peggy

iTrader: (11)

I Have a 94WRX and in the last 6 months i have changed the brake setup 3 times and i keep warping disks. My current setup is an AP 304mm with 4 pots, and i have just come back from a trackday at donnington and the fronts are warped.

What is the likley cause? How do i get my hubs checked for run out?

Nigel

S55 HOT

Fundamentally, you're getting your disks too hot so they are warping out of shape.

On that size of disk you should only be doing a 2-3 of laps of somewhere like Donnington before letting them cool down - that means a slow lap with no braking at all & then prererably a pit stop.

Never hold the brakes on with the car stationary when the discs are hot - the pads just holds the heat in on a single spot & therefore warp. Just parking up can cause the same effect due to the different airflow around the discs - hence the above advice - keep moving as the discs cool down.

Also you may have the wrong pad / disc combination. Many people will put on higher rated pads to reduce brake fade - but that gets the discs too hot. Some fade is your early warning that the brakes are getting too hot !

Al

Pavlo

Riding the brake pedal?

What pads in the APs?

Your car isn't exactly heavy, and others have used similar kits without fade or warping. An infared thermometer might be useful next time you do a track day, and/or some thermal paint blobs.

Have you measured the discs to confirm they are warped? Sounds like you've given them a good hammering, otherwise I might suspect friction material on the discs.

Paul

peggy

iTrader: (11)

After speaking to my mate at WSR, he has suggested similar to you Paul probably compunded by the fact that the disks probably need to be stripped from the bells and all the mountings cleaned and re-set to make sure they are floating properly.

Guess i will be there with the brake cleaner this weekend.

Nigel

stockcar

the other very basic problem that a lot of people forget is "bedding" in discs as well as pads!!
if all you do is fit new discs then hammer them on a track day then you will always warp them.......try doing around 100ish miles of steady braking gradually building the pressure and heat in the disc to "temper" them
alyn - as performance

peggy

iTrader: (11)

Yeah i did that, even though the disks were second hand i had new pads in them ( DS2500 ) and i used the drive up from Southampton to get them bedded in.

Nigel

Luke

Keep you foot off the pedal...as much as possible. Even traffic lights etc after a fast run.

Richard Work

My Sti7 keeps warping discs - its been through 3 or 4 sets in 10K miles. It's a warranty issue as it is not my driving style causing this - its going to the dealers for a few days tomorrow. However they did say that if you break hard and keep your foot on the brakes at say, a roundabout this can cause warping.

I've been told it could be a wheel bearing or a misaligned flange (!) which hopefully they will find tomorrow.

If it is not your driving style causing this then I would get it checked out. I'll get a list of the things they are checking tomorrow in case it helps you - mail me if I forget to post it up.

BTW my 94 WRX lasted 45K between pads/discs!

Cheers

Richard

Hoppy

Nigel, if they are warped, it's probably because of heat-soak when stationary after a hot lap. You must keep the wheels moving until the brakes have cooled - takes several minutes to be safe. AP discs are very hard to warp even on a track day but if you're going to do it, a bit of abuse at Dono is the place I've run your set-up there (as have many others) on a roasting hot day without any problems at all.

You say they were used discs and if they are less than 26.5mm across (new disc 28mm with max 0.75mm wear per side) their hot performance is diminished and liability to warp is greatly increased. If you've also got hot pads in there, you will make things worse (but unlikely to be deciding factor IMHO).

Your discs have separate alloy bells, but they are not floating - if they do move on the bells then you really have got problems!

Richard.

Floyd

iTrader: (9)

Try reading the 'stoptech white papers' on disc 'warp'. It's quite enlightening.

F