brakes

[nando]

So I had my first lapping day yesterday at Mission, and the most obvious weak point on my car was the brakes. I was overheating them pretty badly - especially after coming down from 100mph on the long straight.

mainly, my fluid was boiling pretty badly. I had fresh fluid and even bled them again after the first session - it still didn't hold up. I can tell the stock ducts were working because they always came back, and I don't think my pads were doing too bad. I was using ATE Superblue/Gold, stock rotors, hawk HPS pads. I'm brainstorming for ideas on brake upgrades that don't involve a BBK.

The first things I can identify is every seal/rubber peice around my master cylinder needs replacement. the fluid was coming out the level sensor cap - I had it tight but I guess 200,000 miles of use have taken their toll on the rubber. So I'm going to replace all of that, replace the line going to the clutch master (since it nearly fell off the resivior), and rebuild/replace the master cylinder.

I need to do something about my brake master; it has over 200k on it and it's starting to get mushy. the problem is, an OEM ix master is very expensive, like $1000 expensive. there are cheaper aftermarket alternatives but I don't know how much I trust the chinese, or even if these supposed $200 MCs are really for my car. However, I *do* have a 25mm master cylinder I could drop in.

My question is - how much would it affect my brakes if I were to use it while I rebuild the stock one? I know it will make for more pedal effort, but how much? Stock is 22mm just like the regular E30. I think the regular E30 rebuild kit will work for the ix but I don't have time to replace all of this at the same time as rebuilding the MC (I also need to replace all of my soft lines and do rear bushings). brake modulation is fine with the stock MC, and I have no problems with heel/toe downshifts. I don't want to ruin those aspects of my car.

So aside from replacing every seal around the MC, the next idea that pops into my head is better brake cooling. I know they make backing plates for regular E30s - but I'm pretty sure I'd have to make my own. Are these pretty effective? Anyone built a set who'd like to share what they did? I can have anything welded pretty easily.

Fluid - is ATE not that great, or are my brakes just getting way too hot? I know things like Motul are out there, but at nearly $40 a liter, I'm not sure if I want to go that far. But I may have no choice. Alternatives?

rotors were fine, pads actually seemed okay - didn't glaze them over or anything, and once my brakes cooled down again they worked every time. I've thought about getting something just for the track (maybe Blues or HT-10s or something), but can I swap pads back and forth without changing rotors?

any other ideas? obviously less weight would help, but I'm not about to gut my daily just for a couple lapping days a year. I could conceivably lose about 100 more lbs without sacrificing too much, but I don't want to do much more to my car until next year.

[Dave]

Although it was your first track day, you have been doing some shopping cart-parking lot racing for a while, so I'd guess you were pushing it a little.

HPS pads are not up to that.

Blues will ruin your wheels.

You might go with some HP+ next time and I think you'll see some improvement.

I really dont think your fluid should be boiling - I use "lesser" fluid and even after some damn hot days at MidOhio in the summer I never had an issue with fluid when it was fresh.

I don't know about the differences in how an iX is on brakes.

If I were you, I'd seek advice from alex as he knows a lot about this stuff and knows the iX pretty well.

[JGood]

On my first track day I ran HPS as well, and noticed some fading. After that, I went to HT-10's, and the problem has completely gone away. I am running r-comps. I had ATE superblue in, but recently switched to Valvoline Synthetic (had to bleed the night before an event, no choice). Still no fading. I push my car 10/10ths, as it's just my track rat, and never had problems since switching to HT-10's. I used blues for one event, but they wore quickly and destroyed my wheels with their corrosive dust. Stay away from them.

I swap back to HPS's for street driving, with the same rotors. No problems. I'd say upgrade to HT-10's for track use, and call it a day. All the spece30 guys run stock brakes and usually don't have problems (AFAIK).

If you are going to do brake ducting, remember to aim the tube into the center of the rotor. You don't want air blowing on one side of the rotor face, you want it to suck into the low pressure area in the center and be driven out through the vents.

I put a 25mm master cylinder in a few weeks ago. It's a little harder to do it with the 25mm MC then it is in my 325e with a stock MC. Still possible, though. Especially if you are on the brakes hard (you will be if you are doing a heel-toe...)

[Dave]

^^^^^ Brings up an issue.

Chris, what tires were you running? If you were on Rs, then that is even more overload for the wimpy HPS pads.

And on fluid, I run the Valvoline Synpower all day long. Some guys use it in their race cars with no worries.

[JGood]

And on fluid, I run the Valvoline Synpower all day long. Some guys use it in their race cars with no worries.

That's reassuring. I think I'm going to stick with it because it's available locally, and cheap.

[Stu]

Nando, I share your problem with having too much power for the 4-lug 10" brakes...and it is frustrating. E36 M3's and 911's can drop anchor at the 1-2 marker while you're having to get on the brakes a LOT earlier.

First thing I'd do is ditch the HPS pads--they are definately not up to up to task for any level of track driving (except parade laps maybe :D)

I'd do the master cylinder gaskets and all other weak points to make sure you can bleed it with a lot of pressure (25-28psi) with a pressure bleeder.

Next is pads, I'd have a set of street pads (use those HPS's on the street) and a set of dedicated track pads (Carbotech XP9, Hawk Blue/HT-10). If you have nice wheels, don't let the pad residue stay on the wheels too long (more than a day or two) or you will never get it off. (Though some say that oven-cleaner works)

Also, don't just get aggressive pads in the front, put something quality in the rear too or you will have problems when the heat really builds up. Get atleast a HP+ in the rear.

If you don't want to do ducting, atleast remove the front and rear wheel brake backing plates. This helps with brake temps. But if you can and want to, I'd definately recommend ducting.

All in all, this will help a lot but if you're pushing the car 10/10ths, you'll find that there still isn't enough and that 11-12"+ brakes are required.

[Bimmerman325i]

nando, if you're thinking of going with a brake ducting kit I'd check out Zen's design (http://www.r3vlimited.com/board/showthread.php?t=110742), it looks pretty solid. However, a friend of mine just put the Bimmerworld race brake ducting kit on his e36, and combined with ATE superblue, Hawk HP+, and oem rotors he still managed to boil his fluid on the track. I think the issue has less to do with the cooling options as much as pad choice. A set of race pads would probably combat the boiling, but I've got no data to back it up. If you heavily track the car though, a cooling kit would probably be a good idea though.

As far as switching pads on the same rotors goes, I know it does work but I've heard legit horror stories about it before. For example: my dad used to do expert witnessing for jury trials(he's a mechanical engineer by trade) and had a case involving brake pad changing. A non-semi truck needed new pads but the rotors were not turned or machined down for whatever reason, leaving a worn grooved area that fit the old pad perfectly, but had next to no area for the new pad to be in contact with. Evidently this grooved area was not especially visible to the naked eye. When the truck tried to brake hard, the tiny bits of pad that were actually in contact with the rotor overheated badly enough to have scorch marks, and the truck did not stop in time and people got injured/killed. Dad's findings were that because the rotor was not turned to present a flat mating surface for the new pads, the brakes failed. This is just from what I remember off the top of my head, I can get more details later.

That said, I can see going from street pads to race pads being alright, since the race pads will eat the rotor much faster and will wear in right, but I'm not so sure about going from race to street on the same rotor. At the very least, the pad shapes should definitely be the same. What would be best would be to have a good set of slotted rotors for the track with corresponding pads and a set of good cheap oem blanks for the street with pads.

[nando]

I was on street tires, BFG KDW2's. They got a little hot but I never felt like my tires were holding me back (plenty of response/predictable grip). I was able to build up a lot of speed for at least 3 turns that required hard braking - and mission is known for being hard on brakes. I would have been in real trouble with a set of R-comps though.

I may switch to the valvoline just because I can get it locally and I've heard other people say it's good stuff. ATE is nice but paying for shipping kind of sucks. I'm glad I brought fluid with me to the track though, I got lucky and somebody had a power bleeder that fits our cars, and the guy needed an 8mm wrench to do his. Funny how similar Miata hardware is to E30s. :p

I guess I'll try a set of HP+ next time out. Would it be wise to do all 4 corners, or just the fronts? my rears were dusting up quite a bit so they were working hard as well. On the street these pads hardly dust at all so I was a bit suprised to see how much dust built up. They got pretty stinky too. ;)

My only saving grace was engine braking, especially at turn 1. I felt bad for my clutch but I was getting better and better at rev matching through the day - unfortunately my 250,000+ mile tranny doesn't really like the 2nd gear synchro anymore, so it got a little testy a couple times. I guess a rebuild is in my future!

jgood - thanks for the info on ducting plates. I think i can have something welded up pretty easily - it's just a matter of having the time, getting parts together, etc.

[nando]

That said, I can see going from street pads to race pads being alright, since the race pads will eat the rotor much faster and will wear in right, but I'm not so sure about going from race to street on the same rotor. At the very least, the pad shapes should definitely be the same. What would be best would be to have a good set of slotted rotors for the track with corresponding pads and a set of good cheap oem blanks for the street with pads.

I might just get another set of rotors and swap them with the pads. Come to think of it, I think I have a set sitting in a box under the house. It's one more thing to prepare for, but it would be nice to not have to slow down every other lap just so I can have brakes again. It sure didn't make catching up to that pesky S2000 any easier :p

[jlevie]

If you are like every beginner I've had as a student, at least part of the problem can be blamed on braking technique. Beginners tend to use the brakes far less aggressively in that they get only the brakes early and ride them into the braking zone, never reaching full brakes. The desired technique is to rapidly increase brake application to the point of ABS activation and then roll off the brakes. Almost a binary brake application. Long braking zones cause by insufficient brake pressure just creates a lot more heat in the rotors and calipers.

That said, some tracks are simply hard on brakes. Having never been to that track I can't say how much of the problem was equipment and how much was the driver. Brake cooling ducts and better pads are called for. At least HP+, and better yet HT10's. You'll have the best results running the same pads front and back. And work on your braking technique.

[nando]

I was trying not to ride them, but I know what you mean. I was trying to slow down quickly rather than dragging the braking zone on, and I could shed 30-40mph off easily in the first few seconds of braking, but for that last 10mph they just went away. I'm pretty decent at threshold braking but I never came close to activating ABS - I don't think I could have even if I tried.

[JGood]

but I never came close to activating ABS - I don't think I could have even if I tried.

I'm on the border of ABS before almost every turn, and that's with r-comps. Do you mean your brakes weren't strong enough to lock up the tires (well, engage ABS)?

[joshh]

One more that uses Valvoline Synthetic. It's great fluid for the price.

[nando]

they may have been able to when cold, but not when hot, I don't think so. ABS also seems to be less likely to engage for me when moving at a higher speed - I can nearly make them lock up with threshold braking from ~90mph on the freeway. Threshold braking seems pretty easy in my car actually, but maybe it's because the brakes are just ineffective to begin with?

[PiercedE30]

If you go through and rebuild your calipers (very very easy to do) get some stainless pistons. It will help with heat transfer between the pad, piston, and fluid.