Benton

Are you really serious? Of course I knew what you were talking about, and I addressed it. Who gives a rat's *** if it has a "rust ring?" Your post shows how little you know what you are talking about and what I was referring to.

FWIW, I have the Big Red calipers on my race car, and I wouldn't have done my brakes like Mark did simply because I had the money and going halfway isn't really my style. For the application, this makes perfect sense to avoid having to purchase new calipers.

You are totally fixed on what this will look like, and not realizing the actual mechanical advantage, regardless of the appearance. Oh my! A ring of rust around the rotor!

Benton

Mark:

If you are concerned about this "rust ring," get some of the bake-on high temp paint, paint that portion of the rotors, bake them, and the first time you use them to bed-in, the overspray will get scrubbed of nicely by the pad.

RyanPerrella

The picture you posted, shows the surface of the iron rotor completely (so far as i can tell) covered in pad, there would be no issues on that rotor at all.

mark kibort

That picture is a very rare, GT1 vet brake system, that is really not representive of our discussion. review the pics i posted. second, the actual rotors that are on the S4 have a slight .5" rust ring, along with the entire hub area. AND, if you see the painted area of the new porsche 965 rotors i will be using, there is about the same are that might get a rust ring. However, if you look a the pics I posted, it is common practice among some of the best prepared race cars in the world, to have a portion of the disc exposed. again, look at the stoptech examples, both 6 piston and ST40 calipers with the S4 pads on a 14" rotor.
mk

Benton

That wasn't my point...

Anyway, good luck with the upgrade, Mark. I think it's great; if you are buying new rotors anyway, why not get the larger ones?

mark kibort

Believe me, Im not going into this thing blind. There is a reason, as Ill say again, why stoptech and others have standardized on the S4 sized pads and calipers. sure the GTS calipers are larger, but the only gains are on their size for heat dissapation and the larger pad, ONLY to the hub side of the equation. there is little to be gained in that area, hence the reason for most all racing brakes to make LONGER pads, not thicker pads as the GTS has. if you look at the forces generated by the braking system, it becomes crystal clear of why the larger diameter is much more effective than thicker pads. It doesnt cut it for you, and thats fine. There is a little bit of personal preference here. But saving $700 and having brakes as effective as GTS is time and effort well spent. (Plus the conversion is less than $100 net cost difference).

Again, the S4 brakes worked very well for the performance level of the S4 racer with up to 330rwhp. Now, with more power, the pads and brake system is failing in critical areas in my racing. So, the logical change was to get a bigger diameter rotor seeing that the pads have done the job well on some of the best race cars in the world, using only a larger diameter rotor change and better pads than I have been using. as a side not, everyone keeps on talking about the ability to lock up a wheel at speed. that is not the performance I'm talking about. (heck, the S brakes can do this at any speed) its the abilty to modulate and slow the car down controllably from very high rates of speed, when the brakes system is at the high end of their tempurature operational range) This is where the greater leverage of the larger diameter rotor pays its dividends.

Mk

mark kibort

Driving impressions. Massive stopping power. During the bedding process on the highway , they seemed to have a lot more braking force. However, due to the new pads (pagid blacks) its hard to tell if it is due to the higher leverage or the higher friction of the pad. What i can say is that the here is a dramatic difference of where the heat is concentrated on the rotor and hat. It falls off very fast from rotor/pad contact area to the hub area. that extra 1/2" is probaby going to help with heat dissapation. (as well as the increased mass, additional holes and longer internal cooling vanes.)

After everything was bedded in, I got the 305s up front to get the car to seemingly stand on its nose! It should work out just fine.

the "Rust Ring" for Ryans pleasure.

Mk

RyanPerrella

ha ha thanks mark,

Actually RIGHT now it looks like its gold anodized so looks cool!

if you have any type of GPS method to measure stopping distance i would love to see what you come up with with the GTS rotors and spacers, and with the s4 rotors and similiar pagid black pads.

Actually i have a set of used Pagid blacks i could send you if you would do back to back tests? you think you would?

mark kibort

It does look cool. This is all heat caused. I think with some water, that area will be a rust band as you say, but with a little paint, that could be fixed.

I dont think there could be a measureable difference as the S4 brakes could stop the tires at any point. the difference is still quite different, but in areas of modulation and fade. I would normally bed the S4 pagid oranges and ride the brakes from 100mph to 60 in 3rd gear floored. before i could get them to fade to the point the car wouldnt even slow down. (constant speed, even at WOT). These pads dont seem to brake in the same way. It could always slow the car down for the limited time i do this test. (few seconds). I think the only real difference will be in areas of the very high speed braking abilities after brakes are warm. I have a feeling that i wont have that panic feeling approaching the two highest speed entrys to corners off the mains straights of the tracks we race at. Ill know more on Jan 4th, where we will be doing some testing at Thill.

If you arent doing anything with those used S4 pagid blacks, and they are 8 or 9mm, I would buy them from you.

Thanks,


mk

martin D

Coming in late to this thread , a bit more info I researched a couple of years ago ,but haven't got round to trying .
Further to Mark's big disc conversion, I believe you CAN use the GTS pads if you change the spring plates (parts 12 & 12a in link) http://dcauto.gotdns.com/illustration/index/832970892
The Pagid web site gives the pads as the same length 132mm , almost same width 18mm S4 /17.5mm GTS & height 70mm S4/74mm GTS.
So if you use the later S4/GT callipers which IIRC has the same piston diameters as the GTS you can have the FULL Big Red/Black (or dirty brown in Marks case ) brakes , or have I overlooked anything ?

mark kibort

Hey, a light just went on. Remember the old post i made where i posted a picture of what i thought was "big red" brake pads from my Camaro competitor? His pads had a cut out at the the bottom, where the pad could then use the stock spring stops, but the pad would then continue down to cover more rotor. same as the GTS big red, but with the lower edges cut off. Hard to explain, so here is the pic.

Im wondering if this is the way to do it. use that pad, then you dont have to modify the calipers at all and still get the little extra pad area to fight the rust ring. BUT, you would then have this pad material hanging from the caliper toward the hub. Ill have to see if his pad works and get back to you.

Im still pretty comfortable with the S4 pagid black pads and the larger rotors. I think they are going to help a lot in many braking performance areas.

I also would be concerned about having the piston force not be in the center of the pad, as i wonder where the pistons are located on the GTS big red calipers compared to the S4.

mk

martin D

Great idea about the pads Mark, should work a treat. Where's the pic ?
The pistons on the GTS caliper are in the same place as the S4, so no problem there.

From Pagid web site Re. pad size
http://www.braketechnology.com/support.html

mark kibort

So the bottom of the pad is farther down to the hub. One more reason to like the S4 calipers in this application. Probably a reason for why the Big reds are not on top race cars, and S4 like caliper are. Just a guess, but also comfort in knowing this mod is a good one.

Here is the type of pad. It off the 996TT, but its not the one i was thinking about. need to find one that looks like this and has the 132mm pad length.

http://www.braketechnology.com/brakes/2474.html

mk

mark kibort

By they way, this is right from the Pagid site about the differences of the larger pad vs smaller pads.
Again, as I have mentioned many time in this thread, the top pro race cars, use smaller width pads compared to the GTS pads.

From the pagid site:



Bigger vs Smaller Pad
A larger friction surface will not improve stopping power. The amount of pressure applied, coefficient of friction and the disc diameter determine stopping force. A bigger pad does not apply more pressure, only the same pressure over a bigger area. The size of the pad matters in terms of heat capacity and wear rate. A larger pad will absorb more initial heat and has better wear characteristics.
Back to Top

mark kibort

Here is the porsche Supercup pad, which is very close to the big red, with some cut outs at the bottom of the pad. this might work on our calipers. Ill have to check. the only real gain of using a pad like this would be in areas of keeping the 965 rotors with out a "rust ring" near the hub. a problem easily solved by some high temp paint. otherwise, you are spending money needlessly to have the pad hanging out there at the bottom, identically as the GTS has the pads set in the calipers (if what was said is true about the pistons being aligned at the same position as the S4 calipers).

Once again, the ferrari F50 uses a pad very close to the S4 pad and so does Stoptech St40s. Need I say more? . Well, the 996 GT3 cup came out with larger rotors and used this pad below, after evolving from the GTS pad in the 993 cup. Get the right diameter rotor and you have a comparable braking system. I just bought the GTS brake capabilities for less than $50 more than what it costs for a normal brake change. If you need the red paint, paint them red! its all in the diameter.

Here are the pads that the cup car uses which might, but doubtful, work on the S4 calipers. Ill check when i install my new spacers which just showed up today, are installed.



mk