Installed 335i brakes on 128i

[TheSt|G]

Originally Posted by asbrr

Question for the OP or anyone else - what effect would the 335 / 328 caliper combo done here have on brake bias? Is it safe to assume if the total volume ratios between the front and rear pistons matches the ratio between the stock 128i front and rear pistons the bias remains the same?

This is always something that bothered me about swapping out calipers. I don't hear how anyone deals with proportioning / brake bias, or is it just not significant enough to worry about?

BBK kit manufacturers like Stoptech spend R&D time to ensure they get the bias right, so it should apply generally no?

That is an excellent question. The answer is that everyone largely ignores it, not to their favor.

[Suprgnat]

Originally Posted by asbrr

Question for the OP or anyone else - what effect would the 335 / 328 caliper combo done here have on brake bias? Is it safe to assume if the total volume ratios between the front and rear pistons matches the ratio between the stock 128i front and rear pistons the bias remains the same?

This is always something that bothered me about swapping out calipers. I don't hear how anyone deals with proportioning / brake bias, or is it just not significant enough to worry about?

BBK kit manufacturers like Stoptech spend R&D time to ensure they get the bias right, so it should apply generally no?

The 335i also has a larger torque radius than either the 328i, 128i or the 135i further shifting bias to the front, but that's not necessarily a bad thing if you've swapped out the run flats.

Here's a great white paper from Stoptech:
http://www.stoptech.com/technical-su...alance-matters

[aloksatoor]

If the 135 stockers are that bad, why did bmw ditch the sliding style in the newer f8x M cars? They have 4 pot fronts and 2 pot rears now. I think the reason the 135 fronts hold so much heat is most race setups run 17inch wheels and super wide fronts.

[brocklanders]

Originally Posted by aloksatoor

If the 135 stockers are that bad, why did bmw ditch the sliding style in the newer f8x M cars? They have 4 pot fronts and 2 pot rears now. I think the reason the 135 fronts hold so much heat is most race setups run 17inch wheels and super wide fronts.

Another question would be if the 135 brakes are so good why didn't the 1m get them in 2011 when BMW has had these sitting on the shelf since 2009.

[asbrr]

Originally Posted by Suprgnat

The 335i also has a larger torque radius than either the 328i, 128i or the 135i further shifting bias to the front, but that's not necessarily a bad thing if you've swapped out the run flats.

Here's a great white paper from Stoptech:
http://www.stoptech.com/technical-su...alance-matters

Great link, thanks. Intuition says that a suspension upgrade that stiffens the springs and resists weight transfer would also alter brake bias, but they don't list that in their factors affecting brake bias. Assuming the CG does not change (ie car is not lowered), is that logic sound?

Anyway, this probably means few people have a factory brake bias with any sort of brake and/or suspension changes lol

[Suprgnat]

Originally Posted by asbrr

Great link, thanks. Intuition says that a suspension upgrade that stiffens the springs and resists weight transfer would also alter brake bias, but they don't list that in their factors affecting brake bias. Assuming the CG does not change (ie car is not lowered), is that logic sound?

Anyway, this probably means few people have a factory brake bias with any sort of brake and/or suspension changes lol

Interesting question. I found this: "As well, stiffer springs will increase the speed of weight transfer, letting you more quickly and predictably redistribute the weight of the car with acceleration and braking." but it seems the same amount of total weight transfer will take place. I'm sure someone with more knowledge will chime in.

[Suprgnat]

Originally Posted by asbrr

Great link, thanks. Intuition says that a suspension upgrade that stiffens the springs and resists weight transfer would also alter brake bias, but they don't list that in their factors affecting brake bias. Assuming the CG does not change (ie car is not lowered), is that logic sound?

Anyway, this probably means few people have a factory brake bias with any sort of brake and/or suspension changes lol

"Contrary to what you may be inclined to believe, the amount of weight transfer is not altered by springs, shocks, anti-roll bars, etc. Weight transfer is a result of inertia and momentum. These suspension components cannot change that. What these components can do is impact how much the suspension moves in response to the load change, and how quickly the load transfers to the tire contact patches."

http://www.turnfast.com/tech_handlin...ling_weightxfr

[asbrr]

Originally Posted by Suprgnat

Interesting question. I found this: "As well, stiffer springs will increase the speed of weight transfer, letting you more quickly and predictably redistribute the weight of the car with acceleration and braking." but it seems the same amount of total weight transfer will take place. I'm sure someone with more knowledge will chime in.

Hmmm, yes the speed part makes total sense. Thinking further, this also helps in rationalizing that the total amount of weight transfer is the same. The weight is "rotating" around the CG back to front so spring rate is not relevant....just the height of the CG....


ps: saw your other thread on using 330 rotors, looking forward to seeing how it turns out

[raposka]

Originally Posted by TheSt|G

That is an excellent question. The answer is that everyone largely ignores it, not to their favor.

Hello, fellas! Yes, Stig is correct, most people largely ignore brake bias, and probably not to their own favor. To be fair, braking dynamics are extremely complicated, and, well, dynamic. That is to say they are ever changing and highly dependent on other contextual factors. As the discussion above clearly illuminates, it depends on a whole host of other factors.

The brake proportioning valves on street cars are pretty much set, although you can easily install adjustable valves. Formula 1 cars have electronically adjustable proportioning valves, which allows the pilot to adjust the brake bias while driving. And, they do that often during a race, sometimes on every lap if there is a particular situation that calls for it, e.g. a corner where the pilot is experiencing lockup. Of course, they are also adjusting it more often as the current era puts such an emphasis on managing tire degradation. Playing around with their brake bias becomes one of the chores that F1 pilots have to keep them busy, as they are not busy heel-toe shifting and reaching for a proper gear selector.

In my particular case, I did actually run the calculations, although I am having a hard time finding the paper where I scribbled my notes at the moment. But, as I recall, the conversion I did took my front brake bias up from around 63% to 71%. The biggest factor is the larger front rotor and the additional leverage it creates. I made some rough assumptions on the friction coefficients associated with the brake pads, as I could not find the actual data for these. Either way, it did not make a significant difference.

The fact is that most manufacturers automatically build in front brake bias, because it is much safer to lock up the front wheels than the back wheels. But, let me tell you that I am still able to lock up the rear wheels under extremely hard braking, from high speed, with my new setup. I could interpret this to mean that under those extreme conditions, I probably want even more front bias. But, for normal street driving, and even spirited driving, this setup is more than adequate and still very safe.

Very cool discussion; cheers!

[TheSt|G]

Originally Posted by brocklanders

Another question would be if the 135 brakes are so good why didn't the 1m get them in 2011 when BMW has had these sitting on the shelf since 2009.

[asbrr]

Originally Posted by Suprgnat

"Contrary to what you may be inclined to believe, the amount of weight transfer is not altered by springs, shocks, anti-roll bars, etc. Weight transfer is a result of inertia and momentum. These suspension components cannot change that. What these components can do is impact how much the suspension moves in response to the load change, and how quickly the load transfers to the tire contact patches."

http://www.turnfast.com/tech_handlin...ling_weightxfr

Perfect, thanks.

[asbrr]

Originally Posted by raposka

Hello, fellas! Yes, Stig is correct, most people largely ignore brake bias, and probably not to their own favor. To be fair, braking dynamics are extremely complicated, and, well, dynamic. That is to say they are ever changing and highly dependent on other contextual factors. As the discussion above clearly illuminates, it depends on a whole host of other factors.

The brake proportioning valves on street cars are pretty much set, although you can easily install adjustable valves. Formula 1 cars have electronically adjustable proportioning valves, which allows the pilot to adjust the brake bias while driving. And, they do that often during a race, sometimes on every lap if there is a particular situation that calls for it, e.g. a corner where the pilot is experiencing lockup. Of course, they are also adjusting it more often as the current era puts such an emphasis on managing tire degradation. Playing around with their brake bias becomes one of the chores that F1 pilots have to keep them busy, as they are not busy heel-toe shifting and reaching for a proper gear selector.

In my particular case, I did actually run the calculations, although I am having a hard time finding the paper where I scribbled my notes at the moment. But, as I recall, the conversion I did took my front brake bias up from around 63% to 71%. The biggest factor is the larger front rotor and the additional leverage it creates. I made some rough assumptions on the friction coefficients associated with the brake pads, as I could not find the actual data for these. Either way, it did not make a significant difference.

The fact is that most manufacturers automatically build in front brake bias, because it is much safer to lock up the front wheels than the back wheels. But, let me tell you that I am still able to lock up the rear wheels under extremely hard braking, from high speed, with my new setup. I could interpret this to mean that under those extreme conditions, I probably want even more front bias. But, for normal street driving, and even spirited driving, this setup is more than adequate and still very safe.

Very cool discussion; cheers!

Well look at that - someone modded their car and actually put some thought into the details!! You guys are few and far between. Good on you for thinking this through!

So based on the other thread Supergnat started (using 330i front calipers), is it safe to assume a 335 front caliper and Z4 35is rotor will NOT fit under 17" wheels?

[Suprgnat]

Originally Posted by asbrr

Well look at that - someone modded their car and actually put some thought into the details!! You guys are few and far between. Good on you for thinking this through!

So based on the other thread Supergnat started (using 330i front calipers), is it safe to assume a 335 front caliper and Z4 35is rotor will NOT fit under 17" wheels?

I can only speak for BMW Style 207M wheels. The 335i calipers contacted the barrel of the wheel where it starts to transition into the spokes, even with 15mm spacers. There's a circumferential bulge in the barrel that interferes. BMW supplies 335i's with 17" wheels, so some do work.

I like the 207Ms and what I plan to do is get an extra set and use the 7.5" wheels in the summer, throw the 7" wheels on with winter or all-season tires those few weeks of the year when I need to and, if I ever get the time, a separate set of track wheels and tires.

[M-A]

Originally Posted by raposka

Hey, PJ. That is correct. The 328i rear calipers are exactly the same in every dimension, except for the fact that they have a larger piston (42 mm instead of the 40 mm stock in the 128i). These are the same rear calipers that you would get if you bought the BMW Performance Brake package. They bolt right up to the stock hub and no need to change the rotors in the rear. However, I kind of wish I had now, because they are all rusty and don't look as nice as the fronts.

Hey bud, can you please confirm the 328i calipers are from an E92?

part# are http://www.realoem.com/bmw/enUS/show...diagId=34_1476 :
left - 34216768697
Right - 34216768698

Much appreciated! (firing the order tomorrow...)

[AlexR6]

Originally Posted by M-A

Hey bud, can you please confirm the 328i calipers are from an E92?

part# are http://www.realoem.com/bmw/enUS/show...diagId=34_1476 :
left - 34216768697
Right - 34216768698

Much appreciated! (firing the order tomorrow...)

Click here and you will find the list of vehicles where you can get the calipers from:
http://www.realoem.com/bmw/enUS/part...&q=34216768698

[uberschnell]

Originally Posted by brocklanders

Another question would be if the 135 brakes are so good why didn't the 1m get them in 2011 when BMW has had these sitting on the shelf since 2009.

Bottom line, the 1M/3M brakes perform better. I feel the 135i Brembo's were more a marketing gimmick. They certainly weren't built with the hardcore performance expectations an M buyer might have as is evident in the proportions.

I'm not one of those folks who write off multi-pot as a gimmick. Multiple pistons serve to increase piston surface area and better distribute clamping force across larger pads. What kills the 135i brakes is the dimensions of the rotors. Where I think 135i brakes will stop as quickly as any M brake the first time, they will never hold up after repeated braking. 135i rotors have a smaller diameter then the M or even 335i rotors meaning reduced torque radius. 135i rotors are also thinner meaning they have less thermal capacity. This means the 135i brakes, while being able to brake as well as the M or 335i brakes, will heat up faster and be slower at dissipating that heat. Higher heat means reduced friction coefficient between the disk and the pad, boiled brake fluid and cracked pistons.

[Kubricks]

Just did a set of 335i brakes to my 130i, everthing bolts right on, no modification required not even the dust shield. Is 128i rear handbrake module different from EU 130i? Because the handbrake shoe on my car works on 335i rear disc?

Front


Rear


Pedal feel remains more or less the same, but now with much better brake fad resistance.

[Suhb]

Originally Posted by Kubricks

Just did a set of 335i brakes to my 130i, everthing bolts right on, no modification required not even the dust shield. Is 128i rear handbrake module different from EU 130i? Because the handbrake shoe on my car works on 335i rear disc?

Yes the handbrake is different between the 128i and the 130i. Doing this on a 128i will sacrifice the handbrake.

[c0mmon]

I'm trying to do the same project, and are unsure if my style 262 wheels will fit. Not getting much help. Would you have an idea?

[Zombie_Head]

Originally Posted by raposka

Hello, Highbrowed. I suppose that it is debatable as to whether or not they are better. If you look through the E90 forums, some 335i owners have "upgraded" to the "Performance" brakes, i.e. the same calipers on the 135i, purely for the aesthetics.

The big difference is that the 335i rotors are 348mm, significantly larger in diameter than the rotors from the 135i. They are also thicker, so they have more thermal capacity. If you look around, you will also see that many people have burnt up their composite brake pistons in the 135i, and have upgraded to steel pistons. This is not an issue with the 335i brakes.

My reasons, however, are more simple.

1) I did not want to spend the money, as I could find the used 335i calipers quite cheap on Ebay. 135i calipers, because they are by Brembo, are quite expensive, even used.

2) I enjoyed the winter project of rebuilding the calipers all around.

3) If I had bought the "performance" calipers, I would have spent the extra $500 upgrading to steel pistons, further escalating the total cost of the project.

Hope this helps!

Thank you for this information, im looking at a 125i as we speak (128i for you Americans) and was looking for brake options. Looked liked used calipers will bolt right up with bigger disks, good to know.

Just one question, isn't the EBC red pads for track purposes? Was looking at yellow pads since the car is 90% street and 10% on track (during spring and summer).

[esuyengh]

Hi, quick question. So I have a 2013 e82 128i. I'm installing the BMW Performance Brake Kit on the front because the full front/rear kit seems to be out of stock everywhere and because I'm running 17" wheels (making it tough to bump up to F30 M calipers). For the rears, I have on order a set of F30 328i calipers. When buying matching rotors and pads, should I be buying 300x20mm rotors and pads designed for an F30 328i then, instead of rotors designed for a 128i? Or does it not matter? What about the rotor bolt pattern?

[amg6975]

Does going to a 335/128 rear caliper/rotor on a 135/128 require the narrow hub mod or does it swap straight over?

Answer to anyone in the future: Yes, you need the hub mod to use 335 calipers and rotors. Or find rotors that line up and have the right OD, I chose to do the hubs to keep the brake set up simple, and expand wheel choices.