wobbly braking!

[Rickster]

Hi guys,

can anyone suggest the cause of my wobbly braking?

under normal conditions the brakes are fine but after extended enthusiastic driving and subsequent hard braking they seem to wobble the steering wheel (not the brake pedal).

Please dont say warped discs! Could it be wheel alignment?

Thanks

Rick

 

[jimso]

I doubt if its wheel alignment. I get a little evidence of the sort of condition that you describe when braking hard. My discs are fairly heavily rutted on the inside faces. I think that it is simply a case of uneven wear on the pads and discs.

 

[glewis]

Rutting and corrosion on the brake disks, (especially the inside edge), is a very common problem. If you do a search on the forum for "brake disks", you'll see.

If the disks haven't done a lot of mileage, having them skimmed will be MUCH cheaper than replacing them. I had mine done at 24,000 miles by Autotune-TVR near Hinkley. There are several places around the country, like Autotune, that use a machine which skims the disks whilst they're still on the car.

 

[Rickster]

I have read a lot of the posts on the forum about discs but why do i not feel it at the pedal if it is the brake disc at fault?

 

[Glyn]

This could simply be sticking pistons when hot.
You say after enthisiastic driving, i take that to be braking too and the heat build up.
The calipers have 4 pots (pistons) each, perhaps when very hot they are sticking in the housing through expansion, or on application only partially deploying correctly, When cold it sounds like you have no issues so it must be a heat thing, remove the calipers and strip them, clean and refit.

If you drive in a straight line and let go of the wheel then brake does the car veer to one side? then press harder, does the veering change to the opposite direction? If so its definately a deployment problem

Just thought of something else, have you changed the brake fluid? Brake fluid is Hygroscopic - it aborbes moisture (water) enthusiastic braking will boil that moisture and this results in an airpocket in the caliper, this allows the pistons to move away from the disk as air is compressable - a fluid is not compressable so the braking system will have an imbalance

 

[Black80XSA]

Are you using part worn Pirelli tyres ? - these can be a pain in under hard braking for tramlining, which isn't exactly wobbling steering but could be with a combination of road surface irregularities.

I would place my money on warped discs or corroded discs myself tho.

 

[Rickster]

OPC Chester today told me it was due to discs wear and that they need skimming.

1Hr labour at the OPC to do it. ..... about £150?

Car has relatively new michelins on it. I do wonder about the callipers if they need stripping...... dont want to pay porsche rates for that though....

 

[russtbird]

Not sure where you are in the country, but you could almost halve that cost at an independant. I had both rears on mine done at Northway (Reading, Berks) as part of a service 3wks ago - £80.
If I was you I'd find a recommended Independant and save your cash for fuel[]. Good luck.

 

[Rickster]

thanks Russ, i am in Preston, i will post to see if there is anywhere nearby.....

 

[Black80XSA]

Try Hartech in Botlon, or Ninemeister in Warrington, or Tech9 in Hale Liverpool.

Replacement Sebro discs are about £80 each from Eurocarparts from what i remember.