disc brake rubbing from flex?
 

I have a 2016 giant tcx, which uses 15f/12r thru axles. I thought this would eliminate rotor rubbing, but I was wrong. when I stand up to put power down on a hill or sprint, the front rotors still rub. it's pretty annoying. curious whether this happens to others.

Hydraulic or mechanical discs?

Hydraulic

160 rotors

I have the same issue on my front brakes. In fact, I have aligned the brake multiple times on the stand, and it wont rub. However, once I go out to the road and apply some power and ride, i start getting a local rub every rotation. The rotor must be a bit out of plane but the weird thing is that it doesn't rub when I stop and spin the wheel without load or weight.

Oh yeah, road discs are half baked. Had endless hassle trying to eliminate rub in the shop... I don't miss that.

The pad gap is too small. And there's nothing you can do about it on hydraulic systems, as far as I know.

Have you checked preload on the hubs?

Only if I have a high spot on the rotor or if I've picked up some grit.

I've had this too. There's usually a sweet spot/angle, but it can take hours to find. I wish the caliper mounting system were better designed for precise adjustment, perhaps with some visual guides.

I've never had a disc rub problem that wasn't caused by new pads being installed. This was easy to fix, and has nothing to do with your situation.

Rotor out of true? Also some rotors are thicker than others. Double check and realign the calipers.

all my rotors are 1.5 mm width, they're as true as i can get them. I suspect caliper angle has something to do with it, but there's no way to really change that on the bike. supposedly, the caliper is the one that's at the right angle, and it's the rotor that's slightly angled

what bothers me more is that when I do hard braking down a steep long hill, the rotors rub continuously until it cools off again. this happens on my ice tech rotors as well. I've tried bleeding it and tending to the pistons. hasn't fixed anything

It just happens with some riders. I've yet to ride a road or gravel frame/fork/brake combo I couldn't induce some brake rub on - Until a few weeks ago I worked for the largest bicycle chain retailer in the Southeast so I've ridden a lot of bikes. Some riders just have positions that angle the whole system enough to get brake rub. I mean, even really stiff bikes aren't that stiff. Grab the wheel on any bike and wrench it around and you'll see the rotor/rim move around quite a bit. When you're on the bike, the entire system moves around so many riders never have rub, but many other do. Happens with rim brakes too but most people never noticed because the pad/rim material is quiet.

If it really bothers you try semi-metallic or resin pads, they'll still rub a bit but you won't hear it unless you're in a situation where you're up at 4+ w/kg but going <10 mph.

find a shop that has one of these.

Not sure what you mean. Are you saying that your caliper isn't perpendicular to the axle (like the plane defined by the disc)? Is the disc actually closer at the bottom of the pads vs the top (or visa versa)?

Also, have you tried the business card trick?

Another thing to check is if the pistons can fully retract

how well build is your carbon fork? no rub whatsoever on my 600g way overbuild Niner fork.

Never had caliper rub ever, on two different bikes, three different forks, two different front rotor sizes, 4 different calipers (everything from basic mechanicals to 4-piston hydraulics,) standard QR axles, and always with rotors much thicker than 1.5mm.

Setting up disc brakes is not difficult. At all. If no amount of tweaking can get it correct, then something is wrong with the fork, caliper, or rotor.

Ive seen forks and frames that needed to be faced, but with the right tools it's not a big deal.

https://www.parktool.com/product/dis...ing-set-dt-5-2

This. I thought my front rotor rub was from the rotor heating up, then it was happening the first time I hit the brakes. Checked closer and the outboard piston wasn't fully retracting. It's getting replaced under warranty.

Well, that's pretty much my point. I assume the OP or his shop had fiddled with the setup, and still couldn't get it right. So why hasn't the shop at the very least suggested some corrective measure?

Brakes aren't supposed to rub, and if all parts are mechanically sound and the contact points are straight and clean, there should be no issues. Something on the OPs bike needs to be addressed-- it's not an outright indicator of the fallibility of disc brakes on bicycles.

Not all bike shops have the right tools for the job, and not all mechanics are really good at their job.

ahh I see. but what if I have post mount adapters? there's no real way to shave those very precisely. but I guess if the fork is slightly crooked, it might help. will look into it.

however, it still doesn't really explain why there is continuous rubbing after steep down hills. I'm not a fred (165 lbs). The pistons are retracting like they should. I did a bleed job very recently so I doubt there's bubbles in the caliper. not sure what else could be going on

The guys I ride with that have Ice-Techs, rub a few secs after hard braking, my SRAM Force & Red brakes are silent
Not a deal breaker, but it's noticeable

If there's continuous rubbing, it sounds to me like the caliper hasn't been aligned properly and it's too close to one side. Try again with the businesss card trick or one of the other centering aids.

Edit: and the word you're looking for is Clyde, not Fred.

Not all bike companies can adopt a new standard without glitches too. Had a bunch of Focus through-axle forks where the rotor rubbed on the damn fork leg!