Brembo GTP-L install questions

lally911 · 09-15-2006, 07:12 PM

Did a test fit of the Brembo GTP-L rotor/caliper combo tonight on my 85 track car and ran in to the following problem. The ball joint end of the a-arm nearly makes contact with the rotor. As the a-arm swings up the distance between the end of the a-arm and the rotor is .018mm which is really close. Here is a picture.

I think the end of the a-arm can be ground down a bit to increase the clearance. Did anyone else run in to this and are there other creative solutions to increase the clearance?

Also, is the stock turbo master cylinder the correct one to use to upgrade to 23mm and retain the vacuum assist with this setup?

Thanks for any help.

Jeff Alton · 09-15-2006, 07:29 PM

My GTP kit uses the sam rotor and I had much more clearance than that. I have ERP front end now which also has more clearance. That does not look right. I know TRE has installed a few so maybe they will chime in. How much negative camnber are you running?

Use the 23.8mm turbo MC with the proportining valve left in the rear line.

Cheers

Jeff Alton · 07:45 PM

On second though after looking at some of my pics it seems as though mine is really close as well. here it is with the TRG front end which used the factory ball joint....Since changed to the ERP stuff and it uses its own ball joint which provides more clearance.

Cheers

TimT · 09-15-2006, 07:42 PM

You can get a spacer to move the whole hub out. I used a 1/4" spacer on mine, Or you can grind away on the end of the A-arm to get your clearance.

mmastro · 09-15-2006, 07:44 PM

A few years back, (when I still had the stock A-arms) I ran into this exact problem on my 993TT brake setup on my 77 930. Only I didn't mock it up first, I found the beginnings of a groove on the inside of my rotor.

I don't recall mine being THAT close at the center of the A-arm though.

I did what you suggested, I ground off just enough to get about a 1 to 1.5mm clearance and had no problem after that.

If I remember correctly, you must also turn you wheels lock to lock to make sure you have a full range of clearance for the rotor. You may find that you have to grind a bit off of the sides (circled in your photo) as well. Good luck and keep us posted.

I like the spacer idea....maybe research that!

TimT · 09-15-2006, 07:46 PM

BTW the raised spindle shocks exacerbates the problem, as the spindle is raised the rotor moves closer to the A-arm

Jeff Alton · 09-15-2006, 07:47 PM

If you use a spacer, don't forget to figure out how to space the caliper out a similar amount.

Cheers

lally911 · 09-15-2006, 07:47 PM

Its stock struts and ball joints with ER monoballs and set at about -2 degrees camber.

lally911 · 09-15-2006, 07:55 PM

Spacers on the spindle and on the caliper mount sounds like a good idea. I'll check the clearance with the wheel turned all the way to see if the sides of the a-arm are a problem as well. Good ideas folks, thanks!

mmastro · 09-15-2006, 07:56 PM

I also used the 23mm boosted MC out of an 87 930 for my 993TT complete brake kit....works magnificently well!

lally911 · 09-17-2006, 10:41 AM

I ground off the end of the a-arm and now have enough clearance as shown below. To use a spacer behind the inner bearing race would have also required removing some material from the caliper mount adapter which I didn't want to do. Tim, how did you space the caliper out?

Another problem that came up is that 16x7 951 wheels don't come close to fitting over these calipers. Maybe they'd fit with some very large spacers but I don't want to do that. Also tried some 17" Lindsey wheels with no luck. The bolt ends on the inside of the wheel hit the caliper. For those of you who have these brakes what wheels are you running and what spacers, if any, did you have to use? Looks like I'll be in the market for some new track wheels soon.

Keith

Jeff Alton · 09-17-2006, 11:03 AM

The lindsey wheel is made on a 16x6 fuchs so it will not fit without spacers. I *think* you need to use a 1/4 inch spacer on the front with the 16x7 which makes fender clearance an issue. I ended up going with 17 inch 3 piece wheels to clear my GTP's.

Have you tried the rears yet? Both the GTP and GTP-L use the same rear caliper and I could not get a 16x8 fuchs to fit in the rear with out a spacer either.

Cheers

Rick Ilcisko · 09-17-2006, 01:16 PM

I had the same thing happen with my 83SC. I have the rotors from Steve at Rennsport. It was only on hard right hand turns and ever so slight rubbing. I know others have done this conversion with no complaints. I used a grinder and did the same thing as Keith did. No more problems and its been 3 years. Rick

lally911 · 09-17-2006, 03:07 PM

Got hold of some 1/4 " spacers today and found the following:

front with 1/4 spacer - 16x7 951 fuch - fits but very tight - wheel weights could be a problem
front with 1/4/spacer - 17x8 Lindsey - fits but bolts barely clear
rear with 1/4 spacer - 16x9 fuch fits but wheel weights hit caliper

Jeff Alton · 09-17-2006, 03:42 PM

I know some have ground down the caliper through bolt heads to aid on clearance as well.

CHeers