New bike, problem with front GRX hydraulic disc brake rubbing

21 replies · 11,204 views

KrKAlex
45 posts
#1Mar 6, 2020, 6:09 AM
Hi everybody,

So I received my new bike from Canyon at the beginning of the week. It is a Grail AL 7.0 2020. Since then, I mounted it but I noticed a problem on the front brake. It is rubbing against the disc. I tried to align it by losing the screws holding the mount, holding the brake and tightening it. A few times. But still, it rubs (not the whole perimeter). I tried also to push back the pistons taking out the pads, pushing the pistons back with a tyre lever. But it still does not work. Do you guys have any recommendations on how to tackle this problem? I watched every single video I could find on the topic on the internet, as well as read the dealer's manual from Shimano but couldn't find any solution.
Maybe the disc is slightly tilted and I should untilt it? But I thought the space between the pads and the disc would be larger, but it is also very tight at my rear brakes but it does not rub.

Many thanks in advance for your help.
Alex
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PMC
26 posts
#2Mar 6, 2020, 7:36 AM
It sounds like your forks flat mount isn’t perfectly aligned and needs to be faced. I’d see about finding a shop that can do it for you as the tools to do this are not cheap. This same issue happened on my wife’s Cutthroat and they just swapped the fork as they had another one they hadn’t built up yet.

other option- call canyon and see if they’ll warranty it and send you a replacement.
shimming it seems like the wrong path but that’s me.
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KrKAlex
45 posts
#3Mar 6, 2020, 9:36 AM
Hi PMC, many thanks for your help. In fact, I live in Munich, Germany, but my German is not perfect. I went to one workshop close to my place, told them my problem and they told me that they won't touch my bike because of warranty concerns. I will then contact Canyon again, maybe they have a tracking of the QC and checked carefully this point. I will keep you informed, thank you for the hint it brings back some hope.
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jfranci3
126 posts
#4Mar 6, 2020, 11:24 AM
You need to jam the pads back in. The calipers 'self center' the pads, but they don't center, they just both retract equally. They will walk over to one side or another. With everything on the bike, you can put jam something between the side making contact and the rotor.
Something like this works too - https://amzn.to/2TIRLdz or https://amzn.to/2VOJRSE
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jfranci3
126 posts
#5Mar 6, 2020, 11:25 AM
jfranci3 wrote:You need to jam the pads back in. The calipers 'self center' the pads, but they don't center, they just both retract equally. They will walk over to one side or another.
With everything on the bike, you can put jam something between the side making contact and the rotor. A business card or bit of sheet metal works too
Something like this works too - https://amzn.to/2TIRLdz or https://amzn.to/2VOJRSE
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Curtis
37 posts
#6Mar 6, 2020, 1:10 PM
Is there a possibility that the rotor is not perfectly flat and has a bend in it?
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KrKAlex
45 posts
#7Mar 6, 2020, 3:20 PMedited
jfranci3 wrote:You need to jam the pads back in. The calipers 'self center' the pads, but they don't center, they just both retract equally. They will walk over to one side or another. With everything on the bike, you can put jam something between the side making contact and the rotor.
Something like this works too - https://amzn.to/2TIRLdz or https://amzn.to/2VOJRSE

I am not sure to understand. What I see on my bike, is that on my front brake, the right piston is the one moving, the left one is not moving back and forth that much. But it is the left one rubbing (the one almost not moving). Whereas on my rear brakes, both pads seem to have the same travelling distance.
However, it could be that this impression is given by the fact that the front rotor is close to the left piston so there is already a resistance which explain the lower travellling distance.
Another fact: when I take out the pads in order to push back the pistons on the front one, they are not symmetrical at all. The left one is way more pulled out than the right one. Is it normal? I could not find this information for flat mount RX400

Many tanks to all of you for your help.
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KrKAlex
45 posts
#8Mar 6, 2020, 3:21 PM
Curtis wrote:Is there a possibility that the rotor is not perfectly flat and has a bend in it?

I do not see it with the eyes, it is never 100% flat, but you see no movement compared to what a non-flat rotor is usually.
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ljsmith
762 posts
#9Mar 6, 2020, 5:20 PM
Get one of these Hayes Disc brake alignment tool. They make centering the disc in the caliper very easy. I didn't realize I needed this until I tried it.

https://www.amazon.com/Hayes-Brake-Rotor-Alignment-Tool/dp/B002SQTRXK/ref=asc_df_B002SQTRXK/?tag=hyprod-20&linkCode=df0&hvadid=312049103272&hvpos=&hvnetw=g&hvrand=7369794058499787371&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9007918&hvtargid=aud-801381245258😋la-570331456525&psc=1&tag=&ref=&adgrpid=62837065100&hvpone=&hvptwo=&hvadid=312049103272&hvpos=&hvnetw=g&hvrand=7369794058499787371&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9007918&hvtargid=aud-801381245258😋la-570331456525

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knl2stl
68 posts
#10Mar 7, 2020, 2:52 PMedited
Two things, well actually three.

First, don't push the pistons back without the pads in. You don't want to damage them or the seals.

Secondly, don't center the pads over the rotor, center the caliper over the rotor. Push the pads back, center the caliper over the rotor, tighten down a bit so nothing moves, pull lever and hold and then tighten to spec. Or just eye ball the gap and tighten down before pulling lever.

Thirdly, it sounds like your main issue is that your left piston is lazy. I would start with retracking the pads, taking them out, trying to lube the edges of the piston and seal with a little shimano brake mineral oil, cleaning it up well, putting the pads back in, and then:

1. Grab the rotor (use a clean rag so oil from your hands does not get on your rotor) and flex it slightly toward the pad that is rubbing.

2. Keep the rotor in that position while the helper pumps the lever a couple of times. You need to make sure you have a firm grasp on the rotor.

3. Let go of the rotor and check the pad position.

Just get that left pad moving better. Might even be able to try it first without lubbing up the piston.

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KrKAlex
45 posts
#11Mar 9, 2020, 10:37 AM
Thank you guys for your answer. I noticed that also my rear is slightly rubbing, but I guess it is normal when the pads are brand new.

@knl2stl the bike is brand new, so are the components. I would be surprise to have a lazy piston..
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knl2stl
68 posts
#12Mar 9, 2020, 11:23 AMedited
Rubbing on new pads is not normal for new hydros that have been properly set up. (It could be possible that there is a bit too much brake fluid in the system but not likely if no shop ever bleed them.)

New brakes are just as subject to lazy pistons as are used ones. If your caliper is centered over the rotor and your pistons are not retracking the same, then one is lazy. (Again, that would be if your caliper in centered and the air gap between the pads and rotor are the same.)

Do you have much ride time yet? The brakes just might need some use. If you have not bed the pads in yet, maybe do that and then check the brakes again.
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KrKAlex
45 posts
#13Mar 10, 2020, 7:58 AMedited
@knl2stl Yes, this is what I think too. I expect my bike to be "ready to ride", even more from canyon.
Indeed, my left piston is "more out" than the right one in front, and it seems that the right one is the one pushing the rotor to the other pad and pressing it.
I have never ridden the bike. When I received it, I mounted the wheels and screwed the dropbar. Then I heard this rotor rubbing so I never went out with it. I prefer to solve the problem before doing anyhting, otherwise Canyon might say that I damaged the bike myself. (I tried to go to workshops, they all told me to see with Canyon first as I have never ridden the bike. Because if they make a mistake then it's legally their fault apparently).
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CasualGravel
51 posts
#14Mar 11, 2020, 8:08 AM
KrKAlex wrote:
@knl2stl Yes, this is what I think too. I expect my bike to be "ready to ride", even more from canyon.
Indeed, my left piston is "more out" than the right one in front, and it seems that the right one is the one pushing the rotor to the other pad and pressing it.
I have never ridden the bike. When I received it, I mounted the wheels and screwed the dropbar. Then I heard this rotor rubbing so I never went out with it. I prefer to solve the problem before doing anyhting, otherwise Canyon might say that I damaged the bike myself. (I tried to go to workshops, they all told me to see with Canyon first as I have never ridden the bike. Because if they make a mistake then it's legally their fault apparently).

I had a similar problem with some used Shimano 105 hydro brakes and it turned out it was a lazy piston. Your bike is new, so it probably doesn't need to be cleaned, but you can still push the left piston back in and try it again. It could have also been that the lever was pulled without having a wheel in, so the piston was pushed out that far prior to wheel installation.... which is probably more likely.

I'm not sure why the previous poster said you need to keep your brake pads to push a piston back in, because that is not the case. Even the Park Tools guys (which are the holy grail of bike repair) push them back in without pads and without damage. Here is what I would do:

Remove the wheel
Remove the brake pads
Use a plastic brake lever to gently push both pistons back in
Re-install the brake pads
Re-install the wheel (Don't pull the brake levers yet!)
Loosen the bolts that hold the brake caliper on your frame so it wiggles a little from side to side
Pull the brake lever and hold it
While holding the brake lever, tighten the bolts.

With any luck, you'll have no rub and your caliper will be centered!

Here's the video from Park Tool on cleaning Hydraulic brakes, where it shows how they push the piston back in

https://www.youtube.com/watch?v=vQXFFgRButo

Good luck!

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CasualGravel
51 posts
#15Mar 11, 2020, 8:11 AM
Also, here's the Park Tool video on centering your brake caliper!

https://www.youtube.com/watch?v=uk_nC9anQcM
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KrKAlex
45 posts
#16Mar 11, 2020, 8:58 AMedited
Thank you @CasualGravel for your answer.
I was aware of the videos from ParkTool, and most of the time I rely on their work for my bike maintenance.
Indeed, while assembling the bike, I pushed the lever without the wheel on. I pushed back the pistons and so on but could it be that my mistake damaged the brakes? I didn't press hard, I wanted to catch my bike back which was falling.
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CasualGravel
51 posts
#17Mar 11, 2020, 9:12 AM
KrKAlex wrote:
Thank you @CasualGravel for your answer.
I was aware of the videos from ParkTool, and most of the time I rely on their work for my bike maintenance.
Indeed, while assembling the bike, I pushed the lever without the wheel on. I pushed back the pistons and so on but could it be that my mistake damaged the brakes? I didn't press hard, I wanted to catch my bike back which was falling.

I doubt you damaged the brakes. You would have to keep pumping them enough to have the pistons pop out... but it does explain the brake rub!

Make sure the pistons are pushed all the way back in and do the alignment in that video and I think you'll be good to go. All else fails, a bike shop should be able to sort this out quickly.
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KrKAlex
45 posts
#18Mar 11, 2020, 10:02 AM
Hmm yes, I see. I did it but it is still rubbing. As it is the first time I have hydraulic brakes, I prefer to see with a workshop even though it is hard to find someone who wants to work on a new bike where I live because they are all afraid ot damage it and that I sue them in law. Maybe because I am not German and I live in Germany, who knows. I will see tonight and will keep you informed.
Many thanks!
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KrKAlex
45 posts
#19Mar 12, 2020, 4:11 AM
So, yesterday I went to a bike shop where they spoke English. The technician centered the caliper again, there is a small rubbing, he said it was normal and I should drive for 100 - 150 km and if the problem remains to come to them again.
He looked confident, I asked if there was no more serious problem such as fork alignment that jfranci3 raised on this post, he said no. Let's hope 🙂.
Thank you all!
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edh
29 posts
#20Mar 13, 2020, 11:48 AM
I had same issue (minor rubbing front brake) with 2020 Grail. I talked to the folks at Canyon at showroom and they said ride it and it should go away. It did after first longer ride. Maybe not helpful to original poster but might be re-assuring to others. Aside: I love my Grail.
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