brake calipers to be centered when doing it up without pushing in that part of the frame.

Have you heard of anything like this?

I've also read:
If I do that without pushing in the part of the frame at my drive side, I'll not get a centered disc, same as if I do it up like that with the bike upside down. In my case the key point is pushing in the frame at the drive side.

Just wondering if this is normal or if I should adjust the disc rotor to be centered without this manoeuvre. Could this be the reason why I get some disc rub when I am cornering when going down hills?

I actually have no idea WTF you are talking about.