How to adjust disc breaks...

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How to adjust disc breaks...

Postby AndyTG » Mon Feb 11, 2013 7:07 pm

I've got a Giant Roam 1, fitted with Tektro HDC hydraulic disc brakes.

The back brakes are fine. With the front brakes, they are rubbing (very slightly) when moving in a straight line, and wailing like a banshee when I corner at speed.

I've ensured that the wheels are tightly fixed in place to minimise movement on the corner and adjusted the brake block so that it's well aligned with the disk (the wheel doesn't rub against the pads when spun in the stand).

The issue seems to be that the pads are horrendously close to the disc - and I can't for the life of me work out how to adjust them both outwards to give a bit more gap. I have to move the brake lever a hairs breadth to get full lock so quite happy to lose some of that.

Presumably there's something I have to tweak somewhere - I just can't work out what.
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by BNA » Mon Feb 11, 2013 7:43 pm

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Re: How to adjust disc breaks...

Postby open roader » Mon Feb 11, 2013 7:43 pm

Assuming your disc is not warped......

Undo the tension on the mounting bolts which hold the front caliper onto the frame - just loosen enough so the tension is released.

Then squeeze the front brake lever in firm and hold the brake lever whilst you re-tension the brake caliper mounting bolts. Do not release the brake lever until you have fully re-tensioned both mouning bolts.

Go for a test ride, pump the brake on and off as required and repeat the bolt > lever > bolt process once again if the rubbing is still not quite resolved.
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Re: How to adjust disc breaks...

Postby AndyTG » Sat Feb 16, 2013 12:46 pm

Appreciate the reply - but doesn't that just affect how the caliper is aligned with the disc?

I'm looking to increase the space between the pads to give the disc more breathing space (although appreciate the relevance of good alignment).
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Re: How to adjust disc breaks...

Postby trailgumby » Sat Feb 16, 2013 1:19 pm

When they break, you should throw them away and replace, no amount of adjustment can fix a broken disc.
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Re: How to adjust disc breaks...

Postby zero » Sat Feb 16, 2013 5:44 pm

AndyTG wrote:Appreciate the reply - but doesn't that just affect how the caliper is aligned with the disc?

I'm looking to increase the space between the pads to give the disc more breathing space (although appreciate the relevance of good alignment).


Bear in mind that there have been many disc brake caliper designs and mine isn't the same as yours (shimano).

I've had a rubbing front disc a total of 3 times - once was alignment - fixed by the bike shop, once was the caliper itself, the last time was the beginning of a lip forming on the rotor, so I replaced the rotor (not convinced they are supposed to be allowed to have visible wear). Bit concerned about what it means that the rub worsens when cornering, mine never did that.

The fix that has worked for 3 years for me for the caliper, was to let some oil past the seals, then push the pistons all the way back and then bleed and refill the oil. One imagines a smarter approach might be just to slacken the bleedscrew, and then push the pistons all the way in - the purpose being to resite where the pistons are in the seals. The pistons will come back out fine, but the seals may be more extended again, and thus offer more return action (they and the pad spring are supposedly both part of the return action).

I presume that tektro doesn't use shimano style oil for brake fluid, so you might want to acquire some of what it needs before starting as the reservior is small and any fluid loss would usually need to be replaced.
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Re: How to adjust disc breaks...

Postby AndyTG » Sun Feb 17, 2013 2:33 pm

That sounds spot on cheers - I'll give that a go
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Re: How to adjust disc breaks...

Postby jules21 » Sun Feb 17, 2013 7:13 pm

check that the hub bearings don't have slack in them - end float can allow the disc to float too.

other than that, i had a cheap set of clarks s2s that did that. i tried everything - i eventually figured out that when the pads wore, the slave pistons would become skewed in the cylinder and bind. this led to the dragging as the pads wouldn't retract. i returned them to chain reaction and got my money back!
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