I've had some mods done recently with the suspension and the car handles a lot better now such that I tend to drive it a bit faster and now I'm starting to find the limits of the braking capacity. Not that the standard brakes are bad by any stretch of the imagination, they're not, but they do fade very badly after 2 or 3 really hard stops and the recovery is a slow one.
My mechanic says the first thing to try is just cross-drill the existing rotors and use a slightly firmer pad. He reckons that will more than be good enough for the car given that the engine is stock.
I'm more than willing to give it a try because it's a very cheap mod and easy to do but am sceptical than just drilling some holes in the rotors is gonna make any difference whatsoever.
I have Zimmermann cross drilled discs on my E30. I'm hard on the brakes as I drive the car on quite twisty roads. Cross drilling aids cooling and if you soak the rotors in standing water it helps clear them (so I'm told). But there is less surface area so it actually harms stopping power!
The Zimmermanns have the holes cast in at manufacture. Drilling holes afterwards can weaken the disc.
I agree with John, its dangerous to try and drill out your rotors, they're already thin enough. Remember, *true* and *proper* cross-drilled are cast into the rotor. Drilling only creates stress risers and will weaken the disc.
If you want the proper "factory" upgrade, and don't want to spend the big bucks for a Movit or Brembo kit, get yourself a set of E32 750 calipers and rotors up front; E34 540i calipers and rotors in the rear. You should be able to find the calipers cheap at any junkyard.
The beauty of this setup is your consumables - rotors and pads, are basically standard BMW stuff that can be bought OE from any dealership or OEM through any parts store, e.g., BMA parts as great prices. Further, the bigger brakes are vented for more cooling.
Note - you may need to upgrade to 16" wheels, but since your car came with those obsolete metric TRX tires and wheels, you'll probably need to replace them anyways, if you haven't already done so. Good Luck!
Thanks for this advice. My mechanic now has started to say that he thinks possibly cross-drilling standard discs isn't a good idea either. He admits it does carry with it a slight risk of disc fracture either during the drilling process or under braking (gasp!).
He starting to steer me toward a slotted aftermarket disc instead now. He seems intent on either drilled or slotted discs to "break the gas barrier between pad and disc".
The problem I've got is that with all the new parts I've put in the suspension, the car now rides and handles better than ever before and I've owned it for 12 years. So it is able to be driven much faster much more confidently than ever but the braking now hasn't kept up with that and inducing fairly bad fade and getting a spongy pedal is very easy.
As part of the upgrades I've done, the car already has genuine E28 M5 16" wheels on it. Ditching the TRX 240/45-415s was the very first thing I did to it.
To date I've had replaced:
Wheels (E28 M5 16") Tyres (Yokohama AVS ES100) Shocks (Koni sport adjustables) Springs (King Springs - lowered by 20mm) Steering centre track rod Rear bump stops Rear pitman arms Rear subframe mounts Front radius arm bushes (urethane ones)
And after all that, the car drives like a dream. I actually can't believe how well it drives in fact. I'd never have believed it was possible for a pig of a car like the E28 to drive this easily. My car has always more closely resembled a truck to drive rather than a car.
Only remaining issue is the braking endurance. There's nothing wrong with the braking as such. The car pulls up dead straight, doesn't wander around on the road and everything feels rock solid, but you can only do it once from high speed before there's no pedal left afterwards.
So....this thread is getting long, but I don't recall that you changed pads. It seems quite possible that a higher (and wider!) temperature range pad could resolve your problems at lower cost...
If I was to do this mod, would the standard issue spare wheel fit over either of the E32 or E34 brake calipers?
My spare is the OE rim the cars were delivered with. It has a 200/60-390 TRX tyre on it (also OE from circa 1986). I don't want to do this mod if it means that the spare becomes merely boot space ballast.
You may be satisfied just by changing to different pads. I use Carbotech pads on the track in my E34 M5, and don't experience any fade. I don't use drilled rotors. When did you last change the brake fluid?
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