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[Lizzie Zoom]

Back in January my car passed the MOT, but an advisory stated that there was an oscalliation/fluctuation on both o/s front and o/s rear brakes.

Decided now I better get to investigating the situation.  The brakes though work fine, unless braking from high speed when I can feel some "fluctuation".

Any thoughts or suggestions please?

[VXL V6]

Discs warped
Wishbone bushes
Wheel balance

Take your pick! 

[Kevin Wood]

If it slows up at low enough speed to be visible on a brake tester it's probably run-out on the disks.

[Lizzie Zoom]

Discs warped
Wishbone bushes
Wheel balance

Take your pick! 

Thanks

I am having the wishbone bushes replaced over the next week

[Lizzie Zoom]

If it slows up at low enough speed to be visible on a brake tester it's probably run-out on the disks.

Thanks

[johnnydog]

Unusual though that the two affected brakes are both on the offside.
When the car is parked, is it the offside that gets the weather / rain?
Could be that the offside discs have more corrosion (usually unseen on the inner face), which is causing the problem.
Can it be felt through the pedal whilst gentle braking?

[Lizzie Zoom]

Unusual though that the two affected brakes are both on the offside.
When the car is parked, is it the offside that gets the weather / rain?
Could be that the offside discs have more corrosion (usually unseen on the inner face), which is causing the problem.
Can it be felt through the pedal whilst gentle braking?

No, the car is always garaged.  Only when braking down from high speed (80+) can i feel some "pulsating", but usually nothing at all.

I also thought it was strange that only the o/s brakes are affected, but Vx wanted to charge me £200 (with TC!!) just to look at them, so I am now getting a free brake check at my local very reliable specialist tyre, exhaust and brake dealer.  I will see what they say.

[TheBoy]

My general diags on this is:

Always repeatable, but no vibration when driving at 80-90 = "warped" discs (warped meaning any out of true)
Intermittent on braking and intermittent at 80-90 = suspension/steering wear
Always vibration at 80-90 = balancing

[Lizzie Zoom]

My general diags on this is:

Always repeatable, but no vibration when driving at 80-90 = "warped" discs (warped meaning any out of true)
Intermittent on braking and intermittent at 80-90 = suspension/steering wear
Always vibration at 80-90 = balancing

Thanks TB!

I am pleased that no-one is suggesting any problems with servo's, so the rectification should not be too expensive!!

[Lizzie Zoom]

Well, like any good mechanic, I did what I should have done back in January;  took all the road wheels off, inspected and cleaned the brakes.

All pads, and discs are good, running true.  But,............I found that an amount of crud had built up around the edge of the disc on the o/s front brake and it was not freely turning, catching itself, with a scraping noise, on the caliper / pads!  Cleaned off rusted metal and general muck,with a wire brush, a mallet and screwdriver.  All turns beautifully now, and a road test up to 80 mph, then hard braking, revealed no oscillation / fluctuation that I could detect anyway.

I will now replace the wishbone bushes that have deteriorated, and I believe that should completely cure any problems I may have had

Thanks for all the input, once more it was very useful

[dave the builder]

Well done 
I like to remove the calipers and give everything a good clean ,lube slides etc just before MOT. gives you the opportunity to check all the suspension etc,identify any possible problems ,rust proof, and ensure the brakes are in tip top working order for the brake test .
Don't bury your head in the sand though, get them covers off and treat any rust ,if the sills or anywhere else is holed,at least you have 4 months to work out a solution 
a few hours work now could extend the life of your lovely comfy big vauxhall 

[Lizzie Zoom]

Well done 
I like to remove the calipers and give everything a good clean ,lube slides etc just before MOT. gives you the opportunity to check all the suspension etc,identify any possible problems ,rust proof, and ensure the brakes are in tip top working order for the brake test .
Don't bury your head in the sand though, get them covers off and treat any rust ,if the sills or anywhere else is holed,at least you have 4 months to work out a solution 
a few hours work now could extend the life of your lovely comfy big vauxhall 

Thanks Dave

Please see my last post in my "Jacking an Omega" thread.  The car is going to get professional treatment on the rear end, and the sills have been inspecting with no problems reported.

[TheBoy]

Well, like any good mechanic, I did what I should have done back in January;  took all the road wheels off, inspected and cleaned the brakes.

All pads, and discs are good, running true.  But,............I found that an amount of crud had built up around the edge of the disc on the o/s front brake and it was not freely turning, catching itself, with a scraping noise, on the caliper / pads!  Cleaned off rusted metal and general muck,with a wire brush, a mallet and screwdriver.  All turns beautifully now, and a road test up to 80 mph, then hard braking, revealed no oscillation / fluctuation that I could detect anyway.

I will now replace the wishbone bushes that have deteriorated, and I believe that should completely cure any problems I may have had

Thanks for all the input, once more it was very useful

My bloody discs, well fronts anyway, never last more than 2 years anyway...

[Bigron]

Rumour has it that there could be a reason for that, TB?

Ron.

[BazaJT]

Discs on mine are about due for replacement but I have had it for 7yrs and they weren't new when I bought it.