Calliper alignment woes

I’m increasingly convinced that the greatest lie the devil ever told was “loosen the calliper, squeeze the brake tight, tighten the calliper”.

New Deore calliper/lever assembly; new rotor; new pads. Rotor on wheel, brake on bike, try to centre it. Can I? Can I bollocks.

My usual approach is the above, with the added usage of a brake spacing tool; on my gravel bike, if it centres around the spacer, it should be fine without it. On this… no amount of eyeballing or aligning can get me a non-scraping rotation. Not constant scraping – just the odd rub. Looking at it, it looks like the rotor is t quite straight, and I’ve been told before that even new rotors can need truing. Fitted the rotor to the wheel by tightening each bolt evenly, to the same torque.

So: what am I missing? Other than being about to give my LBS some money to just sort it.

(Front wheel, btw. Rear wheel just worked, after a few passes.)

Odd rub = bent rotor slightly. Rotate it slowly to find the rub spot, gently bend it straight by hand. Realign caliper by eye.

True the rotor

Fully retract pads

Centre caliper split line on rotor

Carefully tighten bolts so caliper doesn’t walk

Apply brake a few times

If that doesn’t work you may have a sticky piston

With the bike in a stand put a piece of white paper on the floor towards the centre of the bike and then look  down through the calliper at the paper. You’ll easily see the white paper, highlighting the gap and be able to tell what the gap is like, adjust by eye until the gap is the same both sides and tighten very slowly as the calliper often moves while tightening up. For trueing, spin the wheel while looking through and you can see if it’s true, you’ll need a trueing tool of some description to very gently apply pressure in what ever direction is necessary. If it’s just a feint rub put your ear against the frame and turn the wheel, you’ll hear exactly where the rub is.

I fitted new discs last night and had to true both slightly. It’s pretty much par for the course 🤷‍♂️

I use my Knipex plier wrench.

Get the caliper and disc centred using the normal process.

Eyeball the caliper and pad and slowly rotate the wheel to see where it rubs.

Use the adjustable spanner/tool of your choice to bend the rotor away from the direction of the rub.

Check for rub, and repeat if needed.

Very easy and no need to pay a shop to do it!

Ordered a truing tool, will give this another crack tomorrow. Thanks all.

I thought this would be about flat mount, which is indeed the devil’s work. But as you say Deore, it must be good old post mount.

I’m increasingly convinced that the greatest lie the devil ever told was “loosen the calliper, squeeze the brake tight, tighten the calliper”.

Has this ever worked for anyone? It’s never worked for me.

Has this ever worked for anyone? It’s never worked for me.

With the little shim tool, yes.

Disc brake spacers

I was having similar woes, assumed a new disc would be expensive… Finally ordered a new one from chain reaction. £2.99 !!

For truing I like to make a wee runout tester. Basically attach whatever you can find into the caliper mount hole- usually I’ll find an old adaptor that fits in, and try and get it so that there’s a bolt hole over the disc face, then use that as an adjustable gauge. It’s a wee bit of faff to set up, and harder with PM, but makes getting a perfectly true rotor dead easy, especially as you can more easily see if there’s twist instead of lateral runout.

sharkattack
Full Member

Has this ever worked for anyone? It’s never worked for me.

For me it usually either works, or gets you close enough that a minor adjustment is really easy. I find it helps to do a wee back-and-forth of the wheel before tightening, just to make sure everything’s moved around and nice and sorted, and then tighten slowly and in steps. That said, I wouldn’t usually bother if it’s got ****ing awful trialign spacers. “We’ve added an extra alignment that can be wrong, for no benefit whatsoever. No need to thank us”. Or those stacky PM mount adaptors where it’s all held together with a single bolt, don’t like those either.

Has this ever worked for anyone? It’s never worked for me.

it only ever works once you’ve got the rotor true first!

seems to be a necessary evil and why i went back to single piece rotors.  Floating rotors are never true and i found them to be an absolute bugger to true as I always seemed to fighting the float.  True on the stand then fairly quickly it seemed to “float” back to out of true.

one piece rotors are far easier to live with IMHO

With the bike in a stand put a piece of white paper on the floor towards the centre of the bike and then look down through the calliper at the paper.

I use that method but with a torch, it’s probably a lot easier especially with brakes that run close.

I use that method but with a torch, it’s probably a lot easier especially with brakes that run close.

Nah, paper is far easier, torch from behind the calliper a) needs holding so you can’t use two hands for holding the calliper in place and simultaneously tightening the bolt and b) shines in your face so you can’t see anything. Paper on the floor works every time.

Of you’ve got a new disc, caliper, lever etc and using a brake shim and it’s still not right then maybe something else is wrong.

As your tightening it, is something pulling it out of line? Wrong bolts, wrong adapter, shims or simply the surface on the frame or fork is out and needs facing?

Before you spend money on other bits and bend a new straight disc, go visit your local bike shop.

@scotroutes yep, on my flat mount brakes, stick the spacing tool in, tighten it up, job’s a good-un. As everyone says, the key is that the rotor’s true, and clearly my front rotor isn’t. (Or… the axle isn’t? But I doubt that). So no amount of spacing will help there.

@damascus all good points – I’ve had LBSes remind me that not all rotors are true from new, hence thinking about truing it. The one thing I did wonder if it was skewing it is the little locking washers – the figure-eight shaped things – that might interfere with bolts unevenly, making the rotor not pushed down properly. (I never used these on my gravel bike, but this MTB brake came with them). Bolts are the ones I was using on the previous brakes, also Shimano.

The rotor very clearly wavers a little when viewed from above, which lines up with the sound it’s making, hence me thinking about truing.

1st true the rotor by hand or with a small adjustable spanner – it does not need much pressure then, once true retract the pads fully and centre the caliper. Then using the white paper or a torch shining across the floor under the bike you can look through the caliper and ensure the pads are set with the correct gap. This is how I set my brakes up.

As your tightening it, is something pulling it out of line? Wrong bolts, wrong adapter, shims or simply the surface on the frame or fork is out and needs facing?

In the past I’ve had hubs that were obviously out of tolerance, and warped the disc when it was tightened. Very thin shim washers behind the disc on a couple of holes worked in the end.

Tbh, it only needs the disc to be out by less than 0.5mm for it to make a difference. A very  little tweak of the rotor is often all that is needed.