Rotor warped, or caliper misaligned?

I have an IS to post adapter on the front and I’ve got a bit of rotor rub going on. I can see a spot through the caliper where the rotor deviates when I spin the wheel.

I’ve tried aligning the caliper (loosened the adapter screw first, spun the wheel, braked, and then tightened the adapter bolts, repeated the steps for the caliper bolt), but the rub persists. I can only assume the rotor may have warped, but I’m not sure how. I’ve never crashed it, it’s not been mishandled, and it was a new Hope rotor when I bought it.

Is it possible it has warped under normal use? It is a 180mm rotor on a rigid fork, and I am less than 65kg even on a bad day. I’m going to take the wheel out and use the bleed block to space the pads out and try realigning it again, but is there a simpler way to identify what my problem could be please?

it’ll be the rotor

work out where it’s bent and use an adjustable spanner to bend it back (go steady, though you do have to overshoot a bit to allow for spring-back)

(I assume the rotor bolts are all tight?)

Cheers. Reckon it’s just duff rotors? I switch wheels (and rotors) between this bike and another one with 180mm rotors, so I could just start using the same rotor on both of them.

Bit annoyed because I paid a bit extra for the Hopes in the hope they’d be less likely to mess up 🙁

rotors do bend a bit; switching wheels, shoving them in the car boot etc can all do it

(the rub is often irritating but rarely actually important IME – spin the wheel and I bet there’ll be little or no deceleration as a result, and that’s without your weight adding to the momentum. I’m not saying ignore it, but don’t fret about it (mine “ting” a bit most of the time))

Try taking the rotor off and putting it on a flat surface like a kitchen worktop, you should see quite quickly if it is bent. Also worth checking there is no grit between the rotor and the wheel. Lastly, when you refit the rotor tighten the bolts in a star formation and do them finger tight all the way around then tighten properly. Should make sure the rotor sites nice and square on the wheel.

I have found you need to make sure the Pistons are central when you fit a caliper and make sure they push evenly on to the rotor. If not one side pushes on to the other and bends the rotor across when braking. The adjustable spanner is how I straighten them.

Sound like a bent rotor. Easy to check. I use one of these to set my calipers up on my Xo trails.
Very easy and good results.

I straighten mine with an adjustable spanner – worth cleaning the spanner jaws with white spirit or similar first to avoid contaminating the rotor

More likely to have taken a knock than warping but either or is quite possible under any sort of use.

As above, carefully have a go at straightening it. Make sure whatever you use to straighten it is clean and grease/oil free!

Tip for everyone above talking about truing the disc, don’t grab the braking surface with the adjustable spanner when truing the rotor, grab the closest spoke and tweak that. You get a much better result because you don’t put a local distortion into the braking surface. Also you don’t need to worry about oil and grease contamination nearly so much.

I managed to true (for the most part) a pretty warped rotor using the adjustable spanner technique recently. Stick a clean rag between the spanner and the rotor to keep it grease free and rinse down and wipe with isoproyl alcohol to clean if you’re worried.

As advised above, it’s worth checking that your pistons are central as well. There’s a video for this on Hope’s youtube channel. It also works for some Shimano brakes.

With IS-to-post, you can basically turn it into a little disc truing gauge, which makes straightening rotors easy. Remove the caliper and remove one of the 2 bolts that holds the adaptor to the fork, and loosen the other. Now rotate the adaptor so that the empty bolt hole is over the braking track of the disc. Tighten it back up to keep it in place, then thread the other bolt back through til it almost touches the disc. Now spin the wheel, and very gradually thread the bolt in further- it’ll touch in some places but not others and show you where the warp is.

“‘ve tried aligning the caliper (loosened the adapter screw first, spun the wheel, braked, and then tightened the adapter bolts, repeated the steps for the caliper bolt)”

once you have the rotor straight – get your pistons pushed all the way back intothe caliper and set the caliper up STRAIGHT by eye to the lines machined into the caliper for this very purpose.

might rub a little initially but now that your pistons are pushing paralel to the disk your brakes will improve.

OP you mention that you haven’t had any crashes or mishandling. From my experience I suggest something to consider and eliminate from the equation before focussing fully on rotor truing and caliper alignment is the wheel bearings. Check that there is no lateral play in the wheel bearings. Evan a small amount of wheel bearing play will make it look like the rotor and caliper are out of alignment, and you will spend hours fiddling with them without realising that it was the wheel bearings making the wheel spin out of true and causing rotor rub.

While it’s on the bike grab the wheel tyre/rim and see if there is much lateral play which is enough to move the rotor within the caliper and cause rubbing. Definitely worth a try if only to eliminate this possibility.

Interesting. I use the wheel on another bike with a different size rotor and it spins freely which makes me thing it’s the rotor or the brake on the SS.

I have a second rotor which I can try first. I’ll try that. Thanks for all the tips so far!

Aligning I do the trick of push pistons back, loosen bolts, stick a piece of thin card between rotor and pad each side, pump brake a couple of times, and hold/fix lever to lock the brake on, then tighten the bolts. Generally works.

If you’ve got Avid’s old style CPS washer thingies the whole process is more faff and may take several attempts. For some reason Avid thought it makes alignment easier, but I find it’s worse. Thankfully they’ve finally ditched them.

Anyway, as said, sometimes the rotor is a little bent. Long nosed pliers or adjustable spanner with rotor surface wrapped with clean cloth and just go round carefully bending one bit, spin, bend another, spin, until it stops rubbing.

Other thing is it might be catching just a little with new pads when spinning the wheel, but go ride and it goes away as you use it.

My rear rotor has always been slightly kinked in one spot. My pistons are centred, my pads brand new, my rotor never hit or ‘knocked’, but have tried several times to straighten the kink with no luck. It always comes back!

Is it possible to simply have a rotor with a manufacturing fault? A poor pressing? For me, it’s only a slight kink, and slackening off the bite point a little works well enough.

GBR.

By the way… do tools like the one in the picture shown, really work?

GBR.

Or simply…