Shuddering brakes/wheels after 70+ mph motorway cruise

[Lee_e]

Okey Cokey boys and girls ....

 

Tough one to explain so bear with me.. For the last few months after thinking my pads/discs need re-newing due to juddering under braking, im thinking its something more serious...

 

When i go above 70mph (private road of course ) i seem to get what i can only describe as unbalanced wheel feel, if you get me..slight judder but nothing too bad... But when i increase speed it seems to get a little worse the quicker i go.

 

Even after me decreasing speed down to say 40-50mph i can feel it shuddering pretty hard and braking for say a roundabout it gets pretty savage, to the point where i feel i can only just control the braking distance

 

This carries on untill i get home, get out and touch all the alloys and check tyres and wheel nuts are done up tight etc and i found the drivers side front is almost too hot to touch ... on the alloy its self not the tyre !! ... The passenger front is warm but no where near as hot as the drivers side , both rears where pretty much cold.

 

Now to me this sounds like either a sticky caliper/warped disc or wheel bearing ...

 

What do we all think ?

 

Any help would be an awesome bonus as im thinking to take it to see dude at afr tomoz morning and see what he makes of it all. cheers guys

[johnny g]

Could be sticking caliper.

 

Wheel weights still on?

[2soops]

Sounds like the caliper is sticking, when its hot jack up that corner and see if the wheel will rotate by hand, i bet it wont

[Lee_e]

Sounds like the caliper is sticking, when its hot jack up that corner and see if the wheel will rotate by hand, i bet it wont

 

Mmmm my thoughts exactly, im off tomorrow so ill see what happens.

 

Thanks for the help fellas, much appreciated.

[Lee_e]

Could be sticking caliper.

 

Wheel weights still on?

 

Cant see if the wheel weights have fallen off ( lack of light), it only does it after i apply the brake's. sometimes its fine going over 70, but as soon as i touch the brake it goes mental , so to speak..

[ripped_fear]

99% it is a sticking brake as I have the same problem at exactly the same speed and i have a brake binding atm.

[Morpheus]

I have the same issue as my car has been sitting for a good while until I bought it and if you have a piston that won't back off due to corrosion, the slightest rotor runout will bind.

 

To solve the problem, (for those that don't know), pump the brake pedal with ignition off until the pedal feels solid at which point the pressure should be backed off of the pistons. Then jack the binding corner up, pull on the rotor opposite the calliper or insert a lever of some sort to loosen the pads, remove them and then carefully remove the calliper, rotor if required, and then the piston by turning on the ignition and gently applying the brakes until the piston pops out into a bowl or tray. It will need to be fully removed to do the job properly.

 

You'll need a litre of brake fluid and a couple of jars or containers for bleeding later, not covered here. Needless to say, avoid contact with skin if possible and car bodywork. Former is unrealistic though.

 

The problem will be rust (and it only has to be a very small amount) around the piston bore or cylinder lip, where the rubber seal doesn't cover it. The seal sits in a groove and can be removed once the piston is withdrawn. You then need to use very fine wet and dry abrasive paper (say, 400 grit or over) to rub the rim smooth where the corrosion occurred. Even if it appears that there's nothing to remove, it will make all the difference, since the piston is a near interference fit in the bore to prevent leakage.

 

The piston itself will also need to be checked for surface finish by using a Stanley knife blade or similar scraper for obvious bumps (being careful not to scratch it) and then very fine steel wool or the paper used for the calliper rim to polish the surface. A very fine single cut (draw) file or diamond hone (Ez Lap etc.) is ideal. Once thoroughly cleaned and checked for smooth operation by hand insertion of the lightly oiled piston, you need to insert a new seal or the original if it's still rust free (as rust sticks to the seal too) and then it gets fiddly, as you need to insert the seal into the groove in the calliper, then the oiled piston into the inside out seal and then when the piston is nearly inserted fully, you obviously have to get the lip in the groove on the piston before fully pushing the piston home.

 

The main problem will be having slippery fingers but there's a knack to it.

 

Hope that helps someone!

 

I've done this a few times and it works a treat but a couple of hours for each calliper maybe. Messy job but won't need doing again. Be careful with copper grease or similar near the rotors, as it gets thrown everywhere once it heats up but it's a good idea to apply some around the seal to prevent it happening again for a long while.

Edited November 22, 2010 by Morpheus (see edit history)