Front disc break rubs when steering left or right?

[WhiteEagle197]

Hi,
A week ago bought a Specialized Sirrus Sport Disc Hybrid Bike (specs here: http://www.rutlandcycling.com/31888...rrus-sport-disc-hybrid-bike---black-blue.aspx) that has a Tektro Auriga break (Hydraulic Disc, Resin Pads, 160mm Rotor). So far I made about 110 miles. What I noticed is that while the bike is running straight there's no problem, but as soon as steer left or right (at bend of road, crossing etc.) the front disc break starts rubbing. Not badly, it's not slowing down or anything, but it does cause an annoying 'hissing' noise. As this is my first ever bike with disc brake, I'm not sure: is this normal? (Today I even removed the front wheel and re-installed it a couple of times, hoping that might solve the problem, but it had no effect whatsoever on this issue.)
Cheers

 

[bonsaibilly]

When you say rubbing, have you actually checked this eg lift up the front end, spin the wheel and then waggle your handlebar left and right and see if it makes the brake disc rub the pads?

bb

 

[mrandmrspoves]

It may resolve itself as the pads bed in. I would check that the front Quick release skewer is tight enough. You should have to push it quite hard to get it to close and it should leave an imprint in the palm of your hand.

 

[fossyant]

You can align the calliper better by yourself. There are usually two Allen bolts that hold the calliper to the post mount or adapter. If you loosen these you can move the calliper to either side to align with the disc so the pads aren't rubbing. Also check for the disc being true. If it's not you can correct these with a firm push or tug at the point the disc is out of alignment (if you are confident to can use an adjustable spanner).

If you aren't confident with doing this, go back to the shop.

 

[WhiteEagle197]

When you say rubbing, have you actually checked this eg lift up the front end, spin the wheel and then waggle your handlebar left and right and see if it makes the brake disc rub the pads?
bb

It produces the noise whilst the bike is being ridden. If I lift it up, and just spin the wheel in the air, it's perfectly fine.

 

[WhiteEagle197]

It may resolve itself as the pads bed in. I would check that the front Quick release skewer is tight enough. You should have to push it quite hard to get it to close and it should leave an imprint in the palm of your hand.

Yes, that's correct, it's quite firmly on. It did leave an imprint in my palm.

 

[bonsaibilly]

It produces the noise whilst the bike is being ridden. If I lift it up, and just spin the wheel in the air, it's perfectly fine.

Then it is more likely to be the wheel that is twisting round corners when under load. I don;t know the fix - check the hub bearings are tight enough?

 

[WhiteEagle197]

You can align the calliper better by yourself. There are usually two Allen bolts that hold the calliper to the post mount or adapter. If you loosen these you can move the calliper to either side to align with the disc so the pads aren't rubbing. Also check for the disc being true. If it's not you can correct these with a firm push or tug at the point the disc is out of alignment (if you are confident to can use an adjustable spanner).
If you aren't confident with doing this, go back to the shop.

The calliper I can't do. The Allen bolts are so tight that I just simply can't loose them at all.
The did wasn't (well, still isn't) completely true. It's wobbling a bit, but really it was just like half a mm. I applied a bit of force at its correct point now it's even less, maybe a quarter of a mm. It's barely visible now. But I don't think this is the source or the problem, as neither before nor now it touches the calliper. When the bike is lifted up and the wheel is spun it's noiseless no matter if I turn the wheel left or right or just keep it straight. Riding the bike on road is still noiseless as long as I go dead straight. As soon as I steer approx. 5° or more it starts the hissing rubbing noise... Strange...

 

[WhiteEagle197]

Then it is more likely to be the wheel that is twisting round corners when under load. I don;t know the fix - check the hub bearings are tight enough?

Thanks, that may be the reason. But it's beyond me to actually check/fix that, so tomorrow I'll take it back to the store an ask the guys to check/fix it.

 

[fossyant]

It shouldn't hiss and this might go when you run them in more. They can rub a bit but that's because of the tight clearances.

My kids bikes have cable operated ones and one side sits very close to the disc. My MTB has SRAM GUIDE R and the only time they make a noise is when grit and mud get in and a quick break clears it.

Might be worth riding a bit more and seeing if the noise dissapears.

Are the pads parallel to the disc (looking in from the rear of the calliper).

 

[fossyant]

It could very well be a little flex in the fork

 

[WhiteEagle197]

Are the pads parallel to the disc (looking in from the rear of the calliper).

They look parallel to me.

 

[fossyant]

You can't usually adjust the distance of the pads from the discs on hydraulic brakes, or certainly not on the Guide R bu I think you can on the more expensive stuff.

See if it settles down, how is it under hard cornering ?

 

[bonsaibilly]

Also, is the disc securely/properly fitted to the wheel hub? I'd imagine the fitting is the 6-bolt type where there are 6 hex bolts attaching the disc to the hub... check all are (approx) equally firm. If the disc isn't sitting properly it might be twisting and forcing air flow while cornering causing a hiss.

TBH it could be nothing to do with the wheel or disc. People have been known to discover that a creaking bottom bracket turned out to be their helmet strap when they turned their head a certain way!

bb

 

[WhiteEagle197]

It could very well be a little flex in the fork

It can. I've just tried to "twist" the wheel by pushing the top of the wheel sidewise. And something (I'm not sure whether that's the fork, or the wheel, or the hub/bearings) does actually twist, as when I apply some sidewise pushing to the top of the wheel, the disc gets touching the calliper. Probably that's why it rubs in corners/turns/bends. I guess that's not normal?