Gtr Brembos On Gtst R33

[Kaido_RR]

Hi,

1st i've done a search and couldnt find much help

ok

-I'm looking at putting R34 GTR Brembos or R33 GTR Brembo (betweens which one i can find) onto my R33 GTS-T, i will be doing both the front and the rear

1- is it a direct bolt on? if i use gtr disc?

2- would it be worth while to use braided brake lines and if so would i use ones to suit gtr or gtst?

3- what issue will have have with the brake caliper and my rims? currently im running 17inch, 9inch wide with around +35 offset, is there a way to see if they will fit or not?

4- i read it is worth while to also upgrade the brake master cylinder, does anyone know where i can source one? (ive yet to be able to find one)

Also any other helpful hints/tips etc would be much apperciated (sp)

thanks Michael

[shozbot]

R33 will bolt on but R34 use bigger mounting bolts so some modifying will be needed

SS braided lines will always be an improvement & I think gtr/gtst are the same

Brembo calipers and 324mm rotors should fit under 17" rims but if you state what brand/style rims you have somebody might confirm this for you

I wouldn't bother with the master cylinder unless you get it for the right price. I think the difference would be minimal

Also, buy the best brake fluid you can get and fit a master cylinder brake brace (if you don't already have one)

[JCMarshall_Law]

I'm pretty sure the 33/34 GTR brakes will not bolt onto a 33 gtst, the mounting points for the caliper are different. You will need a bracket adaptor, you can get one made up if you are keen and good with CAD. Or you can look around and buy a set, I have a feeling UAS sell a kit - but I'm not sure if it is for 33/34 GTR to 33 GTST.

Yes it would be worthwile buying braided brake lines and you would use the ones from a GTST, it is their length and bracket positions that may be different. The fittings are the same (I think) but you will have to check - can someone confirm?

17 x 9 inch with +35 *should* fit, that is only my estimation.

Yes it would be worthwile upgrading the master cylinder, pigger pistons will require more fluid flow which will require a bigger master cylinder. You may find you need to upgrade the master cylinder to be legal.

BTW: This is a very expensive upgrade, what are you doing with the car? some very serious competition racing I hope? The GTST brakes are pretty good, just get good disks, pads, fluid, remove backing plates and a bit of ducting if heat is a problem. They are more than adequate for the street and fine for track days (street trim, 200rwkW, QLD raceway style straights)

[Roy]

I'm pretty sure the 33/34 GTR brakes will not bolt onto a 33 gtst, the mounting points for the caliper are different. You will need a bracket adaptor, you can get one made up if you are keen and good with CAD. Or you can look around and buy a set, I have a feeling UAS sell a kit - but I'm not sure if it is for 33/34 GTR to 33 GTST.

Yes it would be worthwile buying braided brake lines and you would use the ones from a GTST, it is their length and bracket positions that may be different. The fittings are the same (I think) but you will have to check - can someone confirm?

17 x 9 inch with +35 *should* fit, that is only my estimation.

Yes it would be worthwile upgrading the master cylinder, pigger pistons will require more fluid flow which will require a bigger master cylinder. You may find you need to upgrade the master cylinder to be legal.

BTW: This is a very expensive upgrade, what are you doing with the car? some very serious competition racing I hope? The GTST brakes are pretty good, just get good disks, pads, fluid, remove backing plates and a bit of ducting if heat is a problem. They are more than adequate for the street and fine for track days (street trim, 200rwkW, QLD raceway style straights)

Check that info. I think some of it is wrong.

R33 GTR calipers will bolt straight up if you use GTR rotors. R34 will need your hubs drilled out, not a big job, but why pay more for the R34 calipers only to have to mod your hubs. If you are going to do it then may as well throw braided lines and good pads in, otherwise the weakest link could mean a good setup is ordinary

Look up the piston sizes of the calipers..i think you will be surprised...GTSt calipers actually have more piston surface area...so dont worry about the master cylinder. See how it goes, if you find your current master cylinder is dead, or dies in the future then consider you may have to change it. Though personally i dont think you will need to

[GTRgeoff]

Look up the piston sizes of the calipers..i think you will be surprised...GTSt calipers actually have more piston surface area.

Err, wanna check that mate? Ill send you my favourite brake document.

[siksII]

Check that info. I think some of it is wrong.

R33 GTR calipers will bolt straight up if you use GTR rotors.

But the rotor is larger diameter (324mm vs 296mm) so you need a bracket to allow the caliper to clear the rotor right?

[GTRgeoff]

No the mounting points are in the same place, so the calipers have the extra radius built in.

Not my favourite mod for the money asked for these calipers.

[Roy]

Sorry you are right, but the difference is less then 100mm2 . I was answering a PM about APs

[GTRgeoff]

405.2mm^2 actually so this leaves

brake to master ratio 13.76 on a GTR

R32 master/GTR calliper ratio 15.43

R33 master/GTR calliper ratio 17.58

This is the ratio of master piston movement to overall brake pad movement

[dano4127]

what are a set of 33 GTR Brembos worth at the moment anyway?

[Roy]

Im not saying you are wrong Geoff, but are you sure of those numbers. Im at work so cant check...arent the R32 pistons 40.4, and the Brembos something like 44 or 41mm and 38mm?????

And my understanding is that the equation only uses one side of the caliper, this way it allows for sliding calipers. What numbers are you using to get the area difference ?

[Kaido_RR]

thankyou everyone for your replys

looks like i will stick with the r33 gtr brembos, if they are a direct bolt on (save me having to mod. stuff)

are both the r33 and r34 calipers the same? (gtr)

[GTRgeoff]

Amazing as it is, I'm calculating from raw numbers rather than any specific calculator so zero consideration of the sliding calipers. All will be revealed when you check your home email but that is exactly the numbers I used. You must consider for all pistons when looking at caliper takeup and the application timing and this is part of the reason i believe the Brembo front/Sumitomo rear setup is so poor. The rears come on far too early and pinch causing discofort for the driver.

I've been spending some time on it, because of the "guesstimates" that exist and I simply despise the Brembo front/Sumitomo rear setup as imbalanced and "rice", although Michael is fitting front and rear which is better.

Michael the R34's I understand use a larger bolt, much like the 350Z

[Kaido_RR]

does the larger bolt make a much difference?

i was heading more towards the r33 gtr brembo as i have found them afair bit cheaper than the r34 gtr (i think people must like the yellow more than the black hehehe)

edit: is the physical size of the capliers the same ? (r33/r34)

[Ronin 09]

cm (lead) cm (centre) cm (trail) " area (per side) sq. cm " " area total caliper sq. cm "

GTR32 (Sumitomo)

Front Caliper Piston (diam x qty) - 40.4 × 4 4.04 0.00 4.04 25.64 51.28

Rear Caliper Piston(diam x qty) - 38.18 × 2 3.82 0.00 0.00 11.45 22.90

GTR33/34 (Brembo)

Front Caliper Piston(diam x qty) - (44+38) × 2 3.80 0.00 4.40 26.55 53.09

Rear Caliper Piston(diam x qty) - 40 × 2 4.00 0.00 0.00 12.57 25.13

AP CP5555 6 Piston

27mm x 2 / 31.8mm x 2 / 38.1mm x 2 2.70 3.18 3.81 25.07 50.14

PBR 6-piston (front)

33mm x 6 3.30 3.30 3.30 25.66 51.32

PBR 4-piston (rear)

30mm x 4 3.00 0.00 3.00 14.14 28.27

[Kaido_RR]

also:

i need to sort out the braided brakes lines.

does anyone know if the fitting onto the brake system is the same from gts/gtr, ? is the length the same also?

[Ronin 09]

crap that didn't work so well... but you get the picture

[Roy]

Amazing as it is, I'm calculating from raw numbers rather than any specific calculator so zero consideration of the sliding calipers.

I will have a look tonight. But technically speaking sliding calipers suck for pad wear etc, but provided the piston sizes are the same for say the PBR style caliper that some HSVs / Corvettes get, well it can have the same braking force as say a 4 pot caliper as the brake equations only use the pistons frm one side of the caliper.

So, some quick Excel says R32 GTSt has 2564mm^2 and the GTR Brembo has 2655mm^2. Use those numbers and see if you feel the numbers will suggest results as dramatic as you think ?!?!?!?!

Oh fark it!!! At the end of the day, the R33 GTR gear will bolt on. Outside of that we are all talkign out of our asses, usually based on what old posts say, or what some misinformed (sometimes well informed) person has said. Will it work better then your old setup? Throw it on and see what YOU think. If you dont like it then odds are you will get your money back so wont be too expensive a lesson

[discopotato03]

Hi Roy , it sounds like the point you making is that a single piston floating caliper has the same clamping force (in theory) as a two piston opposing caliper with the same bore diametre ie old 240K . I was always lead to believe that the hydraulic force applied to two pistons in effectively the same cylinder is the same as for one in a single acting cylinder . You basically have the same master piston pressurising both sides of the opposing pistons so force or pressure is the same both sides . The way to increase the hydraulic advantage is to increase the cylinder diametre (caliper) . I guess you could use the example of an old wheel cylinder from twin leading shoe drum brakes . One cylinder two pistons with a central fluid supply , the force wouldnt double in a single piston cylinder all else being equal .

Obviously floating calipers don't have the rigidity of an opposing piston caliper be they two four or six pistons .

So the way I see it we need to look at the master cylinder piston area (bore size) in relation to the brake caliper piston area , but treating each effective single piston or opposing pistons as its bore size by one . So I guess you could say that if a four piston opposing caliper had the same size pistons as your Corvette floating two piston caliper the hydraulic force will be the same . How well the structure of the caliper stands up to the forces applied depends on the rigidity of the caliper particularly the floating "bridge" type , these tend to want to spread or flex the bridge just like a G clamp does with too much force applied . Actually the floating caliper is virtually a hydraulic G clamp and flexes like one . Opposing piston calipers are often two piece affairs with through bolts and a large clamping area to keep the pistons on the same axis 90 deg to the disc .

As for cost vs brake performance , larger diametre discs and caliper extentions get you higher surface speed with the disc betwen the pads and more disc material to absorb/dissipate the heat . Also more mechanical advantage or lever ratio from the larger radius . Quick , simple , straightforward . Going the Brembo route (provided they're a bolt on conversion) is expensive but a factory option so no dramas as long as the complete set of components is used . I'm a bit surprised the rear discs didn't grow more in proportion to the front ones on Brembo GTR's but cost and overall vehicle mass probably had a big say in this .

With some of my cars in the past I've tried to keep the rear disc diametre same or slightly larger than the front and used some form of manually adjustable pressure limit or "bias" control valve . I wouldn't deliberatly upgrade front brakes only and rely on higher rear line pressure (brake bias) to compensate because this could work the rear brakes harder than the factory intended and lead to fade when you least expect it .

My 2c spent again . Opinions ? Cheers A .

[Roy]

Yep...i think i agree with you

Perhaps the reason why the GTR doesnt run a rear rotor as big as you would expect is because the GTR has drive shafts, hubs, twin turbos, bigger intercooler, transfer case etc etc all up the front so its nose heavier then a GTSt. Hence it probably isnt able to run as much rear bias??!?!?!?!?!