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any BMW mechanics/gurus?

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  • any BMW mechanics/gurus?

    buddy of mine is looking to do a brake mod on his E39 (530T) -- upgrading from his 300mm disc to the E60's 320mm disc and caliper.

    i have his components on the bench, old and new, and thought i'd do some research before getting to work.

    has anyone done this? thoughts/precautions?
    (his car is worth more than my shop)

    at first glance its looking easier to modify the brake caliper than it is to change the mounting. theres not so much difference that I can make an adapter-flange.. so one of the two pieces will need to be cut.

    the actual discs, apart from the 20mm difference, appear identical.


  • #2
    Will this effect the antilock brakes? You are changing the bias. What might BMW say?



    • #3
      "damn it, Jim, I'm a doctor not a mechanic!"

      sorry couldnt help it.
      have no idea what bias even means.

      they do sell kits for these cars that take the brakes up to 355mm, and if installed by a certified BMW center then everything is... ok?

      i'm not sure.

      basically it comes down to this:
      he has a facny car, bigger brakes, and alot of money

      i have a beater car, a machine shop, and no money.

      i brought "warranty-voiding" to his attention and he didnt much care. as long as i can mount these things without them falling off (ie cover my backside), i'd like give it a try.


      • #4
        I haven't worked in a BMW dealer since 88, so I am not familiar with that particular model. But I would like to make a few points for you to think about anyway.

        1-unless something has changed since my days as a dealer mechanic, BMWs come from the factory with excellent brakes. Why would anybody bother to modify them ?

        2-as you are modifying a safety related piece of the car, I would stop and think what liability you may incur by doing this. If this car is ever in a serious accident, I guarantee you that the inquiring mind of a lawyer will want to know.

        3-I do not believe the antilock braking system will be affected at all. It's true that the braking bias of the car will be affected, which I assume may cause the stopping distance to increase instead of decrease, but I think from the ABS point of view it will appear about the same as having a good set of tires on one end of the car and a slippery set on the other.

        4-is it possible to simply use the caliper and steering knuckle assembly off of an E60 on the E39? This would at least have the advantage of using all factory parts.

        In summation, I can't say that I recommend this modification. It adds possible legal risk, probably will not have a positive effect on the cars drivability, and will take time and money to perform. If the BMW is not high enough performance for him, perhaps he should visit the Porsche dealer?



        • #5
          Tell your friend to ask the question in the appropriate forum here:

          As for a brake upgrade on a BMW yes they do come with excellent brakes but more braking power never hurts especially if they're gonna autocross or track the car. I've got a set of huge brakes all set for my '73 911 chassis whenever I get started on it. Rotors are I think 13" in front and 12" in back with 4 piston Brembos all around. They where takeoffs from a brand new 911 that the owner had upgraded for some heavy track use. I figure they'll be fine for my car since it will weigh about 1300lbs less than a new 911.

          -Christian D. Sokolowski


          • #6
            I'll take a friendly Beer wager the ABS WILL be affected.And in no way is this meant to be in the negative sense......IOW's the slight to pretty noticable change in the way the ABS reacts to this mod "may" be for the better.But if the guy isn't practicing threshold braking and is fairly adept at it,its unlikely he'll notice or care.I know I'd notice(not that we've ever been known to exceed any suggested speed limits)! BM's on the whole work pretty darn well with each other,this model part used on that model vehicle.........we do it alot on their bikes.But its done out of necessity rather than any looks thing.The ABS systems are pretty finely balanced and can be affected with something as simple as a change in pad characteristics.If your friend is looking for increased braking performance just make sure he's willing to run sticky go-fast(and subsequently STOP-fast)tyres,otherwise there ain't a whole lot of point.Best of luck,BW