AlexM

Hi All,

Hopefully someone can tell me what the problem is likely to be...

I upgraded my MY98 2-pots to a nearly new pair of STI 4-pot brakes with Subaru pads about three months ago. I have been pleased with the improvement in braking force and feel with no negative impressions up until now.

While braking from high speed recently, I noticed a moderatly severe juddering vibration. This only seems to be apparent at motorway speeds, and either doesn't occur at lower speeds or is too mild to be perceptable.

There is no cracking visible on the front disks, so I'm wondering where the problem could be. One possible factor is that the car has been unused on weekdays recently, which means a light film of corrosion forms on the disks. Although this cleans itself up after driving for a short while, I wonder if this may have some bearing on the problem. The driving regime has been mostly low speed urban use, and no track days so I'd not expect this problem to occur as a consequence of heat damage.

If anyone can suggest where I should start looking for the cause I'd be grateful.

Thanks in advance,

Alex

Ian Cook

I get this on my 99 car, I even had the disks replaced under warranty, but they did have cracks in them, it appears to be the disk causing it, doesnt affect my steering or anything just the noise really, although it does make me lift off the brakes and reapply. I am going to try some different pads, as mine are worn out again, will see if they make any difference, if not will have to change to Uprated or Group N disks. I know Scoobysport do some, as do Prodrive

MTR

MTR

[This message has been edited by MTR (edited 17 September 2000).]

Ian Cook

The rumbling is caused by excessive heat getting into the disks, hence why you only notice it after braking from motorway speeds, it is a common problem with the 4 pot disks.

MTR

MTR

[This message has been edited by MTR (edited 17 September 2000).]

AlexM

Hi Ian & MTR,

A further observation - the disks are uniform in colour apart from one small patch approx 1cm in diameter which seems to be slightly different in colour.

If the disk were warped, would I still have a vibration at low speed?. When I've suffered warped disks on other cars, a vibration occured at all speeds to some extent.

If I understand the Zebra effect, is this caused by the different expansion of the areas of the disk surface which have a bit of the web between them. I would be suprised if the disks expanded so much during one medium effort stop - could this be so?.

Seeing as it won't be under warranty, can you recommend third party disks which may have a composition which means they wouldn't have these problems?.

Thanks again.

Alex

Ian Cook

Prodrive sell an upgraded disk throught the dealer network i beleive, Scoobysport also sell Group N disks that fit the 4 pots, so again they may be worth a try.