Sudden vibration whilst braking

Just today, the car has started vibrating quite badly when braking. The sort of vibration I get is the sort when your wheels are out of balance, but worse. Its ok when driving so the wheel balance is ok, just when braking.

I fitted new discs and pads on the front as they were quite worn. But that was a month a go and it's been fine up until today.

Not done the rear yet as they weren't worn as much. But I remember reading that most of the braking was done by the front anyway.

What's the first thing to check? I'm going to check nothing has worked loose, but apart from that? Any way to tell if its the front or rear and which side??

Oh and probably not connected, but I'll mention it just in case: Some serious tramlining today. Towing a trailer and moving from the centre lane to the inside lane on the M56 and you'd have thought a gale had hit the car. It was all over the place. Quite frightening actually. I know tramlining is normal on 18" wheels. But this was bad. Shocks worn? Clutching at straws there really...

tnx!

Nik

Normally it is warped discs. Quite common in autos when people hold them on the foot brake.

It could be warped discs or uneven build up of pad deposits on the discs.

Take it for a thrash and burn the brakes up a bit, see if that makes a difference. If not take the wheel off and check if its warped.

Normally you should avoid hard braking for a few hundred miles after fitting new discs and pads.

You have warped your new discs by not bedding them in.

Run a DTI over the disks to check.

When you fitted your new pads and disks did you clean and lubricate the caliper sliders they can become stiff with new pads fitted as the slider part has been unused for some time as the pads wear out lose wheel calipers or sliders or as suggested warped disks .

Datatek said:

You have warped your new discs by not bedding them in.

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Possibly, but they've been fitted a month so what is the definition of bedding in? I've been taking it easy (or rather, my wife has). It was fine on saturday, but vibrating sunday. I admit it was the first time I'd towed since fitting them, but it has still clocked up a couple of hundred miles.

If they are warped and I get a new set, how do I bed them in any better?

Nik

have ya checked yo wheel nuts?

Jack it up so you can spin the front wheels freely if they are not free spinning there is your propblem you have pushed exposed pistons back into their housing did you clean them ? The non freely spinning wheels will hotter than Usual combined with braking on un- bedded brakes causes overheating should never just push pistons back slap brakes in and off you go

always clean moving parts on refitting and going on a test drive you should always check the wheels spin freely any slight binding will cause overheating !

Most people sling then in and get away with it some dont .

Grit Valve said:

Jack it up so you can spin the front wheels freely if they are not free spinning there is your propblem you have pushed exposed pistons back into their housing did you clean them ? The non freely spinning wheels will hotter than Usual combined with braking on un- bedded brakes causes overheating should never just push pistons back slap brakes in and off you go

always clean moving parts on refitting and going on a test drive you should always check the wheels spin freely any slight binding will cause overheating !

Most people sling then in and get away with it some dont .

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I used a clamp to force the pistons back and never cleaned them. Do I clean them with brake cleaner or do you lubricate them with copper grease?

I hadn't done the back brakes and they need doing, so I've ordered a set of rear pads and discs and another set of front discs and I'll have another go.

tnx

Nik

The Mad Hat Man said:

have ya checked yo wheel nuts?

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Yeah. I was hoping it was that simple!!

NikTheGeek said:

I used a clamp to force the pistons back and never cleaned them. Do I clean them with brake cleaner or do you lubricate them with copper grease?

I hadn't done the back brakes and they need doing, so I've ordered a set of rear pads and discs and another set of front discs and I'll have another go.

tnx

Nik

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Brake cleaner on the pistons , only if needed and rubber dust sheilds are willing and the wife's tooth brush clean the sliders copper grease only a light smidgen .
Then when fitted always check for binding but if you have cleaned everything then they should spin nicely un braked

The reason to cleaning the pistons is you can get crystallised fluid and dirt build up pushing it back to the piston seal can cause stiff pistons combined with un greased sliders is a Recipe for disaster

Grit Valve said:

Jack it up so you can spin the front wheels freely if they are not free spinning there is your propblem you have pushed exposed pistons back into their housing did you clean them ? The non freely spinning wheels will hotter than Usual combined with braking on un- bedded brakes causes overheating should never just push pistons back slap brakes in and off you go

always clean moving parts on refitting and going on a test drive you should always check the wheels spin freely any slight binding will cause overheating !

Most people sling then in and get away with it some dont .

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If he can spin them with the VCU in place he should be applying for Christoper Reeve's old job.

G~

gencybay said:

If he can spin them with the VCU in place he should be applying for Christoper Reeve's old job.

G~

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ok then turn then enough to know they are not binding

gencybay said:

If he can spin them with the VCU in place he should be applying for Christoper Reeve's old job.

G~

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Not if he jacks both of them up. Which i think is what was meant.

Cannot see sliders being a problem if discs and pads were changed a month ago. They would not cause the problem anyway. Far more likely to be warped discs caused by over enthusiastic braking to early in their life. If you're the last of the late brakers it's very easy to do. Smooth progressive early braking for the first 250 miles or so.

wammers said:

Not if he jacks both of them up. Which i think is what was meant.

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I rarely doubt you but are you sure on that?

G~

gencybay said:

I rarely doubt you but are you sure on that?

G~

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Don't doubt, believe. If you lift both wheels off the ground when you turn one the other will revolve in the opposite direction through the planet wheels in the diff. Prop shaft and VCU not involved.