Re: e28 M5 RL/BB **Rob

["Rob Levinson" <always_coca-cola@xxxxxxx>]

"Chris Brandt" <Chris.Brandt@domain.elided> wrote:

>Subject: re:e28 M5 RL/BB
>
>A question for those in the know. I have been following some of the
>e28/e32 brake swap threads the last week or so. I will do this upgrade on
>my 85 635...The question I have is how do the e32 front brakes compare
>with the e28 M5 front brakes. The components look cheaper to replace and
>would be easier to get. Not to mention I would have two cars with all the
>same components...If the e32 front stuff is better than the e28 M5 stuff I
>might trickle the M5 stuff down to the coupe and do the upgrade on the M5.



            There are only two comparisons I can make directly; size and
price.

The E32 brake rotors are 302mmx28mm, the E28 M5 rotors are 300mmx30mm.  A
little difference in swept are and thickness.  Considering that they are
both vented, I suspect the M5's extra thickness is air space, not actual
heat-absorbing metal.

The price is another matter altogether; where some people have been lucky
enough to pick up M5 calipers/rotors very inexpensively, I would say that is
anecdotal rather than the norm.  M brakes are usually expensive, used
($200-$300 per caliper) or new.  The E32 brakes, likewise, could be found
for a proportionately cheap price.  However, to Joe Average who hasn't got
the time/resources/luck to find "garage sale specials", the regular price
from most dismantlers is very reasonable, $50-$125 per caliper.  E32 rotors
are a little less expensive (~$50) and more easily found new.

Performance-wise, I have not driven M5 and E32 brakes back-to-back
(especially with every other factor equal - car weight, tire model/size,
road conditions, brake pads).  What I can say is that I have tried and
absolutely cannot warp the E32 brakes... I was warping standard E28 brakes
within a week of bedding them in!  The E32 brakes stop so well that I have
been slammed into the seatbelt with a big "oof!".  I can't complain.  Also,
I took a look at BSR/Summit Point Instructor Tom Baruch's 535is... he runs
the E32 brakes with Hawk Blues at the track and is also apparently
satisfied.

One last thing, and this impressed me greatly... I looked at several M5
brakes and noticed excessive wear/scorch marks right in the center of the
rotor where the 4-piston calipers seemed to grip in-line.  The E32 brakes
have huge single-piston calipers which seem to spread the clamping force
over the surface of the rotor more evenly.  Mine don't show any area of the
rotor more worn than another area.

No matter what, both braking systems are *amazing* and neither is a mistake.
And also, if you buy one or the other and change your mind, you certainly
won't have any difficulty selling them!

- - Rob Levinson
'85 535i Turbo w/E32 brakes, BL/SS Level 3 (prototype CCERK)
'86 535i w/stock wimpy brakes, BL/SS Level 2


www.shortshifter.com

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