Hi there..no problem on the native English…I noticed also in for example aviation that French to English didn’t work well either..
To try and answer your questions…
The 345mm and 370mm brackets are unique and are also handed left and right..so there are 4 versions..
The disc offset (top hat) for the 345mm version is different to the 370mm version..so the rebates for mounting to the ‘ears’ on the trailing arm are different for each of the two versions.
I’ve designed the adapters based on pioneering work by P Morelli…unfortunately he chose a G series brake caliper then got into all sorts of difficulties with a complex bracket, spigot rings, machining of the caliper , machining of the brake pads etc etc.
I’ve done about 10 iterations in the design over the last year. This is the first ‘production’ version intended for sale /use by others.
The adapter requires the rear dust shield to be modified both to accommodate the larger disc 345/370mm vs 330mm and also the caliper is rotated / move backwards to the rear of the car to accommodate the bracket design.
I decided it was too dangerous to cut the outer lip off the dust shield as it would leave a sharp edge which when you are mounting / dismounting the wheel could be very dangerous to your fingers….I found this out the hard way!
Once the dust shield is removed / modified then the caliper cradle bracket can be fitted without ANY. requirement to remove the stub axle ..
It may be possible to find a 345/370 x 24 disc with 120mm PCD that could be made to fit with slightly different offsets but I haven’t seen one…if you can send me a BMW part number of a possible candidate I can look at it.
I’ve used Zimmermann quite a lot and haven’t had any issues bar one where my garage fitted new rear pads and one was cocked over in the caliper cradle and as a result asymmetrical pressure was applied to the disc resulting in one sided wear with fine line cracks appearing between the drill holes.
Because the design uses BMW rear discs that were designed for a brake shoe based handbrake in addition to a caliper they are by design one piece…if you can find a 2 piece design in 345/370 24mm then I’d look at it.
I’ll look at the calculations again but I’ve had two brake specialists look at them and they concurred that the logic was accurate.
I’ve tried the 300mm/330mm/348mm versions of the E89 and the E90 6 Pot and the F series 4 pot in 340mm and 380mm as well as the Shelby Mustang 6 pot on 380mm and I’ve not seen anything that suggests the calculations are not representative ..
Size of braking pad ..has surprisingly little impact on braking force…it does have a big impact on fade and wear ..similarly thicker / heavier discs don’t affect the calcs but have a big impact in terms of fade resistance..
There are other complex interactions..the E90 Brembo 6 pot technically is less effective than the 35is front brake pack..but..it is far easier to finesse the braking especially say in the wet..
For the 4 pot F series the 345 mm is the logical choice
The normal E89 front / rear brake ratios range from 64%-66.2%
With a 380mm 4 pot F series the 345mm rear gives a 64.5% F/R balance
F series 370mm front gives 63.8%
As you say the 370mm rear BBK is for the big bmw 8 series / mustang 550 BHP / Alcon type brake packs..
Although your observations are correct E89 vs E90 in fact over time BMW has moved to increasingly larger rear brake packs…G29 348 x36mm vs 345x24mm
IE almost symmetrical…
I’ve now done a few thousand miles with both 380mm F series and Shelby Mustang 350 front calipers on the same M2 380mm discs with both 345 and 370 rear discs and have not noticed any irrational / difficult / unpredictable/ unexpected behaviour..
There are other DSC unit seems to cope with a wide range of changes with no issue..
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