Atacama Yellow 35is build thread

[B21]

I've spent some time looking at options above a 345 mm rear disc..

It is feasable (now I'vve climbed a learning curve) to look at other BMW rear calipers with EPB ..

So above 345mm you can go to 370 or 380 or just under 400 with the M5 and M8 rear calipers..

But...

Given the normal front rear bias, what would a similar size rear to front do?

I can see on a M5 fully loaded with pax and luggage why a much bigger rear brake is useful..

With a relatively light E89 not sure.

The other issue is that the price jump on a solution goes from around £500 to over £1,500 assuming using some used parts and over £2k with new parts.

I tried to see if you could use the smaller 5 series caliper with the bigger rear discs but the rear pad does not fully sweep the disc..so that's a no go..

So I'll carry on only withy the 345mm disc upgrade with normal 5 series calipers..

Some quick maths shows the following F/R ratios;

Front Ratio Rear
348 1.07:1 324
370 1.14:1 324
380 1.17:1 324
370 1.07:1 345
380 1.1:1 345
380 1.03:1 370

My take from the above is 370/345 maintains the OEM ratio while 380/345 provides slightly higher front bias. I'm no expert but I don't see it being a huge issue with a 3% increase. It's still a better ratio than I currently have with 370/324. I suppose the important question is at what stage does upgrading the brake master cylinder have to be considered? No doubt some smarter/more experienced minds can weigh in on this.

All of this aside a rear brake upgrade solution at the £500 price point would be excellent. I put together the front brake upgrade for <£600 (370/380 calipers including rotors with EBC Yellowstuff pads) which I thought was a bargain for the braking improvement.

It turns out that it’s pretty difficult to change the master cylinder on E89s..another example of similar but not close enough to its E90 E85 cousins..

The brake bias calculation is more complex since it’s a product (pun) of the swept area Pad area and piston size(s)…

Anecdotal evidence suggests that despite given the wide range of combos of calipers / pads / discs the cars seem to tolerate /perform OK..

The M type 2 piston Brembo rear caliper has the same size pistons as my suggested mod..plenty of them used on E90s..

We will find out…

 

[Stealth00]

Getting ready to fit the new Audiotec Fischer Helix 6.6 in woofers in the footwells…

Interesting that the 677 woofers turn out to be the same as the 676 woofers..unlike the 100mm speakers which are definitely nastier on the 676 compared to the 677.



Slight issue is that the new woofers outer rim just kisses the screw holes in the plywood adapters we have made to allow normal round speakers to fit in the odd shaped BMW speaker recesses…

So just had the screw holes counter sunk and now will have to fit the plywood former first to the bulkhead then screw the speaker onto the former..fiddly..

Nice speaker adaptor rings. I was looking on eBay for some 3d printed ones and considered messaging someone to see if they could customise/print me some. I saw some listed for a BMW, but I think it might be easier to make some myself. It will mean I'll need to figure out how to use my handheld router that I've had for a few years

 

[B21]

So reflecting on the various issues I bit the bullet and bought a couple of old rear hubs and bits with a view to being a lot easy to faff around with bits off the car rather than on..

A few head scratching hours playing with the old bits and my new bits…plus lots of washers, spacers, bolts..

As Meatloaf would say 2 out 3 ain’t bad..however in this case you need all 3 things to work for it to be a viable solution..

These parts are for a 345 mm disc with a 44mm piston sliding caliper solution..roughly based on a 5 series non M

I’ve got a set of M5 rear calipers coming with the option of a 370mm or 380mm rear disc….

New disc is 345mm vs an old E89 300mm disc from the non 35i/35is E89s…

 

[Christopher72]

IMHO, you need to take some timbers and build a workbench. Seeing all of that on the ground hurts my back.

 

[B21]

IMHO, you need to take some timbers and build a workbench. Seeing all of that on the ground hurts my back.

Yup the back is hurting….but turrah..

First trial fit of the 345mm E60 discs with F series 5 caliper and my first attempt at a bracket ..looks pretty ok.

 

[B21]

A few people expressed concern about brake bias as a result of twiddling with the front and rear discs..

So I've done a calculator for the E89 with the current used and known discs, calipers and pads to look at how different combos work out.

I've assumed all pads have the same coefficent of friction, which for street pads is not unreasonable..

As you can see, both what BMW did on various E89s and what I'm suggesting for BBK upgrades pretty well match..

For those that want to understand brake bias I refer to .. https://youtu.be/yeuLeDlTqIs?si=mfF8rk6m7nCfbWWS

If you want to noodle here's a copy

https://www.dropbox.com/scl/fi/rt7ceuw6 ... l74bi&dl=0

 

[B21]

So resurrecting my leather trim interior program…I used these guys to provide the leather trim for the dash and the roll over hoops..

I ran out of time / will to live…

So going to do the centre console / arm rest trim and door arm rest / handle trim to match…

Dug this out for the removal shortly..once we get above -10.5c..

 

[B21]

Played around with my rear BBK upgrade today…

Discovered F version 5 series rear calipers are made of alloy not cast iron as on the E89..this E89 caliper carries its 300mm stamp indicating it’s for 300mm rear discs only..

Also the M5 caliper looks to be just a 5 series caliper painted blue..albeit with a taller caliper carrier cradle…not a lot of people know that..

 

[B21]

Trying to get pad alignment on the discs perfect..getting hard work cutting these brackets out in steel so went for 3D printing purely for alignment purposes…

So the good news is that the 345mm version is now perfect with the pad sat nicely on the disc using all the pad and most of the disc..previously the top of the pad was just fractionally past the top flat part of the disc..

The 370mm version needs one more iteration as the front of the pad is siting fractionally lower than the rear..2mm adjustment on the front caliper bracket hole should see it..

Then ready to hand them over to the laser / water cutter boys to fab a few..

Interesting to see how much disc the original 300mm rear disc pad missed..

 

[B21]

Attention moves to the front end..the existing BBK..the trusty E82/E90 6 pot Brembo with 338mm x26mm discs removed for the new owner..

Current plan is still to fit the big Shelby Mustang Brembo 6 pot (bigger pots) with M2/M4 380mm 30mm discs..

However here’s the F series M Performance caliper (340m with adapter for 380mm discs)…

Also trial fit of 380mm M2 front dust shield..will need a little work but 3 out 4 holes line up..

The M Performance caliper is slightly lighter..the old Brembo s bit chunkier..but it does have harmonic weighs bolted on..

Enjoy..

 

[B21]

Well the M2/M4 brake shields didn’t work at all..

The problem once you start modifying things is that EVERYTHING seems to be needing fettling..

On the front end I’m using E90 35i brake shields which fit the stub axle but just kiss at the rear the brackets for the 380mm 6 pot big Brembo…

At the back with the 370mm rear disc and M5 caliper / bracket adaptor I’m using some M5 rear brake shields..they needed quite a bit of cutting n fiddling as it’s all very very tight in there..

 

[john-e89]

Liking the front a lot, rear not so much, purely because it’s still a single pot caliper and doesn’t really do the front justice, nothing to do with the build efforts.

Am I right that you might start selling kits…? I’d be interested in the front but I’d match it with a rear 4 or 6 pot kit from PB brakes with the line lock.

Any particular reason you didn’t go this route other than cost…?

 

[B21]

Liking the front a lot, rear not so much, purely because it’s still a single pot caliper and doesn’t really do the front justice, nothing to do with the build efforts.

Am I right that you might start selling kits…? I’d be interested in the front but I’d match it with a rear 4 or 6 pot kit from PB brakes with the line lock.

Any particular reason you didn’t go this route other than cost…?

Hi John, thnx for your interest…

I agree the rear single caliper doesn’t look anywhere as pretty as those PB or Ceika versions..

The logic was..

It’s all a BMW / Brembo set up..it looks like BMW made it

The rear is cheap around £500 ish as against £2,500 for a similar braking capacity unit

All these solutions are much cheaper than after market other kits

Although the Ceika / PB are very well made and look neat I just don’t like the style when fitted to an E89

And..someone else tried ..got a one off solution but it was never feasible to sell it as a kit..

How does that sound?

 

[john-e89]

Liking the front a lot, rear not so much, purely because it’s still a single pot caliper and doesn’t really do the front justice, nothing to do with the build efforts.

Am I right that you might start selling kits…? I’d be interested in the front but I’d match it with a rear 4 or 6 pot kit from PB brakes with the line lock.

Any particular reason you didn’t go this route other than cost…?

Hi John, thnx for your interest…

I agree the rear single caliper doesn’t look anywhere as pretty as those PB or Ceika versions..

The logic was..

It’s all a BMW / Brembo set up..it looks like BMW made it

The rear is cheap around £500 ish as against £2,500 for a similar braking capacity unit

All these solutions are much cheaper than after market other kits

Although the Ceika / PB are very well made and look neat I just don’t like the style when fitted to an E89

And..someone else tried ..got a one off solution but it was never feasible to sell it as a kit..

How does that sound?

:lol: Sounds fair enough…

We’ll have to disagree on the PB rear kit, personally I think your Brembo fronts and PB rear would work, but point taken on your set being all BMW, personally I couldn’t give a chuff, but that’s the beauty of us all being different.

Cost I get totally, and being fair the bigger M5 rear callipers I’m sure will go some way to evening up the front / rear difference….just not enough for me…. :wink:

 

[B21]

Liking the front a lot, rear not so much, purely because it’s still a single pot caliper and doesn’t really do the front justice, nothing to do with the build efforts.

Am I right that you might start selling kits…? I’d be interested in the front but I’d match it with a rear 4 or 6 pot kit from PB brakes with the line lock.

Any particular reason you didn’t go this route other than cost…?

Hi John, thnx for your interest…

I agree the rear single caliper doesn’t look anywhere as pretty as those PB or Ceika versions..

The logic was..

It’s all a BMW / Brembo set up..it looks like BMW made it

The rear is cheap around £500 ish as against £2,500 for a similar braking capacity unit

All these solutions are much cheaper than after market other kits

Although the Ceika / PB are very well made and look neat I just don’t like the style when fitted to an E89

And..someone else tried ..got a one off solution but it was never feasible to sell it as a kit..

How does that sound?

:lol: Sounds fair enough…

We’ll have to disagree on the PB rear kit, personally I think your Brembo fronts and PB rear would work, but point taken on your set being all BMW, personally I couldn’t give a chuff, but that’s the beauty of us all being different.

Cost I get totally, and being fair the bigger M5 rear callipers I’m sure will go some way to evening up the front / rear difference….just not enough for me…. :wink:

The big Mustang Brembos need a rear with a very large diameter disc/piston area to bring the front /rear bias into the same area as the stock brakes do..so the 370mm disc allied to a bigger piston rear caliper achieves that objective..the world seems to have little empirical knowledge of how the cars are affected by marked changes in front / back ratios ..maybe they aren’t..

I couldn’t get any technical info from the other suppliers to give me any technical confidence as to what they had planned..

 

[B21]

Made some progress today…made a patch pipe to fix one of the broken pipes, managed to unstick one of the others..only one left to make…steep learning curve being a hydraulic plumber….easier to do on a bench ..less so in situ..you need a couple of inches of straight pipe to be able to get the tools in..the plastic coated steel pipes fitted to the E89 are a bitch to work with..

Fitted front brake shields, torqued up the Brembo adapter brackets …awaiting the pad clips which are only available in the US which should arrive tomorrow after a 2 month plus struggle..

Fitted the M2/M4 380mm front discs..big chunky things

Trial fit of 370mm rear disc looks nice n chunky too!

 

[B21]

Another day…finally after over 2 months got some caliper pad anti rattle springs that fit the unique Mustang caliper casting ..surprised bolting them up quite a lot of inboard disc left unswept by the pads..given how big the pads are laterally I’ll have to live with it..in comparison my rear brake design wipes just about every mm of the rear discs..unlike the stock 18i/20/23i/30i or the 35i/35is rears which leave large amount of disc unswept.

Despite much bench testing another issue is the flexible brake pipe routing and lengths..time ran out today ..may need to be creative with routing and/or new flexible pipes..

Apart from that front and rears look ready for brake bleeding and then road test…

 

[B21]

Wheels on…very tight on the front end..need 5mm spacers with 437Ms..need F10 rear brake hose as well..

 

[B21]

Got back in the garage today after a time out looking after SWMBO who has been poorly but slowly recovering…

Anyway..

Had been pondering why my new big Brembo front upgrade pads were not fully wiping the disc (not unusual on BMWs ..the E89 rear pad does the same quite badly)

Was about to torque down the caliper bolts (182nm!) and thought I’d check it out ..

I’d bought two sets of pads for the front ..some famous in America Hawk pads and some Brit Ferodo in the DS2500 street/light track compound )..

Well…the Ferodo pads had more depth to them than the Hawk…

After much googling discovered another super subtlety about Ford Mustang calipers..turns out the GT500 caliper is oh so slightly changed from the GT350 Shelby version..

Anyone want a set of Hawk pads for a Mustang 500?

That’s the trouble going off piste..

Anyway front now buttoned up and all brake pipes torqued up..onto the backs next ..

 

[john-e89]

5mm spacers will push OEM 437’s beyond the wheel arch afasik, you’ll pebble dash the flanks something nasty. :?