Rear brake upgrades - M135i 2 Pot Brembos fitted with installation video

[damocell]

I've been working on a rear brake upgrade for the E85/6 as I'm experiencing high pad wear and temps on track.

I've managed to come up with two solutions.

1, using the 320mm X3 disc, 330i calipers/carriers, a 5mm disc spacer and some weld-in brake show adaptors from VYS Garage to solve the move to a 185mm handbrake

Untitled by Damien Bower, on Flickr

2, a M135i setup using the 345mm rear disc which works with a 160mm handbrake and the two piston caliper. You just need to trim the backing plate and use some £40 adaptors from eBay to reduce the thread size to M10. Dead easy and appears to work perfectly. Custom lines are also required, once they arrive I'll do a full walk through/write up.

Untitled by Damien Bower, on Flickr

Untitled by Damien Bower, on Flickr

 

[axelleveau]

I had seen people hack a shoe conversion but having a pre-cut adapter makes life much easier!
Was the 345mm disc spacing correct to just bolt on? When doing my research I came across Brembo drawings showing the M135i disc would be spaced further out about 8mm compared to the original 294mm from the E85/6. I think that the caliper could be spaced but you would be too far for handbrake to work? Or did I get something wrong?



PS: The puzzle to do a full F30 brake kit on non-M is getting closer to completion...
PS PS: I did not realise VYS garage was in Southam, good to know there is something very local once/if I get this going

 

[damocell]

Was the 345mm disc spacing correct to just bolt on? When doing my research I came across Brembo drawings showing the M135i disc would be spaced further out about 8mm compared to the original 294mm from the E85/6. I think that the caliper could be spaced but you would be too far for handbrake to work? Or did I get something wrong?

You should see the spreadsheet I have with all the calculations

The rear of the M135i disc face is within 1.3mm of the rear of the Z4 disc but without the protrusion the Z4 disc has. The very back of the disc sits 7.3mm further out than the Z4 disc so it covers the hand brake shoes well enough

 

[axelleveau]

Haha, I see we both have gone wild in Excel then I thought of using a 5 series disc to fully cover the shoes but if it works your way it is definitely easier than modify to a 185mm setup.
I have a small database of disc dimensions for various BMW and Land Rovers with some VAG/Merc sprinkled in there...
My current assumption is an F30 340mm caliper with an adapter to mount on a 363mm Land Rover disc for the front... I just have to justisfy myself tge time to spend on it and the missy to spend about 1K on the lot

 

[damocell]

Haha, I see we both have gone wild in Excel then I thought of using a 5 series disc to fully cover the shoes but if it works your way it is definitely easier than modify to a 185mm setup.
I have a small database of disc dimensions for various BMW and Land Rovers with some VAG/Merc sprinkled in there...
My current assumption is an F30 340mm caliper with an adapter to mount on a 363mm Land Rover disc for the front... I just have to justisfy myself tge time to spend on it and the missy to spend about 1K on the lot

Yeah the spreadsheet came in handy for sure

Fronts will fit with a VW Transporter disc that has had the CB enlarged. Or, there are custom discs or disc spacers available on eBay.

 

[Rsipad]

Be careful not to move the brake bias too far back. Rear lock is the last thing you want entering a heavy braking zone. Can also reduce effectiveness of trail braking by reducing weight transfer to the outside front.

 

[damocell]

Be careful not to move the brake bias too far back. Rear lock is the last thing you want entering a heavy braking zone. Can also reduce effectiveness of trail braking by reducing weight transfer to the outside front.

Don't worry, it won't move it too far rearwards, especially with my planned front upgrade. Plus I have a LSD which locks on decel aiding stability.

 

[ChrisQ_Z4]

Don't worry, it won't move it too far rearwards, especially with my planned front upgrade. Plus I have a LSD which locks on decel aiding stability.

Interesting little upgrade. I was also reading your thread on Facebook earlier.

Whats the plans for the front brakes?

I really miss seeing lovely big brakes nestled behind the wheels. My previous cars (M4, M240i, 340i etc) have all had the brembo 4 pots.

 

[1536Z4]

I've been working on a rear brake upgrade for the E85/6 as I'm experiencing high pad wear and temps on track.

Looking forward to the results on this as I thought the brakes on my 3.0si were ok until I got the Z4M with big brake upgrade . What a difference !!

 

[B21]

Don't worry, it won't move it too far rearwards, especially with my planned front upgrade. Plus I have a LSD which locks on decel aiding stability.

Have you done any calcs on the net result on brake forces front / rear ?

 

[Meds]

This is excellent, Damo

What front option have you decided on?

I have a few specific questions relating to my setup with the front 135i 6 pots with 345mm rotors.

I already have a set of the rear calipers in my garage.
But the 44mm piston version.

Would the 44mm version still work, when matched to the 30/34/38mm fronts?

Any concerns with the master cylinder?

 

[damocell]

Have you done any calcs on the net result on brake forces front / rear ?

The only one I have done is on piston area which obviously comes out to be exactly the same due to the 40mm piston. I haven't when it comes to discs size/leverage as it is far above my ability. I haven't used my Further Maths A Level to that extent since 1998

However, the F20 rear pad size is similar to the 330ci rear pad which uses the exact same front brakes as my car and the same master cylinder. So the only actual increase is in the 25mm larger diameter disc. Whilst the 330ci weighs a little more than my car, it has a very similar weight distribution. Therefore, I am not concerned about the increase in rear brake size and can always run a less aggressive rear pad if I experience rear locking.

When I did a similar upgrade on my track M3, I found the car more stable on the brakes as the weight was transferred forward less and the rear sat down in a similar fashion to my upgraded fronts.

 

[damocell]

Interesting little upgrade. I was also reading your thread on Facebook earlier.

Whats the plans for the front brakes?

I really miss seeing lovely big brakes nestled behind the wheels. My previous cars (M4, M240i, 340i etc) have all had the brembo 4 pots.

I've got a 345mm BBK coming which uses an "AP" four pot caliper. More details on this once it arrives

 

[damocell]

This is excellent, Damo

What front option have you decided on?

I have a few specific questions relating to my setup with the front 135i 6 pots with 345mm rotors.

I already have a set of the rear calipers in my garage.
But the 44mm piston version.

Would the 44mm version still work, when matched to the 30/34/38mm fronts?

Any concerns with the master cylinder?

So the stock piston areas are: 5102 front and 2512 rear - or 67%/33%

You have moved to, with the 6 pot fronts: 5494 front and 2512 Rear - or 69%/31%

Fitting the 40mm piston 2 pot will keep this the same

Fitting the 44mm will be: 5494 front 3040 rear - or 64%/36%

So, you've moved your braking from stock 2% forward by fitting the 6 pots (plus the difference in pad size and leverage), fitting the 2 pot rears will move you 3% rearwards from stock (not taking into account the larger pad and disc which moves it more rearward again)

Personally, given that info, I'd fit the 40mm piston as it'll help even out the brakes with the larger disc and pad. Plus, increasing piston size front and rear will give you a longer pedal which may not help.

 

[Meds]

So the stock piston areas are: 5102 front and 2512 rear - or 67%/33%

You have moved to, with the 6 pot fronts: 5494 front and 2512 Rear - or 69%/31%

Fitting the 40mm piston 2 pot will keep this the same

Fitting the 44mm will be: 5494 front 3040 rear - or 64%/36%

So, you've moved your braking from stock 2% forward by fitting the 6 pots (plus the difference in pad size and leverage), fitting the 2 pot rears will move you 3% rearwards from stock (not taking into account the larger pad and disc which moves it more rearward again)

Personally, given that info, I'd fit the 40mm piston as it'll help even out the brakes with the larger disc and pad. Plus, increasing piston size front and rear will give you a longer pedal which may not help.

Wow, thanks for this..
Pretty much what I calculated=guessed, but you backed it up with some math and numbers. Thanks for taking the time.

 

[B21]

The only one I have done is on piston area which obviously comes out to be exactly the same due to the 40mm piston. I haven't when it comes to discs size/leverage as it is far above my ability. I haven't used my Further Maths A Level to that extent since 1998

However, the F20 rear pad size is similar to the 330ci rear pad which uses the exact same front brakes as my car and the same master cylinder. So the only actual increase is in the 25mm larger diameter disc. Whilst the 330ci weighs a little more than my car, it has a very similar weight distribution. Therefore, I am not concerned about the increase in rear brake size and can always run a less aggressive rear pad if I experience rear locking.

When I did a similar upgrade on my track M3, I found the car more stable on the brakes as the weight was transferred forward less and the rear sat down in a similar fashion to my upgraded fronts.

Two things

I can let you have my mega excel spreadsheet for E89 options..the maths is all done..you just need to refill the variables in for E85 related discs/calipers if you pm me an email address..

I believe later E85s had the same DSC unit as E89s..in which case the DSC will automatically cope with all lock up type situations..

What you may do is leave braking capability on the table if you can't get the rears to use their full potential..

IMHO

 

[damocell]

Two things

I can let you have my mega excel spreadsheet for E89 options..the maths is all done..you just need to refill the variables in for E85 related discs/calipers if you pm me an email address..

I believe later E85s had the same DSC unit as E89s..in which case the DSC will automatically cope with all lock up type situations..

What you may do is leave braking capability on the table if you can't get the rears to use their full potential..

IMHO

Peter, I would love to see that spreadsheet if at all possible mate, thank you!

It's the heat I'm trying to manage rather than necessarily an increase in braking potential. At the end of the day the tyres are the limit of grip not the brakes from a friction and capacity point of view. These discs also vent from the inside out rather than outside in like the current E86's, therefore, I sould be able to run some sort of cooling solution too once the backing plate is trimmed

 

[B21]

Peter, I would love to see that spreadsheet if at all possible mate, thank you!

It's the heat I'm trying to manage rather than necessarily an increase in braking potential. At the end of the day the tyres are the limit of grip not the brakes from a friction and capacity point of view. These discs also vent from the inside out rather than outside in like the current E86's, therefore, I sould be able to run some sort of cooling solution too once the backing plate is trimmed

Mass is the primary way to manage the heat with agressive cooling if you can make it happen..

My BBKs discs are all bloody heavy with massive pads to reduce heat fade..

 

[damocell]

Mass is the primary way to manage the heat with agressive cooling if you can make it happen..

My BBKs discs are all bloody heavy with massive pads to reduce heat fade..

Exactly, which is why I'm intersted to move from a 19mm x 294mm disc with shallow pad to a 24mm x 345mm disc with a deeper pad, the way the disc vents is just a brucey bonus

 

[damocell]

This is excellent, Damo

What front option have you decided on?

I have a few specific questions relating to my setup with the front 135i 6 pots with 345mm rotors.

I already have a set of the rear calipers in my garage.
But the 44mm piston version.

Would the 44mm version still work, when matched to the 30/34/38mm fronts?

Any concerns with the master cylinder?

It would appear youve got your piston sizes wrong bud. Thanks to B12 for the spreadsheet as I noticed it on there.

You arent 30/34/38 upfront, you are 28/32/36 upfront.

Rebuild/Upgrade Kit for BMW E82 135i 6-Piston Front Brake Calipers

Rebuild Kit for 2 front calipers - Contains 12 seals and 12 upgraded pistons

www.bimmerworld.com

Therefore.....

So the stock piston areas are: 5102 front and 2512 rear - or 67%/33%

You have moved to, with the 6 pot fronts: 4872 front and 2512 Rear - or 66%/34%

Fitting the 40mm piston 2 pot will keep this the same

Fitting the 44mm will be: 4872 front 3040 rear - or 62%/38%

So, you've moved your braking from stock 1% rearward by fitting the 6 pots (plus the difference in pad size and leverage moving it forward), fitting the 2 pot 44mm rears will move you 5% rearwards from stock (not taking into account the larger pad and disc which moves it more rearward again)