Brake Adjustment

Kornowski

Hi,

I have a 2006 Kona Blast, with Hayes MX2 Mechanical disc brakes... In a previous thread I said that the rear brake was making a grinding noise. I took it to a local bike shop who adjusted them and apparently cleaned the pads, but it still made the noise. I then took the pads off thinking that they'd worn out but they have plenty of meat still on them, they're fine.

I took the pads off, and then blew on them, I didn't have anything to clean them with so that's all I could do at the time.

I re-aligned the rear wheel with the brakes and then tightened it back up, pulled the cable through a little as they weren't as strong.

The grinding noise has gone, I don't know what it was, but the brakes feel soft, sort of spongey, they grip, but not much, do I need to pull the cable through more.

I noticed the brake pads was moving over, pushing onto the disc rotor and then slightly pushing the disc over to meet the other pad.

Really, what can I do, what's up with them?

Thanks for any help

nicklouse

adjust the static piston. to stop the disc moving.

Kornowski

The static piston, what is that? Sorry, do you have a picture or something.

Is what's happening wrong, or damaging? Also, do you think I've fixed the problem?

supersonic

The brake has a moving piston, operated by the brake lever, and a static piston on the other side which you adjust via a 5mm allen key. The brake works by slightly flexing the rotor onto the other piston. Slightly. You need to adjust it so it just clears rthe rotor.

With new pads here is how I do it: wind the static piston all the way in (back into the caliper). Wind it out about a mm, or a set number of turns. Move the whole caliper by hand and push it against the rotor, so the pad touches, and make sure it touches. Tighten bolts on caliper while pushing pad onto rotor. Back static piston off. Spin wheel and check. Set up other piston/cable/lever.

nicklouse

download a manual http://www.hayesdiscbrake.com/support_downloads.shtml and have a read of the fitting instructions.

Kornowski

supersonic, So, you're saying I should loosen the bolts holding the caliper into the forks, and push the pads onto the disc and then tighten it up... Then move the static piston, how much should I move it, just so there is a small gap.

Sorry about this, I am a complete newbie when it comes to this...
Would pulling the cable through more help this also?

nicklouse Thanks for the suggestion, I printed one off before, it helped a little, but you guys talking me through it in simpler terms would help.

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One thing, Why does it feel soft, what is causing it?

nicklouse

6. Install the cable through the brake lever and spin the lever adjusting barrel down tight to the closed position.
7. Install the cable through its housing and through the cable anchor screw and washer.
8. Seat the cable housing snugly at the brake lever and the brake.
9. Pull the cable wire tight and tighten the cable anchor screw to 60 in-lbs of torque
10. Trim the excess cable and crimp a cable end on the end of the trimmed cable.
11. Squeeze and hold the brake lever. While holding the brake lever, shake the mechanical brake to position it in its natural centered position over the
disc. While still squeezing the lever, tighten the mounting bolts.
12. Using a 5mm Allen wrench, turn the fixed inner pad adjuster counter clockwise 1/8 of a turn until there is a .015”-.020” (.38-.50mm) gap.
13. Adjust the amount of lever travel by turning the adjuster barrel at your lever.
14. Spin the wheel. Check that it spins freely and that the gaps, between the pad and the disc, are equal. If the gaps are unequal, or if there is drag,
readjust the caliper position by loosening the mounting bolts and adjusting the caliper as needed.
Hint: A white piece of paper can be used as a background to help sight down the disc looking for equal clearance between the pads and th disc.
15. When the gaps are equal and wheel spins freely (without drag), torque the mounting bolts to 110 in-lbs (12.43Nm).

basically sonic is saying is what is in the hayes info above.

and yes that is what he is saying.

supersonic

Instructions always a good place to start, what do you think to them?!

My method probably does the same. You loosen the calipers bolts on its adaptor, then slide the whole shebang angainst the rotor, so the static pad presses on rotor. Pad should have been adjusted as in my first post, so you can wind it back for clearance. Tighten bolts. Back off static piston and paad until it doesnt rub. Then and only then fiddle with the cable. Pull cable through. You may have to alter the arm position where it clamps. Keep on trying until you get a decent lever feel. Fine tune with barrel adjuster on the brake lever. Spin, test, ensure that the first pad contacts the rotor, and flexes it onto the other pad.Thats as simple as I can put it I'm afraid. As the pads wear, you have to wind the staic piston in and readjust the cable.

supersonic

The Hayes instructions use the cable to set up caliper postion, mine is by hand, either works, as long as you adjust the cable AFTER. The important bit is getting that initial static pad clearance as in step 12.

Kornowski

Alright, thanks a LOT for that!

When I got my bike the barrel adjuster was all the way in... but tomorrow I'll try what you've suggested and see how it goes. Thanks again dude!

One more thing, I don't get alter the arm postiion, what does that mean?

supersonic

The bit the cable attatches to on the caliper is a lever, whcih drives the piston. Move it, you will see it operate. The cable does this for you. So moving it into position, then clamping the cable adjusts it, and barrel adjuster fine tunes it.

Kornowski

Oh right, yeah, I get you, sorry about this.

I'm going to have a go at this today... Is leaving the barral adjuster in all the way a bad idea?

teacherman

Hi Kornowski - beeen following this with interest 'cos my brakes do the same thing but only when they get wet or muddy. Good advice here. If i come across anything that helps me i'll let you know. Will you post if this advice works?

have to say i'd much rather be riding than fiddling about but there you go!

Kornowski

Hi, Mine do it all the time, I took it to the bike shop today and they said that it's down to the composite of the pads, apparently there are plenty of other people that have the same problem, some pads will do it, others won't.

They stlll work and brake fine, they lock up when I'm sitting down so there isn't a braking problem, so I guess there isn't anything to worry about.


teacherman, it may be the same thing, your pads just may not like wet conditions is all

Kornowski

Does that sound right to people?

supersonic

Nope, they are talking balls, but it is a common problem is rubbing. Pad material nothing to do with it.

Kornowski

So what should I say when I go back to collect my bike, as they said there was nothing wrong with the brakes, I told them to tune the gears as they were a little out...

supersonic

Slight free running drag is acceptable, they are a fiddly brake.

Kornowski

So they're talking crap about the pad compound making the noise, it sounds believable, car brakes do a similiar thing, but they squeel.

What should I say to them, tell them to do?

supersonic

Pad compounds make noise when the brake is applied, however it isnt the reason why they rub. They rub because they are not set up properly. However, close is good enough, so as above, slight free running drag is ok. Just ride the things!

Kornowski

Oh, I sorted the rubbing out, I just aligned everything properly, but you're saying it's Ok for the disc to make the small grinding noise, it's just the pads.