Disc brake alignment issues

[old_coyote_pedaller]

Re: Re:

Firstly fit the wheel correctly. The disc rotor attaches to the hub so non central rim is irrelevant to this problem.

Not exactly true when the wheel is having to be aligned to compensate for the incorrect dish, but I get what you mean and this will be corrected.

But are you really compensating for incorrect dish?
Because the wheel isn't dished properly you have aligned the hub in fork dropouts so that the rim/tyre is central between the fork legs? Is that correct?
If that is what you have done, have you thought about where the bottom of tyre is in relation to top? It will be way out to one side and cannot be aligned with rear wheel, interesting handling characteristics there.
As someone else has pointed out the likelihood of the hub moving in dropouts to seat properly once there's repeated load put on it doesn't bear thinking about. The disc will also try to move too and because you have lined caliper up off the square the disc will then jam against pads/caliper. :facepalm:
It would not have even entered my head to do what you have proposed above. It's a very dumb idea.

Get the wheel dished properly and fit it properly in dropouts, only then can you start the process of centreing caliper and disc. The disc is supposed to rotate parallel to pads/pistons in caliper not at an angle. You cannot start to sort the other problem you have with mounting caliper if the disc is at angle due to misaligned wheel in dropouts.

 

[mattr]

I mentioned the doubling of the dish error on the last page i think.......

 

[ishaw]

Re: Re:

Firstly fit the wheel correctly. The disc rotor attaches to the hub so non central rim is irrelevant to this problem.

Not exactly true when the wheel is having to be aligned to compensate for the incorrect dish, but I get what you mean and this will be corrected.

But are you really compensating for incorrect dish?
Because the wheel isn't dished properly you have aligned the hub in fork dropouts so that the rim/tyre is central between the fork legs? Is that correct?
If that is what you have done, have you thought about where the bottom of tyre is in relation to top? It will be way out to one side and cannot be aligned with rear wheel, interesting handling characteristics there.
As someone else has pointed out the likelihood of the hub moving in dropouts to seat properly once there's repeated load put on it doesn't bear thinking about. The disc will also try to move too and because you have lined caliper up off the square the disc will then jam against pads/caliper. :facepalm:
It would not have even entered my head to do what you have proposed above. It's a very dumb idea.

Get the wheel dished properly and fit it properly in dropouts, only then can you start the process of centreing caliper and disc. The disc is supposed to rotate parallel to pads/pistons in caliper not at an angle. You cannot start to sort the other problem you have with mounting caliper if the disc is at angle due to misaligned wheel in dropouts.

It's all true. As it was an xmas present I wanted it to look good when presented so just set the wheel up to look straight. Yes, it's not right at the bottom due to being angles to look central in the forks and will be going to the LBS in about an hour to get them to sort it out so it can be fitted in the forks correctly. I've tried the wheel on another set of forks and it is still out so it's not the forks at fault. I may actually use the other set as they do something to the overall bike look, not quite sure what, but imho it looks better for it. Less adjustment and solo air fox forks, but on this build, looks are probably more important than function. As it is technically not mine now, I will need to refer to the owner of course....

 

[mattr]

TBH, i bought all the tools i needed to build wheels about 20 years ago, for about 40 quid.
They've paid for themselves many times over.

 

[integerspin]

TBH, i bought all the tools i needed to build wheels about 20 years ago, for about 40 quid.
They've paid for themselves many times over.

That was an expensive spoke wrench;=)

 

[02gf74]

Re:

Just curious, how far off centre is the rim?

Have you tried same wheel in another fork or another wheel in same fork to rule out fork or drop out problem? (Im thinking about it but dont see right now how fork can do that when wheel is flipped)

Im sure if i carefully examined my wheels i may find rim offset but if my eye doesnt notice it, then that is well within limits, my eyes are good at spotting that kinda thing.

Also you are using rim as reference not the tyre, right?

 

[mattr]

TBH, i bought all the tools i needed to build wheels about 20 years ago, for about 40 quid.
They've paid for themselves many times over.

That was an expensive spoke wrench;=)

Um, yeah. I prefer using the right (ish) tools for the job. Makes it far easier than turning your bike upside down in the middle of the floor..........

 

[ishaw]

Yes, tried in another set of forks and also reverses the wheel and the wheel is definitely out.

I do have the tools to sort this, jig etc but as I'd paid for the wheel to be sorted as I didn't have the time before xmas, it might as well be corrected. Took it in this afternoon and should have it back tomorrow.

Just need the piston kit to arrive and I can sort the leak out and it's all done.

 

[02gf74]

Re:

The other thing i was going to suggest is to fit an angled shim between the calliper and mount. Make one fom a piece of coke can and fold over about 2mm at one end to give a small angle, may need another under the bolt washer to keep parallelism.

Never tried this but in theory this may work but bear in mind it is the friction of the surfaces generated by clamping it all down that holds the calliper on and this shim is reducing the are due to not being a wedge, will this cause issues i dont know.

If you can file the correcting angle on to two thin washers, then that would be better, you can make thin ones from aluminium which would be easier to file.

In all cases apply loctite to keep bolt from undoing