Judder under braking (Track day)

[marky_p72]

Hi all,

I just did my first TD in the Cup and had braking issues as above, but only after 10-15mins, so being caused by heat build up. I have realised the pads I have in must be 'Green stuff' which I think aren't great for track use and I suspect are the issue. Disks seem fine and not an issue when cold and fluid has been changed in May.

I always used Pagid RS42 (Blues) in the previous 111r, but I'm wondering whether to try RS14's? 

Also, can I get away with changing just fronts for now, or should I do all four? They're just bloody expensive! 

TIA

Mark

 

[chris_h]

I definitely would do all 4 at the same time otherwise you are going to mess with the front rear braking balance.  This will be even worse on track as the pad friction changes with heat this will be an even greater variable on track with higher temps.

Just to say I had an issue with pad transfer on RS14’s creating judder on my old s2 exige with big brake kit.  I tried the bedding in process a few times but couldn’t get rid of it.  It was fine at road speeds, but every time the brakes got hot on track it came back.

Somebody recommended the following and it worked for me…  soak the disks on the car with water (both side with a hose).  Leave it a half hour for surface corrosion to start then roll car forward half wheel rotation without using brakes and then soak disks again.   Then don’t move car for a couple of days ideally. You want the disks to look quite rusty on the surface.  Then drive car with very gentle brake pressure to use the surface corrosion as a abrasive on the surface.  (The other option is to have the disks skimmed.)
 

Then do bedding in procedure  (I’ve always done 70-30mph in groups of 5 close together half a dozen times on an empty stretch of a road at night.  If you’ve done it right you should have some blue discolouring front heat on the disks.

After that I never had it again, but was sure it was caused by the Abs cutting in when the brakes were extremely hot and the disks not being bedded it correctly before and causing a uneven pad material transfer on the disk.  (Lots of pads like RS14 work by transferring some of the pad material onto the disks.)

 

I actually made a video of the judder at the time and put it on youtube 12 years ago when I was trying to solve the issue…

 

[DeanB]

Def do both axles. You could try Carbon Lorraine - I have them and rate them. RC5+ on the front and RC6 on the rear which are higher-friction. It gets the back axle doing a bit more.

[marky_p72]

Thanks for your replies above. 

I think the rear discs are a little old now (maybe original??) and started 'lipping' but the fronts have been replaced more recently, so I have decided to order a pair of 'EP belled discs' to go on the front and move the existing fronts to the rear. I have also stuck with (and ordered) Pagid RS42's as they always seemed good on the 111r.

Fingers crossed!