UUC's Wilwood Big Brake Sport Kit (11.75" rotor)

[Rob@UUC]

How wide is optimal then? I've noticed BMW has increased the width of their rotors drastically over the years and they usually seem to have reasons for everything. I could see a 2" being too much rotating mass to make a difference but aren't e36 M3 rotors almost 1.5" thick?

Width has not changed much in BMW rotors... diameter gets larger, and that's because the cars keep getting heavier and heavier!

Compared to the E30 M3, the E36 M3 rotor is only 3mm thicker (28mm/1.1"), . E46 M3 is the same thickness as E36 M3. There is almost 800lbs difference there from E30 to E46.

But back to face thickness... those OE rotors, while wider than what we spec for the BBK, have very little wear depth... just 1.6mm total. That's 0.8mm per side. "Slightly used" is "almost worn out" for a standard BMW rotor.

Our BBK rotors have at least double that amount of wear depth, and the extra-thick material is a superior heat sink.

- Rob

[Fidhle007]

But if the wear surface is thicker and the rotor is narrower then that leaves less room for airflow THROUGH the rotor, no?

[Rob@UUC]

But if the wear surface is thicker and the rotor is narrower then that leaves less room for airflow THROUGH the rotor, no?

Ever hear of "the law of diminishing returns"? It's an Economics theory that applies to automotive (or many other mechanical) parts also. Basically, it refers to the fact that you can keep adding more of a resource and not necessarily get further gains from it. For example, you want the chassis to be stiff, so you use frame rails with a 1/4" wall thickness. Frame is pretty stiff. Is it stiffer if you increase the wall thickness to 1/2"? Technically, yes. Can you feel it, does the car handle better? Hmmm... maybe not. A full 1" thick would be even stiffer, right? How about a difference then? Definitely no. You have reached the maximum effective strength somewhere around 1/4", and after that you're just adding weight. Same thing with a brake rotor. We've calculated the width of the rotor that we use as an ideal balance between airflow capacity, fitment/clearance, and longevity/wear rate.

- Rob

[Brian D]

I've gotten inquiries about using the forged Superlite caliper as used in other companies' kits. Besides having no advantage in design and actually weighing more, the Superlite, as I have just compared, requires 5mm more spacer to fit. If one were to use an unnecessarily thick rotor, that would make the problem even worse.

Hope that helps!

- Rob

Rob, are you saying that in a general sense, or for E30's specifically? I think the Superlite has an advantage just in the fact that it uses pads that have a greater surface area and are 25% thicker. Reduced pad wear during track days is one of my goals. You are using the NDP now, as shown above?

[Massive Lee]

Hi Rob.

Are you implying that a Dynalite caliper is just as stiff as a forged Superlite, and that a kit using 32mm rotors has no advantage over a kit with 21mm discs?

For your own information, the "other company's" Race kit with Superlite caliper and full race Heavy Duty 11.75" x 1.25" caliper sees the caliper portrude beyond the hat by only 1.72" (44mm) and in the Sport kit using that same Superlite caliper but a thinner 0.81" rotors, the clearance is 1.28" (32.5mm).

The wider Race kit fits a 15" x 7" TD Pro Race 1.2 without spacer, even though a 3mm spacer (supplied for free in the kits) will create a little extra clearance. The reason why that kit fits that wheel, is because of the carefull design of the hat, that locates the rotor about 1/2" more inward than in a UUC kit. Therefore, that design allows to use thicker rotors and stiffer calipers. Also, as far as I remember, the Sport kit will even fit a Kosei K1 wheel with no spacer at all.

[Rob@UUC]

Rob, are you saying that in a general sense, or for E30's specifically? I think the Superlite has an advantage just in the fact that it uses pads that have a greater surface area and are 25% thicker. Reduced pad wear during track days is one of my goals. You are using the NDP now, as shown above?

Good questions!

Pad surface area is almost identical between Superlite and Dyna-series pads. Superlite is wider but not as high, it's roughly an arc where the Dyna has an almost flat bottom.

The pad thickness is a good point, but there are two ways to look at that:

1. All pads, but race pads in particular, heat cycle in a way that initially improves performance, and then degrades performance. We never use up a set of 20mm race pads because they are "cooked out" before they wear out.

2. Cost: The 20mm Wilwood "H" compound pad for Superlite is $191. The 12.49mm Wilwood "H" compound pad for Dyna-series is $93. So yes, the Dyna pad is only 62% as thick as the Superlite pad... but it only costs 48% of the price! From a cost/wear standpoint, Dyna is a better value.

But to review why I said "better", it boils down to:

1. lower weight
2. better wheel fitment
3. lower replacement pad cost

Hope that helps!

- Rob

[Rob@UUC]

Hi Rob.

Are you implying that a Dynalite caliper is just as stiff as a forged Superlite, and that a kit using 32mm rotors has no advantage over a kit with 21mm discs?

Maybe you haven't worked with the new DynaPro much. If anything, it's possibly a stiffer, stronger caliper than the basic forged Superlite that you're using.

And yes, I'm saying the cooling difference due to the wider rotor is negligible. With testing we've done, as I stated before, the law of diminishing returns kicks in and all you're doing is taking up extra space.

For your own information, the "other company's" Race kit with Superlite caliper and full race Heavy Duty 11.75" x 1.25" caliper sees the caliper portrude beyond the hat by only 1.72" (44mm) and in the Sport kit using that same Superlite caliper but a thinner 0.81" rotors, the clearance is 1.28" (32.5mm).

Exactly... that's 11.5mm, almost half an inch. That's the difference between using a reasonable 15mm spacer and needing to step up to a 25mm spacer. As E30 wheel fitments with the shallow hat depth are already a problem, introducing another 11.5mm of interference is very counter-productive.

The wider Race kit fits a 15" x 7" TD Pro Race 1.2 without spacer, even though a 3mm spacer (supplied for free in the kits) will create a little extra clearance. The reason why that kit fits that wheel, is because of the carefull design of the hat, that locates the rotor about 1/2" more inward than in a UUC kit.

Personally, I'm no fan of putting rotor heat that close to a steering knuckle joint. The rotor disk is positioned where it is in the original BMW design for a reason.

Therefore, that design allows to use thicker rotors and stiffer calipers. Also, as far as I remember, the Sport kit will even fit a Kosei K1 wheel with no spacer at all.

Calipers aren't stiffer, we've established that.

I've been talking with a guy that's on his third set of brackets with some Superlite kit, problems with bending. No matter how stiff a caliper is, doesn't help if the bracket is deforming. I should find out who supplied that kit. Has anyone heard of that?

UUC's brackets are mil-spec heat treated 416 steel, stronger than the hub they're bolted to. You will never hear of a UUC bracket bending.

- Rob

[Fidhle007]

Didn't the RPI kits bend?

As for the stiffer caliper not mattering with a bracket that bends, that makes no sense to me at all: the stiffness of the caliper has to do with side yield forces of the piston/pad against the rotor whereas the bracket only holds said rotor in place. With a stiffer caliper, the force applied by the driver to the pedal (which is usually amplified by the booster) is more directly transfered to clamping force of the pads against the rotor. Logically, this should allow for better modulation and control before the lock-up point...?

[Rob@UUC]

Didn't the RPI kits bend?

Maybe, but this wasn't an RPI kit.

I checked with the guy, now I know who it is. I won't say the brand name so as not to cause more drama in this thread. Someone in this thread also knows who it is.

As for the stiffer caliper not mattering with a bracket that bends, that makes no sense to me at all: the stiffness of the caliper has to do with side yield forces of the piston/pad against the rotor whereas the bracket only holds said rotor in place. With a stiffer caliper, the force applied by the driver to the pedal (which is usually amplified by the booster) is more directly transfered to clamping force of the pads against the rotor. Logically, this should allow for better modulation and control before the lock-up point...?

Yeah, except that with a bracket that is either flexible or bent and misaligned, the caliper will not be in the right orientation. Effectively, it will act as a sliding caliper or even worse, not really work right at all.

That bracket issue is a pretty scary thing when you think of the potential consequences.

- Rob

[Brian D]

Maybe you haven't worked with the new DynaPro much. If anything, it's possibly a stiffer, stronger caliper than the basic forged Superlite that you're using.

Any real data to prove that?

Calipers aren't stiffer, we've established that.

You've stated it, that doesn't make it fact.

I've been talking with a guy that's on his third set of brackets with some Superlite kit, problems with bending. No matter how stiff a caliper is, doesn't help if the bracket is deforming. I should find out who supplied that kit. Has anyone heard of that?

I'll let others respond to that, but it's a shitty tactic to divert attention from an examination of your kit.

UUC's brackets are mil-spec heat treated 416 steel, stronger than the hub they're bolted to. You will never hear of a UUC bracket bending.

- Rob

Time will tell, won't it? How long have your E30 kits been out, and how many have seen track usage?


I'm sorry Rob, I just see you making statements without real data to back them up, and resorting to finger pointing and innuendo when some real questions are asked, not to mention an "I said it's so, so it must be!" attitude. I know there are a lot of people that are very satisfied with your products and business ethics, but I find that hard to reconcile with some of your posts here.

[Rob@UUC]

Any real data to prove that?

Wilwood's current literature seems to support it.

You've stated it, that doesn't make it fact.

Ah, it's going to be that kind of discussion.

I'll let others respond to that, but it's a shitty tactic to divert attention from an examination of your kit.

We're discussing brake kits in general. Who do you work for? :D

Time will tell, won't it? How long have your E30 kits been out, and how many have seen track usage?

Over two years now.

We've got them on a D-Mod turbo E30 on the West Coast that seems to be enjoying them, and quite a few others.

We sell a lot of brake kits.

I'm sorry Rob, I just see you making statements without real data to back them up, and resorting to finger pointing and innuendo when some real questions are asked, not to mention an "I said it's so, so it must be!" attitude. I know there are a lot of people that are very satisfied with your products and business ethics, but I find that hard to reconcile with some of your posts here.

Sorry you're disinclined to accept genuine conversation. Those that know me know that I don't BS anyone. My products speak for themselves.

See y'all next week, I'm away for a few days.

- Rob

[StereoInstaller1]

Since so many knowledgeable people are tuned into this thread, I want to ask a question.

It seems to me that as a rotor gets larger it would need to be thicker simply to handle the additional stress of the greater breaking forces...is this true? Is the additional heat dissipation simply a side benefit, or is it just lucky coincidence or what?

Thanks,
Luke

[Brian D]

Wilwood's current literature seems to support it.

I've looked at their catalog, and they seem to view the NDP as a replacement for the NDL. They don't compare it to the FSL.

Ah, it's going to be that kind of discussion.

I'm not trying to be combative, but just because you say something is so, doesn't make it that way. Bring some tech!

We're discussing brake kits in general. Who do you work for? :D

USAir, as a mechanic. Nice try at innuendo, but I have no stake in this besides as a customer. I don't take your, or Lee's, claims at face value. I actually do some research, and your answers and claims don't hold up, in my opinion. I haven't bought a kit yet.

Over two years now.

We've got them on a D-Mod turbo E30 on the West Coast that seems to be enjoying them, and quite a few others.

A real answer! Thank you! I assume they are holding up well?

Sorry you're disinclined to accept genuine conversation. Those that know me know that I don't BS anyone. My products speak for themselves.

Which of course is why you're here.

[Massive Lee]

For the sake of good technical information, please let's keep it civil. Basically, the heart of what is discussed here is simple. 21mm vs 32mm rotors and Dynalite vs Superlite. Many arguments have been put on the table and as I mentionned a few months ago, the e30 market too small for "big" manufacturers to even look at it, but still big enough so that a couple of them dare risk money and time on it. As for everything, there are different schools of thought, and that's very good for e30 owners, as they have the choice. Nonetheless, I can clearly say that Massive's products are aimed at racers. Which is why thick 32mm rotors are used on most kits (e30 Sport kit and 2002 rear kit being the only two exceptions out of the 20 kits available).

As for StereoInstaller's question, I understand you want to know if a bigger rotor needs to be thicker to keep its integral rigidity. My answer is no. Some 15" rallye rotors are still only 1.25"-1.32" thick. Thickness of a rotor is usually dictated by the need of more cooling (air gap) and thicker friction walls (heat burst absorbtion).

[Fidhle007]

Maybe, but this wasn't an RPI kit.

I checked with the guy, now I know who it is. I won't say the brand name so as not to cause more drama in this thread. Someone in this thread also knows who it is.

- Rob

I think you really need to clarify that to be fair. PM me if you need to, but I'm currently in the market for a brake kit but I'm taking my time and observing ALL the options I can before I spend my hard-earned dollars. If you have information about a kit I should avoid, I'd greatly appreciate a straight answer about it and not a namby-pamby "I'm being a good guy and not going to name names" answer.