And when do you say when? If the ABS can engage and the brakes not fade away during the use the car is intended, the brakes are fine. There is more leverage from a bigger rotor, there is also a greater flywheel effect too which has to be overcome and that takes power, especially from higher and higher speeds. Not to mention you *have* to run heavier 17" wheels/tires too, which again adds to the flywheel effect (and unsprung weight).

Larger pads are like larger tires. If you can add swept area you add grip. Thing is it's a myth that C5 pads are really any larger than F-body pads. And F-body pads are pretty big already.

 

I think it's pretty well known that LS1 brakes are slightly small when it comes to open tracking. I just organized a track day this past weekend at Talladega Gran Prix and there was a Firebird present that had a stock brake system except for better fluid {Motul RBF I think} and better pads. He was turning something like 1:13s there which is a pretty decent time I believe. He was fading the brakes by the end of a 20 minute session and he was on Kumho MXs. I would be willing to bet that he would have been much happier with a slightly larger rotor that day. I would be willing to bet he would have loved to have my set-up or another aftermarket alternative that day.

I know there is a point of diminshing returns and most folks don't "need" larger rotors for the street but converting to C5 rotors {I'm still using the stock calipers} is very cheap {around 250 bucks new I think} and will help if one ever decided to do some open track events. You might not need a larger rotor for AutoX and as you said, it will even hurt your times due to the greater rotating mass from the larger rotors and wheels if one was running 16s to begin with which most are not.

 

I have performed two nearly identical open tracking tests (can't control the weather, it controls what days and moments anyone can test on the track, but a significant effort was made for identical conditions) with using the LS1 and the C5 upgrade. Both sessions had their own tyres, brake pads, completely fresh brake fluid, and two sets of rear calipers each with their own sets of pads (identical in make). The only differences were the front rotors (dimensions, however both were brembo blanks) and calipers (and brackets of course). I used brake ducts as well.

The C5 upgrade barely made a neglibile difference in fade resistance from this experience (much of the fade from both systems occured almost along the same duration). The other thing to note about the C5 caliper is while it has a more ideal shape to it (longer and narrow rather than shorter and wider along the friction path) its smaller pistons decrease it's clamping force and smaller overall pad area is what decreases the friction, thus needing a larger rotor diameter.

After experiencing this is what made me just go ahead and sell off the usable parts of both systems and go for a solid caliper big brake kit (and that system too added even more to the MOI, or the flywheel effect).

Now AFA what you mentioned earlier with concern to adding mass along it's diameter as opposed to adding to the width, well guess what? The flywheel effect that Sam mentioned is proven once again. You are significantly increasing the MOI when increasing mass along the diameter (actually the formula uses radius) compared to increasing mass along the width. This is a very old yet very proven effect in classic mechanics in physics.

 

All great, except for the part about "better pads". Being we don't know what they were, or if they were suitable for the use, I can't agree that he'd have been any more happy with bigger rotors vs. a more appropriate pad.

Stock sized brakes seem to hold up well enough on SCCA Touring 2 cars for 20 lap races at the Runoffs, and that's 20 laps @ 1:30 per.

 

Hello...

as brakes are one of my biggest problem with my z28, I want to tell you a few thoughts from germany. I had a few very dangerous situations with my car, when I had to do emergency braking manouvers from more than 140mph.
My brakes were checked everytime than and the dealership could'nt find any defects.

So I was looking around for similar german cars, designed for speeds like this, and their braking systems. A few examples:

Front Rotor sizes:
Audi TT 3.2 DSG (250hp): 334mm x 32mm (13.2")
Audi S4 (344hp): 345mm x 32mm (13,6")

Now the big boys:
Mercedes SL500 (306PS): 330mm (13.1")
Mercedes CL 55AMG (500HP): 360mm x 36mm (14.2")

Now a really big boy:
BMW M6 (507PS): 374mm x 36mm (14.8")

These are examples of cars, that are driven here as daily driver speeds (on the highway), higher than 130mph. I think the tendency is clear...

Please don't get me wrong... I'm not telling that the f-body will not brake better with special brake pads... Or that the brakes wouldn't perform really good from 60 to 0. But I want more...

Just to compare the numbers between the Camaro and the Corvette:
Z28, 130mph to 0mph: 175m ! First try... Second was not possible, already fading.
C5, 130mph to 0mph: 130m !

Even considerung that the f-body is heavier... The difference is toooo big.

I think another point, besides rotors and pads, is to bring enough fresh and cool air to the rotors. This seems to be a weak point in the design of the C5. There are people here, constructing a ventilating system for the C5, to make the brakes more heat resistant.

My resumé: I'll give the stock brakes a last chance with brembo rotors and better pads... If that doesn't perform much better... I will upgrade to C5 rotors.

Holger

 

good, very good.

I must mention though that with concerns to braking between the C5 and the Z28, would also be...

Shocks, and weight distribution as well. Improved shocks and overall spring rates will probably assist you with better body control, so the front brakes might not be so overwhelmed (not quite sure if you have obtained those KW Inox variant-3 gewindefahrwerken yet, but I imagine those should help quite a bit).

BTW, is it really that you want more? Since you drive in Germany, I think you need more. I almost think you ought to go straight for a StopTech ST-40 kit, but then again you may be just okay with the brembo rotors and improved pads (and motul 5.1, if you aren't using that already).

 

Wow im getting hardcore confused now, I'll clarify what I want my car to do and maybe all you guys can figure out what the best application would be. I just orderd some c6 motorsport wheels, 17's for the front and 18's for the rear. The tires are 275/35/17 and 285/40/18 and there Good Year Eagle GS-D3's. I will be mostly driving on the street, how ever I am taking my car to Road America in October with the MFBA. I will only road race the car a couple times a year. Most my racing is drag racing and its full 1/4 mile. I would like to keep my wheels some what free of brake dust. And I am searching for posts on cooling the brakes but not having any luck. Do you guys think I should run C5 rotors or factory and wich pads? And another question, do I have to by the C5 calipers for this? I think we can all agree on Brembo blanks so lets start there. Thanks- Frank.

 

The better pads were Hawk HP Plus {exactly what I have been running on my car}. He has been in my car and felt my brakes agrees that he would like to do the C5 rotor conversion. I have had the stock brakes with Hawk HPS pads. I have had the LG brackets with C5 rotors with both Hawk HPS and HP Plus pads. I know the C5 rotors will lock up the tires easier using the same pads. I have not had my rotor warp since changing to C5 rotors and I'm using 25 dollar Nappa cheapies. F-bodies use stock size rotors in T2 because they have to, not because they choose to. They also throw them away after each race too {most of the time I'm guessing}. Give any one competitor running a F-Body in T2 the option of running a larger rotor and I would be willing to bet most would at most tracks.

 

No need to get confused. It looks like your usage will not be too very hard on brakes. If you simply want a good upgrade, get some front rotors other than stock {Nappa, Brembo, AutoZone-whatever} as the stockers just seem to be crappy. Then get something like a Hawk HPS pad in the front. Leave the stack rear rotors and pads alone as long as they are good. Right before the track day, flush out your old brake fluid and replace with something like Motul RBF fluid. It has a dry boiling point of nearly 600 degrees and a wet boiling point of over 400 degrees {wet is higher than alot of fluid's dry boiling temps}.

If the Hawk HPS pads fade or cannot get the ABS to cycle in the front after a few hard laps, you will need to step up to a better pad which will not work as well on the street {dusty or will tear rotors up}. If you upgrade to better pads and still find yourself wanting, simply spend something like 250 bucks and pick up a set of the relocation brackets and run the C5 rotors. If you want to simply do a upgrade and you need rotors anyway, once again spend the 250 bucks on a set of brackets.

BTW, here is another possible reason to run the C5 rotors. Lets say you are fast enough during your lapping sessions to start fading your brakes towards the end of your session. Lets say that you are running Hawk HPS pads. You might be able to upgrade the rotors to C5s and due to the extra leverage and greater mass giving a better heat sink and heat dissipation, you might be able to sneak buy with street pads rather than having to upgrade to a more racey pad and have to put up with the compromises that accompanies a racy pad. For that matter, you might be able to get by on HP Plus pads vs having to switch to a set of HT10s at the track.

It's all relative, I can almost bet you that a 12 inch rotor will give better performance than a 11 inch rotor given like conditions. AND for the measly 250 bucks that the brackets cost AND the low cost of the C5 rotors,,, it's a win, win situation. The only condition I can conceivably see that C5 rotors are a poor choice over the stock brakes would be if a person had to buy larger wheels to run the rotors or if they truly didn't need them {street driving, drag racing or AutoX with not-to-sticky tires}.

To answer your direct questions-

1. Brake ducting?? Try a search on here or over at FRRAX and you should find a few days of reading on the subject. You can also check out my Cardomain page link in my sig. as I have a step-by-step on a cheapy brake duct setup. I have since replaced my redneck ducts with a duct that is specifically used in this application. I think I have around 100-150 bucks in my ducting and alot of that was spent on the better ducts. It does help to keep the temps down and it's cheap.

2. Should you run the C5 rotors? I think they are a good and cheap upgrade with no real drawbacks as long as you are running the required 17 inch wheels already. Others say they are not needed. It's a cop out but it's your decision to choose based on how hard you run at the track.

3. Which pad? I would recommend something along the lines of the Hawk HPS pads. They are a decent upgrade yet have little drawbacks {little dust and little to no noise}.

4. Do you have to run C5 calipers with the C5 rotors? Not if you are running the LG Motorsports caliper relocation brackets. The only real advantage that the C5 calipers have over the F-body calipers is that the C5s are stiffer and resist spreading better in extreme conditions {which I don't think you will experience}.

 

Nope. There are no free lunches and yes, you can expect more of the flywheel effect from even a slightly larger radius. You need to look up the laws of MOI (moment of inertia). Also be advised that when you add a set amount of mass through increasing the radius rather than the width, you can increase MOI by a considerable amount, which is why a lot of race teams usually adjust their rotor and pad thickness according to what a track may present (if allowed, such as in formula 1). There have been several examples where people have added bigger brakes, then pay the physical penalty of not only lost HP (usually a small amount, but why give it up unecessarily) at the actual wheel, but also next to no gains in braking. The real gains in braking from the feel is mostly through the pads, brake fluid, and somewhat through use of a solid caliper, not through a minimally improved caliper, which unfortunately the C5 PBR caliper is.

Now this article states it very clear about upgrading diameters.
http://www.superchargersonline.com/content.asp?ID=98
Not only lap times, but also the MOT's need to be accounted for as well with concern with brakes.

With their restrictions, no news of T2 cars having brake troubles related to rotor size have surfaced.

I have open tracked with both of the C5 upgrade and improved OE as I mentioned above and as a matter of fact my MOT's ended up being higher with C5 upgrade than with the OE rotors and pads. Once again, with a C5 swap, you lose pad area and even volume as well. The pads are smaller and not a mere changing its surface area shape. Lap times were greater with the C5 upgrade than the OE, by a small minimum. The only real solution for me to brake deeper with race pads was by upgrading to what I currently have now.

What I'd like to ask anyone here is what instruments are being used to record MOT's.

 

Foxxtron, I am fully aware that the larger heavier rotors will slightly hurt acceleration and braking. I am saying that he will not notice it. I still drag race a couple of times a year and I noticed that I did lose roughly a tenth or so after doing the larger brakes but the overwhelming majority of that lose is due that I had to run larger front tires while dragracing. I used to run a set of 16 inch salad shooters with skinny butt tires before the rotor upgrade, now I have to tun my 315/35/17s.

How am I losing pad area? I am running stock calipers. You keep missing that important piece of info. Plain and simple,, larger rotors will give more leverage, larger rotors will give a greater heat sink, larger rotors will dissipate heat marginally better, finally, since the larger rotor does have the before mentiened advantages over the smaller rotor, it will last longer. The only drawback {which I have never argued against} is that they are slightly heavier which will very slightly hurt acceleration and braking {I seriously doubt you will be able to measure that if rotor size is all that is changed}. Seeing that I {and probably the poster of this thread} are not competitively racing and are not too worried about losing a .005-.010 of a second in track time compared to getting a longer lasting and a better braking system during a track day.

I assume that you are saying that you are running the stoptechs not because the rotors are larger and giving you added braking performance but because they were pretty?

 

Then why spend a few hundred more if not needed? Waste of money to minimally gain less and lose slightly more. And you miss the point about keeping temps under control unecessarily. mitchntx, trackbird, and Sam have clearly mentioned this.

 

BTW, there is no more gained. Did you read what Sam mentioned?

You still haven't mentioned whether or not how you measured MOT. I always measure MOT when testing brakes.

 

Hello...

wake up. the stoptechs are being operated because they now are able to properly withstand the temps I am now creating. The C5 system just didn't cut it, even the OE caliper with a C5 rotor, and it was also making things worse, believe it or not. If it was really great, I'd agree, but it didn't.

Also the ST-40 has a floating rotor system, which indeed does a much better job for me not to replace the rotor. I am yielding MOT's of upwards of 900 to 1000 degrees Farenheit. It's able to handle this mostly through it's width, and less through it's radius. Other than those circumstances, I don't recommend them to others, just like with my G2 CO's. Use what fits the situation and no more is the rule to stick by, otherwise it's just money wasted and sometimes performance uncessarily.

 

Why spend 250 bucks on a set of brackets so you can run a larger, longer lasting rotor?? Dunno, you tell me. You say I'm missing a point, no I am not. I have repeatedly admitted that the heavier rotor will hurt acceleration very slightly, I have admitted that the heavier rotor weight will marginally hurt braking {I think the gains outweigh the loses, you don't that's cool with me}. What I have been saying is the bigger heavier brakes will last longer, that is a point in which I do not think you can argue. We can argue back and forth of performance gains all you want but you have to admit to that I think.

I know that I have better braking than I did before with the stock rotors. I know I have less fade towards the end of the session. I know I stopped from 60mph in 100 ft which beat a Mitsubishi Evo with upgraded brakes, a Viper with modded brakes and several other cars. I know I beat all those cars in a 0-60-0 event. The Viper and the Mitsubishi both had better 0-60 times than me, I beat them in braking. I also beat a bunch of stock rotor F-Bodies at the same event, in all likely hood, some were probably on the same pads I was on due to Hawks popularity. I know I have better brakes than my buddy who has the same pads I do, only difference is the rotor size and the brake ducting {which I will admit does help}. His rotors looked pretty bad after five 20 minute sessions at Tally this weekend. Mine have never looked that bad in comparison.

I reckon we will have to agree to disagree on this one feller.

 

It's nice that you mention weight, but the problem isn't the weight (as a matter of fact they weigh not much more) but rotational mass. MOI is what's going on here, not weight (which affects unsprung weight control, which is more of a suspension thing).

FWIW, an inch in diameter isn't going to be effective to absorb heat as well as along the thickness, so that's where what you mention seems really thin.

And yes, the brake ducting makes a world of difference, much more than an inch increase in diameter, or even the same mass added to the width of the rotor.

Stopping in a 100ft. from 60mph? Beating vipers and Evo's? What's the GVW? the weight distribution? Those factors really make a huge difference, even over several brake sessions. This can eventually add up, but so far it's not. What you have or even what I have will certainly not take more than about 5 feet off the distances by themselves. There must be more to this.

Bigger and heavier brakes lasting longer? Even if you have your temps under control? That's pure fantasy on your part, and once again you haven't talked brake temps. If it's the case they can last longer, it would more likely be due to thickness, not diameter. The thickness between the two rotors are negligible. This is once again where your story gets really thin.

In short, the mass is what's very important as usable heat sink material to then be transferred to the vanes for proper dissipation. The rotor friction faces aren't designed to do those things, the width and the ventilation areas are. An ideal method would be to add the same or even lesser mass as thickness to reduce rotational mass (not overall mass, and certainly not gravitational pull by the earth) which also creates much more material along the heat paths to abosorb more efficiently to then route to the vanes for proper cooling, which under many racing conditions are aided by the use of proper brake ducting. Another benefit can be added width for extra wear capabilities, since the pads are against the face, not the outer diameter, which then if the same ventilation area is present, will result in longer rotor life. AFA larger diameters, they don't make the rotors service life extended by that fact alone.

 

Man, I honestly think you are over complicating this stuff feller. Plainly put, it works for me.

Once again I'm trying to agree on not agreeing. That seems to be something that you cannot do. So I will say that you win, my car does not stop better than with the stock rotors, I somehow lucked into beating the other cars at the Year One event and I apparently can't tell how my car reacts when I try different mods. Like I said, I was trying to learn but apparently I have so much to learn that it appears to be pointless. Thanks once again for setting me straight on this. Have a nice one feller.

 

No problem, It's not that I cannot agree or that you cannot tell (many of the factors are unable through SOTP), it's just that what you mention lacks lots of important details. If what you did mention happened, why not go to greater lengths? It's important details that you cannot articulate and not me or Sam overcomplicating things.

Heck, what about clear numbers? A website link will do. You typed a lot so far, why not give more solid details than just simple claims? Everybody is interested you know.

And FWIW, For the majority of street tyres, the extra torque (or actually what negligible amount gained) from going to a C5 rotor is mostly unusable (and definitely unusable with the ST-40), as a matter of fact with GS-D3's, little added torque will exceed their capabilities. Once you pass the limit of adhesion with practically all of the tyres offered for practical street use (discounting DOT legal track tyres), the torque is unused. This has been stressed even in several magazine articles that have discovered that even through they've decreased stopping distances at least by over 20 ft. (that is swtiching from an obsolete 25 year old brake system to a recent day big brake kit with other improved parts as well) they can't get anymore through enlarging the brake diameter for added torque because of their tyres' contact patch and compounds.

Now for what to start with. By saying you will road race the car a couple times a year, you really aren't going to need bigger rotors, but as you said, improved OE replacement blanks, better pads (properly bedded-in), improved fluid, and most of all, proper track time with proper recording methods in order to completely see where you're at, then properly evaluate the problems in order to see what needs improvement, then devise a plan to upgrade exactly what's needed at that point. From that point, it's crucial that you modify carefully with adding one mod at a time. And as always, proper brake modulation and good brake application timing are key factors to keeping you in the game.

The very first thing you should do is talk to Sam Strano. It's amazing what an old-fashioned telephone conversation can help with.

 

What additional details? Can't articulate? I haven't felt the need to articulate them untill you asked me to in the last post {excepting my brake temps}. But hey, here go your details. I've already mentioned my brake setup. C5 rotors, Hawk HP Plus pads, brake ducting {wont help during a 60-0 stop, will help during a track session}. For tires, I'm running what just about every other LS F-body runs- Kumho 700s in the 315 size all around. My cars weighs roughly 3300lbs without me in it. And yes, I already knew tires are a very important factor braking performance.

The 0-60-0 event was put on by Year One and Stainless Steel Brake Corporation. They used a radar gun linked to a computer to check speed up to 60mph, then back down to 60mph. We were making single runs on Road Atlanta's pit area {less than grippy and you could not get your tires or pads to temperature}. As I said before, I pulled a 100ft stop, next best was a Evo with something like a 104ft stop, the Viper did a 108 ft stop if I remember right. There were quite a few other cars at the event also, as I said,,, quite a few late model F-bodies were present. Also as I said, I won the event even though both before mentioned cars beat me in the 0-60 part.

Now on the sustained braking performance. I have a friend with a stock 2002 Formula Firebird. He is running factory sized rotors {aftermarket though} with Hawk HP Plus pads and upgraded brake fluid. He is running a set of Kumho MX tire {a notch down from a BFG KD I reckon}. He has rode in my car and commented on the braking performance {undoubtedly due to our difference in tires}, he has also shown that the stock brakes are inadequate for track sessions {as I already figured out and you also considering your choice of brakes}. His brakes at the recent would get hot and start fading approximately 3/4s of the way through the session. Once again, he is on sticky street tires, not DOR radials. Had DOTs been on the car, conditions would have been exasperated by the extra grip. His rotors looked like crap by the end of five 20 minute sessions.

Now, I recently did a track day at Road Atlanta and I did not experience any intrusive brake fade {I experienced a small amount towards the very of a session but it was a small enough amount that I could work around it. My rotors were worn but looked nothing like his and I think Road Atlanta is probably harder on brakes. Admittedly, I'm running some home brew ducting but at Tally, speeds are so low I don't think brake ducting would help alot especially considering the ineffectiveness of the home brew setup.

You keep asking for brake temps,,, well I ain't got none to give you. As I said, I do not do this competitively and so as long as my brakes work the whole way through a session and I don't use rotors up like fuel I'm happy. That is also why I'm not worried about an insignificant increase in rotating mass that comes from upgrading to "slightly" bigger and heavier rotors. Right now, I'm happy. If I get my times down to the point where brake fade or rotor wear becomes a problem, I will dump my ineffective C5 rotors along with the brackets and get a better performing option. Untill then, I'm happy with my 125$ upgrade {I bought my brackets used}. A upgrade from my stock rotors. Need any more details?

BTW, I didn't say Sam was over complicating matters. Actually I was having a good time debating and learning from him. It just seems that Sam and I can agree on disagreeing.

 

I can agree to disagree, and I think this is a good debate.

Let me point out some things here:

HP Pluses are *not* suitable for sustained track use, they are not race compiund pads and I'd fully expect them to fade away, especially on a small track with little time between corners for cooling. A larger rotor can help here a bit, but very little if the compound is still the same. In short, I have to reiterate that I feel your friend's case has more to do with the pad choice/track than the 12" rotors. And he in all likelyhood has to brake harder than a car on r-comp tires. The biggest difference is in lateral grip, not accel/decel grip (though there clearly is there as well). Hence a car on street tires can't carry the corner speed a car on race tires can, and has to slow down more. I know the last time I was at the track I got a flat and ran part of the day on streets and had to brake earlier than before which builds more heat.

Next. The Viper. Can't be a better illustration of big brakes are the end all. 335mm Brembo's (that's 13.2") at all 4 corners. 4-piston brakes. SRT's website shows 60-0 in less than 100 feet (which is surface dependent).

Maybe I missed what tires you were on for the test, but R-comps do help some. I'm betting the Viper wasn't on those. And they use only a 275 front tire vs. your 315. Given we don't run huge amounts of negative camber, we still end up with more tire on the ground under really hard braking than the Viper does.