Big Brake Upgrade For Gtr

[Roy]

No Ferni. You are not allowed

[Marlin]

Thats good to know that 365 with alcons fit under the R34 GTR rims...

Yeah they're no probs....

<<<<<<<< Judging by your pic you could use an upgrade!

Don't hesitate, just do it!

[STATUS]

this may seem like a dumb question, but how and where did you ring Greddy? I have spoken to a few of their guys in japan, but the only ones that could speak english were mostly just sales people, all the guys with the technical knowledge speak japanese only (unless you speak japanese?).

Im not sure who he talked to but i speak to GREDDY japan daily, and yes you are correct all technicians other than two (emanage and suspension) speak only japanese. In sales YUKO, RYO, LIU and Daniel speak fluent english but they will not take general calls or enquiries from the public.

That said GREDDY brakes are designed to run off factory master cylinders, i have asked this question in the past when building the supra and onselling GTR parts in the past. i have the 6 pot fronts and 4 pot rear on the supra with std mastery and it is awesome.

Edited March 13, 2007 by URAS

[ferni]

No Ferni. You are not allowed

Yeah they're no probs....

<<<<<<<< Judging by your pic you could use an upgrade!

Don't hesitate, just do it!

Ahahah maybe if somoene had a spare 9k they wanted to donate, otherwise my poor little brembos get it!

[Sydneykid]

Gary...You answered my question by elaborating in your next post...thank you. Now here's two more...what is the ideal hydraulic ratio? how is it calculated?

A simplification follows.

The common pedal movement ratio is between 5.5 and 7.5 to 1 ie; the pedal moves 70 mm and the master cylinder piston moves 10 mm.

This give a 7 to 1 leverage ratio, ie 100 kgs on the pedal = 700 kgs on the piston

You also generally want around 50 mm of pedal movement (varies from car to car) but that is enough to give some progression.

Average guys can push around 150 kgs with their right leg, with a stab on the brake pedal. More than that and you loose feel, much less and it becomes too touchy. (Road cars are, of course, set up for less effort than that)

So 150 kgs at the pedal means 1050 kgs on the master cylinder piston.

The next step is to look at the specs of the brake pads that you are running. They should tell you a rule of thumb pressure that the pads "likes" plus you will need the diameter and the number of the pistons in each calliper.

That's pretty much all the information you need, now it is simply a matter of maths.

For example if you have a pad that "likes" 3000 kgs then you need around 3 to 1 hydraulic ratio.

If you want 50 mm of pedal travel you need (allowing for 1 mm of pad knock off) a master cylinder piston that is around one 30th the surface area of the pistons in a pair of 4 piston callipers. (ie; a 50 mm calliper pistons needs around a 20 mm master cylinder piston).

Obviously this varies from car to car, pad compound to pad compound and calliper to calliper.

There is nothing black magic about brake hardware, simple high school maths gives you the answers you need. The real tricks (secrets) are in pad compounds and temperature control.

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I should also mention the excessive predilection with rotor diameter, when experience has taught me that rotor thickness is in many ways more important when it comes to temperature handling capacity. Not to mention the ever present penchant for cracking rotors. Keeping in mind that often cracked rotors are caused by bad driver habits, rather than any under sizing in the rotor itself.

As an example, I recently changed one of the race cars from a 343 mm x 30 mm rotor to a 336 mm x 32 mm rotor. The small reduction in overall rotor diameter overcame a premature front brake lock up problem and gave the driver better feedback. The extra rotor thickness overcame a temporary pad/rotor over heating problem.

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I hear a lot about feel, Roy raises some good points in that area. However most of the feel comes from things other than rotor diameter. Things like pad compound and hose selection (braided versus rubber) and sometimes the mystical calliper flex. However testing has shown me that standard Nissan 4 spot (Sumitomo) callipers don't have excessive flex. For example at the start of last season we did an upgrade from a pair of Sumitomo 4 spot callipers to monoblock AP Racing 4 spot callipers. The data logging showed ZERO increase in G forces, ZERO increase in pedal travel and the driver (more importantly) reported no discernable difference in feel. The control tyres were the limiting in braking performance, not the actual brakes themselves.

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Lastly you shouldn’t over look the issue of the weight of the rotor and its effect on the handling and acceleration (positive and negative) of the car. We use rotors that weight from 8.0 kgs to 10.6 kgs, and we have to use different shock absorber settings to compensate for the difference in unsprung weight. In addition larger diameter/heavier rotors can be viewed simply as flywheels, adding 5.2 kgs to the front “flywheels” certainly uses up some horsepower that would otherwise be used to accelerate the car. Not to mention the extra weight when it comes to slowing the car down (braking).

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In summary, despite what the sellers would have you believe, you CAN have brakes that are too big, brakes that actually increase your lap times. That's bad value for money in any one's terms.

cheers

[ferni]

Thanks Gary, still waiting for photos of some ducting on your cars

[djr81]

I should also mention the excessive predilection with rotor diameter, when experience has taught me that rotor thickness is in many ways more important when it comes to temperature handling capacity. Not to mention the ever present penchant for cracking rotors. Keeping in mind that often cracked rotors are caused by bad driver habits, rather than any under sizing in the rotor itself.

As an example, I recently changed one of the race cars from a 343 mm x 30 mm rotor to a 336 mm x 32 mm rotor. The small reduction in overall rotor diameter overcame a premature front brake lock up problem and gave the driver better feedback. The extra rotor thickness overcame a temporary pad/rotor over heating problem.

With vented rotors you have to be a bit careful. The width of the rotor is not necessarilly the whole story when it comes to temperature handling. Bear with me for a little bit....

The ventilated rotor is mostly just fresh air. You have the middle section (for want of a better name) where the vanes in the rotor provide the cooling. The more vents the more cooling. The more vents the more weight.

The actual bits of the rotor that do the work are the sections on either side of the vent. These are not the same thickness for all rotors. By way of an example an R32 GT-R will allow you 2mm wear on these. Some aftermarket rotors only have a 1 mm limit. Guess which one carries more metal? Always check the allowable wear limit when buying new rotors. You may be in for a nasty shock.

Lastly you shouldn’t over look the issue of the weight of the rotor and its effect on the handling and acceleration (positive and negative) of the car. We use rotors that weight from 8.0 kgs to 10.6 kgs, and we have to use different shock absorber settings to compensate for the difference in unsprung weight. In addition larger diameter/heavier rotors can be viewed simply as flywheels, adding 5.2 kgs to the front “flywheels” certainly uses up some horsepower that would otherwise be used to accelerate the car. Not to mention the extra weight when it comes to slowing the car down (braking).

In short if you buy aftermarket buy hatted.

[Sydneykid]

With vented rotors you have to be a bit careful. The width of the rotor is not necessarilly the whole story when it comes to temperature handling. Bear with me for a little bit....

The ventilated rotor is mostly just fresh air. You have the middle section (for want of a better name) where the vanes in the rotor provide the cooling. The more vents the more cooling. The more vents the more weight.

The actual bits of the rotor that do the work are the sections on either side of the vent. These are not the same thickness for all rotors. By way of an example an R32 GT-R will allow you 2mm wear on these. Some aftermarket rotors only have a 1 mm limit. Guess which one carries more metal? Always check the allowable wear limit when buying new rotors. You may be in for a nasty shock.

In short if you buy aftermarket buy hatted.

Pretty much spot on, although wear limit is not always a precise answer on the thickness of the material. Sometimes it is limited by the calliper piston depth. I should add that the above quoted weights are of the rotors themselves, not including the alloy hats.

cheers

[Roy]

I wonder if Lunatikk has his setup installed and running. I am very interested to hear hwo he goes. Nice 330mm x 32 rotor with a kick ass caliper with plenty of pad area to keep temps under control...all fitting inside an R32 GTR wheel.

[88silhouette]

some tops writeups there fellas

extremely informative

[Ronin 09]

I wonder if Lunatikk has his setup installed and running. I am very interested to hear hwo he goes. Nice 330mm x 32 rotor with a kick ass caliper with plenty of pad area to keep temps under control...all fitting inside an R32 GTR wheel.

you talking about the 8pots?

[VHR32]

yep, it's me. going to try for 340mm 2 piece rotor, standard GTR sumitomo caliper.

If you want the pads to sit on the disc properly you will need to grind out the inside radius of the caliper or the pad will overhang. Like this:

http://www.driftshop.com.au/twinvl/pics/modedcalliper2.jpg

I'm not sure how they will go over 340mm discs, here is a pic of GTR calipers on 330x32mm discs, as you can see they sit out alot and they 'just' don't quite fit under 16" rims!

Edited March 19, 2007 by VHR32

[Lunatikk]

Well it took awhile but I finally got around to fitting the 8-spot Brembos a few mths ago. The package I bought came with 3 sets of new 330mm rotors (Brembo, Hawk & PFC) with 1 set (8 pads, 4 per caliper) in Hawk HT-10 compound & 2 sets of PFC 93's, custom alloy hats & offset brackets for the calipers. I had some custom brake lines made up (ADR approved, PM me for more info) & bolted everything up. The Brembo rotors were pre-bedded so I went with them & the HT-10 pads.

Initially I was concerned how they were going to work with the std master cyl & the F/R balance as my GTR still has std non-Brembo rear brakes but to be honest I was worried for nothing in the end. The pedal feel & travel is as close to std that I cannot honestly say if there is a difference at all & the HT-10 compound pads are absolutely fine for everyday road-use, even though they are considered a race pad (rated at 150-700c). They ARE a bit on the noisy side but whilst it might piss others around the car off it doesn't worry me at all.

One thing that helps is the pistons in the calipers have springs behind them which both help minimize pad knock-off but also supply a small amount of pre-load of the pad on the rotor surface, which is not enough to actually cause wear but does a magic job of keeping enough residual heat in both the rotor & the pads. End-result is, within a few km's of driving from dead cold & without any pedal application what-so-ever there is enough heat in there for everyday road use. I had RB74 pads in the std calipers that came off the car & they are comparable for cold-bite but as I said, within a few km's it becomes irrelevant anyway.

The only fault I can give so far, which is really no surprise, is the wet weather performance. Believe it or not, even with us being in the grip of the worst drought on record I got caught in a heavy tropical down-pour on the 2nd day of having the brakes on the car. At highway speed & around 40km's into the trip (so there was already heat in the brakes) the rain hit & within minutes an idiot in a 4WD tried to change lanes on top of me. The end result was a pretty violent shudder from the brakes but even though I'd had 2 good bedding cycles (8-10 progressively harder stops from 160-40) with a full overnight cool-down in between some of that may well of been the fact everything was "new" & still settling in but of course it hasn't rained enough since to replicate & compare.

I've only had 1 6-lap session at QR & all this has done is highlight the inadequacies of the road rubber rather than any advantage the brakes might give over the std setup. I do have some 2nd-hand Dunlop semi's here that will be on the car next time out but with a std sump etc on the car I'm looking to fit an AccuSump that I've got here before I start G-loading the chassis too much. I'm also working towards putting some logging capability in the car so as soon as I can collect some quantitative data on braking performance I'll post it up but one thing I can say is that even without ducting & on a 32c ambient temp day I had no fade or sponginess at all, even with Dot 4 fluid. The car was an under-steering pig, but the brakes were brilliant

I did have some pics but it looks like my phone ate them. I'll post some new ones later.

Don't know if any of that helps but if you've got any Q's, fire away!!

[Sydneykid]

I've only had 1 6-lap session at QR & all this has done is highlight the inadequacies of the road rubber rather than any advantage the brakes might give over the std setup.

As usual, the tyres are the limiting factor. Past experience has taught me that a set of properly maintained standard R32GTR brakes with decent pads and fluid will outstop any road tyre.

cheers

[Roy]

I will find you John and steal your brakes.

[shanef]

I will find you John and steal your brakes.

he lives up here in brisbane

coming to dinner tonite john?

[Roy]

he lives up here in brisbane

coming to dinner tonite john?

But next time he is in Melb with work i will lure him to drive down with tall tales of laps at Phillip Island...only to feed him full of fine scotch and bad seafood so he will be held up in bed long enough for me to steal said brakes

[Lunatikk]

Don't worry Troy it won't take much tempting to get me back to the Island

Around 15yrs ago I was lucky enough to spend a day running round the track on a big-bore Jap bike & needless to say had an absolute ball!!

There were 28 of us there on the day & I had the 2nd fastest lap, but the fastest bike was an ex-Malboro Yamaha OWO1 Superbike so I was pretty happy all up. Curious to see how the GTR will stack up in comparison.

When you get the chance Troy (or anyone who might have the info for that matter) I'd appreciate it if you could PM me any info on track events coming up in Vic this yr & I'll see if I can't get myself down there for at least some of 'em.

& Gary, please don't at any point think I don't hear what you've got to say in regards to the performance of the std GTR braking hardware but in my situation, & especially considering I ended up with 3 sets of brand-new rotors & pads, compared to the price of buying say 3 sets of DBA 5000's, 3 sets of good quality pads & 1 pair of hats etc I effectively ended up getting the Brembo calipers pretty cheap if not for free which in anyone's language is a deal too good to pass up.

[Sydneykid]

Gary, please don't at any point think I don't hear what you've got to say in regards to the performance of the std GTR braking hardware but in my situation, & especially considering I ended up with 3 sets of brand-new rotors & pads, compared to the price of buying say 3 sets of DBA 5000's, 3 sets of good quality pads & 1 pair of hats etc I effectively ended up getting the Brembo calipers pretty cheap if not for free which in anyone's language is a deal too good to pass up.

I hear you, availability and total cost beats everything.

Why we went in this direction is so that we could test the 336 mm x 32 mm rotor. There simply wasn't enough room for a calliper spacer with the Brembo calliper being for 324 mm rotors. The 12 mm incease in diameter (6mm radius) wasn't enough to fit the spacer retaining bolts in. So I came up with the concept of using the Sumitomo callipers for testing the rotors. It has just gone on from there.

cheers

[Bunta]

Don't worry Troy it won't take much tempting to get me back to the Island

Around 15yrs ago I was lucky enough to spend a day running round the track on a big-bore Jap bike & needless to say had an absolute ball!!

There were 28 of us there on the day & I had the 2nd fastest lap, but the fastest bike was an ex-Malboro Yamaha OWO1 Superbike so I was pretty happy all up. Curious to see how the GTR will stack up in comparison.

When you get the chance Troy (or anyone who might have the info for that matter) I'd appreciate it if you could PM me any info on track events coming up in Vic this yr & I'll see if I can't get myself down there for at least some of 'em.

& Gary, please don't at any point think I don't hear what you've got to say in regards to the performance of the std GTR braking hardware but in my situation, & especially considering I ended up with 3 sets of brand-new rotors & pads, compared to the price of buying say 3 sets of DBA 5000's, 3 sets of good quality pads & 1 pair of hats etc I effectively ended up getting the Brembo calipers pretty cheap if not for free which in anyone's language is a deal too good to pass up.

I saw those brakes on a black R32 GTR parked near me at the Gatton street sprints...was it you by any chance??