Spridget big brake issue

F

Frogeye

Well-known member
I lost my brakes at the Runoffs and thought it was a master cylinder, not. Found a leaking caliper but that wasn't it either. The outer piston on both front calipers are rubbing the hats on the disks. It's not the caliper housing, I've already relieved that area. MGB calipers, Spitfire disks. I had to change to EBC-UPR 198 disk because I couldn't find any Brembos. Never had the problem with Brembos, but have been using the EBCs for a while without apparent issues. I had changed the calipers before Runoffs and installed new pads. Didn't have the problem initially, seems to have started as the pads wore. I just noticed there are 2 Spit disks #20815 for Mk 1 &2 and #20715 for Mk 3, IV and 1500. I think those may be original numbers. Can't find any differences in EBC disks available. Noticed EBC makes another disk #RK-198, anyone used them? Anyone else having this problem?
 
The problem is with the calipers and is associated with the lack of precision with the machining of much of the British stuff. It probably didn't create a problem with the original use of the calipers in an MGB, but for our use it does cause an interference. The first set of calipers that I bought required me to make eccentric bushings on the mounting holes in order to pull the calipers out away from the top hats of the rotors. The set I have now has no such problem and only requires that the caliper be relieved a bit in order to get clearance. I haven't used anything but the Brembo rotors so far, but I suspect that they are not the problem. You said that you changed the calipers before the Runoffs - try your old calipers for fit and see if the problem goes away.
 
I have had issues in other applications with cheap rotors glazing over, Switching back to a quality rotor fixed it every time.
 
I ran the last half of the race with very little brakes left. I still run the smaller front brakes and have never had this problem when running new pads. I understand Laguna Seca is particularly hard on brakes and now I must think about installing the bigger brakes. This information should be helpful if I do make the change.

Thanks again Rob for the help in getting my battery charged so get back to my paddock in the dust bowl.
 
I always put hats on the lathe and relieve that area. It is a very tight fit. I keep one old hat as a hanger queen so when I buy new ones I know from where to take metal. It isn't a lot of relieving, just critical. My bet is you should try your old ones and they will work.
 
I measured this weekend and hat diameter is the problem. It's about 1/8" diameter larger (EBC disk vs. Brembo), just enough to conflict with the piston. Wish I had known this before the runoffs, I'm going to turn them down. Wish Brembo still made them. Anyone tried the different style EBC rotors (UPR-198 Premium vs. RK-198 Ultimax), any difference?
 
I use the UPR-198 on my car and have for 3 years. I've never had an issue with the rotors. They were better than the last set of brembo's I got as far as machining setup on the casting (runout from casting to machining).

I put a new set on every year and save the old ones that have little to no wear, overkill but hey.

Like I said, never a rotor problem, no glazing, no brake issues.

I don't run any brake ducts and generally have very high brake temps to work with the pads I've chosen (damned hawk for not making them any more on the spitfire backing).

aaron
 
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