Big Reds or GTP ?

[NoLift911]

All,

On paper it looks like a no brainer - if you had the option or access to both which would you choose?

Looks like Brembo did they're homework on the new GTP's. Anybody install these yet (not the lightweight kit) the intended replacement for big reds.

-Jeff
nolift911@hotmail.com

[Bill Verburg]

Its not so obvious at all when the very significant question of bias is factored in.

If the specs for the GTPs that I got are correct then they are very front biased compared to a stock 911, the Big Reds are slightly more rear biased than a stock 911

[OZCarrera3]

Hmmm, in my mind that raises fruther questions relating to bias.

Obviously the bias is different on 911's due to the fact there is a lot more weight over the back wheels and the fronts are less laden and therefore liable to lockup. Does that mean that retro-fitting the callipers from a 944 S2 or 951 would have the wrong bias also? Have people retro-fitting these to their cars experienced any problems with weight bias and premamture lockup?

[Lukesportsman]

Did Brembo not change the piston size to customize these kits for the 911/930 chassis and weight bias? Why would they design a top shelf part with a fairly premium price that doesn't improve on pre-existing kits?

I can't think of a brand of brakes that I would rather have on my cars, so why doesn't even the best get this "right"? Bill, I'm not questioning your statements as much as I'm trying to figure out why this is still an issue after brake kits have been around for so many years. Don't they get feedback in their R&D and therefore make corrections based on this. What are/did the true racers use.....something all together diffferent with larger calipers and bolt together rotors for sports car racing?

[NoLift911]

Bill -

How are you figuring the bias issue? According to Brembo they say the GTP's are much better balanced than the big reds -

http://www.rennsportsystems.com/1-sf.html

I am sure there is some hype in there...

Put aside that fact the for the most part a new big red kit is NLA...

These seem like a viable alternative...bias issue aside. Heavy front bias cannot be worked out? Rear can?


-Jeff
nolift911@hotmail.com

[Craig 930 RS]

Same ?s I had.

Refer to:
* BIG red brakes - soon to be NLA *

[porsche356a]

I just put the Big Reds (Brembo GT kit) on my mostly street car...

They are more brakes then you would ever need.

Btw, I used my stock 20.8mm M/C. The pedal is softer, but given the ease of locking up these brakes, I am glad I have a little extra room in a panic.

The only downside is that there is a lot of brake dust (and hence an intermittent squeal).

[Bill Verburg]

Does that mean that retro-fitting the callipers from a 944 S2 or 951 would have the wrong bias also?

No, as long as matching sets of 36/40 & 28/30 or 36/44 & 30/34 on appropriate(304 & 309mm) rotors are used

[Bill Verburg]

nolift911, The info I recieved from Race Technologies, states that the GTP kit uses 40/44 front and 28/30 rear calipers on the same rotors as the Big Red kit. That takes the rotors out of the bias equation.

For those calipers bias works out to ~2.1 favoring the front w/ neutral rotors. For comparison the Big Red/993RS kit on my car is ~1.472 front w/ neutral rotors, stock 911 is 1.596 w/ the rotors pulling it back a bit, stock 930 is ~1.6 front w/ the rotors pulling it back a tad.

Now if the information I recieved is correct the only other car w/ 2 front is a 993tt w/ a very sophisticated ABS system backing it up.

It is quite possible that Race Tech sent incorrect info, at one time they told me their Big Red kit was a 36/44 & 28/28 as used on the 993tt, this of course I know to be false because I can see and measure the ones on my car. I would love to hear some actual #S from a GTP kit owner.

[Bill Verburg]

Btw, I used my stock 20.8mm M/C. The pedal is softer, but given the ease of locking up these brakes, I am glad I have a little extra room in a panic.

I hope that this is taken in the spirit it is given, but it is actually easier to lockup the brakes the smaller the slave to master ratio is.

I am unsure as to what brakes are on your car but lets assume it is the normal RaceTechnology Big Red kit. In that case the slave to master ratio w/ a 20.6mm m/c is ~25.6. W/ the better 23.8mm m/c the ratio is ~19.2 and w/ the best 25.8mm it is ~16.8. Again, for comparison purposes only, stock SC is ~17.6.

The lower the ratio the more easily modulated and the harder to lock the brakes will be at the cost of higher effort.


On my cars I have used as low as ~16.2 unboosted and wouldn't recommend anything lower, The lowest boosted is 993tt at 14.9

[NoLift911]

Thanks for the info Bill -

The GTP kit is on it's way to me as we speak so you may just get those numbers.

With Brembo phasing out the BR's it remains to be seen if these(GTP) can live up to BR's past. Lighter is good caliper wise with the thermal reserves of BR's - heavy front bias is not.

I will be installing a 930 m/c and was intent on removing the p/v. Is this still a good idea for the GTP kit IYO?

I assume Brembo spent some time on this system but am curious how much of it was engineered/tested for a 911 if any.

The car (84 Carrera) will see light track duty.

-Jeff
nolift911@hotmail.com

[Craig 930 RS]

"I assume Brembo spent some time on this system but am curious how much of it was engineered/tested for a 911 if any"

What I was thinking.
I would assume these are brakes for many purposes - the trend now is not only towards BIG wheels on vehicles, but shifting also towards bigger brakes for stopping/bling on non-911 rides. Perhaps the GTPs are for many other cars --- most of which do have ABS.

I still wonder why Steve Weiner said they have better rear bias.

Hell, I'll ask him now and post his answer.

[Bill Verburg]

The GTP kit is on it's way to me as we speak so you may just get those numbers.

Great, please take lots of pics and weigh everything, 4 critical #s that are needed are the f/r piston sizes. If you just measure the seals I can only estimate the piston sizes, if there are anti-squeel spyders there may be piston sizes printed on them as well.

Lighter is good caliper wise with the thermal reserves of BR's - heavy front bias is not.

Thats true.

I will be installing a 930 m/c and was intent on removing the p/v. Is this still a good idea for the GTP kit IYO?

From what i have seen, yes, but it does depend on the piston sizes.

[porsche356a]

Thanks Bill... I am not opposed to the turbo M/C. I may give it a try and see which I like more.

Now, how am I supposed to get the brake dust down? At lease, I assume it is brake dust. It could be the black paint coming off of the rotor. I am not sure which pads are in the kit, but they look like street pads. My wrench thinks they are Pagid blacks.

Btw, the kit was the Brembo GT Big Red Kit. Brembo Calipers (993TT), rotors, hats, mounting h/w. Worked with the stock e-brake. Only thing I had to do was cut the ears off the trailing arms for the brake dust shields.

[Craig 930 RS]

Who & what is the make model m/c that is larger than the 930 m/c?
Seems it would be a good choice for larger brake setups.

[NoLift911]

Craig not sure who but I believe the size is 25 - I asked this question some time ago and Bill said it was alot of work. Correct me if I am wrong) Along with the fact that the 930 m/c should be very good for either setup. My take was it wasn't worth the effort save for a dedicated track beast maybe...

-Jeff
nolift911@hotmail.com

[Bill Verburg]

Now, how am I supposed to get the brake dust down?

It' brake dust allright, learn to live w/ it, or pull the wheels every week and clean them inside and out, that's what I do.

Unless you changed them the pads are Textars, Pagid will dust as badly or worse.

the kit was the Brembo GT Big Red Kit. Brembo Calipers (993TT), rotors, hats, mounting h/w

Sounds like what I have, which is 993tt(Big Red) font and 993RS rear

[Bill Verburg]

Who & what is the make model m/c that is larger than the 930 m/c?

You would need to t/p a full hydraulicly boosted setup from a 993tt or 993C4S or 993RS.

You would need most of these parts

[Craig 930 RS]

Then I'll be staying with a 930 m/c....

THX

[Bill Verburg]

Another option, that would be only a little easier, is a dual master setup, twin 1" masters would do the trick.