Rotor rub when out of saddle

mtbrider123

Hi Guys,

I have a disc brake road bike but I think that you’re (mtb group) the best people to ask for some help. So my front rotor keeps on rubbing when I’m out of the saddle. This happens only when I lean my bike to the right. The calliper alligneremo has been checked by myself and lots of other riders + mechanics, everything is aligned properly, the disc is in the middle. Does anyone know what might be causing this, and how to solve it?

Thanks

JBA

Flex in the forks maybe.
Have you checked your qr is tight and that the wheel isn't moving slightly in the forks?

JGTR

Flex, it’s normal.

imafatman

Could also be wheels flexing. are all your front spokes correctly tensioned?

cooldad

Rotors are attached to the hubs, so wheel flex won't effect the brakes.

mtbrider123

JBA wrote:

Flex in the forks maybe.
Have you checked your qr is tight and that the wheel isn't moving slightly in the forks?

Yes, the qr is very tight. It didn’t happen before, started doing that 2 weeks ago.

mtbrider123

JGTR wrote:

Flex, it’s normal.

I don’t think so as it didn’t do that before. Wheel flex happens towards the edges of the rim, but the shouldn’t be any flex at the hub (that’s where the rotor attaches)

mtbrider123

imafatman wrote:

Could also be wheels flexing. are all your front spokes correctly tensioned?

It’s not wheel flex as I’ve said before (responded to another person). Hmmm, I’ll ask the bike shop to check the spike tension, even though the tension seems fine on all the spokes, nothing loose.

mtbrider123

cooldad wrote:

Rotors are attached to the hubs, so wheel flex won't effect the brakes.

Exactly, so maybe spoke tension? Can a slightly loose spike cause this? By slightly I mean, not that you can feel with you hands. Hmmm, if it was the spoke, wouldn’t the wheel move side to side (but it doesn’t do that, it’s straight) ?

The Rookie

3 causes usually
1/ axle loose in fork/frame allowing the hub to move (tighten up qr/nuts/through axle)
2/ hub loose on axle allowing the hub to move (sort the wheel bearings, if cup and cone may need adjusting)
3/ pads loose enough in calliper to move and lightly touch the disc (suck it up......)

figbat

You acknowledge that it isn’t the wheel flexing, then ask about spoke tension? The disc is attached directly to the hub; the spokes and rim are not going to influence how the hub and disc move (within reason).

The Rookie has outlined the things that can physically effect the pad-disc interface. Maybe now your pads are running closer to the disc than before? Perhaps the calliper/pistons need a clean? Maybe the disc is warped? Is the disc mounted tightly? Maybe the fork is flexing.

kajjal

Another less likely thing to check is there may be too much fluid in the brake causing the pad clearance to be very tight. This leads to excess rubbing.

I had this on one bike, solved by removing wheel, undoing the port on the brake leaver , gently and slowly pushing pads back with large flat screw driver while wife with kitchen roll mopped up the brake fluid that was released, while pads held back wife screwed port cover back in. After that much better, no rubbing and brakes worked fine.

A normal symptom of this is it can be hard to get the wheel in without the pads rubbing or the clearance is extremely tight compared to the other wheel / brake.

figbat

Yep, I have almost killed myself riding against a dragging, overfilled caliper! My method was to apply a little brake pressure with the lever and open the bleed port slowly until a drip or two came out, nip the port back up and then release the lever.

JBA

OP - what brakes have you got on your bike?

mtbrider123

figbat wrote:

You acknowledge that it isn’t the wheel flexing, then ask about spoke tension? The disc is attached directly to the hub; the spokes and rim are not going to influence how the hub and disc move (within reason).

The Rookie has outlined the things that can physically effect the pad-disc interface. Maybe now your pads are running closer to the disc than before? Perhaps the calliper/pistons need a clean? Maybe the disc is warped? Is the disc mounted tightly? Maybe the fork is flexing.

It’s definitely not the disc as I’ve put a brand new one. Don’t think that it’s flex in the fork as i didn’t have this problem before. Maybe removing 1–2 drops of the fluid will help as others suggested?

mtbrider123

Kajjal wrote:

Another less likely thing to check is there may be too much fluid in the brake causing the pad clearance to be very tight. This leads to excess rubbing.

I had this on one bike, solved by removing wheel, undoing the port on the brake leaver , gently and slowly pushing pads back with large flat screw driver while wife with kitchen roll mopped up the brake fluid that was released, while pads held back wife screwed port cover back in. After that much better, no rubbing and brakes worked fine.

A normal symptom of this is it can be hard to get the wheel in without the pads rubbing or the clearance is extremely tight compared to the other wheel / brake.

Thank you for your idea, I’ll try that and see how it goes.

mtbrider123

figbat wrote:

Yep, I have almost killed myself riding against a dragging, overfilled caliper! My method was to apply a little brake pressure with the lever and open the bleed port slowly until a drip or two came out, nip the port back up and then release the lever.

I’ll try that, thank you!

mtbrider123

JBA wrote:

OP - what brakes have you got on your bike?

Sram Red etap hydraulic brakes

JBA

I used to have SRAM/Avid brakes on one of my bikes and every summer I would get brake drag or the pads clamping the disc.
The DOT brake fluid expands in the heat and effecrively operates the brake. The only solution was to bleed a drop or two of fluid from the brake.

JGTR

It’s flex, the fork flexes when you are out of the saddle and you get a bit of rub (in fact the whole bike will flex to some degree) especially if you have replaced the disc and the clearances may be less. It’s common, it’s normal.....you many need I bleed a bit of fluid or there may be other contributory factors but the cause is exactly the same, flex.

02gf74

Mtbrider123 wrote:

It’s definitely not the disc as I’ve put a brand new one. Don’t think that it’s flex in the fork as i didn’t have this problem before. Maybe removing 1–2 drops of the fluid will help as others suggested?

The fork is flexing.

You didn't get disc rub with the old disc so it is the new disc that is causing it.

If the old disc was worn, a new disc, assuming it is not warped and is same type as the old one, will be slightly thicker.
Did you spread the pads apart before fitting the new disc, you need to do that to get the clearance.

mtbrider123

I’ve just noticed that one piston is coming out more than the other. So one comes out and goes back to its original place, however, the other comes out but doesn’t go back. If I press again, it comes out even more, so I think this causes the brake pad to get closer to the rotor. Any idea how to fix this?

figbat

Strip and clean.

kajjal

A quick way is take out the wheel, gently and slowly press both brake pads back to reset the pistons. Then put the wheel back in and do a few hard stops from speed. Assuming the caliper is lined up that should sort it. It is not unusual for one piston to be a little slower than the other but not by much and it should not stick or cause rubbing.