[Blackhawkup]

Originally Posted by SUHleen

Decreasing the size of the rotors is going to negatively impact the braking performance by quite a bit... This wouldn't really be an upgrade but a downgrade with merely better looking calipers

I am not using the Boxster rotor.. I am still using the 335 rotor. What I was pointing out was with the increased diameter of the 335 rotor the braking of the 335 would be more powerful then what you would feel in the Boxster S if the weigh of the car were both equal.

[Blackhawkup]

Originally Posted by Cloud9blue

Say you manage to fit the boxter calipers to the stock 335i rotors, you still won't be able to get the proper pad swipe area unless you go with custom pads...

The difference of 30 mm diameter or 15 mm radius should not make to big of a difference to the swipe area seeing that there is 15 more mm of surface area to work with.

[SUHleen]

If you are planning on spending $1500 and using the OEM rotors, then why not just get the F30 BMW Performance BBK that uses a 370 mm rotor, uses a Brembo caliper, and is made for BMW? For a few hundred extra you can get the whole front kit with pads and new calipers...

[Cloud9blue]

Originally Posted by Blackhawkup

The difference of 30 mm diameter or 15 mm radius should not make to big of a difference to the swipe area seeing that there is 15 more mm of surface area to work with.

fixed caliper alone will do very little. you are better off switching to brass brake guide bushings if you want to eliminate the slack in the stock sliding caliper... $50 vs. +$1000, it was an easy decision to make for me.

[The HACK]

It pains me to say this. If all you're doing is upgrading the calipers because they're Porsche Brembos? You're better off just buying one of those caliper covers to make your brakes look like they have fixed caliper Brembos. Chances are pretty damn good that they will work just as well.

My MZ4 Coupe was the test car they used for RacingBrake to develop both their big brake kit for the E46 M3 and MZ4 Coupe. Even before they started on the drawing board, they took my car in for almost 2 days, weighed the car, took careful measurement of each and every components, from hub size, hub to wheel clearance, hub radius, king pin dimensions, caliper piston size, detailed rotor dimensions...2 whole days of measuring just to get an idea. Then they started with building their rotors, then customizing piston sizes for the 2, 4, and 6 piston calipers to match what came on the car and fix the offset bias natural to BMWs so you can either install just the front calipers, or front and rear matching calipers and either way it will retain factory brake bias.

All that work that went into it, and they still had problems getting the first batch of calipers to fit right. It took them two iterations before they were ready to release their caliper kit, and we still had to run an 8mm spacer to clear the front wheels. This is from a brake vendor with decades of experience.

So what makes you guys think, by simply slapping a set of Brembos from Porsches, that you can POSSIBLY upgrade the brakes on your BMW? Especially from a chassis that has a natural REAR brake bias since, unlike BMWs, there's usually less weight up front on a Porsche?

The REAL question.

If you are doing this for performance purposes, you are still leaving the BIGGEST weak link of your brake system stock. The 1 piece solid rotors on the E9X simply isn't as effective at evacuating heat and reducing unsprung weight as any good 2 piece floating rotors, such as the rotors that came on BMW's M division (the center mounted 2 piece floating rotors on the E46 M3 ZCP and MZ4 Coupe are an engineering marvel). "Upgrading" to a fixed multi piston caliper only gets you a slightly more "rigid" or firm brake pedal. Meanwhile, you're putting a caliper designed for a 28mm thick rotor on a rotor that's 2mm thicker? That means you'll need custom made pads that are 1mm thicker than what manufacturers are used to make, plus less thermal capacity and lifespan because they're each 1mm thicker (about 8-10% less than factory). And we haven't even started calculating the difference in piston area yet, which could result in a dramatically different pressure generated at the piston, hence a significant change in pedal feel. On top of that, the change in piston count will dramatically alter the sweep area and the actual surface area between the pad and the rotor, and without actually calculating the effect that may have on the actual pressure and friction generated between the pad and the rotor, how would, or could you account for the change in brake bias to maintain optimum performance on the brake system?

(Pause to take a breath. Or give my fingers a break)

So, it seems rather ironic to me, that anyone would see simply slapping on a set of Brembos from a Porsche as an upgrade, without at least doing all the measurements and calculations into how said caliper "upgrade" would actually affect performance. It again seems to me, that the main priority for said "upgrade" is the larger, colorful calipers applied. So if that's what you're after, and to be honest, anyone simply looking at swapping a square peg into a round hole as a performance upgrade, would probably be better served by just simply buying a "brembo" caliper cover for their sliding calipers. It serves the same purpose.

Now, I'm awaiting someone to bring up the popular MASSIVE Porsche 911 caliper upgrade for the E36 M3. Those that know what I'm talking about, you get bonus points. Yes. MASSIVE took a run of the mill Brembo caliper designed for a 996 911 and made them work on E36 M3s with custom brackets. And they were one of the numerous solutions available during the early 00s for club racers. But believe it or not, those guys at MASSIVE spent a ton of time and money trying to figure out which calipers will work, in addition what rotors they'll need to source to make it work, because they took the steps to measure, calculate, cut, test, cut, test again, then took it to a track and test test test until they are confident what they're offering is a decent performance upgrade for the budget minded club racer in the right class. Not some yahoo posting on a Facebook group about some customized caliper brackets to adapt take-offs from random cars on an E9x.*

So, I say again. If you want to REALLY upgrade your car's brakes? Go with a reputable vendor who has already spent the time, money, and resources to design a kit that works for your car. If you just want the caliper upgrade look, go buy a set of caliper covers. If you just want the caliper upgrade look, but is ashamed to admit you have caliper covers? Go with a reputable vendor who has already spent the time, money, and resources to design kit that does not COMPROMISE the second most important active safety systems on your car.

* Side note: Interestingly, when I was working with RacingBrake to develop the kit for the E46 M3 ZCP/MZ4 Coupe, they already had a couple of caliper designs they know would fit/work. Turns out most of these brake manufacturers have a handful of designs for each caliper piston combinations (2, 4, or 6), and they also have a combination of sizes of pistons that fit within a certain range for overall piston area. So after they measured, they figured out their 4 piston front would be about 10% smaller in piston area than OEM, but their rear 2 piston would be about 5% smaller, thus effectively shifting some of the brake bias to the rear, while increasing marginally the pedal stiffness on my car. Then they had to hunt through the FSMI (I think that's the acronym?) database to find a set of pad backing that would fit the factory rotor size AND their upgraded, 360mm rotor size. Unfortunately, the factory rotors are too thin for their calipers and standard pad sizes, so they decided to update their rotor kit by increasing the thickness by 2mm.

That was the extent of the amount of work to get a system that should have been fairly straight forward to work. Just to give you SOME idea. And then comes the TESTING ON TRACK.

[vwetish]

Originally Posted by Blackhawkup

The difference of 30 mm diameter or 15 mm radius should not make to big of a difference to the swipe area seeing that there is 15 more mm of surface area to work with.

I have Boxster S calipers on my VW 2.0t. the rotors are stock 312x25.
I tried fitting them over VW r3.2 rotors 345x30 and the calipers wouldn't fit.
Rotors are too thick and the pads are missing quiet a lot sweep area on the rotor.
That being said, e90 335i 345x30 wouldn't work either. I have discussed this previously already.
e46 csl rotor is better fit for these calipers.

[vwetish]

Originally Posted by SUHleen

If you are planning on spending $1500 and using the OEM rotors, then why not just get the F30 BMW Performance BBK that uses a 370 mm rotor, uses a Brembo caliper, and is made for BMW? For a few hundred extra you can get the whole front kit with pads and new calipers...

f30 full set front and rear with ss brake lines and m3 master cylinder cost me little shy of $2k

[WedgePerformance]

http://www.ecstuning.com/BMW-E92-335...nce/ES2834551/



http://www.ecstuning.com/BMW-E92-335...nce/ES2834551/

[vwetish]

Originally Posted by WedgePerformance

http://www.ecstuning.com/BMW-E92-335...nce/ES2834551/
http://www.ecstuning.com/BMW-E92-335...nce/ES2834551/

I can't believe you post this.

[justpete]

Originally Posted by The HACK

My MZ4 Coupe was the test car they used for RacingBrake to develop both their big brake kit for the E46 M3 and MZ4 Coupe. Even before they started on the drawing board, they took my car in for almost 2 days, weighed the car, took careful measurement of each and every components, from hub size, hub to wheel clearance, hub radius, king pin dimensions, caliper piston size, detailed rotor dimensions...2 whole days of measuring just to get an idea. Then they started with building their rotors, then customizing piston sizes for the 2, 4, and 6 piston calipers to match what came on the car and fix the offset bias natural to BMWs so you can either install just the front calipers, or front and rear matching calipers and either way it will retain factory brake bias.

All that work that went into it, and they still had problems getting the first batch of calipers to fit right. It took them two iterations before they were ready to release their caliper kit, and we still had to run an 8mm spacer to clear the front wheels. This is from a brake vendor with decades of experience.

This is the sort of info I've been looking for to make me finally get off my lazy azz and get a pair of two-piece RB rotors for the front 135i calipers on my 328i. Leaving the rear sliding calipers and OE rotor alone since solid guide rod bushings have worked so well, at least so far... Couldn't get RB to build a 135i rear rotor with a 160mm 328i offset hat to use with rear 135i fixed calipers. Not that it matters really, I think. So, thanks for the detailed history!

[vwetish]

Originally Posted by justpete

This is the sort of info I've been looking for to make me finally get off my lazy azz and get a pair of two-piece RB rotors for the front 135i calipers on my 328i. Leaving the rear sliding calipers and OE rotor alone since solid guide rod bushings have worked so well, at least so far... Couldn't get RB to build a 135i rear rotor with a 160mm 328i offset hat to use with rear 135i fixed calipers. Not that it matters really, I think. So, thanks for the detailed history!

don't forget to replace the stock pistons in the 135i calipers as they are of very poor quality.

[justpete]

Originally Posted by vwetish

don't forget to replace the stock pistons in the 135i calipers as they are of very poor quality.

Yep, absolutely. I had the Stoptech pistons, seals, and boots (TMS upgrade kit - yeah, I'm lazy...) installed before they went on the car. And I put in 0.5mm Hard Brake titanium shims, ya know, cuz racecar.

[Cloud9blue]

Originally Posted by justpete

This is the sort of info I've been looking for to make me finally get off my lazy azz and get a pair of two-piece RB rotors for the front 135i calipers on my 328i. Leaving the rear sliding calipers and OE rotor alone since solid guide rod bushings have worked so well, at least so far... Couldn't get RB to build a 135i rear rotor with a 160mm 328i offset hat to use with rear 135i fixed calipers. Not that it matters really, I think. So, thanks for the detailed history!

I personally wouldn't go with those open-slotted RB rotors if you are going to put some serious amount of heat cycles into them. Those huge open will act as stress concentrator, the same way that drilled rotors do when undergoing heavy track abuse.

In addition, it seems like they have some pretty major quality control issues as well. The S2000 and various JDM forums reported cracked rotors from them after just a few track days, from the searches I did last year when I was considering them as an upgrade to the stock one-piece. I can only imagine the issue would be more prominent with our 3600lbs e9x.

If someone like Girodisc or Performance Friction makes a two-piece rotor with just a simple and tested slotted disk, I would buy it in a heartbeat...

Anyway, the ECS kit is overpriced gimmick... If you want a Porsche branded caliper, go for it. For the same price, you can get a properly fitted Stoptech 6-pot that is actually designed to work with our brake distribution...

[justpete]

Originally Posted by Cloud9blue

I personally wouldn't go with those open-slotted RB rotors if you are going to put some serious amount of heat cycles into them. Those huge open will act as stress concentrator, the same way that drilled rotors do when undergoing heavy track abuse.

In addition, it seems like they have some pretty major quality control issues as well. The S2000 and various JDM forums reported cracked rotors from them after just a few track days, from the searches I did last year when I was considering them as an upgrade to the stock one-piece. I can only imagine the issue would be more prominent with our 3600lbs e9x.

If someone like Girodisc or Performance Friction makes a two-piece rotor with just a simple and tested slotted disk, I would buy it in a heartbeat...

Anyway, the ECS kit is overpriced gimmick... If you want a Porsche branded caliper, go for it. For the same price, you can get a properly fitted Stoptech 6-pot that is actually designed to work with our brake distribution...

All good points. I'm aware of the discussions about QC and about cracking on the surface of RB rotors but I consider that normal. I'm not sure QC is still an issue these days but we'll see. The open slots will act as stress risers and yes they can lead to cracking of the rotors, possibly catastrophic. But I'm not putting as crazy a thermal load into them as most since my car is a momentum car.

I still have the Stoptech Sport slotted rotors as backup and the Zimmerman 135i front rotors aren't particularly worn so they'll be around for backup too. The only concern is how much abuse the pads will take from the slots or how quickly if at all the slots will get filled up with pad material.

It'll be fun to try them if nothing else. Will probably put the slotted Stoptechs back on the rear just to keep them visually similar and to have the same ratio of available rotor surface although I don't think that matters all that much. It's a science experiment!

They don't recommend using their rotors with Carbotech pads but that's another bit of experimentation as I'm not convinced it's a real problem in my use. If so, them's the breaks. Maybe I'll try some different pads, dunno. Not a big deal really.

[SUHleen]

What about the two piece ECS rotors for your 135 calipers?

[Cloud9blue]

Originally Posted by SUHleen

What about the two piece ECS rotors for your 135 calipers?

drilled and not a true floating 2 piece design...

[WedgePerformance]

Originally Posted by vwetish

I can't believe you post this.

It's an option... I never said I would install them on my car.

I do however like the rotor. Just the LOOK, but I would go with StopTech and not waist my time.

[stanlalee]

So what about EVO X Front calipers? Their factory rotors are 350x32mm vs 335i 348x30mm. Evo weighs 3571lbs so it has just as much (a little more) weight to haul down and even with factory pads it is supposedly capable of track days (its a track oriented car after all). Already have ECS 2pc semi-floating rotors (like I'm the only one who has ever bought anything for looks). and YES I want the calipers for looks BUT at the same time I wan't calipers that fit and work properly. I noticed they are putting these brakes on a lot of RWD/AWD Nissans.

[vwetish]

Originally Posted by stanlalee

Front calipers? Their factory rotors are 350x32mm vs 335i 348x30mm. Evo weighs 3571lbs so it has just as much (a little more) weight to haul down and even with factory pads it is supposedly capable of track days (its a track oriented car after all). Already have ECS 2pc semi-floating rotors (like I'm the only one who has ever bought anything for looks). and YES I want the calipers for looks BUT at the same time I wan't calipers that fit and work properly. I noticed they are putting these brakes on a lot of RWD/AWD Nissans.

those are lug mount calipers and therefore very difficult to install especially when both rotors are similar size. You are better off concentrating on radial mount calipers.

[The HACK]

Originally Posted by Cloud9blue

I personally wouldn't go with those open-slotted RB rotors if you are going to put some serious amount of heat cycles into them. Those huge open will act as stress concentrator, the same way that drilled rotors do when undergoing heavy track abuse.

Interestingly, I came across this over the weekend @ Chuckwalla Valley Raceway for a combined HPDE/Race. Looks to be their latest open slot design.

If I had brought my MZ4 Coupe there would have been 3 cars total running the same open slot RB designs. There was an E92 335i with front open slot RB rotors, the Total 135i, and my MZ4 Coupe. Had I not made the total NOOB mistake and thought the event was NEXT weekend I would have had my MZ4 Coupe with the same RB open slot rotors at Chuckwalla.

When RB was developing the E46 M3/MZ4 Coupe rotors, I told them specifically that I would prefer slotted only, or if there's an option for solid, even better. The developer assured me that the new open slot design will be as strong as slotted rotors with no risk of stress cracks developing from the openings in the slots. Something about the internal vanes and ribs being the gaps between the openings, thus those spots are the strongest part of the rotor disc.

Didn't make sense to me, and I, again, would have personally preferred a slotted only design. But after 6+ years of running their rotors, I'm not going to question them about the quality of their design. It's been working well for me.

And I'm sure if repeated heat cycles are going to be a problem for their design, it would have reared its ugly head on that 135i race car, since I know the owner pretty well.

I do agree though, to an extent, on an unknown rotor design/company, first preference should be given to solid or slotted rotors.

Y'all should do your due diligence, of course. I did mine and stuck with RB and can't be happier.

[vasillalov]

Listen to THE HACK. The man knows his stuffs.

[Knonsense]

Originally Posted by Blackhawkup

I am looking to upgrade the calipers on my 2007 E90 335i. ... please comment on ... brake feel.

Brake feel is determined by the ratio of the surface area of your master cylinder and the sum of the surface areas of your brake pistons.

pedal effort will increase if you decrease the master cylinder surface area and hold brake piston surface area constant. A smaller master cylinder will need to work harder to apply the the same force to the same brake piston surface area.

pedal effort will increase if you hold the master cylinder surface area constant and increase the brake piston surface area (as happens in big brake kits). the master cylinder has to apply the same force to a larger surface area, thus it has to work harder. If you want to retain oem pedal feel with larger/more pistons in your calipers, you need a proportionally increased brake master cylinder.


If I recall my Sport Compact Car Tech Corner articles correctly.