Grrr, somethings not right

[cirian75]

Giant Defy 2 Disc

on the way home last night the front disc on my deft disc started to make a bit of a wurring noise when applied.

pulled up, had look, mmm, nothing, so released the wheel and redid it.

still makes the noise on the brakes.

got home, stuck it on the stand wheel out, had a look, mmm, nothing to see, sticks it back in the bike, loosens the caliper and does the re-centring job to no avail, starting to assume the disc in warped, after 40 minutes of swearing at the bike while trying to recentre the caliper

looks at bike from the the front, wheel is tilted over to one side.

ah, that explains it.

bike off stand, , loosen wheel, a little weight on top to centre it on the dropouts and re-tighten..............ok, its better but its still not straight in the fork, tries again, newp, ok, tries again, newp, screw this, I'm having my shower and food and I'll look again tomorrow.

I'm thinking bent QR skewer, wheel is out of true, or something on the fork is wrong (poorly finished dropouts etc.)

[Fluffsri]

I have bought 2 bikes in the past when the front wheel does not sit central in the forks. one of them it still does, only by 5 mmish but the other one was so bad I had it realigned. Also with the whirring noise my Spesh does this when the pads are low, it just catches the pad spring on the disc. Good luck finding it.

[tuffer]

My Wife's cross bike is doing this, one of the brake pistons appears to be pushing the pad lightly onto the disc. If she applies the brake it goes away for a while then slowly comes back, the piston must retract and then slowly come back out again.

[Steamer]

tuffer said:

My Wife's cross bike is doing this, one of the brake pistons appears to be pushing the pad lightly onto the disc. If she applies the brake it goes away for a while then slowly comes back, the piston must retract and then slowly come back out again.

That sounds like a sticky piston - can be cured by taking wheel out and carefully pumping brake to expose piston - then apply a little brake fluid to the piston body. (YouTube has a few slightly more detailed explanations). Doesn't sound like its the same as the OPs problem though.

[Kermit power]

cirian75 said:

I'm thinking bent QR skewer

Highly unlikely. I've bent plenty by virtue of being an enthusiastic fat knacker on a mountain bike, and it makes no difference, as the QR just holds the hub and dropouts together. It shouldn't be influencing where they sit together.

cirian75 said:

wheel is out of true

If they were rim brakes, then that might be the problem, but disc rotors mount direct to the hub, so as long as the wheel isn't so out of true that the tyre is rubbing against the fork legs, that shouldn't matter.

cirian75 said:

or something on the fork is wrong (poorly finished dropouts etc.)

Unlikely if it has been working fine until recently?

That's probably not very helpful, is it?

Have you got another bike you could put the wheel onto, or another wheel you could put onto your bike? That would at least tell you if the problem lies with the fork or the wheel.

[cirian75]

well have had a good look now, something is amiss on the non disc side of the fork, does not want to centre properly, it feels like the dropout has been milled to wide as well.

I can't flip the wheel as the non disc side is not dished enough to clear the caliper.

wheel is in straight now, but needs precise locating and tightening.

[richardxjr]

More weight on front ie belly on bars whilst leaning over to tighten skewer, should centre it every time.

[JustinF]

I read this as...
1) had an issue with rub
2) took sensible steps to resolve with caliper re-centring
3) realised you'd done so with the wheel askew
4) centred wheel

5)failed to repeat step 2
?