MTB annoyance

Dogoid · 11 Jun 2007 at 13:45

im sure a good few people here understand the mechanics of a mountain bike , and i would be grateful of some help.

for the life of me i cannot get the front wheel rotor from grazing the brake pads.

i have tried loosening the quick release skewer and it does seem to work, but its to loose, its when i tighten it it pushes the wheel and rotor against one of the pads.

the pads themselves seem to be even in wear and tear, so i don't think i need new ones, but as you look down on the mech,{ with the front of the bike ahead of you } the pad on the left position , no matter which pad you use in the left position, is always further out then the right pad.

many thanks

cheers

SiriusB · 11 Jun 2007 at 13:50

Am I to assume you are talking about Disk Brakes? If so, the "rotor" is called the Disk.

Have you had any knocks or crashes with your bike? It could be that the machanism has been knocked out of whack and the pad is now too far out/forward/whatever.

Can't remember how to adjust this off the top of my head but I am sure if you find a mountain biking forum they can help you. MBUK is where my mountain bike mad mate usually goes.

Clarkey · 11 Jun 2007 at 13:52

might help if you give some indication as to what brakes you have :confused:

Droolinggimp · 11 Jun 2007 at 13:53

Probably suited in the sports forum.. lots of bikers there..

I too have this isssue. More so on my rear brakes. I think you have to adjust the little screws on the brake pads to align them up evenly.

M0KUJ1N · 11 Jun 2007 at 13:55

You'll probably get a better response to this question in "Sports Arena" or a dedicated MTB forum but if theyre hydraulic discs then there should be a barrel on the levers which can be turned to increase/decrease the biting point of the brakes. IIRC mechanical disc brakes work in a similar way to standard V-brakes so adjusting the tension in the cable would be the way to do it

Dogoid · 11 Jun 2007 at 14:07

i will attempt adjusting the brakes in a min, maybe this would have been best in sport.

thanks

dog

Topper · 11 Jun 2007 at 14:21

Pistons might be jammed also. What type of brakes are they? Mono's? 9's?

Dogoid · 11 Jun 2007 at 14:51

Topper said:
Pistons might be jammed also. What type of brakes are they? Mono's? 9's?

vented disc brakes. if you were after more info, i have no idea, don't know that much about mtb's

all i know there is a caliper the rotor disc itself and 2 pads.

Jonny ///M · 11 Jun 2007 at 15:47

Firstly you want to centre the caliper the disc rotor. Undo the pinch bolt holding the cable to the arm of the brake,and unwinding the pad that doesnt move out of the caliper.

Undo the two bolts that hold the caliper onto the brake mount(im assuming it does) so you can move the caliper around. Allignt he disc to the centre of the gap in the caliper,bolt it up tight,wind the non moving pad inwards till it just about touches the disc rotor but dont let it rub. Now you want to unscrew the barrel adjuster fully,pul the lever on the caliper really tight and bolt the cable to it. You shouldnt be able to spin the wheel at all,now screw the barrel adjuster back in until the wheel spins freely. This should give a decent feel to the brake.

If the rotors bent there is no way in hell you will get the brake set up to bite hard with a decent lever feel to go with it.

If the caliper doesnt bolt onto a mount like in this pic then you need to buy shims and space the caliper using them(i.e a pain in the arse).

ScarySquirrel · 11 Jun 2007 at 16:06

I have this exact problem. I will try the above when I actually understand what it means

I tried adjusting the cable but it makes the brakes really loose and they don't really work as they should. Might have another play with it tonight

Dogoid · 11 Jun 2007 at 16:45

jonny thats great , i will try that after some food.

i will let you know how i get on.

thanks

dog

noob · 11 Jun 2007 at 16:52

If they are new brakes expect some rubbing after a while they will bed in.

Jonny ///M · 11 Jun 2007 at 22:09

noob said:
If they are new brakes expect some rubbing after a while they will bed in.

I dont understand this........its just something that halfords employees tell customers when they moan the brakes on there shockwave Xt***(does it matter the higher then number the heavier the damn thing is) dont work!

Any disc brake i haev fitted myself has been fine,my rear saint i just bolted on and set it by eye.....i have VERY VERY VERY slight rubbing but i can bet you it doesnt rub once i get my bike in a workstand and check it over.

noob · 11 Jun 2007 at 22:39

Jonny ///M said:
I dont understand this........its just something that halfords employees tell customers when they moan the brakes on there shockwave Xt***(does it matter the higher then number the heavier the damn thing is) dont work!

Any disc brake i haev fitted myself has been fine,my rear saint i just bolted on and set it by eye.....i have VERY VERY VERY slight rubbing but i can bet you it doesnt rub once i get my bike in a workstand and check it over.

Both my Whyte 46 and Merlin Rock Lobster had slight rubbing. Considering I spent 2.7k on my Whyte you can imagine I was very annoyed. After speaking to them they said go for a few blasts and they will be fine and they were right.

BTW I wouldn't be seen dead on something from Halfords.

LordSplodge · 11 Jun 2007 at 22:40

Jonny ///M said:
I dont understand this...

True. The bike should work perfectly from the moment it comes out the bike shop. OK, my GT did go back a few times for some adjustments but nothing was not working when I got it.

I suppose the people who buy a Shockwave "full suspension" mountain bike would fall for the "the brakes are bedding in line"

Raymond Lin · 11 Jun 2007 at 23:00

Is it a constant rubbing ? not just a certain section of the disc ?

I had that problem, and it turned out that the disc wasn't 100% "flat". Took it to the bike shop and all the guy did was gave a quick "bend" "flick" and the rubbing was gone.

Dogoid · 11 Jun 2007 at 23:27

Raymond Lin said:
Is it a constant rubbing ? not just a certain section of the disc ?

certain section of the disc, and you could be right there, i will see what happens with the above 'to do' from jonny, but its likely the disc rotor.

dog

scratch · 12 Jun 2007 at 09:51

I bought a new bike with disk brakes at the weekend from the local bike shop (read: not halfrauds) and they also advised me that the disks/pads would take a week or so to bed in. Apparently the pads on disk brakes are ceramic and have a film on top which needs removing before they will work at full effciency. I rode a good 25 miles over the weekend and the brakes have certainly improved from when I first got the bike.

It makes sense to me because you have to do the same thing with new brakes on a car.

Andy

Butters · 12 Jun 2007 at 10:06

Jonny ///M said:
Firstly you want to centre the caliper the disc rotor. Undo the pinch bolt holding the cable to the arm of the brake,and unwinding the pad that doesnt move out of the caliper.

This is a cable operated disc brake and probably has no relevance if his bike is remotely worth more than £300

Ignore the image of the crappy cable operated Disc Brake above. If you have these, scrap them and get hydraulic efforts. I don't see the point in people going to half measures to get disc brakes. V Brakes wet all over cable operated discs anyway so I see no point in them.

If you have hydraulic caliper with brake fluid unfortunately you are par for the course with binding as when you shut the QR you clamp the forks towards the wheel hub so everything squished together.

Two options I see here are:-

Add a small washer to the caliper mount to space it out. I'm talking, very thin.

Or,

Step up to the new 20mm front axle system. You loose QR but will also solve all your binding problems.

Good luck

Jonny ///M · 12 Jun 2007 at 14:40

Butters said:
This is a cable operated disc brake and probably has no relevance if his bike is remotely worth more than £300

Ignore the image of the crappy cable operated Disc Brake above. If you have these, scrap them and get hydraulic efforts. I don't see the point in people going to half measures to get disc brakes. V Brakes wet all over cable operated discs anyway so I see no point in them.

If you have hydraulic caliper with brake fluid unfortunately you are par for the course with binding as when you shut the QR you clamp the forks towards the wheel hub so everything squished together.

Two options I see here are:-

Add a small washer to the caliper mount to space it out. I'm talking, very thin.

Or,

Step up to the new 20mm front axle system. You loose QR but will also solve all your binding problems.

Good luck

Well im going from what he has said in his posts and the bike pic in his sig......you set the damn brake up once the wheel is on and bolted up tight so you should have no binding issue if you set it up properly,if you take the wheel off and on then you will most likely need to set the caliper again.

Maybe the guy doesnt need the sheer power of hydraulics but just wants a disk that is going to stop him when he needs it.

The spacers you are talking about are only really needed in one piece calipers (i.e old hope monos) but most new brakes have an adapter that bolts to the fork and then the caliper bolts to that to give you some side to side movement.

and finally 20mm axles are hardly new if they were around 5 years ago