So I heard you can put RX7 Brakes on an E30

[hobbes567]

Watch out for those apex seals on the rx-7 brakes... :-)

[ekdemos]

So the stock e30 brake set up is just fine right? Wrong. The all knowing BMW gods at the factory took the e30 did some body work, added an s14 (25 more hp), and took a look at the brake set up and said, "This needs to be changed for a track car." They went with a five lug hub and used 11 inch rotors. Guess what size rotors the CBi Kit has one on my car? 11 inch rotors.

Why is it when you do all kinds of other work to a car people are ok with it, but as soon as you touch the brakes they start saying, "you don't need to do that, just get better pads and change the fluid." Maybe you like coasting on the track, but if my foot is not to the floor on the gas it is to the floor on the brake.

[Rob Levinson]

I love how every thread around BF nowadays turns into a UUC ad.

Perhaps it's so many people use UUC that's the reason for the frequent discussion? ;-)

The word cobbled was in quotes because I was referencing another poster's comment about the RX7/Corrado setup as being cobbled together. It was in no way derogatory or slanderous in regard to any of your products.

Perhaps a more careful phrasing would have been preferable to avoid confusion... I know if I read it that way, so did others.

A bit preemptive, don't you think? Or maybe I'm wrong. Perhaps you'd like to share with everyone the technical details of the BBK on Ekdemos's car.

What I do know about the setup is that RX-7 calipers have inappropriate sizes (given the rotor used) for a) proper bias and b) proper use of the OE master cylinder. I don't know anything about the brackets and was specifically (and quite clearly) commenting on other home-made brackets that I have seen.

The basic dimensions of all these parts are publicly available, do the brake torque calculations yourself.

You've done the brake torque calculations to compare them to the OE setup for bias results, right?

We'll get back to brake bias shortly.

You know, Rob, it's interesting. I just took a quick gander over to your e-store and what do I see in the BBK section? a WILWOOD caliper on a BMW rotor. You and I both KNOW those parts were NEVER designed to work with each other!

Actually, the calipers we use are specifically designed for the BMW rotor sizes. It's in the manufacturer's engineering specification sheets, which you can download from http://www.wilwood.com

Hm, let's see, what else....you know, the caliper clocking looks a bit odd there....I guess BMW just picked some random position to clock the caliper, it shouldn't matter, right?

Again, the clocking position is within the engineering specification for the caliper.

You're referring to the E36 setup, of course, not the E30. The E30 UUC/Wilwood configuration is clocked exactly the same as the original E30 brakes.

What you may be aware of is that our Wilwood kit for the E30 is about to be replaced by a purpose built E30-only caliper, as posted earlier.

Oh wait, what's this...you make a flywheel to put an 850i clutch in an E39 V8? That clutch was NEVER DESIGNED to be in an M5!

I am so glad you brought up that product. It gives me an opportunity to display what real engineering is all about.

The genesis of that product was simple; the 850CSi clutch is the clutch that should be in the M5 gearbox, as originally specified by Getrag.

The S6S420G gearbox in the M5 is very similar, mechanically almost identical, to the S6S560G in the 850CSi. Fundamentally, what's different is the bellhousing bolt pattern as the V8 and V12 have different patterns.

Then we compare the two cars... each about 4000lb, each about 400hp.

Then we look at original equipment clutch life; M5, fairly bad and 15K-30K mile replacements not uncommon. 850CSi, quite normal with 50K-100K replacements.

Hmmm... so if we have two cars nearly identical in weight, power, drivetrain layout, and transmission... what is the difference that's causing the M5 clutches to burn out so rapidly?

It's the clutch itself. For various reasons including reduced cost, the engineering decision to use a small 240mm (same size as an E36/E46 3-series and barely bigger than the E30) was used instead of the 280mm monster in the 850CSi, that the transmission was originally designed to use.

So what this is, in essence, is "correcting a mistake" and putting in the right clutch. The adaptation to the M5 consists of little more than a flywheel built with the M5's integral ignition timing ring that accepts the larger clutch.

Yes, it's a great idea and thoroughly engineered. Thank you very much for giving me the opportunity to show that UUC's focus is on designing proper solutions.

I hope you get the point I'm making here.

I hope you get the point that there's a difference between understanding real engineering and slapping some parts together from the used parts bin.

FYI - I'm the guy that invented the RX7/Corrado setup. I can assure you I have spent an IMMENSE amount of time, research and testing making sure every aspect of my design works properly.

First of all, let me congratulate you on the efforts and thought you've put into this. That is something to be proud of.

Second, let's make sure our discussion here stays on engineering, and it's not personal. You sound like a great guy, and I welcome all fellow enthusiasts as friends.

Third, let's address some of my issues with assemblies like this:

1. Bracket - I don't know anything about how you've made yours, whether you're using aluminum, steel, heat-treating, specifications, etc. I don't know, so I won't comment other than to say the bracket is the most important safety consideration before looking at any other parts.

2. Caliper - the RX-7 FC (I assume you're using 2nd-gen FC calipers, but comments here apply to FD as well) are excellent for OE parts in the '80s. But, as for race use, they're still OE parts with undesirable rubber dust boots... the first thing to burn up in hard track or race use. There's a reason why OE calipers need frequent rebuilds in track cars, they're not built for it.

3. Rotor - nothing intrinsically wrong with a Corrado G60 rotor, aside from being 1-piece. For track use, 2-piece rotors are preferred. What is wrong is that the hub size is off by 1mm and does not fit. Every time you need new rotors, the rotor should be machined to fit the E30 hub. Or, conversely, you have to modify the E30 hub, which means you do it again each time you need a new wheel bearing.

3. Brake bias - the most important aspect for track performance, is off by approximately 6%. That's 6% more front bias. This is not a good thing in an E30, a car that already has a light rear end.

To put 6% into further perspective, it's like running mild street pads in the rear of the car and race pads in the front. When people say "wow, the car really stands on it's nose", that's a bad thing. A car with correct brake bias should have minimal chassis upset and feel like it gets lower under braking. If anything, many of the true track/race brake setups are adjusted for slightly more rear brake bias to settle the chassis.

For those unfamiliar with brake bias, it's the ratio of front brake force (brake torque) to rear brake force. I'll quote this short passage from our website:

A brake system is designed to change the forces acting on the car; the obvious observation is that it decelerates the car as a single mass. However, this is a simplistic view that does not take into account other factors such as the car's front-to-rear weight bias and more importantly, the shift in weight bias that happens under braking, and in turn most importantly, what effect that weight shift has on the suspension. A car's stability in any direction is only as good as the connection between the tires and road surface, and a sudden upset (such as excessive unloading of the rear wheels) can upset this stability. The goal of a good brake system is to maintain this balance.

Vehicle manufacturers take the vehicle dynamics into account when designing the original brake system, and adjust the size of the various components. These components include rotor diameter, caliper piston size, caliper piston quantity, pad dimensions, and even pad friction index (which varies by compound). Some original equipment systems utilize different types of pads front and rear to adjust bias as much as 15% instead of modifying the mechanical components.

Aftermarket performance brake manufacturers should take all of those factors into account when applying their components. They must also analyze whether their pre-made components (specifically caliper piston size) are too large or too small, and whether this affects bias or is inappropriate for the car's hydraulic system.

4. The larger master cylinder - there's nothing wrong with using a larger master cylinder if there is a benefit, but it's an expense that should be avoided if necessary. The E30 OE master has sufficient capacity for appropriate calipers.


Again, I applaud your efforts, and am glad to discuss engineering details with you or anyone else.

[e24mpwr]

This thread started as something I really like about this community - guys sharing some experience, ideas and opinions and offering to settle their differences by meeting up and swapping cars at the track!!



From an E30 braking perspective, you probably get as much from SS lines, quality fluid, good, sticky tires and maybe a little breathing as anything. Pads can improve upon that even further. Look at the braking performance of race cars running stock E30 setups.

There are clearly gains to be had, especially on the track, but anyone calling out the stock setup doesn't have a lot of credibility to me. UUC is offering a step up from that, and I'm sure they'll be terrific brakes, but the factory didn't ship garbage in their car, either.

CBi - I'm sure you are getting riled up at the use of the word "cobbled" - and I'm sure you put a lot of thought into your swap. I'm not sure why you're taking swipes at Rob/UUC. Not only are they a sponsoring vendor (who helps this community exist) but UUC comes from the best kind of heritage - a bunch of car nuts modding cars who figured out how to do it for a living. At the end of the day, you clearly know more than the average Joe and you made your kit work - that is pretty cool. You also have to admit that you weren't able to do the kind of testing and measurement that people like UUC/Wildwood, etc. must put into their commercial products. As a sponsoring vendor, Rob has every right to discuss his products here. I've learned a lot from his posts, too...

I've heard a lot about Rob from a variety of people who I respect greatly, and this is about as close to negative as I've ever heard. From what I can tell, he and UUC do it right, and I'm glad for his presence.

[sl0ride]

Rob while i understand its in your best nature to try to push people to buying a $2000+ BBK kit from you, i think its more in the nature of the true budget racer to find a cheap alternative to the inferior single piston factory set up. This setup has been done over and over with positive results. You cant beat the fact the more even breaking of 4 pistons over a wider area and bigger rotors results in more stopping force.

Bias solved,

http://www.summitracing.com/parts/WIL-260-8419/

[Rob Levinson]

Rob while i understand its in your best nature to try to push people to buying a $2000+ BBK kit from you, i think its more in the nature of the true budget racer to find a cheap alternative to the inferior single piston factory set up. This setup has been done over and over with positive results. You cant beat the fact the more even breaking of 4 pistons over a wider area and bigger rotors results in more stopping force.

It's in everybody's interest to point out safety and technical problems with major parts like this... especially if you expect that person to be on the track at the same time as you are.

Bias solved,

http://www.summitracing.com/parts/WIL-260-8419/

That's a kludge, and often more dangerous than worthwhile. Most people do not have a good "feel" for bias and are not doing appropriate testing to utilize an adjustable setting to any real benefit.

[Chbimmer]

http://www.e30tech.com/forum/showthread.php?t=83511

Here is a RX7 caliper write up.

[RangerGress]

Rob's posts here are really good. Don't just read them, study them.

The easy way to figure out if someone is full of shi re. brakes is when he says "my brakes stop you faster". Brakes stop rotors. Tires stop cars. (With a caveat towards the roles of F-R bias and suspension)

There's no question that the OEM brakes are perfectly adequate. There's hundreds of folks racing on them. That being said, aftermarket systems have their charms. High quality aftermarket systems can provide for a stiffer pedal, more resistance to heat fade, faster stopping via better biasing, and longer lasting pads.

A stiff brake pedal is a wonderful thing. The E30 brakes aren't all that stiff. I started tracking in 911's and they had wonderfully stiff brakes. E30 brakes were a big letdown in that respect. A high quality aftermarket brake system would fix that right up. OEM brakes are perfectly adequate, but adequate isn't the same as terrific.

Aftermarket brake systems are an opportunity to fix the E30's brake bias. It has too much front bias so the rear brakes don't do their share. This has to be approached carefully tho. Anyone that talks about aftermarket brakes needs to spend a lot of time lot of time talking about bias.

It's always risky to disagree with someone smarter then you, but I'd have to say that I disagree with Rob re. the adjustable bias valve. Done with care, this would be very nice. Don't screw it up tho.

Aftermarket brakes can be more heat resistant because of more surface area and the use of metals that move heat faster. The rubber boot going away is nice too. These are only a track issues tho.

Aftermarket brakes can mean longer lasting pads and rotors. Bigger gear lasts longer. This too is only a track issue. But aftermarket pads and rotors also cost more, so it might not be a win. It's hard to beat $22 E30 rotors.

ekdemos: I'm sure you're a great guy, but I gotta tell ya man, it's hard to buy a lot of what you are saying.

1) Great brakes can cause slower lap times. What?
2) My brakes stop me faster then yours stop you. Only if your brake bias is set up better then ours, and nothing in this thread suggests that.
3) Your brakes are more resistant to heat fade. Certainly could be true.
4) Your rear pads last forever. Something isn't right there, pads and rotors used good and hard just don't last that long. And the fact that your rear pads are lasting so long indicates that you've got brake bias issues. Your rear pads would wear away faster if they were contributing.
5) "Bigger brakes are like having a big hp car. It takes more time to learn to go fast." "I have also had people follow, me and end up off the track because they ran out of brakes." Both of those are silly.

[tryintokeepup]

Maybe I missed it, however, no one has talked about surface area of rotors and pads. While its true that slotted/drilled rotors reduce brake fade, they hurt stopping force/distance. The people who are on the OEM side of the argument have it right in the sense that OEM rotors (because of their greater surface area over slotted/drilled ones) actually stop cars faster.

What I never understood was why people dont use OE stuff for the road because (as has been mentioned) they are more than adequate in street driving. The reason its funny to me is that if youre a serious track rat, than changeing the rotors at the same time as the pads (which are changed relatively frequently) takes maybe an extra 5 min per corner. That way one never has to worry about brake wear because they are always being inspected every time theyre removed.

As for the OP, I too am at a loss as to why one would put an unproved brake system on their car. While its obviously "proved" for the application it was intended for, there was no way of knowing what kind of reaction the car would have from a system that wasnt balanced for his car... I suspose if he would like to take his life into his own hands, who am I and who are we to stop him!

[Chbimmer]

http://www.e30tech.com/forum/showthread.php?t=80344

This should answer the question on the balanced issue.

[ekdemos]

1/5. Larger brakes can cause a slower lap time because (as you said) it is like adding hp. It takes time to feel it all out. At first you brake to hard to soon and you have to spend time finding your marks on the track. I am sure you do this every time you are at a track no matter how many times you have driven it, because your car and the environment is in a constant change.

The pedal is terrific on the car all the time every lap all weekend long.

[tryintokeepup]

http://www.e30tech.com/forum/showthread.php?t=80344

This should answer the question on the balanced issue.

Thats fine... but the point still stands! To what end? Basically what this guy has done is take OE brakes that work well and waste a whole bunch of time and money to fit different OE brakes that have not been proven to work well on an e30! The logic escapes me! As we all know the e30 brakes stop the car very well so with that said the reason could not be for better stopping power (because its not needed). So then the only other reason one would change their stock brakes is to allow for better cooling. How could this reduce brake fade heat if its still useing OE parts from another type of car? So if its not for stopping power and its not for brake fade than what for ???

[RangerGress]

1/5. Larger brakes can cause a slower lap time because (as you said) it is like adding hp. It takes time to feel it all out. At first you brake to hard to soon and you have to spend time finding your marks on the track. I am sure you do this every time you are at a track no matter how many times you have driven it, because your car and the environment is in a constant change.

The pedal is terrific on the car all the time every lap all weekend long.

Your're not going to stop sooner just because you put bigger brakes on. As I said before, brakes stop rotors, tires stop cars. If this basic idea is not understood, it becomes harder to buy everything else that is said.

The places to make some headway on the value of your brakes is on stiffness and resistance to fade. But you're not putting much emphasis on those.

A bias issue that remains unresolved is the distance from pad swept area on the rotor to the rotor's center of rotation. More distance means mechanical advantage.

The bias issue that is resolved is that these brakes will increase front bias because of larger net piston size, which will absolutely have an adverse affect on stopping distance.

I try to counter the e30 brake bias problem by using high bite rear pads. You make the bias problem worse. Your rear pads last forever, but I work them hard enough that my rear rotors get hotter then my front (rear rotor cooling sucks). And you think that you can stop faster then me? Physics says probably not.

[T444E]

Corrado rotors and RX7 calipers must be the whores of the brake world. I can put that set up on my Impulse RS, it's been done a few times before.

[sl0ride]

We need a before and after performance report. Im sure there are pleanty of people who are thinking of doing this swap. We need a before and after test using the same tires on the same section of road with the same road and tire temps for braking distance. Also you would need to use the same brake pad material and allow time to bed in the new pads and rotors.

[RangerGress]

We need a before and after performance report. Im sure there are pleanty of people who are thinking of doing this swap. We need a before and after test using the same tires on the same section of road with the same road and tire temps for braking distance. Also you would need to use the same brake pad material and allow time to bed in the new pads and rotors.

I did a lot of brake pad testing last year using g data from the Traqmate. A couple lessons learned:
1) You won't find a pad combo such that the rear brakes will trigger ABS first. The front is just too over biased.

2) The limiting factor will be rear brake cooling. Rear brakes cool so poorly that if you put on some of the highest bite pads made for our rear calipers (Carbotech XP16), the rear brakes will get too hot and fade.

3) It is hard to compare pad material brake torque between companies. There are no objective numbers published. Like how do you find out what has more brake torque, the Hawk HT14 or the Performance Friction PFC01? There's only one way....test them.

[Chbimmer]

Thats fine... but the point still stands! To what end? Basically what this guy has done is take OE brakes that work well and waste a whole bunch of time and money to fit different OE brakes that have not been proven to work well on an e30! The logic escapes me! As we all know the e30 brakes stop the car very well so with that said the reason could not be for better stopping power (because its not needed). So then the only other reason one would change their stock brakes is to allow for better cooling. How could this reduce brake fade heat if its still useing OE parts from another type of car? So if its not for stopping power and its not for brake fade than what for ???

Yeah, I am turbo and I use OE rotors and OE Pads. I have no issues stopping hard one time (once per run down the strip), It should be a different story heating them up turn by turn but right now I got works great on the street but I have not used this car for any Track or AutoX events. Since i don't really drive hard on the street, I guess that is why they seem to be great.

I understand the logic here, but I think it was said that setup had not been proven to be balanced or just period. I just provided a thread that did show some evidence of this not being the case. Not arguing, just helping the OP since this is something that he wanted to do. There are several instances of this being done several times but they don't seem to be on this form. The feel that I normally get from BF.C is people are in the E30 section talking about performance because it is a dedicated track car. Unfortunately, buying a 2000 dollar set of breaks from Rob is not reality for a lot of E30 owners. As Rob had MANY valid points, sometimes people on a budget just cant do it with out compromising the whole project's budget.

As a E30 owner on a budget, rather than compromising my budget, it has taken me 4 years to get mine on the road. If i cant do it right this time, I am not sure if I want to do it at all. If i wanted brakes, I would save until I could get them from Rob since I assume everything would be provided and the Testing would be there (in the price). I don't have a problem with expensive parts but I have had problems in the past with cheap parts and having to start over. You do have to pay to play.

I have seen many E30 projects that have been done on a budget with all DIY type parts that run flawless, unfortunately that has not been the case with mine.

[ekdemos]

Here is some proof from the track.

[ame]http://www.youtube.com/watch?v=Sj60dlvtCtg&feature=player_profilepage[/ame]

[ame]http://www.youtube.com/watch?v=QyxAm2-cyDA&feature=player_profilepage[/ame]

[ame]http://www.youtube.com/watch?v=U62WRadcNRw&feature=player_profilepage[/ame]

[RangerGress]

That's not proof of anything. Different cars, different drivers, and different lines. I have many hours of video of me getting my ass kicked, and a few of me kicking ass. And it doesn't mean a thing. You want proof, run a couple hours of laps with one set up and then run a couple hours of laps with the other set up. Do it weekend after weekend for a couple months a the same track. Then study the data.

[Chbimmer]

That's not proof of anything. Different cars, different drivers, and different lines. I have many hours of video of me getting my ass kicked, and a few of me kicking ass. And it doesn't mean a thing. You want proof, run a couple hours of laps with one set up and then run a couple hours of laps with the other set up. Do it weekend after weekend for a couple months a the same track. Then study the data.

there is not better why than this, I like to call this datalogging.

[fastpat]

LOL!!!

Actually, it's the E30 content.

While it's been kept kind of quiet, UUC has been obsessing over E30s lately, new items recently added to our catalog:

SpecE30-legal swaybars
E30 OE-fitment performance clutch options
All-new E30 BBK
H&R E30 suspension components

We've got five in-house E30 development cars at the moment... virgin E30 M3, M3/S50, 325iX, 325/S52, 325 racecar build.

- Rob

No joy on the e30 brakes yet. What's happening?

[DmcL]

@ anyone who replied to me on page 1, my brakes work just fine, correct fluid/level, all 4 corners working, etc, etc. the car will stop and can stop quickly but what i was trying to describe was something else.

reading page 2 and 3 i figured out whats giving that feeling of "not gonna stop" its the bias.. jam on the brakes and the nose dives hard enough to think u might be on the front wheels only.

so what i should be looking at to fix the problem is either installing a F/R bias adjuster or fitting rear pads with a higher bite than the fronts.

[Rob Levinson]

No joy on the e30 brakes yet. What's happening?

They've been available for a few months already! The kit has been extremely popular, selling faster than we can manufacture them.

Product info:
http://www.nexternal.com/uuc/Product563

Big thread on r3v:
http://www.r3vlimited.com/board/showthread.php?t=164552

[fastpat]

They've been available for a few months already! The kit has been extremely popular, selling faster than we can manufacture them.

Product info:
http://www.nexternal.com/uuc/Product563

Big thread on r3v:
http://www.r3vlimited.com/board/showthread.php?t=164552

Thanks, Rob, those look mighty good, and, I suspect, work well too.

Any chance they've been clearance checked with AC Schnitzer 15x7 wheels? I downloaded the clearance template, so will use that if there's no experience with the wheel and your BBK.

The back side.

[Rob Levinson]

Thanks, Rob, those look mighty good, and, I suspect, work well too.

Oh, they certainly do!

Any chance they've been clearance checked with AC Schnitzer 15x7 wheels? I downloaded the clearance template, so will use that if there's no experience with the wheel and your BBK.

Sorry, we have not checked them with those wheels. The template should give you an accurate idea.