Originally Posted by climberrn
I have read the thread and am very interested in upgrading. It seems like you guys are just upgrading the disks (rapco), making the spacers so it fits properly and upgrading the o rings on the stock matco calipers. Am I missing something? Need to change the master cylinder or calipers? I see the Cleveland kit for $700. Are you getting that also, or just getting the disks separately and making your own shims?
Sorry if it’s need answered before, but I just couldn’t figure it out.
Hey climberrn, here's what I did:
Purchased the new thicker Rapco discs and installed them on the wheels.
Fabricated a 1/8" thick aluminum shim, same shape and hole pattern as the gold Matco caliper spacer, to put the calipers 1/8" further apart to accommodate the thicker discs. Bought new AN4 caliper bolts, 1 grip length longer, to account for the new spacing.
Bought (actually a kind forum member sent me his spares) two arbor shims to fit on the inside of the axle (one on each axle), along with the Vans spacer, to put the wheel 1/16" further outboard. This helps to keep the thicker disc from hitting the wheel pant mount bracket and keeps the centerline of the new disc in the same location as the centerline of the old disc, so your calipers are happy. Someone else recommended part number 5GA99 from Grainger. That looks like it'll work.
Then you'll have to shave either the outboard axle spacer or the axle nut by the same amount (1/16") to keep the wheel pant from getting stretched and possibly cracking. I chose to shave the inboard side of the wheel nut. With some careful attention, you can even get the cotter pin holes to line up where they were before and still have the right compression on the bearings.
Once this is all done, check that the inboard wheel pant bracket isn't rubbing on the new disc and that all is still rotating and working freely. On my plane this all fit OK, but inspect carefully because you're stuffing more junk into the same space and possibly changing geometry in an already tight area.
I didn't do anything to my O-rings.
I may have mis-remembered on the thicknesses. Since other posts seem to indicate the new disc is 1/4" thicker than the original stock, you'll need to shim the caliper by that amount and get new caliper bolts to take up that extra distance (2 grip lengths for 1/4"). Then the arbor shim would be half that (1/8") and the axle nut would be shaved the same amount (1/8"). Bottom line, measure the thickness of the new discs relative to the originals (when they were new) and shim for the difference. Be careful not to shim too much, or as the pads and disc wear you might push the piston out of the caliper or un-seat the piston o-ring before the pads contact the disc, losing all braking action.