Rotary-MG

iTrader: (1)

I'm Looking for front rotors for my 85GS and would like some input as to which would be good for an RX7 that'll be used on open track days and twisty mountain roads.

I would like slotted rotors, but can't seem to find any. No powerslots for an 85GS !

Tire rack sells plain Brembos for $41 each. Kinda leaning this way because of the name and plain rotors offer more mass as a heat sink.

I hear x-drill are a pain because they have a tendency to crack around the holes.

Found these on JC Whitney's site;
http://www.jcwhitney.com/autoparts/P...004287/c-10102
They are slotted and x-drilled. $80 each (edit: funny that the left rotor is in stock, but the right will ship in 4 weeks)
Does anyone have any experience with these?
They don't offer the brand name, so I don't know what to think of them.

Who has a suggestion as to a good front rotor to use?

mustanghammer

iTrader: (3)

I purchase Wagner brand rotors from O'Rielly's auto parts in KC for my IT racecar. In the past I have used OE Mazda, Brembos, and cheap Chineese rotors from Autozone and Black Dragon. None of the rotors performed allot better than any of the others so I buy what is cheap and available.

In IT we are not allowed to use grooved or drilled rotors so I have no personal experience there. From other drivers I have learned that drilled rotors are prone to cracking.

From my experience stopping power and fad resistance comes from comes from the pads, the brake fluid that you use and brake cooling ducts. For pads I use Hawk Blues front and rear. For fluid I use Motul 600. Brake cooling is provided by ISC backing plates and 2.5" hoses that run to the front air dam. I have never had a braking issue with my car whether it is a 20 minut regional or a 2hr Enduro. Frankly, if the brakes fade on my racecar in a race I am using them too much!

P_Lav

Drilled and, or slotted rotors do nothing to help cool your brakes. The actually make it worse by removing mass from the rotors, and allow them to get hotter faster. They can also decrease the life of your brake pads. The only advantage is they look pretty to little rice boys in the Tim Horten's parking lot. If your gonna do anything, just stick to the vented rotors, you can increase the size if you want more stopping power, aswell as calipers. But theres nothing really that cools them down more, just plain vented work fine. Plus removing all that mass from the brake rotors makes them more prone to cracking, and warping under high stress. If you have a gsl, swap them out to a gsl-se spec. If you still need more, you can upgrade to a turbo 2 setup, or even go with a FD setup.

dj55b

iTrader: (2)

personally its better to invest in good brake pads than just rotors, a good set of pads like hawk, or the ones that g-force engineering sells (they utilize the entire surface of the rotor from edge to edge) is the better way of going.

mar3

iTrader: (8)

I hear x-drill are a pain because they have a tendency to crack around the holes.

If the machinist doing the work knows his metallurgy, this won't be a problem for a street driven/occasional track warrior car as light as our RX-7's. I had a set drilled by Binion Machine in central Arlington that saw 2+ years of hard street use and track days at TMS and MSR in Cresson, TX that NEVER exhibited any cracks at all. I still got a pic of them somewhere.

In the old days, the holes were meant to provide an escape from gases being generated by the brake pads so as not to "lift" the pad off the rotor surface. The newer pads don't really have this problem, so cross-drilling really is an aesthetic issue along with slots.

Same thing as running an IMSA-style air dam or a rear wing of any kind. You really don't need it for a street daily driver, but it sure looks good.

Jeezus

iTrader: (4)

I heard that slotted rotors are better than drilled because drilled rotors tend to crack. Also, chamfered holes in the rotor are better than just straight drilled, as the straight ones kinda eat through brake pads quickly. Also, the best drilled rotor you can buy is one CAST with chamfered holes in it. This way the metal properties are not "distorted" (for lack of better words) when you remove parts from the rotor, as in drilling.

Also, don't slotted rotors help dissipate the hot gas that forms from heavy brake use causing brake fade?

OnlyOnThurs

i use slotted rotors on my FB (not drilled)....i never had a problem with them

7SpringsMisfit

i think its kinda funny when you guys say cross drilled rotors do nothing. look at all the higher end makes. notice what they come with from the factory? thats right you guess it. cross drilled or slotted rotors. i just picked up a pair of slotted and cross drilled rotors from mazda trix along with some hawk hp + and some ss brake lines from racing beat.

justint5387

iTrader: (1)

Higher end cars has carbon brakes.

2wankel

iTrader: (1)

I don't know, but I'm going by the seat of my pants. I had slotted and x-drilled rotors with hawk HP and stainless braided lines. That thing stopped on a dime. Incredible braking. I also had new tires, tires make a big difference. So dont leave tires out of the braking equation.

Rotary-MG

iTrader: (1)

Thank you for the feedback!
OK then, time to stop procrastinating and get some parts on order.
I'm going to go with the plain rotors along with the Hawk pad and good fluid. I've been over thinking this. I just want to drive the RX!

I just got this car, and all the pads are below 1mm. One front pad made metal on metal contact with the rotor.
Taking this as an opportunity to upgrade without getting flashy.

I experienced total brake fade (failure) coming down a loooong straight mountain pass. It was a stock 68 Mustang, 4-wheel DRUM, 5 dudes in the car. Doing 90mph and dodging cars, flashing high beams, waving arms out the windows, and honking horn all at the same time was no fun at all. The people ahead of me actually moved to block me in!!!!!!!! After enduing 3 miles of this the road leveled out, and the brakes cooled.

7SpringsMisfit

some do. most dont

justint5387

iTrader: (1)

The higher cars that has drilled/slot rotors that doesn't have carbon brakes, have it just for looks. It gives them a higher performance look. There is a lot of information out there about rotors cracking during high stress track temperature. Thats why when you look at race cars, most has only slotted rotor and not drilled/slot.

trochoid

iTrader: (6)

Even though I'm installing fake Brembo drilled/slotted rotors for my TII brake upgrade, good pads will make the most difference.

7SpringsMisfit

there also is a a lot of information out there about how rotarys are not reliable. cant always believe what you read. most of the guys i run with either swear by just slotted or slotted and cross drilled. any of the guys running cross drilled and slotted never seemed to have any problems with them cracking and yes this is after heavy track use.

i think much of the information out there about the cracking issue is dealing with lower quality rotors. you do get what you pay for.

BlackWorksInc

I would have to agree, speaking from a purely analytical point of veiw. Cast slotted rotors would be the best to go with. First think of the construction; By casting the rotor you eliminate the possibility of altering the composition of the metallic crystaline structure, thus reducing the chances that the metal will be weakened. Look for rotors that are cast of high temperature resistant materials (if you have the cash and the crazy CF would be best), but the better the grade of steel, the better your chances of reducing heating and cooling related cracks. That is very important, because often its not the mechanical stress that breaks the rotors, its often the constant jumping from high temps to low. (Think about it this way, lets say your rotors jump to 500F when you're braking, as soon as that friction is reduced or stopped; i.e. slowling the car down and letting off the brakes. That superheated metal will no longer have a heat source to keep it warm, so lets say 70F versus a piece of metal that cannot ontinue to maintain a temperature of 500F will rapidly cool, which can alter the metallic crystaline structure of lower quality alloys.)

In short, Cast Slotted Rotors of High Quality Steel Alloy wold be the best choice for resistantce to thermal stresses and properly vent heated gases.

O.o Any questions class?

DriveFast7

iTrader: (1)

Used brembo chamfered crossdrilled and slotted rotors on the blue 1st gen.

Full interior, Performance Friction streetable pads, several track days: no cracking

Gutted interior, same pads, bigger chokes in carb, more track days: some very small cracking by some of the holes.

Gutted interior, roll cage, Hawk Blues, Hoosiers, tow to track so driving at 10/10ths now, much faster and lower lap times: every single hole had several cracks. some cracks played dot-to-dot and connected holes

I'll never buy drilled rotors again. Crossdrilling is a dead technology. Slotting is enough to clean the pads *and* allow gasses plus used pad material to escape. The fancy Porsche's still use crossdrilled rotors for BLING and heritage which means a lot to them.

Good call on the solid rotors.

mar3

iTrader: (8)

Yeah...where would one get "Cast Slotted Rotors of High Quality Steel Alloy " for 1stgen RX-7s? If you see "Made in China" on the box, that's an automatic disqualification. Just because it says Brembo, just because the eBayer says it's Brembo, absolutely doesn't mean it's the real deal. Do the Aussie's or Germans make such a rotor? Has anyone in America stepped up to the plate for such a delicacy?



I heard that slotted rotors are better than drilled because drilled rotors tend to crack.

I heard that, too. Problem is, that's what you hear at the track, not in the street. What's the application? If you're running a heavy car that is a track car, you're asking for problems with a cross-drilled rotor. If you're running the same car as a daily driver, you're prolly not going to ever see cracks. If you run a light car on the street, you won't see cracks.



Also, chamfered holes in the rotor are better than just straight drilled, as the straight ones kinda eat through brake pads quickly.

How could that be if everything is 90 degrees to each other? Once finished, there isn't some mystery lip at each hole slicing brake pads like a cheese grater, for Pete's sake. I ran the same pair of brake pads during those two years and they were simply stock Mazda pads. No wear problems and I see the same amount of brake dust as I see on Furious now with plain rotors. Although chamfered seems like the way to go on drilled rotors, that's just more heat stress to the rotor and now a bigger circle circumference where the infamous, but seldom seen on the street, cracks can begin.



Also, the best drilled rotor you can buy is one CAST with chamfered holes in it. This way the metal properties are not "distorted" (for lack of better words) when you remove parts from the rotor, as in drilling.

Again, if you're machinist is good, the stress will be minimized and you won't have any problems on the street with your cross-drilled rotors. Cast drilled and chamfered would be preferred, but who makes a QUALITY part like that not made in China, which WON'T be quality?



Also, don't slotted rotors help dissipate the hot gas that forms from heavy brake use causing brake fade?

No, because modern pads don't exude that hot gas and that isn't what causes brake fade, anyway.

Cross-drilled brake rotor = Not a problem or concern on a STREET daily driver.

n2318r

Just like the oil question above, this slotted/drilled brakes subject has been covered in excruciating detail in countless other threads. There is nothing to accomplish in beating a DEAD HORSE.

Please read the following entire thread, it covers everything you want to know, and the people who are posting have much more first-hand track experience. You are better off reading what they have to say:

More on drilled vs. slotted rotors

(there's another version of the same thread in the suspension/wheels/tires/ brakes archive, not sure why)

/thread

mar3

iTrader: (8)

AGAIN, track experience does not always translate to identical results on the street.

BlackWorksInc

That's a good question who makes good cast slotted rotors, I'm still looking for someone who sells them, if not I may just settle with regular high end plain rotors.

But, they are right, exhuast gases from the pads are not that bad and really unless you're doing some LeMans (C6 front left CF Rotor blow out anyone?) racing your rotors will not be getting that hot.

But the metal that they are made from and the quality of the manufactuer will be the best indicators of a good rotor. And if you have to get slotted go for cast, if you can find them because of the way it is structured...

Here we go...

http://www.j-w-racing.co.uk/acatalog/Brake_System.html
http://www.project-mu.co.jp/e/product.html

Matt_S3_RX7

Check out these slotted rotors, I went back to normal after this! if you want aesthetics then they look great, but if your after stopping power upgrade to TII or equivalent. (and like its been said choice of pads make a big difference also)

n2318r

Yes, that's true. The OP in this thread said he wanted brakes for "track days and twisty roads". Depending on the driver, that usage pattern could be more like more like track use than street.

Sorry I didn't describe well enough: The thread is an exhaustive discussion of brake rotors, including their suitability for street use as well as track use.

^^ Ok I see you're wearing sunglasses, does that mean you didn't actually read the thread ? If you read it, you'll find it agrees with what you're saying. It just has more sources and more detailed information.

https://www.rx7club.com/showthread.php?t=480084

elwood

iTrader: (1)

1. I don't think anybody on this forum is looking at anything but cast rotors. The other reasonable options are too expensive and not available for FBs. You imply that there are stamped or forged or some other type of construction out there that the unwary buyer should avoid -- not true.

2. You say cast, then steel. Brake rotors are cast iron -- not steel. There's a big difference. A few motorcycles and drag cars use steel rotors, but virtually all passenger cars use cast iron.

3. There is a difference in the quality of cast iron rotors, but I don't know how anybody can know ahead of time without going by subjective feedback from other users. I had heard that road racers found the OEM Mazda rotors to be significantly better than most of the aftermarket pieces -- YMMV.

BlackWorksInc

^.^ What I meant by Cast rotors, was mostly those that have been cast with the slots... which albet is hard to find...

There are some different materials that brake rotors are made of, commonly iron and CF are what come to mind, but as you pointed out there are steel rotors.. and I am not sure, but I believe I may have seen an aluminium rotor... which makes no sense...
http://www.bobhindsonracinginc.com/S...BHR%20EP%20911

^.^ You're also right about the difficulty of finding out the quality of the rotors, ussually most makers don't supply a code for the iron/steel they use... I think I have only seen maybe two out of my looking around that state the acctual metal used. But some digging and you can find that material... just means a lot of work...