Disc rubbing when out of the saddle

The spirit of Grav-lo-cross. No but seriously, cyclocross and gravel go here!

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Steve Curtis
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by Steve Curtis

Or just use a couple of bits of card / plastic.

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ms6073
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by ms6073

The Birzman shims work well enough, but Hayes also makes a nice brake pad alignment tool. For Shimano flat mount calipers, if the mounts are properly faced and the pads centered in the caliper, then why wouldn't you simply be able to loosen the mounting bolts, squeeze/hold the brake lever, then alterantely torque the mounting bolts? Problem is with flat mount calipers, as I mentioned earlier, if the mounting surface is not faced properly, then the caliper will be a lot more difficult to get aligned.
- Michael
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Loukas
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by Loukas

I have spent more time fine tuning the brake system on this gravel bike than on any other bike (I've had many), and still...., that's why I asked for tips
I use a Birzman shim like tool for centering, so I was on the right track there
I am going out for a ride tomorrow, let's see if the super careful centering and add'l torque to the axle helps
thanks!

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ryanw
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by ryanw

Air in system not allowing pistons to retract fully.
Even with warped rotors, if the system in bled correct and the calliper is moderately centred, you'll be fine since they'll be enough clearance each side due to the fully retracted pistons.

Obviously make sure rotor is not badly warped, but you should just be able to align the calliper by applying brake with loose mounting bolts and tightening up.

Putting credit cards or whatever won't help if the system isn't bled properly and pistons not retracting efficiently.
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Loukas
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by Loukas

I've tighten up the Axle a bit more (14 Nm) and it has improved. I still get some noise from time to time, but most of it is gone!

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ryanw
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by ryanw

Way too tight. You're trying to solve a problem using the incorrect methods.
Do it right or don't do it at all.
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MattMay
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by MattMay

Wait, if when you replace your gravel wheel with your road wheel the problem disappears, doesn’t that mean the problem is most likely with the wheel (hub, rotor, rim flex, etc) rather than calipers and forks?

And you said you put a new rotor on, right?

Did you inspect the hub carefully? Maybe some micro play that is compounded when you’re adding weight and torsional force when standing?

Spitballing but...

ghostinthemachine
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by ghostinthemachine

MattMay wrote:
Wed Dec 30, 2020 7:56 pm
Wait, if when you replace your gravel wheel with your road wheel the problem disappears, doesn’t that mean the problem is most likely with the wheel (hub, rotor, rim flex, etc) rather than calipers and forks?
All it means is that the caliper is centred "better" on the road wheel than the gravel wheel, equal clearances on both sides. (the discs will almost certainly be in different places, or if the OP is recentring the caliper for the new disc positiion, there is some feature between caliper and mount allowing a cleaner position on one than the other, paint, suface damage, etc)

The fractions of a mm you'd need to move the disc to get it to rub (if clearances are equal/correct) would require enough clearance (or flex) in the system that you'd be able to feel it at the rim.

I'd just be cleaing up the piston/seals/bores (clean and lube) making sure the mounting faces (caliper/flat mount) are set up correctly (no burrs, marks, paint debris etc etc) and doing a clean install.

All that 14Nm does is pull the fork legs tighter against the endcaps and minimise the (miniscule) amunt of flex, and i don't think that is the issue, or you'd have rubbing on both wheels.

Loukas
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by Loukas

I agree, over-torquing the axle works but doesn't address the root cause.... it just works for now

After all the testing and with all the ideas you've brought here, I believe the root cause might be with the Hub, even if this is a brand new DT 240 with 1000 km...., I will service it and see....

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ryanw
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by ryanw

It's air in the system and /or a badly centred caliper.
Please listen to people who build bikes.
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Loukas
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by Loukas

Thanks Ryanw..., I hear you .... and btw, your bikes look awesome :)

Re. air in the system, bike is new (1000km) and I don't feel the brake lever 'spongy' or experience longer lever travel...., do you still think that's a possibility?
On Centered Caliper, I believe that's a relatively easy task..., I have and have had several disk bikes and that was never a problem for me.
Last edited by Loukas on Fri Jan 01, 2021 7:35 am, edited 1 time in total.

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ms6073
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by ms6073

I suggest giving this a try:

1. Loosen mounting bolts of efected caliper.
2. Squeeze and hold, alternately clamp the brake lever for applicable caliper.
3. Alternating bolts, apply torque until caliper bolts are tightened.
4. Release brake lever and inspect caliper alignment.

Now if the caliper has not remained centered over the rotor, then that suggests the mounting surface is more than likely not properly faced as the canted surface forces the caliper out of alignment as torque is applied.
- Michael
"People should stop expecting normal from me... seriously, we all know it's never going to happen"

fignonsbarber
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by fignonsbarber

OP,
I highly recommend this tool. Spin the wheel slowly and mark where its rubbing. Use the truing slot until rotor spins without rubbing:

https://pedros.com/products/tools/gener ... sc-wrench/

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MattMay
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by MattMay

Rubbing occurs only when OP is peddling out of the saddle, not when he’s seated or bike is in the stand. Note the thread title!

Loukas
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by Loukas

Final update on this issue so someone else can use the experience

After all the testing, it was clear to me that the disc rubbing stopped with higher torque at the axle. I used 14 Nm even if the axle spec was 10 Nm, so I purchased a new axle with a higher torque spec. I bought the standard DT Swiss one, which have a 15 to 20 Nm spec...., I'm tightening now at 17 Nm and issues are gone

thanks for all the advise!

by Weenie


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