Brake cooling and upgrades

[wvumtnbkr]

This past weekend proved that our brakes are not up to the task with our new drivetrain.

 

We FRIED our front AND rear brakes on Saturday.  Like, no pad left.  This was with the same brake compound and break-in procedure we have been using for 5 years.  These pads have lasted the VIR 24 hour race for us with no changing required.

 

We hurriedly added 3" brake ducts that enter through the front of our airdam and dump right near the center of our rotor.  This helped a good bit, but did NOT solve the issue.

 

In 7 hours of racing, we WAY overheated the brakes (boiled fluid or VERY close to it on Sunday after adding the ducts).  The pads are almost down to nothing and they were brand new for the start of the day (minus being bedded in at WGI).

 

What can I do?

 

Solutions I am going to try:

1) I am looking at trying to find a slightly larger rotor (possibly a 2 piece rotor).

2) Add the dust shield back into the system and attach the ducting to the dust shield.

3) Go from Hawk Blues to DTC60 pads (or other high temp pad).

 

Any other ideas?

 

Any other teams running into similar issues with their 2nd gen RX7?

 

 

Thanks!

 

Rob R.

[scottyk]

We went from blues to 60's, actually got less hr's out of the 60's. I also don't believe 2 piece rotors are free, might want to check rules on that.

 

Edited August 28, 2017 by scottyk
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[Wink]

I wasnt impressed with 60's at COTA, We run 3'' ducts and I was getting a lot of fade.  

[wvumtnbkr]

16 minutes ago, scottyk said:

We went from blues to 60's, actually got less hr's out of the 60's. I also don't believe 2 piece rotors are free, might want to check rules on that.

 

they are part of the 2 x rule.  or, at least it were.  Lemme go check the rules again.

[Andrew D Johnson]

[enginerd]

- You mentioned that you boiled the fluid but didn't state what type...  definitely upgrade to a higher BP fluid.

- You said that brake ducts helped on day 2... keep going on that route. Do a really good job on them and they will help even more (maybe using the backing plate like you said).

 

Keep it simple... don't go changing rotors just yet (sounds like a PITA). I think if you upgrade fluid, pads, and cooling it will solve your issues.

Edited August 28, 2017 by enginerd

[Black Magic]

Rob you were probally well outside of the upper temp limit for blues. You can probally fix it with a real race pad, like st43s or work on rotor mass and cooling to get the temps down to the operating range of the pads you have. If you truly boiled the fluid you need to get the temps lower, if it just faded higher temp limit race pads can do it.

 

The neon eats brakes on the stock rotor size. Went from 24hrs on blacks to 5 hrs. St43s will last races.... We run slightly thicker rotors (mass and a little better cooling flow) with forced air blowers on the caliper and into shrouds that guide it to the center of the rotor. This also saves the wheel bearings. The forced cooling is worth a ton, most cars arent fast enough in average speed to out flow good blowers. 

 

Braking a little early also can do alot for brake life, the drag does more of the decel work per lap that way (lower brake energy input). 

Edited August 28, 2017 by Black Magic

[Ron_e]

What did you change on the car to go from acceptable performance to unacceptable?  Is the engine that much heavier?  The new trans is lighter.

[wvumtnbkr]

35 minutes ago, enginerd said:

- You mentioned that you boiled the fluid but didn't state what type...  definitely upgrade to a higher BP fluid.

- You said that brake ducts helped on day 2... keep going on that route. Do a really good job on them and they will help even more (maybe using the backing plate like you said).

 

Keep it simple... don't go changing rotors just yet (sounds like a PITA). I think if you upgrade fluid, pads, and cooling it will solve your issues.

We were running motul 600 fluid...

[jmabarone]

13 minutes ago, Ron_e said:

What did you change on the car to go from acceptable performance to unacceptable?  Is the engine that much heavier?  The new trans is lighter.

That's where I am leaning too.  Are you having to drive the car differently with the new engine?  Has the brake ducting changed because of the swap?  

[enginerd]

1 minute ago, wvumtnbkr said:

We were running motul 600 fluid...

That's an impressive fluid to boil.... *these are not the droids you are looking for*

[wvumtnbkr]

13 minutes ago, Ron_e said:

What did you change on the car to go from acceptable performance to unacceptable?  Is the engine that much heavier?  The new trans is lighter.

 

The engine and trans are about 75# heavier together.  The T5 is heavier than the 2nd gen non-turbo trans (from my garage scale measurements).

 

The real difference is the speed at the end of the straights...   We are averaging about 10 to 15 mph faster than we were before....

[wvumtnbkr]

1 minute ago, jmabarone said:

That's where I am leaning too.  Are you having to drive the car differently with the new engine?  Has the brake ducting changed because of the swap?  

We went from 0 brake ducting to now having the 3 inch ducts.

 

The car is now easier to just mat your right foot and go VERY fast down the straights AND between corners.

 

The car still handles well.  Suspension, in general, was mostly unchanged.  We are running new springs and bilstein dampers instead of KYB.  No huge difference.  Same alignment.

[Alex3000]

2 minutes ago, wvumtnbkr said:

 

The engine and trans are about 75# heavier together.  The T5 is heavier than the 2nd gen non-turbo trans (from my garage scale measurements).

 

The real difference is the speed at the end of the straights...   We are averaging about 10 to 15 mph faster than we were before....

 

Not a terrible problem to have.  Poor rotary.

[wvumtnbkr]

Just now, Alex3000 said:

 

Not a terrible problem to have.  Poor rotary.

Don't worry!  That engine is the one that is going in Bryan's car.  She is still alive and well.

[Ron_e]

What kind of shape were the rotors in?  Micro-cracking can chew through a set of new pads in no time.

[wvumtnbkr]

3 minutes ago, Ron_e said:

What kind of shape were the rotors in?  Micro-cracking can chew through a set of new pads in no time.

That's true.  The rotors were on the car for a few races.

 

However, these rotors and pads got HOT!  When we pitted, the calipers and pads were smoking.  The brake lines were CRAZY hot to the touch.  The master cylinder was actually a bit warm.

[Ron_e]

With the extreme heat you are talking about you may have to increase your rotor size.

 

When we went from 11" to 13" (within the 2X rule of course) we went from changing rotors every race to lasting 2-3 races.  Everything ran much better.

[Xph]

17 minutes ago, Ron_e said:

When we went from 11" to 13" (within the 2X rule of course) we went from changing rotors every race to lasting 2-3 races.  Everything ran much better.

 

Yep this will help quite a bit, get more surface area... but

 

first I might try "active cooling"  get some of those blower fans like nascar uses..

 

The other "trick" is to make a seal plate that just fits on the inside of the brake rotor...  (think of it like a tiny brake dust shield)...  run your duct there, and it will force the air through the rotor  ideally duct right between the rotor and caliper...  on our car, we reduced the size of the duct to 2" but tightened up the tolerances by better controlling where the air goes

 

Note running higher temp pads will trash your rotors in a hurry...   if you ever see tracked vettes, they crack them all the time...  I would do what I can to cool what you have first..

Edited August 28, 2017 by Xph

[revvhappy]

Yup, increase rotor and pad size if possible. Are there any bolt-on caliper upgrades? My Supra has 4-piston Nissan 300ZX calipers and rotors from a Mazda MPV minivan that bolt right on. All of the information for the upgrade came from an active Supra forum. 30 years of trial and error have led to some amazing bolt-on brake options (up to 14" rotors now).

 

I also found out about the negative effects of heat on brake pads during my first two races many years ago. The first race was a shakedown where I asked my team to run 80% for the weekend. I ran some cheap upgrade pads from Rockauto and they were perfect for that pace with lots of life left after 15 hours of track time. The next race on the same track I installed a new set of the same pads and cut my drivers loose - 6 hours later the pads were down to metal. Once your pads go beyond their thermal limits wear becomes exponential. 

[Alex3000]

22 minutes ago, wvumtnbkr said:

That's true.  The rotors were on the car for a few races.

 

However, these rotors and pads got HOT!  When we pitted, the calipers and pads were smoking.  The brake lines were CRAZY hot to the touch.  The master cylinder was actually a bit warm.

 

These are the second gen 4 piston fronts right?  Those are pretty beefy as far as brakes people run in chump go. It just seems crazy they would be so inadequate. Especially considering your car can't be more than like 2,300#s or so.

 

May I throw the idea of brake balance out there? Maybe a bit more rear bias could take some strain off the front

 

 

[wvumtnbkr]

3 minutes ago, Alex3000 said:

 

These are the second gen 4 piston fronts right?  Those are pretty beefy as far as brakes people run in chump go. It just seems crazy they would be so inadequate. Especially considering your car can't be more than like 2,300#s or so.

 

May I throw the idea of brake balance out there? Maybe a bit more rear bias could take some strain off the front

 

 

We destroyed the rear pads too.  This is only the second set of rear pads I have EVER had to put on the car....  Hawk HP+.  Same as always.

[mhr650]

 

DTC60 are way better than Blue pads, that is a start. This is the way that I installed my brake cooling hoses, they are as close to the wheel centerline as the strut allows. I am using 2.5 inch hoses instead of 3 mainly because that is what fits into the turn signal hole in the bumper but it is also the max size that will fit into the inside section of the rotor so that the air gets pulled through the cooling slots of the rotor. Another often overlooked thing is to make sure  you don't have a bunch of rubber blocking the slots in the rotor, it is amazing how much can collect in there especially with well-aimed cooling hoses.

 

 

If you want to do the full update I can hook you up with my Wilwood contact, I am sure he can help you out. This is the biggest brake package that you can fit inside a 15 inch wheel, I have designs to mount this on a first gen but it shouldn't take too much modification to work on a second gen car since I based my design around replacing the same calipers and rotors that you have now. I was stuck having to use custom hats due to the stupid first gen bolt pattern but I believe that you can get a stock hat to work on your car, and if not I can design a custom hat up for you. If you want to go bigger it will mean moving to 17 inch wheels and adapting for the changes that they bring.

Edited August 28, 2017 by mhr650

[rod rammage]

You used the wrong brake pads. Way wrong pads.

[mhr650]

11 minutes ago, wvumtnbkr said:

We destroyed the rear pads too.  This is only the second set of rear pads I have EVER had to put on the car....  Hawk HP+.  Same as always.

 

I use DTC30 rear pads which are probably way better than the HP+, the DTC60/30 combination is a very popular setup that a lot of people have had success with. Another thing I like to do is machine off all of the parking brake hardware and install a ½ NPT plug in the hole, probably doesn't really improve performance but it is one less thing to fail, and it makes changing pads way easier.