Fullpower

Edit: It's been a year, and these are still, by FAR the strongest brakes I've ever pushed the pedal on.
. Easy fit, and very good upgrade for the half ton GMT800
.I have assembled the following parts, in attempt to UPGRADE 2003 Suburban front brakes:

Rotor, 6 Lug 4Wheel Drive 13.5" Raybestos 582458ZN (Zinc coated )
or Carquest YH653387P ( painted )
.
Caliper 4 Piston LEFT ACDelco 13545382
Caliper 4 Piston right ACDelco 13545383

Pads, Raybestos Ceramic MGD2173CH
Carquest PXD2173H

Fullpower

13.5" Rotor vs 12.99"

Fullpower

13.5 rotor is taller than 12.99" rotor ( near an 1/8" more backspace.

Fullpower

How much can I " SAFELY " grind off this HUMP to allow 17 inch factory GMT800 wheels clear ?

adriver

iTrader: (1)

What I have read, you can't. The factory 17's won't fit because of the barrel. I'm pretty sure they won't fit because of the face either, and I'll bet its too much. You would also need a shim to center the caliper over the rotor, by what should be the difference in those two heights right there, (unless its half, but I can't think right now). That will make clearance even tighter. Either way, Not with the FACTORY, 17s.

wardlws

I've seen the bump ground down flat, but you risk catastrophic failure. Those calipers are cast (not forged) and are weaker than say Brembo calipers. The bump is there to keep the caliper from splitting / cracking under hard braking. If it cracks, you will immediately lose hydraulic pressure and quickly lose front brakes.

I recommend that you get some wheel spacers until you can find wheels that will fit them. A wheel shop can help with this.

Also, be prepared for the brake pedal to travel further for the same amount of brake force, since these calipers require more fluid to push the pistons the same distance. You can compensate with a larger bore master cylinder, and hydroboost to compensate for the increased pedal effort from the larger master cylinder.

1FastBrick

iTrader: (17)

has any one taken the piston out of one of those? My thought is the rib was for a fluid passage that may be in the casting.

I know people have ground it down and so far we have not seen or heard of issue's with part failure.

shakenfake

It's not it is just a cast mark. You can grind it down with no adverse effects. I don't see why that would help caliper strength unless you are saying that they crack down the middle. In which case I'd like to see a documented failure of that. @dantheman1540 has ground them down and has been on them for a while

17s won't fit though, need 20s or bigger.

wardlws

Yeah, my first thought was also a hydraulic tube in the casting... great idea on taking a piston out to see. I've seen the bump ground nearly flat without issue, but it could be that only leaves a razor thin amount of material for such a fluid channel.

I still think the bump is for strength; regardless if there is a fluid channel. You might grind it some, but I would recommend extreme caution here.

If you do pull a piston... please snap a picture for us!

Fullpower

.....
My measurements and posted picture indicate that the 13.5" rotor is about an 1/8" taller ( ie more BACK SPACE) as compared to the older NNBS 12.99" rotor. Using the correct, appropriate 2020 spec 13.5 inch rotor should NOT require additional, non factory SHIM or spacer to center the 2020 spec 4 Piston caliper.
..... I "think": that those shimming/spacing the caliper are trying to compensate dimensions to continue running the old, smaller rotor with the NEW 4 piston calier, which I wish to avoid.
.... " We don't want no STEENKING Shims"
I will update this thread when I get everything lashed up..
.
.EDIT:
Adriver is correct, shims were required to center the caliper.
I used 9/16 ID flat washers, stock thrust washers from 40MT Delco starter worked well.
Any starter repair shop will have 50 or so in stock.. Next time I have a wheel off, I will verify the total shim thickness.