Re: E28 Brakes **Rob

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

Derek Atkin ( Atkin11J@domain.elided ) wrote:
>Subject: E28 Brakes
>
>The rotors on my 85 535i are warped again. You can see the warp with the
naked
>eye. Front suspension is in good shape and no apparant bearing/hub
problems. I
>pulled them off 6 months ago and had my buddy put a very fine cut on them
>because they were warped. Big mistake, as I have no recourse for exchange
at
>this point. The previous units were Balo based on a recommendation from my
BMW
>tech. He told me that he has only has one set of Balo's come back on all
the
>E28 cars he has done. He has used ATE powerdisc with some success. I am
>curious as to any current information and experince on what E28 owners have
on
>their cars. I am running 14" wheels and the car never sees the track. The
pads
>are Metalmaster F/R and seem in good shape. The upgrade to 7 series
componets
>is intriguing but a bit expensive at this point for a relatively stock
5'er.



            Cutting heat-warped rotors doesn't do any good; the heat has
affected the metallurgy of the rotor so that the warp is a "product" of the
altered rotor, a symptom rather than a cause.  When the rotors get heated up
again (as in a hard or long stop) the warp gets temporarily worse -
temporary as long as the rotor is hot.  You still have the same effects of a
warped rotor (pedal vibration, shimmy, decreased braking ability) even
though the rotor may be "cut straight" when cold.

            The best results I had with stock-size rotors was with the
regular ATE, not the slotted ATE (never tried them on my cars).  I'm not
sure I'm sold on the idea of the slotted Powerdisc... as far as I can
figure, it isn't designed to dissipate heat (as the venting in vented rotors
does), but rather to allow the escape of brake pad gases that form when
too-hot pads start to boil out the resins and binders which form a layer of
gas that decreases braking effectiveness (similar to a tire hydroplaning on
water).  However, I doubt the slotted discs can be bad.

            No matter what, the stock-size E28 brakes are undersized for
agressive use.  If you drive relatively easy (and don't expect 110mph-30mph
slow-downs) then they are acceptable.  As your car has 14" rims, you would
also have to upgrade to 15" (or bigger) wheels to accomodate E32 brakes.
That certainly increases the expense level and I sure do understand why you
would be hesitant to make the swap!

- - Rob Levinson
'85 535i Turbo
'86 535i


www.shortshifter.com

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