Rear brake upgrade question

[BigKriss]

With the e34 M5 3.8L rear brakes, do they fit under stock 15" - ET 20 wheels?

http://www.bmwe34.net/e34main/upgrade/brakes.htm

[Scott H]

that you need a 16" wheel similar to how the 850 front brakes are 324mm and require a 16" wheel or bigger.

Kriss, you have truly gone awry with your modding.

With the e34 M5 3.8L rear brakes, do they fit under stock 15" - ET 20 wheels?

http://www.bmwe34.net/e34main/upgrade/brakes.htm

[mholbrook]

I'd say these definately will not work on 15" wheels and that some 16" wheels may not work. More than likely, you will need 17" wheels for sure. What are you running for brakes in the front? My concern is brake bias with really big brakes on the rear and smaller on the front.

Previously I had E34 M5 3.6 brakes front and rear on my last 535. I ran 17" M5 wheels on that car. Now I have M5 wheels on my present 535 but my brake upgrade is going to be the 540/7xx front and rear so as to be able to use my 15" wheels with snow tires.

[Espen]

I was looking at that article on bmwe34.net
Went to my local car parts store, they could get me new 850 front brakes for a very good price ($600) for the complete set. The problem is that I have only 16" wheels. Can someone confirm that 16" is to small for the 850`s.

Sorry for the thread hijack, but I kinda figured this is the same topic.

[fukem5]

mate i shpoke wif my cousins at bmw and thay sed u should shpeak wif unkle spiro mate. He dun a mod on his new m5 mate. he put charger calipers at the frunt and 225 slant vf pacer drums on the back mate. pulls up like ur nana on her wedding night mate!

[BillionPa]

the 850 brakes do NOT fit under 16" wheels.

for an "upgrade" to your rear brakes, i would no do it simply because the solid rotor is significantly lighter than the vented one on the 3.8.

the additional unsprung weight means more car that the front brakes have to stop, at the expense of additional cooling that the rear brakes just dont need.

get cryo treated rear rotors instead and rebuild the calipers.

[BigKriss]

Thanks for everyones responses. I ask because I have some front e32 750il 4 piston calipers. At first I thought they would not fit under 15" wheels but Barry in Dubai told me that he had the same setup on his e34 535i and the fit under 15" wheels ET20. I then asked Shogun and he replied that the 750il came stock with 15" wheels and those brakes also. They accept a 324x30 rotor. I was thinking a 328mm rotor at the rear may fit also. I'm not just asking this question to be a dick as I have e34 540i brakes for the rear - I just thought a member from here had tried it before.

I asked over on e34.de also. One member "Ralvieh" said "The rear brakes (328 x 20) need a bigger "protection plate", to change them you also have to replace the "angular contact ball bearings".

[632 Regal]

after all this modding you will be ready to drop in an S32 or 4.0 soon huh?

[Scott H]

first of all, the 850 front brakes DO fit under 16" wheels.....which is what the 8 series cars all came with (turbine or basket weave), including the 840 with 4-pistons calipers.

On the track, the rear brakes do a lot more work than you think, evidenced by their temperatures, tires temps, and just the amount of brake dust blown out. The additional cooling provided by a vented rotor is NOT minor. The additional cooling and braking benefit provided by the vented rear rotors far outweighs the 1kg difference (per ETK) in weight. Why do you think the PhDs at BMW used the vented rear on the 540/M5?

the 850 brakes do NOT fit under 16" wheels.

for an "upgrade" to your rear brakes, i would no do it simply because the solid rotor is significantly lighter than the vented one on the 3.8.

the additional unsprung weight means more car that the front brakes have to stop, at the expense of additional cooling that the rear brakes just dont need.

get cryo treated rear rotors instead and rebuild the calipers.