M235i Brakes on a 135?

[WhatsADSM]

Originally Posted by bNks334

Why do people feel they need to upgrade the stock 6pot calipers?

I have 255's up front (200tw tires on 9in wheels) with PFC-08 pads and I have way more brake then I do tire... I generate about .9g to 1g of braking force right now and it's the tires that are the limiting factor for me. Once a PFC-08 pad is up to temperature it delivers almost double the brake coefficient a stock pad can and PFC-08 is a more endurance oriented pad than a comparable higher coefficient pad. Once these pads are hot, I can lock my tires up at will.

I have never had any issues with dust boots or pistons melting. I have always had my rotor shield bent all the way out to scoop air. I recently added brake ducts up front and I actually think I am over-cooling the pads now.

http://wiki.seloc.org/a/Brake_pads

Sounds to me like people are feeling a bit of a placebo effect with the F-series setup. The larger rotor means less brake pedal effort to achieve the same brake torque. This may feel better, but consider you'll now have less feel for modulating the pedal. I doubt the F-series brakes are decreasing stopping distance by any meaningful amount. In fact, stopping distance in the real world goes up the more you bias brake torque frontward. BMW has actually programmed DSC to shift brake line pressure rearward when you are riding on the threshold of ABS. The result is an undeniable decrease in stopping distance.

I'd argue that putting f-series brake up front is detrimental unless you increase the rears to match. You'll also need the master cylinder to match in order to maintain a bit more brake pedal effort (easier to modulate). Without the master cylinder upgrade you'll probably end up with a softer pedal and very grabby brakes (as people have noted above).

https://www.zeckhausen.com/catalog/i...Path=6446_6565

The 340mm setup is nearly identical in terms of brake bias and hydrolic bias. So having a detrimental affect is NOT true.

In fact the F30 setup doesn't have pistons that crumble and it has rotors that are dramatically thicker so it has better thermal performance than the thin stock 135i rotors. I argue the following: Why would anyone spend hundreds of dollars upgrading the 6 pots when you can buy an F30 setup which is more capable for cheaper.

[WhatsADSM]

As a follow-up I will say I think that the stock pads that come with the F30 aren't great in terms of feel. It is a bit soft in terms of initial bite, which i could see people disliking. They are good at keeping the dust away tho... And I got them for free with my calipers so I'll run them as my street pads anyways.

[juld0zer]

Wouldn't the better designed F car rotors be a significant gain over the 6 pots with their standard style vanes? The F car rotors are not just larger, heavier and thicker but they have a far superior cooling vane design. Reduced rotor temps means less heat transfer to the pads, reducing heat transfer to th caliper/pistons surely?

[juld0zer]

All things considered, the F3x Brembos have a lot of potential but they are held back by the stock pads and the biasing limitations of our platform.

I mean.. up to 370mm discs, over 30mm thick, massive pads.

I wonder if adjusting the rear bias somehow would make the whole package work better. Something like loosening the rear subframe lines for a few seconds to deliberately add some mush in the middle of the rear circuit to get some more volume into the front circuit. But you cant get gains without some sort of loss.......

[bNks334]

Hey, I was just asking. Based on my personal experience, I don't see how a larger brake setup would benefit me (lets leave the phenolic pistons out of it for now). Stopping distance itself is more dependent on tires and brake pads.

I was hoping people would add their own anecdotal experience for why they feel they needed the better cooling capacity of the larger rotors... You did say your caliper pistons were sticking, but curious what others have to say...

Originally Posted by WhatsADSM

The 340mm setup is nearly identical in terms of brake bias and hydrolic bias. So having a detrimental affect is NOT true.

I said retrofitting only the fronts would be detrimental to real world stopping distance. Fitting different rear calipers requires quiet a bit of work, no?

Originally Posted by WhatsADSM

In fact the F30 setup doesn't have pistons that crumble and it has rotors that are dramatically thicker so it has better thermal performance than the thin stock 135i rotors.

I acknowledge the larger rotors have a greater thermal capacity. On paper it SEEMS like a nice upgrade, but what I wanted to know was what makes people think they need?

Originally Posted by WhatsADSM

I argue the following: Why would anyone spend hundreds of dollars upgrading the 6 pots when you can buy an F30 setup which is more capable for cheaper.

No arguing with this. If you can replace old worn out 135i calipers with a set of the BMWP 370/345mm rotors for the same or less money, then go for it... the 335i calipers are not worth the cost/effort for what will amount to 0 real world gain. Also consider if you do retrofit the BMWP kit, you won't be able to run 17" wheels which is a huge loss in my eyes.

The only reason you'd need to spend any money on 135i calipers is maybe to replace the stock pistons every few years (not a big deal). Phenolic pistons will stick/crack from age no matter what you do. You trade that extra maintenance for the benefits of them not transferring heat into your brake fluid lol. Replacing stock pistons is cheap and you can even get rebuilt 135i calipers on rockauto (core deposits applies) for $100 each.

[bNks334]

Originally Posted by juld0zer

All things considered, the F3x Brembos have a lot of potential but they are held back by the stock pads and the biasing limitations of our platform.

I mean.. up to 370mm discs, over 30mm thick, massive pads.

I wonder if adjusting the rear bias somehow would make the whole package work better. Something like loosening the rear subframe lines for a few seconds to deliberately add some mush in the middle of the rear circuit to get some more volume into the front circuit. But you cant get gains without some sort of loss.......

DSC and ABS functionality already biases brake force rearward as much as possible until thresholds are exceeded (resulting in reduced braking distance and less dive). Increasing bias frontward is detrimental to stopping distance. Performance oriented BBKs' shifts braking bias rearward.

[WhatsADSM]

Originally Posted by bNks334

Hey, I was just asking. Based on my personal experience, I don't see how a larger brake setup would benefit me (lets leave the phenolic pistons out of it for now). Stopping distance itself is more dependent on tires and brake pads.

I was hoping people would add their own anecdotal experience for why they feel they needed the better cooling capacity of the larger rotors... You did say your caliper pistons were sticking, but curious what others have to say...



I said retrofitting only the fronts would be detrimental to real world stopping distance. Fitting different rear calipers requires quiet a bit of work, no?



I acknowledge the larger rotors have a greater thermal capacity. On paper it SEEMS like a nice upgrade, but what I wanted to know was what makes people think they need?



No arguing with this. If you can replace old worn out 135i calipers with a set of the BMWP 370/345mm rotors for the same or less money, then go for it... the 335i calipers are not worth the cost/effort for what will amount to 0 real world gain. Also consider if you do retrofit the BMWP kit, you won't be able to run 17" wheels which is a huge loss in my eyes.

The only reason you'd need to spend any money on 135i calipers is maybe to replace the stock pistons every few years (not a big deal). Phenolic pistons will stick/crack from age no matter what you do. You trade that extra maintenance for the benefits of them not transferring heat into your brake fluid lol. Replacing stock pistons is cheap and you can even get rebuilt 135i calipers on rockauto (core deposits applies) for $100 each.

If you put *just* the 340mm version on the front then bias is essentially the same. That's what I did. I continue to use the stock rears.

But yes I do agree with you that people don't understand the primary reason for upgrading brakes has NOTHING TO DO IT WITH STOPPING DISTANCE! The 135i brakes are totally fine in terms of having enough brake torque. With any halfway decent pad they are more than powerful enough to lock up probably any tire you throw at them (soft slicks included). No way you will ever have any issues in the street, unless you are a total danger to society! What a brake upgrade really does is make sure that you can continue to get the same performance out of the brakes when you start driving very fast on track lap after lap after lap for a half an hour straight. That's where the 135i brakes will show flaws. Hard laps at an aggressive pace on sticky tires will expose the thermal issues. Brake cooling is probably the most effective way to combat issues, but even that can't totally solve the issue if you have pistons that are crumbling due to localized heat.

So in my case I know that I push everything hard on track and I tend to use the brakes the hardest as over the years I have learned to use them as a weapon on track. I remember last year I took a buddy for a ride in my M3 and we did a few hard laps and about half a cool down lap. When I came back in and dropped him off he had a student that had his mouth half open as we approached. He was pointing at my brakes which were billowing smoke from the fronts... And that was with an aftermarket StopTech 380mm 6 piston kit!
So when it came time to setup my 135i it was a no brainier upgrade since I got the grey 340mm version of the calipers for unbelievably cheap, they came with pads which were nearly new (the calipers we're off a 2015 with ~6000 miles on it!). Additionally my stock rotors were nearing end of life as well so I needed to buy rotors anyways. Essentially i got an appropriately biased brake upgrade kit (few mm taller and like 4mm thicker), bolt on, for a fraction of what it would cost me to upgrade by stock calipers so they wouldnt disintegrate on track. The only issue I have really had is that they did require spacers to fit my stock wheels.

[juld0zer]

Originally Posted by bNks334

DSC and ABS functionality already biases brake force rearward as much as possible until thresholds are exceeded (resulting in reduced braking distance and less dive). Increasing bias frontward is detrimental to stopping distance. Performance oriented BBKs' shifts braking bias rearward.

I'm not totally convinced on this one. Wouldn't a rear biased setup create instability, rapid rear pad wear and overheat the rear brakes? It might be true and hence why the F20 M135i has larger diameter rear discs versus its front but that car also is more tail happy than an E82 so it could be there for the eDiff?

[bNks334]

Originally Posted by juld0zer

I'm not totally convinced on this one. Wouldn't a rear biased setup create instability, rapid rear pad wear and overheat the rear brakes? It might be true and hence why the F20 M135i has larger diameter rear discs versus its front but that car also is more tail happy than an E82 so it could be there for the eDiff?

It's hard to explain, and it seems counter-intuitive, but that's the science and that's what BBK kits and manufactures aim to do with brake systems to improve performance.

Google "BMW EBV." Not sure if it is even an active function on 1-series... but basically MK60 module uses line pressure, wheel speed, pedal input, and other things to ride the threshold of ABS. It only shifts line pressure rearward as much as possible WITHOUT causing instability.

Instability on a 1-series is known on track to be that the rear gets light under heavy braking. That is usually a sign of too much front brake bias.

[bNks334]

Originally Posted by WhatsADSM

So in my case I know that I push everything hard on track and I tend to use the brakes the hardest as over the years I have learned to use them as a weapon on track. I remember last year I took a buddy for a ride in my M3 and we did a few hard laps and about half a cool down lap. When I came back in and dropped him off he had a student that had his mouth half open as we approached. He was pointing at my brakes which were billowing smoke from the fronts... And that was with an aftermarket StopTech 380mm 6 piston kit!

Makes sense. I am still an "upper intermediate" driver so definitely more room to grow in aggressiveness. I am really looking forward to getting some real tires on the car. I've outgrown 200tw I think. I'll have to see how the brakes hold up with stickier tires.

[juld0zer]

Originally Posted by bNks334

It's hard to explain, and it seems counter-intuitive, but that's the science and that's what BBK kits and manufactures aim to do with brake systems to improve performance.

Google "BMW EBV." Not sure if it is even an active function on 1-series... but basically MK60 module uses line pressure, wheel speed, pedal input, and other things to ride the threshold of ABS. It only shifts line pressure rearward as much as possible WITHOUT causing instability.

Instability on a 1-series is known on track to be that the rear gets light under heavy braking. That is usually a sign of too much front brake bias.

I will do some more reading.

I definitely do notice stronger braking with less pedal pressure going above 80kmh, compared to braking at low speeds which oddly enough feels like it takes more pedal pressure to achieve similar response

[AndyW]

It can't be this easy...can it?

http://www.ebay.com/itm/L-CALIPER-FR...53.m1438.l2649

http://www.ebay.com/itm/PASSENGER-CA...53.m1438.l2649

[Gangplank]

Originally Posted by AndyW

It can't be this easy...can it?

http://www.ebay.com/itm/L-CALIPER-FR...53.m1438.l2649

http://www.ebay.com/itm/PASSENGER-CA...53.m1438.l2649

I believe the 320/328 non-Msport has smaller single piston brakes and calipers.

Turner Motorsport F30 328/320 brake differences:
https://www.turnermotorsport.com/t-b...ke-Differences

Vs

Turner Motorsport F30 335i brake differences:
https://www.turnermotorsport.com/t-b...ke-Differences

[juld0zer]

Those are just the standard Bosch brakes. Ask for photos to be sure

[feuer]

Originally Posted by WhatsADSM

If you put *just* the 340mm version on the front then bias is essentially the same. That's what I did. I continue to use the stock rears.

Were you at ACC South two weeks ago? With GPSTrack? I think I saw 135i with F30 front brakes. There were few 135i's and I don't remember what color it was. I remember one white with red interior. Blue one. Camo wide body. Well....maybe you can just post photos from yours. Are you coming to Gingerman tomorrow with Northwoods Shelby?

[WhatsADSM]

Originally Posted by feuer

Were you at ACC South two weeks ago? With GPSTrack? I think I saw 135i with F30 front brakes. There were few 135i's and I don't remember what color it was. I remember one white with red interior. Blue one. Camo wide body. Well....maybe you can just post photos from yours. Are you coming to Gingerman tomorrow with Northwoods Shelby?

I wish it was hard to find time to go to much lately with two young ones.

I'm hoping I can go more next year. I am REALLLLLY missing ABCC, want to get back there badly! Next year for sure.

[Suhb]

In case anyone is wondering, these do not fit the stock 17 inch 128i wheels. They clear the spokes and even the dampening “ears” on the pads clear the barrel. The front facing section of the caliper hits the outward most part of the inner barrel where it tapers and has less clearance. Going to slap on some spacers and try again.

[juld0zer]

Im surprised even the spokes clear the caliper? Unless the front of the caliper is fouling the wheel preventing you from getting it that far?

I am currently riding on 17" F20 type 379 rims. Fits perfectly. No spacer required