Brake Tech Rules

[JeffYoung]

More to move this forum's discussion off of the SM issue than anything else, let me ask some opinions on brake heat control ideas and legality. I'd like to hear people's opinions on (and let me disclose I have a vested interest in this I have a severely brake challenged car):

1. Titanium or stainless steel backing plates siliconed to brake pads to insulate the piston and caliper seals from heat.

My take: Legal, as brake pads and pad material are free. This is certainly less of a tortured rule intepretation than the one that "allowed" spherical bearings.

Your take?

Disclosure: I do this already. I think this is legal.

2. Insertion of a shim that includes a heat sink that dissipates heat out of the caliper. I'm not describing it well enough, but it is basically the same as (1) above except the "shim" extends on out from the back of the caliper and has a heat sink that allows heat to escape as opposed to being transmitted to the piston and caliper seals.

While a much more tortured analysis than 1 above, I still think it legal if the shim is attached to the pad.

Your take?

I am aware this is being done by others (hell, the website for the product shows an ITS car), and have a set of these, but they don't fit under my current wheel setup.

3. Brake recirculator. Circulates fluid through the caliper so new fluid (and hopefully cooler) goes in the caliper with each pedal stroke. Legal under the brake circuitry may be revised rule? It is simply additional lines and check valves?

I had this in 2004, and removed it for a variety of reasons, one of which was concern over legality.

Your take?

[lateapex911]

I think the first two are perfectly legal, and am looking to add them to my car for longer tracks that have pushed my brakes before.

I am thinking that you;d use the bleeder screw hole on the caliper to get the recirc going? My first impression is that this is tortured, but it might just be legal to the letter of the rule. Will think on it.

[mbuskuhl]

the website for the product shows an ITS car[/b]

What's the website? I'd like to look into these.

[JeffYoung]

Correct on the recirc. I didn't install it on my car, I had someone do it before I started doing all of my own work. But, if I remember it correclty, fluid went in the caliper in teh normal place, and then out at teh bleeder screw adn back to the master. Air in the lines were released in teh master. A check valve made sure that pressure was applied to the pistons.

Basically, your brake fluid circuitry became a "loop" with check valves, and no bleeders.

While I don't think the IT rules progenitors ever anticipated something like this being legal, and it is a stretch from what IT is about, I have to think that as George used to say, if it says you can, you can. The rules clearly state that "brake circuitry may be revised."

EDIT -- Website is here: http://www.fourproducts.com/FSBC_Right.html#Graph

Interestingly enough, the ITS Z car picture that had as their lead ad is gone. If they don't have an application for you, I understand they can make you one. For me, the shim for a 240z is close enough that I can modify it and make it work.

[Z3_GoCar]

Hey Jeff,

Have you considered a high temperature pad? I'm running Hawk HT-10's without brake ducts just bent backing plates. I've heard may racer dis-like HT-10's, but this may be due to over cooling. If the pads don't get up to temperature they won't work like they should. I've still got lots of pad left after running four weekends, 2 SCCA and 2 BMWCCA. If cooling is an issue have you considered a water spray system? Not sure of the legality of this but maybe a good use of a washer fluid bottle

James

[Ron Earp]

James, Jeff's brakes work but we can't get the heat out of them fast enough. The pads are up to temperature, no problem there. But the heat fade is a definite problem, we need to keep them cooler.

At CMP he can eat a set of front pads (and yes the rears are working for all they are worth) in about 45 mins of track time.

That website did used to have a blue Z there. I also have a set of those sinks, but at least at my level of driving they haven't seemed necessary. While I can kill a set of pads at CMP and must manage brakes, I don't overheat and lose braking capability like the TR8.

I'm not sure the recirculator will do much. There is little thermal mass in the brake fluid, at least compared to your iron calipers which weigh about 13lbs each and get to 500F pretty quickly. You circulating two or three ounces of brake fluid through the caliper isn't going to cool the caliper off much at all. And, the lines aren't set up to dump the heat either. It isn't like you have a brake system with pumped through fluid and a brake fluid radiator to dump the heat.

R

[JeffYoung]

James, tell me more about the HT-10. I definitely have noticed a difference in caliper seal length based on the pad I am using. I got a bad recommendation to run high bite pad from Porterfield after PFC quit making 90 compound in my pad shape, and I think that was a large part of my problem. I'm now with Hawk Blues and the caliper seals are at least lasting a race weekend.

Is the idea with the HT10 that the pad runs cooler and operates at a lower temp? If so, I may do that. However, I suspect you have vented rotors, and I do not, which is a huge disadvantage for me. My brakes do not work without proper ducting.

I think Ron is right on the recirc although some swear by them. When I had mine on, it did not seem to help. I am not having a fluid boil issue so much as I am having a claiper too hot, seal melting problem. The recirc seems to help fluid temperature (which I know affects the seals, but still) more than anything. Not keeping the caliper temps down.

[Ron Earp]

The recirc seems to help fluid temperature (which I know affects the seals, but still) more than anything. Not keeping the caliper temps down.
[/b]

The heat transfer does not only work one way - the way that is benefical.

While the fluid might not cool the caliper, it means the inverse of that is definitely true - I bet the caliper can heat up a few cc's of fluid much faster than you can move it around in the lines.

We can easily test it though. I've got a logging meter and thermocouple that can be put in there to collect the data.

R

[BlueStreak]

On my last car, the RX3, with solid front discs, huge ducts, running Motul600, I was getting 2 sessions out of a set of pads, and 6 sessions out of a set of cryo'd rotors. If I had enough rear brake dialed in to get the car to handle right, I got less than 1 session out of the rear wheel cylinders before the plastic caps in the wheel cylinder extruded themselves over the "spring". It was the "less than 1" session part that really bugged me, or more importantly, bugged the poor guy who I was passing under braking on the inside when the brakes died.

I could have upgraded to the RX3SP "large" rear drums, if I could have found a set, but I couldn't, so I ran the nonSP base car rear drums. You can't purchase, at any price, a rear wheel cylinder for an RX3. The places that show it in stock can't actually deliver it if you try to purchase it. The story on the front rotors is the same.

My solution was to manufacture replacement parts myself that were dimensionally identical, but made of materials that could take the higher temps. Not having the money for carbon fiber :P , this usually meant replacing plastic parts with aluminum. Legal, NO, but it was a SAFETY issue, and having brakes was more important to me than losing positions due to a potential protest. Without the mods, I had two choices:
1) Run X seconds off the pace (unsafe).
2) Run on pace, knowing that at some point during the race, I was going to lose the brakes and potentially hurt someone (unsafe).

When I decided to quit racing, I sold the car to someone who had a large cache of stock parts, so it won't be an issue for them, but for me, it was a big problem.

Now that I'm racing (albeit not very often) again - I know there are guys out there that have to do these sorts of things to get their brakes to make it to the end of the race, and I don't have a problem with it. However, the rulebook does. I'm pretty torn on these brake issues. Brakes are critical to safety, BUT they can also be HUGE performance advantages, so where do you draw the line? I'm not sure. What I do know is that it is sad to see the number of formerly competitive vehicles that have been parked over the years because brake parts have become unobtainable. I wish I knew of a simple solution for these issues.

How do the guys in the historic series handle these kinds of issues?

Jeff - I, for one, applaud anyone with the tenacity to make a set of TR brakes last through a modern IT session using stock components with some added cooling.

[Z3_GoCar]

Jeff,

You're right that my rotors are vented, but I get enough air flow with only the bent backing plates and a hole in the finder well. Check this out:
Hawk Pads at Bimmerworld

The temp range on the HT series is 300-1600, I suspect they work better at the upper range of that, while the blue's only go to 1000. If BW uses them for a 4-6hr World Challenge race on a ~3000lb car they'll work for our cars for many weekends.

James

[JeffYoung]

James, I might give that a try. Thanks for the information. I never thought to move down to the HT-10s.

Eddie, I am lucky in that all parts for the brakes on my car are readily available, except the calipers, and I've managed to acquire a few of them over the years....lol.....

To make it all work competitively, which really happened for the first time this season, requires (a) Castrol SRF; ( ducts to rotor AND caliper with a good spoiler set up up front to actually get air in the ducts; and © shims to keep heat off the caliper pistons and seals. Then, you have to manage the car and the brakes to make them last. My plan now is to use the torque to squirt out as far as I can at the start, and then hold on as best I can to finish, taking it easy on the brakes when race situations allow. It can be done, it just takes a lot of work.

I too was in the quandary you were in. Brakes are definitely a performance issue, but a safety one as well. I have nearly taken people out twice due to brake failures (one was an unexpected m/c failure that was scary) and I never want that to happen - again. I also, admittedly, considered cheating -- not many would know if I put some of the easy upgrades on my brakes (2.8 Capri calipers and rotors bolt right on). But that is just not an option for me or how I want to run my program. So, we set about to make sure that everything on the braking system on the car was NEW and working CORRECTLY and that the ducting was as good as we can get it. It finally worked.

Thanks for the props though. I pulled a second and a fourth this weekend in a pretty competitive field at a brake intensive track, so the hard work (and Ron was in on it too) paid off and it was satisfying.

[Chris Wire]

I am thinking that you;d use the bleeder screw hole on the caliper to get the recirc going? My first impression is that this is tortured, but it might just be legal to the letter of the rule. Will think on it.
[/b]

About 5 years ago I talked to Tech in Denver (now Topeka) about this very issue. I could not see why a recirculating system would not be legal, given the brake circuitry language in the ITCS.

The opinion I got (and that's all it is, an opinion, with no more legal standing than my own) was that while brake circuitry was indeed unrestricted, the recirculator valve introduced an active component to the system where there previously was none.

I never pushed the issue to the point of actually installing such a device, even though I think they could be technically legal. The 86-91 RX7 is blessed with tremendous braking and therefore isn't really a candidate for this sort of upgrade.

[JeffYoung]

Chris, I heard that as well, which is why I removed it.

However, the recirculator doesn't actually DO anything active. It is not a pump -- your pushing on the pedal provides the "activity" in the line. The recirculator is just a check valve that controls the direction of fluid flow...kind of like a.... speed bleeder?

[Chris Wire]

Chris, I heard that as well, which is why I removed it.

However, the recirculator doesn't actually DO anything active. It is not a pump -- your pushing on the pedal provides the "activity" in the line. The recirculator is just a check valve that controls the direction of fluid flow...kind of like a.... speed bleeder?
[/b]

I agree fully, that's just how it was explained to me. I never followed through on the installation.

I don't see anything "active" about the recirculator either. I wonder if someone would draw the same conclusion with the Wilwood Residual Pressure valves. They are inline devices that keep the fluid pushing against the piston (although they are much more common in drum brake setups) to keep it from flowing back toward the m/c and creating a "soft" pedal. Would that not be "active" as well, simply because it performs a different function from a recirculator?

[JeffYoung]

Good analogy on the pressure valves. I have one in my rear circuit (drums) and it is really no different from a check/recirculator valve system. A speed bleeder is the same way. Just allows fluid to flow one way and not the other.

[its66]

Jeff,
On the legality questions, I think(my opinion, no more) that number one and number two would both be legal as long as they are attached to the pads. Number three might be technically legal, depending on who you ask and how they are feeling that day. I don't think that was the intent, but you didn't question the intent of the rules...

On your braking issues. I remember you telling me at Daytona about it cooking the seals. While the HT-10's are good pads(currently on the front of my 7), I don't think they will fix the problem for you. If you were complaining of a pad fade, or heat at that end, they might help. I don't think they will reduce the heat(much) which is being carried through them into the pistons. This is whats cooking the seals, and I don't think that a pad with a higher temp range will help. Now, when you get the calipers cooled off enough that they don't cook the seals, it might be a different story....

[Joe Harlan]

YOu have to direct the heat the way you want it to go. If I remember correctly the TR8 runs the same pad as a 240z. To start you have to focus the largest part of your cooling on bringing the rotor temp down tot he operating range of the pads yoou are using. HT10's operate at a mid to very high temp and are a much more agressive pad than the R4 compound. With solid rotors you need to build a cooling can that goes over the top of the rotor and directs air to both sides or you rotor will warp and bend to one direction. Also remember heat will travel toward the coolest place first so if you cool the caliper body you will pull the heat from the pads toward the fluid which is a pad thing. Cool the rotor! Allow the pad to transfer its heat in to the rotor. The other thing that you need to do is use themo paints to know what your rotor temps are getting to so you will know how much yoou are bringing them down.

[JeffYoung]

Thanks Joe. We are working on cooling the rotor, and it seems to work.

I appreciate the information.

[bldn10]

"This is certainly less of a tortured rule intepretation than the one that "allowed" spherical bearings."



Of course, that ain't sayin much.

[JeffYoung]

Amen Bill. That spherical bearing stuff was out of hand.

Of course, as soon as the CRB said "Legal!" I went and dropped $2k getting them made for my car.