Real-World NSX Brake Upgrades
 

By: Marc W.

So, you wanna improve your brakes, but you don't want to fork out quadzillion bucks on a huge aftermarket brake system. In this article, we will touch upon what other NSX brake mods are available, and unlike any other article on the subject you have ever read, we have real-world unbiased temperature readings to back up our research and help you chose what's best for your car.

If you are serious about high-performance and track driving, you will one day find that the stock brake system is really not up to the task. Now, some people may tell you "well, learn to drive the car better and conserve your brakes" or something along that line. While that is very good advice, we are simply concentrating on the car itself in this tech article. Many people complain about their brakes "fading" under heavy and repeated use. While there are several different types of brake fade, what is most often being experienced with our cars is "fluid fade". This is loosely defined and otherwise described as "boiling your fluid". That is, the heat generated from the friction between the rotor and the pads causes the calipers to heat up, which in turn gets the brake fluid in and near the calipers so hot as to boil. Air bubbles form, and the driver feels a sponginess or "fade" on the brake pedal. Not a good feeling when you are downshifting after a long straightaway into a tight turn!

So, in essence, what we are looking to do here is to stop the brake fluid from boiling.

One approach is to simply switch to a brake fluid with a higher boiling temperature. Some popular choices are Motul 600, which is a DOT 4 fluid with a dry boiling point of 585 degrees F, or ATE Super Blue which has a dry boiling point of 513 degrees F,  both of which are higher than the regular Honda fluid.

Changing out the brake fluid will only get you so far. The root of the problem is the generation of the heat in the first place. There are several proven methods that sports and racing car owners have come up with to reduce heat in the brake system. 

The first method is to get more cool air to the rotors and calipers. This is typically done with various combinations of air ducts, air deflectors, re-arrangement of body and/or suspension components, and the like.

The second method is to use larger rotors and/or calipers which have more surface area. Greater surface area = better cooling. Of course, a larger rotor and caliper will also allow you to stop faster, assuming (and this is a big assumption) that your tires are up to the task. 

Getting More Air to The Brakes

Let's first concentrate on the first method- getting more air to the brakes. We did an interesting experiment not too long ago at a recent track event at Texas World Speedway. It just so happened that we had six experienced NSX drivers attending this event, each with a slightly different brake system configuration! I brought my handheld laser point-pyrometer which would allow me to simply point the laser on the brake rotors to instantly read the brake rotor temperature when the cars came in from running on the track. While this test really was not 100% scientific, it led to a greater in-depth understanding of what brake mods are the most worthwhile. Basically, each driver was more or less an advanced or intermediate level track event driver. Each run session went on for about 20 minutes on the same track. The last lap was a cool-down not using the brakes, so the actual high temps experienced by the brake system out on the track were higher than the temps we read when the cars came into the pits. To get a baseline temperature, here's a bone-stock NSX's temps:

Like the rest of the NSX guys out there that day, Chris is a good driver and has no problem getting on his brakes to outbrake the Vettes and Vipers, etc. For his first run session, his front rotors read 400 degrees (averaged left to right), and his rears read 250 degrees. If we want to get a rough average, we can say that on this day, at this track, a bone stock NSX's brakes run about 450 degrees front, and 300 rear.

Splash Guards

Now, let's get to the first, most basic brake modification we can make. This mod does not require the purchase of any parts. It only requires some labor. On the inside of each of the four brake rotors is a tin plate. Some people call this a rock guard, others call it a splash guard. It's true purpose on the NSX is a total mystery.... 

We do know however, that the splash guard reflects rotor heat right back to the rotor, and blocks the cool air underneath the car from cooling down the inside of the rotors.

Vaughn took off his front splash guards, but otherwise has a totally stock brake system. He unfortunately did not get to do too many runs that day. Click here to find out why But, we did get take his rotor temp after one run. His rear temps where the same as Chris, as you would expect, but his fronts were 150 degrees cooler!!!  Again, we know we did not run a totally scientific test here, but our observations seem to indicate that removing your front splash guards will make your front brakes run about 150 degrees cooler! These results seem to be validated by the fact that Vaughn's rear rotor temps where the same as Chris'. Anyway, if you are interested in learning step-by step how to remove your splash guards, click here for instructions.

Dali Deflectors

Next is yours truly. I had basically the same setup as Vaughn, except that I also had the big Dali Air Deflectors up front, and I had also taken off the rear splash guards. 

In addition to that, I also had slotted rotors, but everyone I have talked to has indicated that all other things remaining the same, the temp difference between a slotted and solid rotor is next to nothing. It become a theoretical argument - "well, the slots provide more surface area"  While the fact that my rotors were slotted, and made by a different manufacturer with probably a slightly different metallurgy, I don't feel qualified enough as an engineer to discuss the differences such details make. Slotted and for that matter, drilled rotors look nicer than solid rotors, but most folks on the track, or who really race typically go for plain solid rotors, or maybe the slotted, but generally eschew the drilled rotors. We aren't going to get caut up in discussing the differences between rotor designs here. For our simple purposes, I'll have to chalk up the temp differences to the deflectors up front, and the lack of splash guards in the rear.

I ran way hotter the second run session. My rear temps were 80 degrees hotter than a stock system should be. Not exactly sure what happened there. Even on the first run, im still running the same rear temp as everyone else. Looks like removing the splash guards in the rear does not make any difference in rear brake temp. Maybe this is because the rears do something like only 20 percent of the total braking. Ok, well, at least my rears match my fronts in that they have no splash guards! :)  I did run 50 degrees cooler up front the first run with my Dali deflectors. Of my two runs, I'd say the first was more in line with what it should be, seeing that my rears were the same temp as everyone else. Therefore, we can conclude that the Dali Deflectors are worth about 50 degrees of cooling.

Air Ducting

Now, brake ducting is something really only see on racecars. Don't ask me how he did this is, but Andy made his own brake ducting kit. 

It looks like he gets an additional 33 degrees or so of additional cooling above and beyond what you can expect with the deflectors and splash guards removed, but hey, on his first and third runs, his rears did not seem to get as hot as you'd expect. Maybe too much slower traffic on the track? Andy's second run session yielded the expected 300 degrees on the rears, but his fronts were the same as mine without the ducts - 250 degrees .  Andy's ducting was of very small diameter tubing (at least smaller than I have seen on true race cars) and they ran a pretty torturous path from under the airdam, up over the suspension components. My feeling is that for an air ducting system to work properly on an NSX, you'll have to remove the air conditioning system, or at least remove the evaporator units in front of each of the front wheels, use large diameter race ducting, and a fittings both on the intake and the output side where you'll want to get a fitting that directs the cool air right into the inner section of the rotor's vanes. 

A good example of such a kit is the "cool -brake" system by OG racing, although of course it's made for Porches. Speaking of Porsches, it seems you can also us the bigger air deflectors of a 993 to fit on the front brakes of the NSX like the Dali ones. The parts in question are Porsche #993-341-083-00 (left) and 993-341-084-00 (right).

Bigger Brakes

OK, so 200 degrees cooler is not good enough for ya!!!??? We have exhausted all the common ways to get more air to the stock brakes. We are such macho hard drivin' track junkies, that we need something bigger and badder to stop our cars. If you are still boiling your fluid with all the air cooling mods, you need bigger brakes! Put quite simply, bigger rotors give you more surface cooling area, so they will stay cooler. 

1997+ Stock Brakes

A little known NSX trivia fact is that the NSX came from the factory two different sizes of brakes. All 1997 and up model year cars have the bigger brakes. The increase was not dramatic. 

The 11" rotors came on all NSX's from 1991-1996

The larger 11.7" rotors began production in 1997. Notice the gap between the inside of the wheel and the outside of the caliper.

The rotor diameters went from about 11" to about 11.7". We were very surprised on our day at the track to see how much of a temperature difference this 7/10 of an inch made:

S.L. was driving in the instructor's group, and not pussyfooting around. The car was fully broken-in from just completed cross-country trip. Remember, his temps with the bigger rotors are to be compared to Chris' bone-stock '92, which averaged 450 degrees front and 300 rear. Damn! S.L.'s was the only car to really be cooler in the rear, as you would expect with the larger diameter rotors. What's surprising is that you would expect to see the fronts hotter than the rears, but that was not the case. S.L.'s brakes were running cooler than anyone else's, and without the assistance of any of our air deflection mods. 

I later thought to myself: "wouldn't it be great to have both the bigger brakes and the air cooling mods??" Well, it just so happens that I finally got my wish come true!  Recently, I found a set of basically brand new 2000 model year brakes for sale on ebay! Compared to other big brake upgrade options, the price was too good to turn down! Buying this set was a bit of a risk, because there is no published data out there on what's involved in installing these on my '94. Well, I figure, since we have gotten to this point in the discussion, let's take a look at putting the larger 1997-up brakes on the earlier cars. This would be the ultimate setup using OEM parts, as the earlier cars were lighter then the latter ones. I guess when Honda fattened up the later NSX'es with the heavier frame rails, T-top, and power steering, they figured they better put on some bigger brakes, (not to mention adding another 20 HP to the motor). First off, the 97-up brakes are supposed to have slightly larger pistons. When I had both my old and new brakes out next to each other on the workbench, the pistons looked like the same size. I should have taken out my calipers to measure. Anyway, the really visible difference is the length of the mounting brackets. Take a look at this picture: 

the '97-up front caliper (left) has a longer bracket than the 91-96 front caliper on the right, so that the calipers can properly clear the larger 97-up rotors. Happily, the bigger rotors & calipers slip right onto the earlier cars with no modifications. There are a few caveats, however. The 97-up front rotors are too big for the OEM 91-93 15" (5-spoke design) wheels. You will need to use either the 94-up 16" front wheel or something of equal size or bigger. Everything wonderful so far, except for the little known fact that 91-96 cars still came with a 15" folding spare tire, even though 94-96's had 16" front wheels! I guess it really didn't matter, because the brakes were the same until 97 anyway. I wanted to make sure that there were no unforeseen drawbacks to changing to the bigger rotors....so I located a used one of a wrecked '98.

The 91-96 15" folding spare (left) as compared to the 97-up 16" compact folding spare. The uninflated outside diameter of the 16" spare is slightly larger than the 15", so you will have to slightly bend back the aluminum bars that protect the ABS unit on the driver's side of the radiator compartment to get the bigger yellow spare to fit properly without rubbing on the inside of the hood. 

Results: Easy bolt-in installation. A fantastic and very noticeable difference in stopping power. I hope to get on the track soon and take some temp readings to see how this setup performs with the air deflection mods. If I boil my fluid now, it will be time to take the next step: Brembo time! Going to one of those great big aftermarket brake systems will solve all my brake problems, but to go with the bigger equipment, id have to also get a new set of 17/18" wheels as well! The next step is one heck of a big step.......we'll see how our system holds up at the next track event! :)