Big Brake Kits?
 

Just went up to VIR (only 40 miles away now!!!!) Monday and Tuesday. Running stock brakes with drilled rears and slotted fronts and HP+ pads. We only ran on the south course, but I was up close to 140 by the brake zone... BAD brake fade lap after lap to where I could only get to 130 before having to back off and brake, UP HILL to where I can make the turn. After my last session I found 3 large cracks in the left rear rotor. So I think it's about time to upgrade. (yeah I bled the brakes and pads were new and bedded properly)

I've looked at the Racing Brake thread, seen an SCCA track car with Stop Techs and read a little about Rotora's. What is the best performance, cheapest for 4 track events a year, and will fit under 18" (probably all of them). Thanks!

PS- I'm sure the rotational inertia of the 18" is killing my stock setup, but oh well, I'm keeping them.

Its your pads. You really should be running proper brake pads for the track. Hawk pads are also known for killing rotors.

The cracks on your rear is because you're running drilled rotors. They're notorious for that, as those holes are just stress risers. Switch to plain rotors, not drilled or slotted, and that'll also save you some $$$, both for purchase price and frequency of replacement.

A properly optimised stock setup can be quite good. Get some real racing pads (I like Porterfield R4's), run some good high temp brake fluid (550 degrees or more is good), get some Titanium backing plates for your pads (slows heat transfer to the fluid), duct the fronts and that'll help a ton.

where do you get titanium backing plates?

slots aren't so bad for the track, are they?

http://www.2dperformance.com/shims.asp

Slotted rotors aren't bad for the track. The drilled rotors are not like the ones you typically see on higher end cars like Porsche's and Ferrari's. Those typically are not drilled but cast. The drilling weakens the rotors which can cause them to crack and fail quickly under extreme use (like on a race track). Unless you have a "need" for slotted rotors, its better and cheaper just to use blanks.

eh, bling factor is always nice by having the slots, though my next set will probably be blanks. Still, nothing like knowing that my rotor cleans my pads!

The cheap drilled rotors are usually cast blanks which are then drilled in a pattern.

The high-end "drilled" rotors are usually cast with the holes.

Would I be able to use Hawk HPS street pads for my first HPDE or should I get some N-Tech Lapping Day pads?

Probably not. You should at very least get some street/track pads more like the HP+, or get some real racing pads like the Hawk Blue/Black/HT10.

I run a combination of HPS and Motul RBF 600, I haven't noticed brake fade yet, but I have an NA FC. I do feel that the initial bite is better with the HP+ though.

On an aside.....don't ever run normal pads at a track event.....I was forced to one time and ate all the way to the metal after one day of driving. Duralast my ass.

Aren't the stock brakes biased extremely front??? And there's enough heat in the braking to crack the hell out of a rear rotor on street-ish/track-ish pads?

So 'racier' pads, back to stock rotors, better brake fluid and brake ducts will fix the brake fade? I know the idea is to remove the heat as quickly as possible, and there's so much heat currently being removed to cracked the drilled rotors. It seems like there's just not enough mass to dissipate the amount of heat.

Ducting air to the brake area can only do so much because of the vortex created behind the rim from the aero up front.

More aggressive pads will grab the rotors harder, but will create even more heat for the whole system.

Race fluid will resist the heat to a higher temperature, but the pads should generate even MORE heat now that they're grabbing harder and could potentially go past the better fluid threshold.

Correct me if I'm just misunderstanding this, but by going to larger rotors, you gain torque by increasing the rotational radius and not having to increase pad/rotor surface area or clamping force. The longer circumference allows more time to remove air, and usually your larger, upgraded rotors are designed for better air flow within. Seems like there's only so much you can gain by tweaking the stock setup, but it will be severely limited due to the size of rotor.

That was just on the South Course... Full Course should pick up another 30mph... That's 170mph!!! I'd like to have some confidence knowing that my rotors aren't going to explode. So, if my understanding is correct, what are everyone's opinions on big brake kits?

Thanks for your help!!! :)

If you really need high temp fluid because you're worried your fluid will boil, look into wilwood's EXP 600 plus fluid, 626 F dry boling point.

I know someone with an LSI FD running Kumho V710's and Hawk HP+ pads, with Motul RBF600. No brake fade issues at all.

I don't have the power to go that high, but I work my brakes as hard as possible to save as much time as possible since I drive an underpowered car. I haven't noticed brake fade on my HPS/Power Slot/Motul RBF600 setup. Even with more power, I doubt you're boiling your fluid anyway, past the 593 F boiling point of Motul RBF600. Make sure you bleed your brakes before every event if you're that worried.

Stock systems on RX-7's are very respectable for being able to stop most whatever you throw at it.

That reminded me... I was running on BF Goodrich KDWs... not even on real tires yet, just a quick shakedown... and only running 10psi so more like 330rwhp.

I used to race Star Mazda and a lot of races in a Formula Continental in SCCA... So I feel ya on the momentum driving with braking and not having to stop heavy horsepower. Maybe I'm spoiled by lightning quick stopping and should cut a 2800lb car some slack, but it's getting worse every lap. I don't think it's the fluid. It seems like the pads/rotors are overheating from a simple size issue. We used to use some crazy German Blue fluid that was pretty damn high on the dry BP, need to track that stuff down.

Reading the Racing Brake thread, a good point was made. Challenge cars are weighing 2600lbs and only 220 hp, yet they run 13" fronts to be able to stop... Any high hp cars out there making it on stock size setup? I'm planning on running up towards the 430rwhp mark once I have a car that I'm comfortable with from a safety perspective.

Do not use hps for anything roadcourse related! I have been using n tech lap day pads for the last year or 2 and they are great pads.

For an affordable 4 wheel big brake kit it is hard to beat the '99 rz setup imo. I believe you can get the whole enchilada for ~ $1500. I am running them with autoexe 2 piece rotors up front and have no complaints. The rz rotors are ~ 12.4" diameter all around, the fronts are 1.25 " thick (vs. stock .8"). The front calipers have staggered piston sizes so your track pads will wear evenly unlike the stockers.

What's wrong with HPS? I'm guessing it's the higher HP cars that might have some problem? I only have a lowly 155-170 whp car.

They overheat pretty quick. A friend of mine signed up at the last minute at road america with a pretty much stock audi a4 last weekend. He could only get ~ 1.5 laps in a session before the hps pads were smoking and pretty much useless.

Try ebc reds if you absolutely have to have a dual purpose pad.

Yes, the fronts are more bias. However, your rotors cracked from being drilled, not because they overheated. I guarantee you that blanks wouldn't have cracked under the same use. Rotors will crack eventually, no doubt but cracking in a single event means you had the wrong rotors.


Race pads are made to handle the extra heat from track usage. One version of fade is the brake pad overheating. In this case, your brake pedal stays firm, but you have no braking power. If this is what you felt, it was pad fade. This is because the pads overheated.

The problem is there is no real pad you can run on the street and then abuse at the track. You really need a street set and a track set. There are some pads which can double as both, but you have a compromise: You won't brake as well when they are cold, and they won't take real extreme amounts of heat like a true track pad.

Track pads are not necessarily more aggressive. As mentioned above, they are design to work at higher temps, verses a street pad which needs to be able to work at low temps.

Yes, race fluid will resist the boiling much better. You shouldn't run regular street fluid on the track regardless of the size of brakes you are running. If your brake fluid overheats, your brake pedal will go to mush.

Yes, you can gain torque on the braking system. However the stock brakes, with the appropriate pads, are enough to bring the car to braking threshold. So there is no real need for increased torque. You are looking at adding more material to help dissipate the heat better.

Either way, you should run pads for the track even with the BBK's. I would recommend going with some real track pads, blank rotors and some good brake fluid. If you are still experiencing fade, then it would be time to upgrade. That upgrade could either be a BBK or brake ducts.

as an aside, I have a car which I use to commute and drive to events, and I run the car at both autox's and road course. I have another DD which gets me around otherwise. How aggressive of a pad can I go? HP+? Can I even take a chance on running Hawk Blue's for my autox/track car that gets driven to the events?

It sounds like you have enough experience driving that you're going to be quicker than the average first-timer.

First up, as others have mentioned, no-drilled rotors, good fluid (Motul 600, AP 600, SRF, or ATE Super), and real track pads. You can't get PFC's in FD pad shapes, so some remaining options are N-Tech Competition, Porterfield R4, or Hawk Blue (if you don't care about your wheels or paint). You can also set up dedicated ducts (rotor backing plates available at N-Tech) or Titaniaum pad backing plates.

If you're exceeding that set up, I've really liked my StopTech front kit. It bolts right on, matches both the stock rears and stock master cylander (many BBK's require an upgrade MC for good pedal feel), and you can get PFC compound pads for $200. They've been doing just fine slowing me down from 155 at VIR and WGI. You can get the kit for well under $2k

I'm glad you mentioned the N-Tech lapping day pads. Although these are my first 'track only' pads, I have no complaints. Fast 30 min sessions at Sebring this past weekend with no fade....at all. Fresh 522* fluid w/ new rotors. All stock system.

Ofcourse, my sticky Hoosiers are what REALLY stop the car.

Just to play Devil's Advocate here...

So use stickier tires, brake harder and transfer more weight to the front. Balance is perfect! :) More seriously, the stock setup has pretty good bias. Bias is effectively the same as stock in both Stoptech's and Racingbrake's kits. The problem comes with the older kits that massively upgrade the front brakes, giving more front bias than stock.

Not in the rear. The rears produce something around 25% of the total heat.

More accurately, mass allows the rotor to absorb heat during braking. A more massive rotor will reach a lower temperature than a stock rotor.

Strictly speaking, the amount of heat is dictated by the car's mass, max speed before braking and final speed when the brakes are released. E.G., braking from 100mph to 60mph puts the same amount of heat into the brakes whether it takes 2 seconds or 3.

For a given MPH, the rotor's RPM is set by the wheel's diameter. The time doesn't change.

Changing pads won't increase the heat in the system. Going to a larger radius rotor won't decrease the heat in the system. It's a function of the mass of the vehicle, the amount of speed being lost and the time in which that happens.

Think of it in terms of energy. The kinetic energy that you're getting rid of when braking is converted to thermal energy. This happens through friction between the pad and rotor. A set amount of kinetic energy will produce a set amount of thermal energy. The brakes are continuously shedding this energy through convection to the air and through conduction to the wheel, caliper, hubs, etc. The faster you slow down the less time the brakes have to get rid of the heat so the more the temperature rises. Getting bigger brakes improves the rate of heat shedding and gives you a larger heat sink, which both help to reduce peak temperatures and average temperatures, helping to cure fade.

With that sort of power, especially if you're going to be running race tires, a BBK is probably a good idea, as you'll be needing one eventually anyway.

"Think of it in terms of energy. The kinetic energy that you're getting rid of when braking is converted to thermal energy. This happens through friction between the pad and rotor. A set amount of kinetic energy will produce a set amount of thermal energy. The brakes are continuously shedding this energy through convection to the air and through conduction to the wheel, caliper, hubs, etc. The faster you slow down the less time the brakes have to get rid of the heat so the more the temperature rises. Getting bigger brakes improves the rate of heat shedding and gives you a larger heat sink, which both help to reduce peak temperatures and average temperatures, helping to cure fade."

Yeah, what he said. Y'all can probably tell I'm not so good at articulation!

I'm basically trying to transfer the kinetic energy to heat faster, thus giving me quicker braking. If I'm reaching the temperature where the pads are overheating or the rotor or caliper or fluid are overheating in the amount of time I'm trying to decelerate, then there's not enough mass to conduct and release the energy or the pad or rotor lose their coefficient of friction at the temperatures necessary. I haven't locked wheels up, so torque may be part of the issue also (fixed by pads, not necessarily radius.)

So, I think I'll just go back to blank rotors, dedicated track pads, better fluid, track tires and keep it around 10psi... If that doesn't hold, RZ or StopTech is what I'm hearing...

Thanks a lot, I appreciate everyone's input!

Richard

Another thing you want to consider are cooling ducts for the rotors. There are minimal air scoops on the front brakes. I would consider running a 3" air duct line from the front to the rotors to help provide lots of cool air.

That was already mentioned above. However, IMO, that borderlines on going just straight to a BBK. Once you do all the work and the costs for the NASA style ducts, the hoses and then the backing plates for the rotors; that would be a sizable amount which could be put towards a BBK. That's the choice (and the time) to make IMO when blank rotors, track pads and track brake fluid still cannot prevent fade.

Well, by that reasoning, a BBK is a significant chunk of the money necessary to buy a track car that doesn't need a brake upgrade.... lots of the newer cars have pretty massive looking stock calipers.

And don't forget a BBK means bigger than stock wheels (x2 for separate track and street tires) too. And more expensive track tires... It is VERY cost effective and very performance-effective to add cooling to the stock brakes.

Plus, well-cooled stock brakes have the proper bias, so stop better than many BBKs.

High HP (I would say > 300 rwhp) cars probably need BBKs. Mine is at 300 rwhp and I couldn't be happier with the stock brakes on the track. Someday I will probably get a BBK (as I upgrade to higher HP, try more brutal tracks, and continue to improve my driving skills), but first I'm going to squeeze everything I can out of the brakes I have.

Most cars are also a lot heavier than 2700-2800 lbs too! I know guys who have track 350z's, EVO's, RX8's, STI's, E46 M3's, and the list goes on. About the only one in that group which didn't run into a brake issue on the track at some point was the RX8 (as its very similar to the FD in that its fairly lightweight so much easier on the brakes than most cars).

There are only a handful of 'performance' cars I think of which you can buy for under $50,000 which are not really going to have too much of an issue at the track with brakes. Aside from the RX8, the Lotus Elise (another light car) would be the next one and maybe the Vette. However, even that is on the edge as I know some guys who had to go with BBK's even on the C6 Z06.

Absolutely. However, if you are running your car hard enough to need brake ducting and/or BBK's, you'll most likely be cracking the stock rims as well.

Ok, I'm not going to go into detail here but brakes do not stop the car. Tires do. BBK's are there to help dissipate the heat better. I'm not aware of any BBK available for the RX7 which hasn't been setup to keep the stock brake bias. Most BBK's available for the FD keep the stock rear brakes to maintain the stock bias. You really don't run into an issue with changing the bias until you start trying to fit calipers from another vehicle. However, changing the brake bias isn't the end of the world. The brake bias has more to do with your driving style rather than the car. If you've ever seen professional race cars, they have adjustable bias. The drivers can and will adjust the bias from the drivers seat while racing. If its an endurance race, one driver may like more front bias, the other driver may be more of a trailbraker and like more rear bias. They will also adjust the bias based on the track conditions (i.e. wet racing verses dry racing). F1 drivers actually adjust the bias constantly each lap where they want the braking bias different for some or all corners. Michael Schumacher was famous for this as he adjusted the bias for basically every turn on every lap.


Now, I will be adding ducting to my car over the winter and plan to keep using the stock brakes for as long as possible. The reason for me doing it is that I can cheaply keep an extra set of front calipers handy. It would be a little more expensive to keep an extra set of Stoptech's laying around. ;)

OEM rear brakes won't maintain the original bias when the front brakes change. A front BBK which increases front braking power moves the bias forward, and I believe this covers all of the pre-Stoptech kits. Those early kits use a larger rotor AND bigger-than-stock pistons, giving much more front braking power. Stoptech reduced piston sizes to balance the big rotor.

Racingbrake began working on an FD kit because Howard Coleman was dissatisfied with the bias from his AP front BBK/stock rear combination.

Exactly. They tested and fixed their issues. However, once again, changing or manipulating brake bias is not the end of the world.

I think the point he's trying to make is that if you're at the point where the stock brakes aren't cutting it anymore, than the ducting can only help so much and if that does cure the fade then you're operating right on the edge and any future upgrade to the tires, hp or driver will likely push you over that edge to where you have fade again. Admittedly ducting is a lot cheaper than a BBK, the BBK may well be needed sooner or later anyway.

Yes, I don't mean to suggest that adding ducting is the be-all and end-all braking solution, but I do believe the benefits of ducting are generally under-appreciated. You get more margin adding cooling than one would think, and it can be enough to keep you running happy for quite a while.

We can get quantitative about this - Majik, if you are game, buy some temperature sensitive paint from McMaster-Carr and quantify your rotor temperatures before ducting, then do the same after your winter upgrades. I bought paint for 800, 1000, 1200, 1400 deg F, as well as some stickers for the calipers that are sensitive between about 300 to 500 deg F. Unfortunately, I didn't do this BEFORE adding ducting, but my rotor temps after ducting are at about 1000-1200 deg F, and the caliper stickers never register (i.e. caliper temps are under 300 F).

No one is discounting ducting. However, as Black91n/a and I mentioned, ducting may not work for everyone. There have been several owners here who have tried ducting and it still didn't help them. Now, they could just had improper braking techniques, riding the brakes all around the course and/or using not-so-track-worthy pads. Not all of the variables were expanded on in those situations. But for the "average joe", a BBK while costing more, is easier a little easier to deal with:

1. Most people aren't going to fab their own backing plates for the rotors. N-Tech backing plates, if you can get them, will run about $250. That's just the plates, add in another $60-100 for the hoses.

2. Next you need ducts for the front to direct the air. NASA style ducts, good ones, run about $20-30 a piece. So just there you are about $400 in parts which is a sizable chuck from $1700.

3. Add in the fab work of making a generic NASA style duct fit/work on the FD as well as installing the backing plate and the ducting; all that compared to just swapping front rotors and calipers.

You can see that many people will op for the BBK, as sometimes its just not worth the effort.

Unfortunately, even if I did that, it wouldn't be an apples to apples comparison unless I waited until this time of year next year. It's much cooler now than what it will be when I start tracking again in the spring. This isn't California over here! ;)

And of course there have been owners that have added a BBK and then still needed the ducting (John Magnuson being one notable example with his Willwoods). And that RacingBrake BBK doesn't appear to be exactly zero effort to get working right, although the issues have nothing to do with ducting of course.

Hmm, its worse than that - I'd suggest fabbing your own fiberglass front piece. It will fit tighter and route the piping more cleanly. You really, really want to make sure you have an airtight duct. Its about a weekend's worth of work.

Hey, move. We'd love to have you! Actually, the central valley (where Thunderhill is) can get reasonably hot in the summer. I was out there in Aug and it was about 100 deg F. Brakes still worked though... ;)

Anyhow, I think we've done a good job explaining the different perspectives. Good luck with your upgrades, and send me a PM if you'd like to know more about what I did.

Ducting from front???
 

Feed front bumper, Chuck's dual oil cooler kit, greddy 3 row... Where to duct from??

I'm planning on sealing the bottom of the car, going with the stoptech/99 setup and going with some backing plates.

The only thing I can think of is the small triangular area under the oil coolers. Doesn't seem like enough area to pull from.

Would naca ducts on the belly pan pull enough possibly?

PS- I just noticed when posting the pic how hard the rear squats!!!! Apex'i N1s set at 8 of 13 rear, corner balanced with a decent amount of rake... WOW, I love hp :) Just can't stop it yet!

Yea, you don't have a lot of options. I would probably use the small triangular area and also steal a little bit of the lower oil cooler opening. Are you oil coolers ducted?

Yeah, they're ducted. I guess I can redirect some of the ducting to the brakes. Oil and water temps are low enough. Good idea!

Would it be possible to have the brake ducts take air from the side of the oil cooler or rad/IC openings? You could maybe make a hole in the side of the ducting and take the air from there.

I can't find a web site for N-Tech, but are you serious that backing plates are $250 a set?
I'm making some right now for my track car (not a RX7) on the water jet, and if people are really looking for a set for the RX7 and willing to pay $250, I'll design and make up a few sets for sale.

People are willing to pay money for them, but to be competitive we expect you to be able to make them cheaper :) I have access to a pretty cool fab shop so I won't need them. You'd do well making them as tight as GooRoo's on the StopTech kit though.

To be honest, I don't know if Nick is making them anymore. They aren't listed on his site anymore and he usually only makes them when there is a demand (i.e. he doesn't do one-off's usually). His new site doesn't seem to have any of his custom work any more, but I'm sure some of it is still available on request:

www.ntechengineering.com

Yes, they were around $250 for the set. He had templates to make a few different sizes depending on the brakes they were going to be used with... There wasn't a lot of demand for them so he only made runs when there was enough interest.

Depending on the radiator configuration, I don't think that would be easy or even possible. His best chance is to borrow a little air from the oil cooler ducts as well as the little triangle opening. I'm pretty certain he could get a substantial amount of air at speed from that as well as not really hamper his oil cooling ability.

I suppose he could cut up the bumper and make the triangle opening and the oil cooler opening one big opening like the Mazdaspeed bumper. :)

EWWWW, no... I'll steal from the oil cooler. I don't think the triangle part will do anything really, I'm only needing about 10 sq in of area per side I figure.

WTF do you think those 'little triangle' openings are for? OEM brake ducts were provided for our cars. That is the ONLY reason the OEM front lip has 'little triangle' openings in it. Don't be a 'tard and track your car without the ducts that it was made for. The '99 spec front ends and splitters require...you guessed it, '99 ducts.

In plain English, proper front ends have dedicated oil cooler/trans cooler, radiator/FMIC/PS cooler, and brake ducts.

Here is a link to a post I did a few years back about my brake ducting:

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/pictures-my-custom-brake-duct-inlets-397125/

It has worked well for me since. I've never had brake fade.

The hard part is the making the mate for the front R1 lip intakes. Here is how I did it. Feel free to steal it all if you find it useful.

https://www.rx7club.com/showpost.php...4&postcount=31

Picts of the ducts installed:

https://www.rx7club.com/showpost.php...2&postcount=29


Some additional comments:
- The stock-sized R1 lip intake appears to work great - no need to enlarge. I suspect the limiting factor for airflow is the mouth of the NTech backing plate - another area for improvement, pincusa! A cone-shaped hose mount would allow more airflow than the "pinched cylinder" design of the NTechs, but probably be hard to fabricate. Others (see GooRoo) just cut off the front bolt for the rotor plate, but I think that could be avoided with a cone.
- While I wasn't getting brake fade without the ducts, I was cracking rotors and running through pads in a single track day. The ducting helped in both respects (pads last me two track days, and the rotors, hmm, I guess about three or four).
- Don't buy the black hose shown in the pictures - it is double-walled and the inner layer collapses, closing off the duct. Buy the single-wall orange silicone hose.

One other key point I forgot to list:

The rubber piston dust boots on both the front and rear will bake and crack when the pads are new (i.e. when pistons are fully retracted and the pad is closest to the dust boot) if you don't have a good backing shim. I recommend buying stainless 302 shim stock from McMaster-Carr in .025 and .015 thicknesses, and cutting with aviation snips. The .025 is right at the limit of what the snips will cut, so buy a high-quality pair. Use the stock steel backing shims (both front and rear) as a template. This doesn't need to be all that precise - if one is careful, snips are more than enough.

I am using stainless steel because it has 1/3 the thermal conductivity of steel, is cheaper than titanium, and is enough to do the job. If buyng Ti, be absolutely sure it is grade 5 (actually a Ti alloy) and not the far cheaper grade 2 (pure Ti). Grade 2 is no better than stainless. There was a discussion of all this in some other thread (search my posts if interested).