Dave Z - Will 540 brakes fit '01 525 ?

I have seen your many expert posts over the last 3 years on both boards, and want your input as I start my 1st brake DIY. Will a 540 setup make a big difference ? What do I need? Thanks.

Jim

I have read on a different forum that you can take brakes from 8 series and put them on your 5 with no mods. I wish I could find that forum again.

Originally Posted by 528iheat

I have read on a different forum that you can take brakes from 8 series and put them on your 5 with no mods. I wish I could find that forum again.

I think that only works if your 5-Series is an E34. The 8-Series shared some components from the E34 front end. The E39 is totally different and the 840/850 brakes won't fit.

Originally Posted by ///-Power

I have seen your many expert posts over the last 3 years on both boards, and want your input as I start my 1st brake DIY. Will a 540 setup make a big difference ? What do I need? Thanks.

It will make several differences, some good and some bad. The first thing I need to ask is, do you plan to track your car? If so, then it's a no brainer. Go for the 530i/540i front brakes.

If not, then it gets more tricky to decide. The calipers on your car are aluminum and the ones on the 530i/540i are cast iron. So there's a big weight jump from 2.6 pounds for your current calipers to 9.9 pounds for the 530i/540i calipers. The rotors go from 16.6 pounds to 23.5 pounds, a gain of 6.9 pounds per rotor. That's not only unsprung weight, but it's also rotating mass. So it's going to introduce gyroscopic effects into your steering and it's going to impact your acceleration. Even the caliper frame and pads are slightly heavier on the 530i/540i, so there's at least another pound there. You're looking at a weight gain of at least 14 pounds at each front wheel.

While that may be bad for handling and acceleration, it's terrific for storing and shedding heat. The extra mass of the rotors mean the peak temperatures will be far lower and the combination of greater rotor surface area and larger air gap between the friction plates means that cooling by radiation and convection will be greater and cooling by conduction (into wheel bearings, brake fluid, etc.) will be less. Your rotors and pads should last much longer and you won't have to worry about brake fade under almost any conditions you could subject the car to on the street.

To do the conversion, you will need new calipers, caliper frames (BMW calls them "carriers"), spring clips, brake pads, and rotors. The brake lines do not need to be changed, since all the 5-Series cars from the 525i right on up to the M5 use the same brake lines. However, this would be a great time to upgrade to stainless braided brake lines, since there's no extra labor involved.

Dave - 1st of all many thanks for the excellent post. I have all 5 BMW CD's, which one tells you about the caliper material/design ? I did not know there was that much difference in brake mass. I will not be tracking the little 2.5 ltr. motor...not worth the exposure in my opinion. Its just a city car, but Houston requires really good brakes with the traffic no matter how small your engine. So the problem becomes the fact the increased rotational mass would be met by the smallest E39 US engine - so I think I will just upgrade my pads to the Axxis Ultimates and keep what little torque I have. I have kept my car stock knowing it would be traded in eventually because it is not a keeper engine-wise, but at the time I could not convince my wife to upgrade to the 530i. This car was actually ordered by me from Germany...has manual a/c,leatherette,Steptronic,sunroof,CD and Xenons only. No Sport/Premium or any other stuff. So its a real lightweight E39, probably a good candidate for an engine swap - but that will never happen. I just want a 530 that I can upgrade with RDS cam/exhaust pkg. one day. Anyway - you have helped steer me in the proper direction, so gracias.

Jim