vibration on braking

[cbarrow]

V40 1.9 D (2004). When braking, there is a vibration which comes through the front and the steering wheel. It's frequency appears related to speed and the steering wheel "wobbles" in time to it. I got the discs changed a while ago and that cured it last time, but it is back again after about 20k miles. I'm trying to work out what is causing it, and any precautions to take when changing the discs (again!) to try to stop it happening. The previous pads were green-stuff but now running on Mintex. Any help appreciated.

[dcw]

Hi

My first thought was warped discs, but if they are new discs then probably not.

Could be a seized caliper bolt, or perhaps a caliper piston that is sluggish/slightly seized.

David

[Anadinolin]

warped disks is my immediate thought, it could be alignment aswell, has the car had tracking done recently? also as dcw said, could be a sticky caliper

to prevent the warped disks, dont brake hard for the next 2k miles...i would suggest searching google for "bedding in new brake disks"

[malteser]

My bet would be the discs too. The previous owner had put some cheap discs on mine and if I recall rightly I done about 5000 miles and they got warped

[stephend]

May also depend on whether the hub flange was cleaned up properly when the new discs were fitted. If they don't go on perfectly true, the new ones will quickly warp. You're supposed to check the run-out with a dial test indicator, but I don't think that often happens...!

[cbarrow]

I'll try changing the discs (the current set have done around 20k) and clean the flange as well as I can (though won't be able to test them since I don't have a run out gauge). the small screw that holds the disc in place is missing on both sides - does this make any difference? Many thanks for your replies so far.

[Lou Ferrigno]

When I first bought my car, it had just been fitted with new discs.
After only 2000 miles, I had awful juddering when braking.
I replaced the discs and 8 years on and 70000 miles they are still perfect.
Whether the hub was not cleaned or a bad disc ? ?

[Anadinolin]

the screws on both sides are just to hold the disk flat while you put the wheel on. they dont matter so much as the wheel clamps the disks to the flange anyway. get a wire brush and clean off the muck from the flange, check for any visual damage, put a thin layer of copper slip ( so that the disks arent hard to remove if they are on there a long time)

im not sure how you would check for sticky calipers, but that can and will warp ur disks my guess would be to go for a 5-6 mile drive on a straight, get out and feel the wheels for heat, the hottest of the two will be the one with the sticky caliper, you can get them serviced or get another previously refurbished set, both have the same effect: free and easy calipers

[dcw]

As others have said, if the new discs were not properly fitted onto a clean hub, then they will effectively have been doomed from the start.

Checking caliper for heat is the simplest way to see if it might be sticking a bit one side - but be careful!

David

[cbarrow]

Thanks everyone. Will get some new discs and give the hub a damn good clean! That's my Christmas job sorted now. Always some tinkering on the car required!