severe vibration on steering

[David's8]

Originally Posted by moltuae

How long are your fingers? I'm pretty sure I wouldn't be able to reach one of my discs with a knuckle, not without taking a wheel off.

I'd recommend adding one of these to your toolbox:
http://www.amazon.co.uk/BENETECH-Non...J3U/ref=sr_1_1

I used one to check my disc temperatures when I had some brake judder issues a while ago.

They're a fun gadget too. You'll find yourself checking the temperature of everything and anything.

Ah, i have 18" Avus so its not a problem! But another gadget is always a welcome addition to the xmas present list!

[oldnick]

well , it's the spring , my neighbour has his tractors out of his workshop , so time to get out and get under
having taken delivery of the device to measure temperatures as advised by david went for a spin down the mountain , some moderate brake applications , pulled into a layby and checked temperatures

rear discs approx 100C , nearside front 150C , offside front 300C !

well , that doesn't leave much room for doubt !

so left overnight , next morning bright and early [ 11 am ] next door ,trolley jack and pneumatic impact wrench made short work of wheel removal , then the fun began ...getting the pads out ...grr ; started at the top but getting enough movement to get the pads out was a pain ; combination of screwdrivers , pry bar and a lump hammer later was able to push the piston back enough to get the tops pads out , bottom piston went back easily with a little leverage fortunately
at this point I suspected the caliper would be difficult move but not a bit of it , just slid to and fro with a slight push

ok , so sticky piston it is ; push the pistons back as far as possible , small push on the brake pedal to get them out a bit , levered back again , repeat , and being an optimist cleaned up the edges of the one third used pads and re-assembled ; so far so good
so back on with the wheel [ am I the only person who struggles to get the security nut adaptor off ? ] and off for a test

good news and bad news

slightly different test route , same methodology

back discs 100 C , both front discs 180C [ hotter today ]
and no vibration while running along

BUT every time I brake ...big vibration !!!
maybe this is because the old pads need to bed in ....my neighbour had a quick look at them , could have put them down in a different order ; does anyone have any experience of this ?

current plan is to put up with it for the moment and see what happens , see if the piston stays free , followed by a new set of pads if the vibration doesn't go away

all comments gratefully accepted

[Dezzy]

If you can find a garage that has a brake lathe, they can be skimmed on the car. That or new disc's will fix it. They've got hot and you've sat on the brake pedal maybe at a junction or roundabout and you have either a warped disc or brake pad material embedded into the disc and that's what you're feeling every time the it goes past the pad, making a vibration.

[oldnick]

don't think it can be that insofar as it now runs smoothly except when the brakes are on whereas before it didn't vibrate when braking but did after the brakes were off

as alice said...curiouser and curiouser

[Goran]

I'm going to take a guess that it could be down to mixing the pads up.
Perhaps each pad took a slight set on the side of the disc where it was originally, and now it is on a different disc face and doesn't sit perfectly flush?

[briang9]

Originally Posted by Goran

I'm going to take a guess that it could be down to mixing the pads up.
Perhaps each pad took a slight set on the side of the disc where it was originally, and now it is on a different disc face and doesn't sit perfectly flush?

this or/and the sticking caliper has caused damage to the disc, suggest you replace the front discs and pads and I think it should be fine

[Dezzy]

Originally Posted by oldnick

don't think it can be that insofar as it now runs smoothly except when the brakes are on whereas before it didn't vibrate when braking but did after the brakes were off

as alice said...curiouser and curiouser

It's because when you brake the caliper starts to grab the disc, when the contaminated part of the disc or warp passes through the closing pads you get a bump, that sped up to the wheel speed turns into vibrate. The reason you were feeling if after braking before is because of the sicking caliper i.e. it wasn't letting go properly so you could feel the bump.

Go down the road and stand on the brakes i bet you don't feel it so bad, go down the road just touching the pedal and it'll be bumping away.

[oldnick]

Originally Posted by Goran

I'm going to take a guess that it could be down to mixing the pads up.
Perhaps each pad took a slight set on the side of the disc where it was originally, and now it is on a different disc face and doesn't sit perfectly flush?

that's my feeling at the moment , only problem is none of the local suppliers list the particular set which was only used from 1999 to 2002 on the sport model so will have to order in england ...£12 postage !

incidentally dezzy , the harder you stamp on the brakes the worse it is !

going out today , maybe a little use will show an improvement !

[oldnick]

just to say that after maybe 100Km of gentle driving [ shmbo ] the vibration has 90% gone so it does look like it was the pads were positioned wrongly

however , it has just occurred to me that the discs were positioned differently on the hubs , maybe that made a difference as well ?