Toilets

I am scheduled to get a few HPDE’s under my belt and will need to change out the rotors and pads after I burn up these stockers. I had this set up in mind and would like pros and cons (or if it is even feasible) from you roadcoursers if you don’t mind.

What I was thinking was:

Front- Performance AFX 2 piece rotors (love the front weight savings) with Carbotech XP10 in the front (or maybe XP8). Will retain stock calipers
Rear- DBA T3 4000 1 piece slotted rotor with Carbotech XP8. Will also retain stock calipers.

Would this work or is there a better solution? Do I need different pads with the Performance AFX rotors? This set up will also be used for the street (kinda why I was thinking XP8’s in the front)


On a side note in regards to stopping power, do aftermarket pads/rotors have more stopping power then OEM or are aftermarket brakes purely designed to increase longevity but keep stopping power the same as OEM? 103 feet 60-0 is very short for OEM brakes.

Thank you- oh, I have a 2012 GS centennial with MRC.

sothpaw2

Rotors will make no difference whatsoever to stopping time. Pads do in a majory way. I think XP10/8 as described would be a good combo for you; try single piece front pads. Don't replace the GM rotors until they crack to the edge. My opinion thus far is that Centrix Premium rotors that have been used for 3-4months on the street are the most cost effective solution for track rotors and I would recommend putting those on and getting some street miles logged.

RDnomorecobra

search and read a lot on race brake pads. yes they have more stopping power. also more noise, dust, and will eat your nice new rotors for lunch when used on the street. very abrasive when outside their operating temp range. there are a few pads you can use for both street and track when starting out since you really wont be using the brakes to their max. but after a few days of this you will need to step up to track pads that should not be used on the street. translation: you will need to swap pads when heading for the track. either that, or you will need to nurse your street pads while on track. i dont know your budget but I would recommend staying with cheaper stock-ish rotors for a while.

63Corvette

Brake pad material is all about TEMPERATURE window!!! Street pads don't need nor do well with very high temperatures, but race pads do not do well with low temperatures. Make sure that you match your pad material with the needs of your intended driving. ie RACE pads are so aggressive that they will tend to lock street tires prematurely. RACE pads need the traction of RACE tires for properly matched performance.

rayk

If your just getting started, I wouldn't worry about the rotor weight savings.

I put the T3 4000 on the fronts with XP10's and left the stock rotor on the rear using XP8's. Once bedded at the track, the braking was very good throughout the 30 minute sessions. I had to adjust to the high torque initial bite while balancing the car with the brakes, but got better and faster as I adjusted. I purposely challenged the brakes toward the end of the session and was able to set off the ABS.

I don't think you want to run your track rotors and pads on the street. On the way to the track, people were looking for a dump truck as I pulled up behind them with the brakes squealing like crazy. They also dust like you wouldn't believe until bedded. I'm not sure how long the bedding would last on the street.

Keep a set of rotors and pads for the street and a set for the track.

Don't know if you have, but you must put in high-temp fluid like Motul 600 or the rotors and pads can't do the work.

I would replace the clutch fluid with Motul at the same time. I thought my clutch was grabby, but after I changed to Motul, the clutch action got very smooth and controlled.

I will either put the DBA 4000 T3's or solid high carbon rotors on the back and save the stock rotors for the street.

Bill Dearborn

Don't spend your money on two piece rotors if GM Stockers will work. My experience with two piece rotors is you pay $250 including shipping per replacement rotor ring and they last a day or two longer than a stock unit from one of the forum GM parts vendors that costs ~$75 plus shipping. I have added Quantum Spindle Ducts and taken out the fog lights and installed brake ducts in their place with 3 inch hose running from them to the plastic GM duct. Just cracked a brand new front AFX Coleman Rotor after 6 track days and the other one isn't looking too good. I got 7 days out of the original Coleman rotors. I used to get 5 days out of the stock rotors and I installed a well used set of them to get through the weekend.




In the second picture you can see where rotor has cracked all the way through and where the inside face separated from 5 of the internal fins. There was no thumping just a feeling of a grinding in the right front brake and the car not slowing properly when going into a down hill hard braking zone after several hot laps.

I was using Wilwood H pads in a Wilwood W6A caliper mounted on a bracket that lets the caliper work with stock size C6Z rotors.

Bill

argonaut

As others have stated the rotors have little effect on braking distances. A larger rotor, with its longer 'lever arm' will offer slightly more torque and thus require less pressure to produce same effect but that doesn't appeciably shorten stopping distances all else being equal. But it does change the feel.

Its very difficult to compare the stopping distances between street pads vs. track pads. Its kind of an apple-and-oranges thing. The best you can do is say 'it depends'. On the street, with street tires there will be little difference. In fact for a single cold stop its likely the street pad would stop shorter because the track pad get into ABS to quick (overwhelms the available grip). The point of track pads isn't to stop in a shorter distance but rather to survive the extreme heat and repeated stops seen on track, where a street pad can quickly give up.

By far the biggest factor in stopping distances is the tires. The friction between the surface and the 4 tires is what stops the car. The more friction (grip) the shorter the stop. The weight of the car obviously plays a big roll as well, as does the weight distribution and f/r bias of brake system. Then we have the surface and the ambient temp. There are many, many factors that affect braking distance, the pads and rotors are just a very small part of it. This is why I hate the magazine articles that make such a big deal about minor differences between stopping distances during comparison tests.

argonaut

Bill - have you ever thought that maybe it's your brake cooling that causes them to crack prematurely? I run ducts just like you, always have. It's clearly the prevailing school of thought. But I've begun to question this wisdom, at least for some tracks. Take VIR for example with its very long straights. The temp differential between braking for oak tree and 2/3 way down the back straight is huge. The rotors go from very hot to cool in less than 30 sec. Heating up rotors doesn't crack them, its the cooling down that does. So I've begun to wonder if brake ducts are too effective at some tracks and actually end up shortening rotor life.

I've read a few other posts on various forums that have also started questioning the 'brake ducts all the time' philosophy and I know a very well respected BMW racer who has removed his ducts and is reporting much less spider cracking and rotor failure. Just food for thought...

BEZ06

No - use any pads you want. Just make sure you properly bed the pads to get a good layer of pad material transferred onto the rotors for good adherent braking properties.

However, as mentioned in an earlier post, the tire contact patch is what creates the friction with the road/track surface and what really stops you. If you're running street tires you can overpower them with too much brake and might not be able to get an aggressive track pad up into its proper temp range.

Hmmmm - pad compounds are designed with operating temperatures in mind.

Street pads are designed to work at much lower temps than track pads. Race/track compounds don't even get up into the bottom of their temp range until you do a warmup lap. The warmup lap isnt just to get your engine up to proper temps, it's mainly to heat up your tires and your brakes.

If you use a track pad for street driving you may never get them up to their designed operating temperature range where the pad and the transfer layer of pad material on the rotor work in an adherent friction mode. In that case, you'll be braking using strictly abrasive friction - which, as it sounds, is where the pad is grinding away on your rotors to stop.

Read Carbotech's info on their website about the temp ranges of their compounds:

You can see above that the 1521 Bobcat street pads are designed to work well at ambient temps - i.e., with no need to be heated up to give good stopping power. The XP8 doesn't start working well until you heat them up - they'll stop you, but not as well as if they're heated up, and if cold you'll be using abrasive friction to stop which will be grinding down your rotors.


As mentioned above, pad compounds are designed to work in the temp range they will be used for. The OE pads are great for a high performance street car - but they do put out a lot of dust. Many owners will forfeit some stopping power to reduce dust bt going to a ceramic compound.

So....stopping power??? Although XP12's may launch your eyeballs out of their sockets when the brakes are heated up on the track, a street pad may stop you better if the brakes are cooled down from cruising along and you come up on a panic stop situation!!

Longevity??? Pads and rotors are consumables - like a bar of soap, they're designed to be used up. Some track compounds will last longer than others, but they're all going be used up as you transfer kinetic energy into heat energy when you stomp on the brakes.

Rotors? The rotors you mentioned are all cast iron. They are all going to get used up with the braking forces and mainly the temps they experience on the tack. Single piece rotors have the hub cast into the center of the rotor and one side of the rotor is rigidly attached to the hub. When the rotor heats and cools, one side can expand more freely than the other, and leads to a slight "coning" of the rotor and a lot more likelihood of earlier cracking than 2 piece rotors. The rotor ring of 2 piece rotors is not so rigidly fixed to the hub, so both sides of the rotor ring can expand/contract at more of a similar rate, and that may lead to a longer life of the 2piece rotor ring - but it's still a consumable that will get used up!!

Bottom line - use your track pads on the track and swap to street pads for street driving.

You say you'll be using Carbotechs, and they are one manufacturer that says you can swap from their track pads to street pads without re-bedding because they have similar compounds.

I'd recommend you get some 1521 Bobcats for street driving and install them after a tack event. You'll save your track pads for the track, you'll save abrasive wear on your fancy rotors, and you'll stop better at street driving temps.

Just MHO, YMMV!!

Bob

bdanyluk

Go with XP12's up front and XP10's out back....start working at same temp as XP10/8 but give you much more headroom on the high temp side....you will grow into them soon so don't waste money on the cheaper ones....only 10 or 20 dollars difference.

Adam@Amp'dAutosport.com

Use your stock rotors untill they crack, pad options are up to you. I would start with 10 or the RP2 in front and use the 8 in the rear. Give me a call I will be happy to help you.

Toilets

You are in concord? I work out there. Am I able to pick up the pads?

Bill Dearborn

I am glad you mentioned that. I have been wondering if I had too much cooling. A fellow C6Z instructor has StopTech brakes with two piece rotors and cooling fans built into the stock ducts. The ducts empty into the wheel well without any connections to the spindle. The fans don't do much at high speed and may actually hinder air flow at any thing over 35 mph but they are on all the time. He turns them on when he heads out to the track and turns them off after leaving them run for 15 minutes or so when he gets back to the garage/paddock. His rotor breakage is far less than mine.

I have the AFX Coleman's on the rear and they still look good although I have 14 track days on them. They have a funny looking waviness to them but so far don't even have any real heat checking. The stock rear rotors never went more than 5 days so these are doing much better and have almost reached the break even point (about 20 days). Rear cooling is unchanged.

When you watch the C6 development videos GM did a lot of brake cooling tests at the Ring and they specifically picked the ducts they have in the car based on air flow through the ducts and around the car, brake temps and the amount of space allotted. I watched several videos where they changed ducts and ran the car on the Ring with instrumentation providing feedback in addition to the driver's comments on what was happening with the brakes.

There is another viewpoint on replacing the fog lights with brake ducts. The air flow may actually be less than through the under fascia duct. One of my students has a Viper and he was looking to add ducts in place of the fog lights and one of the Viper teams said their testing showed less air flow than stock.

Bill

Toilets

Wow everyone! This is fantastic information! I truly am grateful for all the great feedback thus far.

Thank you

Adam@Amp'dAutosport.com

Yes, but I need to charge sales tax. Give me a call i will set you up.

Soloontario

OE style rotors are directional while DBA 4000 are not but the actual braking surface is thicker.

Which is better?

BEZ06

Huh???

Maybe I've got what you're saying backwards, butt.....the OE C6 drilled rotors on the Z51, Z06, and GS are all left side rotors; the DBA rotors are side specific - there is a left side and right side.

Bob

Soloontario

Sorry, on a C5Z, the OE front rotors are curved vaned and side specific but the DBA 4000s are not.

I had heard that about the C6Z i.e only L side rotors OE. Do people find much difference in the time their OE rotors last from Left to Right? I guess my question is really, how much better are the curved vane rotors than just the straight veined ones ?

rayk

The DBA 4000 T3's are new design and supposed to be more durable. So far so good after 1 track outing with mine. I agree, the DBA 4000 T3's are not specific to a side.

yooper

Very interesting, same failure as Bill with Coleman rotors last October at Road America. I was running a 1st gen CTSV with a LOT of air ducted directly to the center of 15" rotors. Cobalt Racing XR1 pads.

Broke the 1st rotor last run on Saturday (cooler air temps) T12 brake zone and the 2nd one broke during late morning Sunday (cool air temps) T5 brake zone.

Now I know why the BMW driver left his nerf ***** stuffed in the brake cooling ducts. Expensive lesson for a rookie.