mark kibort

what kind of calipers are they? they look a little narrow, but longer. Do i see 6 pistons?????? Nice!

What size pads are they? New GT3 cup?

Looks like that kit could fit the side mount 928S brakes. very cool

mk

mark kibort

you do make a good point though, as im wondering since the parts will be made this next week, if we should change the material to steel. If there is any chance of this spacer made of aluminum to compresse, the bolts could become loose over time. Now, that scares me a little.

should I change the spacer material to steel?

mk

Olli Snellman

Fronts are 996 GT2 and rears are 996 GT3. Adapters are built for 951.Most likely 928S have similar brakes.

dr bob

Mark--

Steel will eliminate differential expansion issues, but is most likely not needed. Solid AL spacers should be fine. I would make it a point to verify the bolt torque at least a few times before/after a session. Clean threads (chased!) and a drop or two of Loctite on the threads a plus. IIRC, there are no lockwashers under the caliper bolts so keeping them tight is a must. Use the right length and strength bolts, NEW of course. Two shear planes on them now.

Lizard928

Mark, the aluminum would be OK.

the problem with your spacers is the thinner edge on them, this is where it will be able to VERY easily deform. The REALLY need that large mating face on both sides. If you put the thin face towards the caliper it will dig into the caliper, if you put it towards the hub it will crush slightly, but it will deform more as used. where this will not be the case with one that has a proper face on both sides.

mark kibort

Thanks Colin and Bob,

Thats why for the test, i put the narrow side down toward the steel hub. I only used about 20ftlbs and went for a test drive. first with one side with the larger diameter rotors. couldnt tell much, but i couldnt really simulate a threashold brake, but they didnt favor one side or the other. then i put on the other side and it started to rain. so, i wont do a test to see how they feel and bed the brakes until the real spacers show up. however, i did check the tension after the 2 mile test and they were still lightly torqued.

They look great and the dremmel work was pretty easy. about 20min tops.

There you go. the brakes the car SHOULD Have had from the factory!

I predict much better wear, better braking capacity, and less cracking. all for REALLY CHEAP!!

mk

Vilhuer

IIRR 928 S has slightly different mounting points. This would be easy to check.

mark kibort

Some final pics. Now that I knew how much material to take off at the ends of the calipers, the second pass was easy.

Pretty easy upgrade considering what is gained!

Now, looking at a week of raining, so no chance to street test for a while. Jan 4th we have a test day at Thunderhill so I will be digging deep to see what these brakes can do now! (and new pads.)

mk

Lizard928

Mark,
How much time per lap do you think you could shave with true slicks?

mark kibort

Most of the guys I run (or know that run both ) with as well as Anderson, at the tracks we have a ton of time at, generally see about 2 seconds a lap for slicks. I lost near 4 seconds a lap using 280 tread wear tires, and so did anderson, so I figure slicks must be 2 seconds faster in the other direction vs DOTs. Plus, i use a very moderate DOT tire compared to the new stuff most of the guys use in SCCA .(i.e. new hoosiers. some even use autocross A6s vs the R6s!)

mk

mark kibort

I was waiting for someone to catch the rotors being installed backward.

I was just doing the mock up test, but when it started to rain, i had to back my car into the garage to work on it, and the wheel i started with was not the one that was fitted with the rotor that I unboxed. The error propogated when I then went to fit the other side.

I should be getting the "real " spacers by this weekend to finalize the job and bed those new fancy racing pads!

Mk

Lizard928

I think everyone was too busy cringing at the thought of your nut spacers to even be thinking about the direction to rotor would be turning!

RyanPerrella

mark

do a couple laps on these, then wash the car, let it dry, wash it again some time down the line, let it dry.....you will have massive rust rings around the rotors.

I am glad you finally got the rotors, you can always in a few months time or whatever just buy the GTS big black calipers and their larger pads to complete the upgrade, otherwise its really a bit shadetree for me in all honesty. Sure the rotors are larger and the torque will be greater as the contact point is farther from the hub, but i think you really need to reconsider getting the actual big black calipers and pads.

the flyin' scotsman

Intresting comments Ryan.............I've thought same all along.

Given the Holbert car is at minimum weight a stock GTS set up maybe a great starting point with racing pads............MHO.

mark kibort

Have you looked at you rear hubs lately? There is a rust ring around the bottom there as well as the entire zimmmerman hub up front. IN FACT, there is a rust ring around the stock zimmerman front rotors of exactly the same size as the exposed area that will be on this rotor, so basically, there wont be any difference. (see pic of stock S4 rotor below) If I really cared what the disc looked like .5" from the center hub, i could paint it with high temp paint. again, the pads are near the same size as the ferrari F50 brakes and the only difference really, is in the fact that this is a smalller rotor, but the same as the GTS, and its not a 2 piece set up. Ill post pictures after the first few races. Im certain that it will look fine.

the inner area of the pad is hardly worth the extra $1000 to upgrade. IN fact, i believe that the area separating the hub from the disc /rotor contact area is useful in cooling the rotor, and transfering less heat to the hub.why do you think all real racing brake systems have thinner and if any larger, longer pads? The GTS pads are the largest pads available in thickness, and I dont know how usefull that is in a racing situation, but i feel confident that when you look at the other racing brakes available, you suddenly see length might be more important.

mk