Mahjik

iTrader: (1)

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.

Eggie

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.

Mahjik

iTrader: (1)

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

Black91n/a

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.

primerGrey

iTrader: (13)

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).

Mahjik

iTrader: (1)

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!

primerGrey

iTrader: (13)

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.

Roadracing7

iTrader: (2)

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!

Mahjik

iTrader: (1)

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?

Roadracing7

iTrader: (2)

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!

Black91n/a

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.

pincusa

iTrader: (1)

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.

Roadracing7

iTrader: (2)

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.

Mahjik

iTrader: (1)

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.

Mahjik

iTrader: (1)

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.

Roadracing7

iTrader: (2)

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.

rajeevx7

iTrader: (11)

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.

John Magnuson

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.

primerGrey

iTrader: (13)

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.

primerGrey

iTrader: (13)

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).