Brake Pad & Caliper Questions...

[djr81]

I had a quick look, but didnt readily find it. I get home on the weekend, ill post them up then

<{POST_SNAPBACK}>

cheers mate.

[Roy]

Found it (LOL, from 2004)

R32 GTST

Master Cylinder diam (mm) - 25.4

Front Caliper Piston(diam x qty) - 40.4 ×4

Front rotors (diam x thk) - 280×30

Rear Caliper Piston(diam x qty) - 38.18×2

Rear Rotors (diam x thk) - 297×18

R33 GTST

Master Cylinder diam (mm) - 23.8

Front Caliper Piston(diam x qty) - 40.4 ×4

Front rotors (diam x thk) - 296×30

Rear Caliper Piston(diam x qty) - 38.18×2

Rear Rotors (diam x thk) - 297×18

Now the interesting bit...

R32 GTR (Non V-Spec,)

Master Cylinder diam (mm) - 25.4

Front Caliper Piston(diam x qty) - 40.4 ×4

Front rotors (diam x thk) - 296×32

Rear Caliper Piston(diam x qty) - 38.18×2

Rear Rotors (diam x thk) - 297×18

R32 GTR V-Spec / R33 / 34 GTR with Brembos

Master Cylinder diam (mm) - 26.9

Front Caliper Piston(diam x qty) - (44+38)×2 ... leading pistons smaller then trailing

Front rotors (diam x thk) - 324×30

Rear Caliper Piston(diam x qty) - 40×2

Rear Rotors (diam x thk) - 300×22

So there isnt much difference between the Brembos and the std Nissan R32/33 GTST calipers and R32 GTR calipers.

[djr81]

Thanks Roy, you are a champ. Now atleast I have a snowballs chance of balancing the thing front to rear.

Did some quick calculations:

Basically worked out a number that is the

front piston area * the rotor diameter

divided by

rear piston diameter * the rotor diameter.

In each case these worked out to be

R32 GTS-T 2.11

R33 GTS-T 2.231

R32 GT-R 2.232

R33 GT-R 2.282

So should I try & keep these ratios similar if/when I spend large on new front end brakes?

Edited February 8, 2006 by djr81

[omrae]

Thanks Roy, you are a champ.  Now atleast I have a snowballs chance of balancing the thing front to rear.

Did some quick calculations:

Basically worked out a number that is the

front piston area * the rotor diameter

divided by

rear piston diameter * the rotor diameter.

In each case these worked out to be

R32 GTS-T 2.11 (67.9% front 32.1% rear)

R33 GTS-T 2.231 (69.1% front 30.9% rear)

R32 GT-R 2.232 (69.1% front 30.9% rear)

R33 GT-R 2.282 (69.5% front 30.5% rear)

So should I try & keep these ratios similar if/when I spend large on new front end brakes?

<{POST_SNAPBACK}>

I would try and keep them similar as possible but the front could range anywhere between 72% to 65% and it shouldn't be a drama

[Roy]

LOL...this is where i get in trouble

The pros that know can tell you from experience...but ill have a look through all the equations etc, i dont think you need to worry too much about the rotor size when trying to maintain brake balance after a front caliper upgrade.

From memory, if you maintain a similar front caliper area/volume and leave your rears std...then the balance should be good irrespective of the new front rotor size.

Without considering the suspension, tyre and inertia aspects of brake balance, essentially you can increase the front brake bias by increasing the front rotor diameter. Subsequently reducing the rear rotor size will also increase front bias.

Increasing the front pad coefficient , or decreasing the rear pad coefficient will increase the front brake bias.

Increasing the front caliper piston diameter or decreasing the rear caliper piston size will increase the front brake bias.

The the flip side is you can change the the above ratios if you desire less front brake bias

So you can do a lot of things to change the bias without worrying about master cylinder size, piston diameter/volume...bias valves etc

Thing to remember when upgrading brakes is that they have to be able to handle the temperature you throw at them, whilst you try to maximise the braking torque.

The only things that increase brake torque are the diameter of the disc, the calipers total piston area, the brake line pressure, and the pads friction coefficient.

So upgrde the fronts with a larger rotor, and a caliper to suit that rotor size. Try to maintain the overall piston area of the caliper, as whilst it may increase your braking torque, it also introduces more dramas with master cylinder sizing and pedal ratio.

If you increase the caliper piston area, you increase the brake pedal travel. In a Nissan road car it is very difficult to change the pedal ratio so need to consider that. And the only way to get the brake line pressure back is to change the pedal ratio (hard to do) or decrease the master cylinder size.

Again if you decrease the master cylinder size to get good brake line pressure and clamping force, but you end up with an even longer pedal. You rally need to start to be able to change your pedal ratio.

Increasing the master cylinder size may give you a shorter pedal, but it will reduce your brake line pressure.

LOL, so have about 36 reads of all that and you will still be confused like me ........

If i write it all down it makes sense, but its hard to explain in words over the internet.

Basically the easiest and least complicated wat to increase brake torque is with rotor size and pad compound. The best way to improve the brakes ability to handle big stops is improve their thermal performance, again rotor size is the biggest factor.

Thats why im keen on upgraded curved vane rotors in std size on the rear, with serviced rear calipers with good pads and brake lines. Then as far as the front goes, decide what wheel size you want to run. That will dictate the rotor size you will run, which then allows you to go shopping for a rigid caliper that suits that diameter and width rotor, which uses a similar piston area.

LOL, can you tell im back in my hotel room and off the pi55 tonight

[Sydneykid]

That's pretty damn good effort Roy, there is one bit I would add;

Increasing the front caliper piston diameter or decreasing the rear caliper piston size will increase the front brake bias.

Increasing the front caliper piston diameter means more fluid needs to be moved to get the clamping pressure. In a tandem master cylinder you have to be carefull that the additional fluid movement can be accommodated without affecting the rear piston movement.

An example, at a suspesnion set up clinic I drove a Supra (sorry) that had an 8 piston front calliper upgrade and standard rear callipers. It didn't stop as well as a standard one and after spending $6K, the owner was somewhat peed off. We have a pressure guage that can be screwed into the brake bleeding holes on the callipers. It tells you the pressure that the pistons actually see. I found that the front hydrualic pressure was substantially less than standard, hence insufficient pad clamping pressure. What was happening was the front piston in the tandem master cylinder was effectively running out of travel, limited by the rear piston travel.

The suggested fix (not by me) was to upgrade the rear to 4 spot callipers. This fixed the hydraulic flow biasing problem but resulted in a very long pedal that was hard to modulate. Result, after spending $8K the car still stopped no better than a standard one and had this long pedal that did not instill driver trust.

But the brakes sure looked impressive.

cheers

PS, the trick is not to ignore the fluid flow requirements in the quest for hydraulic ratios.

[djr81]

My plan a was to use an R33 master cylinder to allow for larger piston areas front & rear. Yes it will make for a harder brake pedal, but only 12% by my calculation (ie26.9 sqrd/25.4 sqrd) - so I can fix this by going to the gym. If I then get some cheapoid Brembo rears & match them with some sort of new front caliper with approx 5300mm2 of piston area on a 324 rotor things should be sweet. I would use the front Brembos as well, but they are too expensive & they only use the same size pad as the poverty pack GT-R's. I will just have to trawl around the various shops & find the info/prices. You ever tried asking technical questions of the 17 year old answering the phone? Quote: "I will ring you back" - yeah, sure you will.....

The knee point for the R32 GT-R braking system is at 284psi & then a reducing ratio of 0.4. Hence line pressures front & rear are different. This is why I wanted to use the calculated ratio shown earlier rather than express it as a % front to rear braking bias. The numbers are not the same.

I have seen some brake upgrades that do wonderful things to the front & nothing to the rears. It actually makes the braking performance worse as the balance is then out. Mostly, from what I understand, for your (lowered, R compound tyred, unladen) road/track car you can usefully run more rear bias than the standard car.

For anyone interested there are some very useful articles on www.stoptech.com which I would recommend.

And Roy, it is not good form to leave site on your week(s) off and not get on the plane three parts p!ssed.

Cheers

Richard

[BBGTR]

This will give you an idea of how hard Calder is on brakes .

Pic was taken of my car at our twilight sprints last night.

Regards

Andrew

[omrae]

Pretty impressive.

I hope this was at the end of one the straights and not in the pits, how did the brakes actually stand up to the punishment of calder which is hard on brakes and what brake pad compound are you using, are you happy with the pads

[cefiro]

hey guys just in relation to master cyl diameter sizes I ripped this off ns.com

does anyone know which realtes to what cars???

BM33 is 13/16

BM38 is 7/8

BM44 is 15/16 (32 gtst)

BM50 is 1"

BM57 is 1 1/16

Also can it be detremental to go too big??? Just trying to figure out some spongy initial then rock hard (not touching floor) pedal feel, brakes on my car (200sx front 300zx rear) its got minimal bite and lockup ability, got some endless SSY on the way. I also noticed atm that the front are stock and the rear are already endless ccR (not good for street) and running a BM57 master cyl. So I am hoping the new pads and good bleed will cure the prob if not then going to go R33 on front. Any thoughts???

Edited February 12, 2006 by cefiro

[BBGTR]

Pretty impressive.

I hope this was at the end of one the straights and not in the pits, how did the brakes actually stand up to the punishment of calder which is hard on brakes and what brake pad compound are you using, are you happy with the pads

<{POST_SNAPBACK}>

Hi, yeah it's at the end of the front straight - after 4 laps.

I'm usng DS3000 pads in the front where I would normally use Hawk Blues. To me, they don't feel as progressive but will absolutely not fade - even with rotors like that. If anything they got better as they got hotter. I just need to stand on the pedal harder.

Regards

Andrew

[Roy]

<{POST_SNAPBACK}>

Eek. Do you think Calder is harder on brakes then Sandown?

Does the car have ABS?

[BBGTR]

Eek. Do you think Calder is harder on brakes then Sandown?

Does the car have ABS?

<{POST_SNAPBACK}>

Yes Calder is harder as the laps are about 17 secs shorter (less cool down time, about the same top speed).

Yes, the factory ABS is in place. I'm not a good enough driver to out guess a computer as far as pedal modulation goes.

Regards

Andrew

Edited February 12, 2006 by BBGTR

[Roy]

Yes Calder is harder as the laps are about 17 secs shorter (less cool down time).

Yes, the factory ABS is in place. I'm not a good enough driver to out guess a computer as far as pedal modulation goes. 

Regards

Andrew

<{POST_SNAPBACK}>

LOL...yeh i love those guys that say i prefer no ABS as you can stop quicker etc etc. They have never locked and ruined semi slicks

Wish i had ABS

My only run at Calder was a waste of time as i was only hitting 170km/h on the straight (boost problems ) ...so wasnt really sure how hard it was on the stoppers.

[Roy]

Also can it be detremental to go too big??? Just trying to figure out some spongy initial then rock hard (not touching floor) pedal feel,  brakes on my car (200sx front 300zx rear) its got minimal bite and lockup ability, got some endless SSY on the way. I also noticed atm that the front are stock and the rear are already endless ccR (not good for street) and running a BM57 master cyl. So I am hoping the new pads and good bleed will cure the prob if not then going to go R33 on front. Any thoughts???

<{POST_SNAPBACK}>

Could be anything really. Best take it to an expert.

How old are the rotors, been machined lately? My guess is its two things. One, is you may have a bit of pad knock off as the rotors may not be running true, so that would explain the firm pedal, but poor intial feel as the pistons are being pushed back inside the calipers.

Secondly it sounds like a pad compound problem, be it pads are glazed or jsut crap.

But unless you are sure on what you need to be looking at being the problem, talk to a reputable place as it could be anything.

[cefiro]

Front rotors seem fine only machined about 5000km ago, rear will be machined before the new pads go in , which should narrow it down. I think its prob the later, if they were not running true then surley there would be some shuddering effect.

[Roy]

I wasnt getting any shuddering and i had rather bad runout on my front rotors. It only has to be 40thou or so. Actualli cant remember what mine were pre and post machinging, but it made a high difference, and there was never any sign of vibration.

Another thing to be careful of is behind the rotor where it matches the hub face. Make sure that is clear of rust and scale as that can also cause a little bit of alignment issues

[cefiro]

Cheers Roy, will def check it all out, thanks for the info.