I’ve been getting a lot of front disc brake judder but only at low speeds. It feels that a rotor slipping through the pads and then being grabbed again. The judder can be quite severe and was feeding back into the sus. forks (it was suggested that the bushing may have worn). Everything’s aligned and I’ve cleaned the rotors. I’ve recently replaced the Rockshox suspension forks with carbon rigids and the judder’s still there (although not quite as bad).

My brake set up is a mix of old Shimano LX and Deore and is totally reliable and powerful enough.

I was beginning to wonder if there was some sort of mismatch between the old Deore callipers and much newer Zee rotors (perhaps the pads catching the rotor arms) so took a closer look at the rotors.

My previous XT rotors were perfectly round with small circular cut outs to save weight. The Zees are wavy rotor with a strange design where by the rotor arms split into 2 before merging into the braking surface below a large triangular cutout; at this point there appears to be noticeably less braking surface for the pads to grip and I’m wondering if this is what I’m feeling at low speeds.

Any thoughts or suggestions appreciated.

What sort of pads and how old are they? That would be the first thing to check and change over. Rotor looks OK but wonder if the surface is scored as well?

Check headset, I’m assuming rotor is straight.

Take the pads out clean check calliper goes in and out smoothly.

Next slacken off brake calliper bolts. Apply brake hard and keep it applied. Do up bolts.

Stil not right? Replace calliper

It won’t be the rotor unless it’s not straight. Any rotor the right size and round will be ok. I have a SRAM rotor on the front XT setup after bending one in Canada. Works fine. Cut outs hole etc make no difference.

I get the same thing with XT rotors on all my bikes.
At slow speeds you can feel the brake pulse with the waves in the rotor.
Can’t feel it at higher speeds though.

If nothing was messed with before it happened then first check is headset and second is pads. My money is on headset. I’m getting the same as the moment and may be headset as it’s seizing up a little if left for a few days (is in a warm place after being out in the wet) which indicates rust/crud and therefore is shot. I’ll give it a rock with front brake on and see if there’s play, bet there is.

It’s not the headset as I’ve had it checked at the LBS. The pads are new but I had the same judder with the previous set; there’s flutter at the end of the fork when it happens (but less so with the new carbon rigids).

The brakes are pretty ancient anyway and certainly on the list for an upgrade to XT when funds allow.

Sounds like a contaminated rotor to me. I had the exact same symptoms, which were resolved by changing the rotor. Try cleaning with isopropyl alcohol or a brake cleaner or swap the rotor.

It sounds very much like you’re just feeling the cutouts in the rotor, I notice it sometimes with my TRP rotors and R685 calipers. It won’t hurt, just get over it or change the rotors if it worries you so much.

Experienced it once before, the rotor wasn’t screwed on tightly enough to the hub, easy/cheap one to test before splashing the cash.

I had this donkeys years ago with a Shimano brake and some random Wavy Rotor – really unnerving.

Switching to a normal rotor fixed it immediately.

It was definitely setting up a resonance at low speed – probably some unlikely combination of peak to peak distance between the waves on the rotor coupled to fork length. god knows but definitely the rotor.

Yeah, I’m having the same symptoms with Magura Storm SL rotor and M615 caliper!

Perhaps not directly applicable to lightweight mtb’s but information as to why brake judder happens here on brakeworld

It’s probably just that because the pads don’t contact the rotor as much aove and below the waves (assuming a wavy rotor that the pad is effectively concave and the pulsing is the high bits passing across the face of the rotor arms.

I’ve had it with Saints and Aztec rotors and the fix was to simply file a chamfer onto the edges back so it doesn’t occur again too soon.

Even fitting new pads won’t cure it permanently as it’ll come back as the pads wear.

HTH

G

A horrible juddering sqwawk just as you roll to a stop means your pads and rotor are contaminated with oil.

Pads in the dishwasher and clean the rotor with alcohol, hot water with detergent or glass cleaner.

I’ve had it with Saints and Aztec

Aztec! I remember now, those were the ones I had issue with too.

I have also experienced some brake judder from rotors with wavy bits on the outer edge or the cut outs inside of the braking surface are within the contact area of the pads.

Perhaps try adjusting the position of your calliper a bit to make sure you’re in the middle of the braking surface of your disc.

mismatch between the old Deore callipers and much newer Zee rotors (perhaps the pads catching the rotor arms)

Some Shimano brakes (Eg 515s) had a deeper pad than the newer brakes (XT 775, Deore 535/596, current gen are similar if not the same, not 100% offhand) so that could be it, depends which Deores you have. Approx 5mm difference in pad depth between generations of Shimano brakes so it’s quite a difference if the rotor wasn’t designed for that pad.

Some wavy rotors just don’t have very consistent surface area in total in contact with the pads at any time, or a mis-match of pad/caliper type and the rotor design, depth etc can create vibration or judder, usually the spars of the rotor contacting a pad that’s deeper than the rotor was designed for. Rotors and calipers aren’t always cross-compatible between years or brands and oddly I don’t remember seeing pad depth recommendatons for aftermarket rotors.

I’m not sure what model the Deore callipers are, but they take the old hook and eye style pads rather than the newer type; perhaps there is a compatibility issue (hopefully still safe to use though).

Something odd has happened to the original image, so I’ll repost it here.

Spent ages with this problem. Got the forks serviced and everything. Then the same started happening on my other bike. Did some more googling and sanded down the brake pads and properly aligned the calipers and hey presto no more judder.

Turns oit i do a lot of comfort braking and don’t notice I’m doing it. It glazed the pads on both bikes and this meant the taller bits of the rotor gripped more than the shorter bits making it judder.

I still comfort brake but make sure i grab a full handful of lever regularly to burn all the crud off.