Hey all,

I’ve recently got sram level TL brakes and shimano ice tech disks, 180/160.

All new parts, the rear 160 is fine but the front can give a pulsing sensation under heavy braking, feels a bit like ABS on a car of that makes sense but it sends a bit of judder through the handlebars.

Everything works fine and looks true etc. But it’s a bit annoying and disconcerting.

I’m thinking the sram calipers don’t like the larger shimano disk, possibly due to the shape of the disk/pad contact area, as the sram equivalent is more circular but the ice tech have a more wavey profile.

Either that or somethings worked loose, admittedly I haven’t checked the bolts on the disk or the caliper adaptor since fitting.

Any ideas? , thanks.

I had this recently. I tried a few things….

Check that the caliper is totally straight. If it’s slightly off, but the pad isn’t rubbing, when you apply the breaks the pressure will he inconsistent.

Obviously check caliper and disc bolts and fixings.

Is the disc a bit warped? That can cause pulsing.

Bushings in the forks ok? If there’s even a little movement between the stanchions and lowers it could manifest as juddering/pulsing.

Try different rotors. Mine turned out to be a mix of point one, and the fact I was running hope floating rotors. The washers/eyelets where the disc and spider are attached were running very close to the caliper mount/adaptor, and when pressure was applied they were just rubbing.

Warped disc? There’s a bit of float in them, if you tighten them down anti/clock wise rather than at opposites it can put them out.

Thanks, may have answered my own question, the disk looks true eyeballing it when it’s spinning.

Think I need to check disk and caliper adaptor bolt tensions and check the caliper/pad is aligned to the disk.

Fox 32 fork?

No epixon 120mm fork, it was fine before I upgraded the brakes and the disk size.

Fairly sure it’s a brake tuning issue.

Ignore . I just reread the post, this post was not relevant.

Is the caliper centred. If it grips to one side first it could bend the disc slightly. Might this cause uneven pressure and a pulsing effect?

It’s possible, I understand that concept.. But with them being so new I’ve been applying front and back brakes equally, with putting a lot more force on the front to shave speed off if going in a downward direction.

The back brake is fine and will break steadily and lock the back wheel up smoothly without much effort.

Maybe the front just needs more bedding in.

What about, the shape of the sram pads and position of sram calipers on the shimano disc shape cause pressure variance, which you feel as the pulsing?

I had this problem with a front ice tech rotor.

It looked ok but thought it might be warped so replaced the it with a new ice tech one. Same problem.

Happened with both XT and Saint brakes.

Replaced the rotor with an Uberbike one, no more problems,

Could be a few things, you are on the right lines with alignment of caliper and bolt tightness, these would be the first areas i looked at. The other things it could be are contamination of the pads and/or air in the system.

If the alignment and bolt tightness does not resolve the issue i’d be looking to bleed the brake then check it is bedded in right, there was a Park tools tech Tuesday video on how best to bed in your brakes not that long ago that gives a great example of how best to do it.

Good luck.