Best way to shave down brake pads?

69427

69427

The Artist formerly known as Turbo84
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Clinging to my guns and religion in KCMO.
I'm thinking about moving to a slightly different compound for the front brakes. This means new (full thickness) pads. I've got (IIRC) .034" stainless shims in there at the moment for a bit of thermal impedance, and a set of .058" SS shims for the future. I got a bit of spongy pedal a couple times at the track yesterday as I was still getting to know the course and was entering a couple of the corners too hot. I'd like to use the .058" shims for a bit more piston insulation, but I can't fit them yet. I realize I only have about 500 miles on these pads, but these are all track miles (I don't have the car licensed yet due to it being apart most of the past couple years). So, I'd like to take about .050 off the new set of pads so I can go straight to the .058" shims. What's the best way to shave the pads without contaminating them?

Thanks,
Mike
 
Belt sander worked like a charm. :thumbs:

While stuffing in some additional stainless shims (.038" in addition to the .058" I've been running) between the pads and pistons of the front calipers I noticed a bit of uneven drag when I spun the rotors. I put my dial indicator on the front rotors and got .005" runout on both of them. Re-indexing the left side rotor got the runout down to .003" (I haven't pulled the rightside caliper off yet to pull the rotor and re-index it). Obviously I'd like to get rid of all the runout, but how do I shim something this thin?

Also, I haven't put the dial indicator on both sides of the rotors to see if they're absolutely parallel (equal runout). Perhaps I'll play around with my micrometer or caliper to see if I get any differences in thickness around the circumference.

Thoughts or input is appreciated.
 
69427 said:
... how do I shim something this thin?...
Click to expand...
My machinist buddy gave me a metal sheet calibrated to 0.001", it was bronze like.
I did cut some washers shaped shims out of it.
If I had to put two of those shim on a stud, adjacent studs get one too, "smearing" the shiming thickness if you see what I mean.
I had 0.005 at worst after dialing, got four rotors to 0.002 with 3 to 5 of those shims per rotor.
From my understanding this kind of sheet is common supply for machinists.
It was feeling like household aluminum sheet....
 
denpo said:
69427 said:
... how do I shim something this thin?...
Click to expand...
My machinist buddy gave me a metal sheet calibrated to 0.001", it was bronze like.
I did cut some washers shaped shims out of it.
If I had to put two of those shim on a stud, adjacent studs get one too, "smearing" the shiming thickness if you see what I mean.
I had 0.005 at worst after dialing, got four rotors to 0.002 with 3 to 5 of those shims per rotor.
From my understanding this kind of sheet is common supply for machinists.
It was feeling like household aluminum sheet....
Click to expand...

I did one with tin foil from the kitchen some years ago on back of my car, still there....and I like Jeff's idea there too......:hissyfit:
 
McMaster sells steel shim washers down to .001 (or less) that you could put on the studs.
 
why not remove a bit off one side of the rotor? (in short, the opposite of what my brake calipers did to my rotors) :)
 
Well, got the runout reduced a bit on the fronts. On the left side I rotated the rotor 144* (two positions) which reduced the runout to .003" (from .005"). I then used Gene's aluminum foil suggestion and got the runout to about 3/4 of a thousandth. The right side started at the same .005", and rotating the rotor two positions got me to .001". Every time I tried to shim it "straighter" I ended up with additional runout so I left it at .001" for now.

Still have to check the rears when I get done with a couple other things.
 
69427 said:
Well, got the runout reduced a bit on the fronts. On the left side I rotated the rotor 144* (two positions) which reduced the runout to .003" (from .005"). I then used Gene's aluminum foil suggestion and got the runout to about 3/4 of a thousandth. The right side started at the same .005", and rotating the rotor two positions got me to .001". Every time I tried to shim it "straighter" I ended up with additional runout so I left it at .001" for now.

Still have to check the rears when I get done with a couple other things.
Click to expand...

Mike, I dunno where I got the tin foil suggestion, but I just did it by feel years ago, before the HB conversion everyone hates.....and got the right rear to be un feelable on runout, compressed the pistons, fired up engine, used my fingers to feel runout on rotor, when I didn't feel anything, I thought 'close enough for .gov work' and bolted it up....been fine...course I not flat out racing, just quicker than average street driving....

:ghost: :trumpet:
 
Well, got everything put back together (and a home re-alignment after changing the upper control arm pivot height), but damn the brakes are giving me problems. I've bled the crap out of them, but they're still not as good (travel-wise) as they were before I took everything apart. I've been trying to get stuff back together for a track day this week (Wednesday), and I'm going to be pissed if I can't make it, or if I end up with excess pedal travel issues on the track.

I'll give it another try tomorrow.
 
are your stainless heat shield shims providing any spring action against the pistons?

That's one concern i've always had about heat shields.

What you have now is a sandwich of 2 shims. If they're not completely flat against each other that will give you some sponginess.
 
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turtlevette said:
are your stainless heat shield shims providing any spring action against the pistons?

That's one concern i've always had about heat shields.

What you have now is a sandwich of 2 shims. If they're not completely flat against each other that will give you some sponginess.
Click to expand...

We're on the same wavelength here. I was wondering the same thing. I have looked at then up close several times, and visually there's no indication of an issue, but it's a cheap "experiment" to pull one shim out and see if the pedal improves.
 
Only way we could get all the trapped air out of the EP BMW we used to race. Was to take the caliper off the rotor, put a block of wood between the pads. Bleed it at all angles. Hopefully you will have enough movement in brake line. Tap on the caliper with a steel hammer as you bleed to dislodge bubbles stuck to the walls of the caliper.
 
Well, I pulled all the shims out, and still have some shitty brakes (long pedal travel). I didn't mess with the rear rotors/calipers when I was doing the runout/camber-gain changes, so nothing should have gone wrong there. I'll pull the front wheels off again and try bleeding the calipers again (I did tap the calipers with a hammer last time). It's a bit of a PITA pulling the calipers too, but if that's the only thing that gets me back in business then I guess I got no choice.
 
69427 said:
Well, I pulled all the shims out, and still have some shitty brakes (long pedal travel). I didn't mess with the rear rotors/calipers when I was doing the runout/camber-gain changes, so nothing should have gone wrong there. I'll pull the front wheels off again and try bleeding the calipers again (I did tap the calipers with a hammer last time). It's a bit of a PITA pulling the calipers too, but if that's the only thing that gets me back in business then I guess I got no choice.
Click to expand...

Are you using a power bleeder? Some say it makes a difference. I guess it just blasts the air out.
 
turtlevette said:
69427 said:
Well, I pulled all the shims out, and still have some shitty brakes (long pedal travel). I didn't mess with the rear rotors/calipers when I was doing the runout/camber-gain changes, so nothing should have gone wrong there. I'll pull the front wheels off again and try bleeding the calipers again (I did tap the calipers with a hammer last time). It's a bit of a PITA pulling the calipers too, but if that's the only thing that gets me back in business then I guess I got no choice.
Click to expand...

Are you using a power bleeder? Some say it makes a difference. I guess it just blasts the air out.
Click to expand...

DARE I say it???


:hissyfit::surrender::censored::bounce:
 
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