+2 Brake Disc Minimum Thickness + Run Out

[david.g.chapman]

I had a look at the old posts for this, and was not quite clear on the front disc thicknesses (new/worn out).

So I am posting what I think they should be:

+2 Front (same as Triumph GT6) New 13mm, worn out 11mm

+2 rear (also applies to 2 seater Elan): new 10mm, worn out 8mm.

Run-out (both front and rear): less than 4 thou. I found this hard to achieve on the rears, and had to resort to shimming the disc mounting points. As this stresses the discs a bit, the run out changes as the discs heat up and I get sight vibration under heavy braking - not too bad. I will have a reshim this winter and maybe try and eliminate them

Good luck out there!

Dave Chapman.

[alan.barker]

for the rear disks you need to machine the disk locating lugs on the driveshafts square to shafts where the Wheel bearings locate. The best way is to remove drive shafts and machine in Lathe or Milling machine square
Alan

[david.g.chapman]

I totally agree Alan.

I think you would have to replace the rear discs as well when starting from a true mounting plane, as the discs would have worn out of true.

A long way behind second best might be to ease the ears the disc is mounted on by trial and error, refitting the discs each time . In this case you run the risk of taking off too much material if you get it wrong

I think I will go for an easy route for now, and adjust the shims to give minimum run-out. That way I get to keep the discs. If I can't achieve 4 thou I will think again.

Cheers

Dave.

[alan.barker]

you can get peelable shim and each layer is .002"
In the past i had a lot of vibration with brakes on a +2 and it had cracked a rear disk. It also damaged the rear Wheel bearings. One bearing had wasted the driveshaft
Alan