dgmattingley

Went to a DE tech inspection on Saturday and they noticed that my rear brake rotors have grooves that feel like a series of bumps when you run your finger across them. The passenger side rotor has the grooves on both sides, the driver's side the grooves are only present on the inside face of the rotor. The tech, although not a pro mechanic, said he hadn't seen grooves like this before. I took the pads out (Hawk Blues installed at same time as rotors) to inspect them and noticed they have matching grooves.

Meanwhile, the front rotors are completely smooth. All four rotors were replaced in March of this year and have 6 track days on them plus minimal road use. I had the car at Watkins Glen a few weeks back and the braking performance of the car was great, no shudder or vibration or anything that felt weird.

I know that the usual explanation is stones/debris between the pad and rotor, but the multiple concentric grooves on all rear rotor sides, except the outer side of the left rear, makes me think it must be something else. Any ideas about what might be going on and is this cause for concern? Is there another explanation besides stones on the pads?

trophy

I have always had my stock drilled rotors get grooves in them, front and rear. It always happens with more aggressive brake pads.

Bill Verburg

grooving is normal, but it should be essentially even on both sides of the rotor, it sounds like you may have stuck pistons on the outer drivers side.

It is also unusual to have the rears that much more worn than the fronts. W/ RS brakes I go through at least 2 sets of fronts(closer to 3) for a set of rears. But the fronts always crack out before they wear out.

Greg H.

I don't think there is cause for concern. I always get grooves front and back. I'm servicing my car right now, ordered new rear rotors but decided to keep my heavily grooved rears on a bit longer since the pads are only 30% gone and the cracks are minimal. The only problem I have had with grooves is that it takes a while to bed in new pads. In the old days I beleive your mechanic could "turn" the rotors - clean up the grooves on a lathe, but I don't think that is an acceptable practice any longer.

Greg H.

Paul902

+1.

BTW, nice set of mods, Don!

race911

It is. Just that no one wants to do it. If you can make your margin by replacing rotors and have near 100% guarantee of no "comeback", who'd take the risk? Rotors are cheap now, anyway.

(Missing my brake lathe, but have no realistic need to get another one.)

Mark in Baltimore

Was this Jamie Ford's old car?

dgmattingley

Yep, that's the one.

Thanks, same to you. RS uprights and tie rods are next on my list.

John H

increased surface are equals better rear bias.

dgmattingley

I'll have to pull the calipers off and have another look, the pistons looked fine and even the dust boots from my winter rebuild seem to be holding up nicely. The outer driver's side did have some very mild grooves, but nothing like the ridges on the other three sides.

My Cayman wore the fronts a lot more than the 993 so far...even after 6 track days the fronts have no signs of cracking and no grooves.

Bill Verburg

A Cayman is much more front biased, when I take rotor temps on them I get more than x2 the temp in front as in back

I wouldn't expect much grooving after only 6days, that's why the rears stand out anomalously

mhm993

As always, BIll offers a useful answer.

Enjoy Jamie's car--he drove the wheels off of it.

dgmattingley

Interesting about the Cayman brake temps, and that mirrors my experience, those front brakes got HOT.

Out of curiousity, what are the relative rotor temps on your 993? One thing I like a lot better about the 993 is the brake feel and overall stability under hard braking, the Cayman sometimes felt squirrely in the rear when braking from 120+.

Since I haven't had any problems with the brakes in terms of performance I think I'll just keep running the rotors/pads and keeping a close eye.

Thanks, enjoying it a lot so far and sliding my way down the slippery slope of never-ending mods.

Mark in Baltimore

Cool, congrats on getting a nice car.

race911

Something about 40/60 weight distribution. Never driven a Cayman (nor a Boxster hard, really), but it was always a challenge with 914/6s way back when. Except for the one car we had Tilton dual master cylinders in........