[Closed] Raidon fork brake caliper always out of alignment

Just to throw another option in there, I've seen a couple of bikes where the hub axle was not concentric to the hub shell. What that meant was that each time the wheel came out and went back in, the rotor was in a slightly different position relative to the caliper.

This is unlikely if all that changed was the fork, but worth eliminating if you can.

Do both pistons move the same at the same time when you pull the lever and release?

Try taking the pads out, cleaning the calliper and resetting the pistons back and try again.

If they do then it may be worth getting the mounts faced.

The usual loosening the bolts, squeezing the lever and re-tightening never works

No, it doesn't!

10 years as a pro mechanic and I stopped trying this after about 3 months. Get a bit of white card and put it behind the calliper. Look through the calliper at the card and you will see where there is a gap between the pads and the rotor and where there isn't. Adjust accordingly. Feeler gauges (like we used to use for spark plugs) may well help. If you spin the wheel, you will see if the rotor is warped or not.

With some mounts, as you tighten the bolt, the calliper moves. If that happens either use a very thin washer or if you are confident a file - it's often just a but of paint on the mount.

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I had a similar issue and assumed it was a bent rotor but a new set of wheels did the same. I just adjust mine by eye now looking through the calliper. It's worth grabbing the calliper firmly and holding it in place while you tighten the bolts a just little bit so you can still just about move the calliper and then adjusting again so it's square to the disc before nipping up.

Oh and make sure you've got one of those concave type washers in.

Do both pistons move the same at the same time when you pull the lever and release?
Try taking the pads out, cleaning the calliper and resetting the pistons back and try again.
If they do then it may be worth getting the mounts faced.

I'll try this at the weekend

Get a bit of white card and put it behind the calliper. Look through the calliper at the card

And this

With some mounts, as you tighten the bolt, the calliper moves. If that happens either use a very thin washer or if you are confident a file – it’s often just a but of paint on the mount.

Do you mean file a bit of paint off the mount on the fork to make the adapter more stable?

Eyeballing/guaging gaps is fine but quite often pistons don't advance at the same rate so you get rotor deflection where one pad engages first then pushes the rotor away against the other pad.
The cause I mostly see is the caliper twisting under bolt torque even with washered bolts..can be mitigated going bit by bit on torquing but still a pain

Scrape any paint off the mounting faces of the fork. This can throw off caliper alignment. Check the mounting faces of the caliper on both sides (i.e. where it contacts the fork and also where the bolts tighten down. If there are burrs, file them down flat with a flat file. Make sure that the washers you are using are flat and don't have any burrs. In my experience, most of these problems are just because the mounting faces aren't flat and the caliper twists when you tighten it.

Most bike ships/mechanics offer a facing service that machines the surfaces that the callipers mount to. This ensures that you’re starting with a surface parallel to the rotor. I did this for free with new brakes, made set up a lot easier.

Don't assume that the discs are perfectly flat either.

Got a Reba that came with brake mounts that were way off perpendicular to the rotor. Did my head in for a while until I twigged and carefully realigned with use of a large flat file (better tools available!). If you really can't get it aligned them worth a check.

Done hundreds, probably thousands of Suntour forks, and it's more likely than not that the mount isn't square to the disc (i'd say around an 80% chance of it).Pull down hard on the stem as you tighten the qr to seat the wheel fully, sight down through caliper from above (a sheet of something white, lit with a torch, as a background helps a lot), check the rotor is straight, and once you've done all of this you'll probably find the caliper to be about 5 degrees from square to the disc. Mounts can be faced if you're not confident, but I usually use a large medium-cut flat file (safe edge towards the disc) vertically across both mounts at the same time. Only a handful of strokes at the correct angle is usually needed to get it square (do it as many times as i've had to, and it'll usually be right first time). Other suggested problems listed above are also a possibillity too, and worth checking, and they're right about "squeeze lever, tighten bolts" not working too, just walk the caliper into place by moving one end a touch, nip the bolt, do the same at the other end until it's right.

So I found a few problems thanks to the advice on this thread

Firstly, the caliper does move when tightening up the bolts - quite a lot - nothing to be done about that but now I'm aware it makes it a bit easier to allow for that

Secondly, a few strokes of a file were indeed needed to correctly align the pads parallel with the rotor - I filed the post mount adapter rather than the fork because I didnt trust myself to get it right the first time, but seems better now and allows me to "walk the caliper" into place as described above

Thirdly, the brakes are aligned at a very specific QR lever tension. If remove and replace the wheel, I have to get the exact same tension in the QR to get back to non-rubbing brakes, so I need to faff for a few minutes applying and removing tension to get the brakes perfect each time I remove the wheel. I guess this is a disadvantage of QRs and an advantage of thru axles, but I didnt notice it as much on the XCR fork that I took off, more on the Raidon.

There we have it. Thanks for the advice, i'm in a better place now than I was before.