brake piston size

[Chip]

What are the piston sizes on the front calipers for the 535 and 3.6l M5?
Are the brake lines the same?

Thanks-

[Jeff N.]

Hmm...don't know the piston size of the top of my head. I think this is listed on BMW e34.net in the upgrades section. I recall a pretty good discussion on brake upgrade options.

That said, you can easily swap in brakes from the E34 M5. I have the 3.6L single piston fronts on mine and they just bolt in. To swap, you'll need the caliper, the carrier and M5 rotors. You can also put in the 850 4 pot brakes (also used on the 3.8L M5 I believe). They look really sweet....

Stock master cylinder works with all of these combinations. Stock brake lines work as well.

[Chip]

Thanks Jeff-
My 'new' M5 brakes should arrive tomorrow. I was just wondering if I'll get any more pedal travel due to an increase in piston size. I know the master cylinders are the same. I checked e34.net and found nothing referring to piston sizes. Do you have the 540 on the rears? How's this setup on the track? What pads are you using for the track? I think I got my last track session out of my Carbotech Panther Plus pads.

Hmm...don't know the piston size of the top of my head. I think this is listed on BMW e34.net in the upgrades section. I recall a pretty good discussion on brake upgrade options.

That said, you can easily swap in brakes from the E34 M5. I have the 3.6L single piston fronts on mine and they just bolt in. To swap, you'll need the caliper, the carrier and M5 rotors. You can also put in the 850 4 pot brakes (also used on the 3.8L M5 I believe). They look really sweet....

Stock master cylinder works with all of these combinations. Stock brake lines work as well.

[Jeff N.]

Hi Chip,

Are you trying to setup your brakes for lapping days? I have some good input if that's what you're working towards as I have mine well sorted.

What issues - if any - have you experienced with your brakes.
Under what situations do these issues arise?
What's the "current configuration" you're running?

To answer your questions - I noticed no change in pedal travel when I went to the M5 brakes. Currently running the stock rears. Running PBR Metal Master pads on both street and track. Very happy with them. Work well enough on track, quite price effective ($45/set), and quiet on the street.

Thanks Jeff-
My 'new' M5 brakes should arrive tomorrow. I was just wondering if I'll get any more pedal travel due to an increase in piston size. I know the master cylinders are the same. I checked e34.net and found nothing referring to piston sizes. Do you have the 540 on the rears? How's this setup on the track? What pads are you using for the track? I think I got my last track session out of my Carbotech Panther Plus pads.

[Chip]

Jeff-
Currently running a stock 535 setup for the brakes (w/SS brake lines), and for the track days I install the carbotech panther plus. As I improve during the weekend and from school to school I find that I'm increasing my speed around the track and just need some more brakes. The setup has been fine with no fade and very predictable and the ABS only kicks in a couple times during the weekends. The ABS thing is usually going deep into a corner that I'm trying to carry speed into, but it's just me pushing the car closer to the limit and I know when this will happen. It's just time for some upgrades.
Thanks for any input/suggestions-

Hi Chip,

Are you trying to setup your brakes for lapping days? I have some good input if that's what you're working towards as I have mine well sorted.

What issues - if any - have you experienced with your brakes.
Under what situations do these issues arise?
What's the "current configuration" you're running?

To answer your questions - I noticed no change in pedal travel when I went to the M5 brakes. Currently running the stock rears. Running PBR Metal Master pads on both street and track. Very happy with them. Work well enough on track, quite price effective ($45/set), and quiet on the street.

[Jeff N.]

Hi Chip,

The "problem" with our cars is weight. Weight + braking = heat. Lots of it. IMHO, the best thing you can do for your brakes is get some cooling. You already have the M5 calipers coming, the next thing i would do would be to install the 540 brake ducts. See bruno's site for the parts list and instructions.

I found that getting some serious air over the calipers really helped with the pad life and the predictablity of the setup.

I'm an instructor for our local chapter and routinely run in the "A" group with lots of M cars. I've found that I have more than sufficient braking with my setup in almost every situation. If you can get into the ABS, you have sufficient brake torque - you need more tire if you want to stop faster, not bigger brakes.

Not sure what demands your tracks puts on your brakes. Ours has two *significant* braking zones back to back (within 30 to 40 seconds). The first is a 120 to 65 or so, the second is a 100 to 25. I'd suspect that your track won't do much more than that...

My advice - stuff in your calipers, add some brake ducts and call it good. Remember if you can get the ABS engaged, it's a friction problem at the tire level, not at the caliper level.

Oh yes...one final thought. Consider with wisdom of pushing up the braking zone on the turn-in. If you're racing - yes, this makes sense. For lapping, you have to decide how many 10th's you want to run. The consequences of carrying too much speed into the turn are ...well.. pretty bad in all cases. Better to focus on a tad slower in and finding a way to hit your line and really get on that throttle early to get the maximum exit speed. More fun and safer to boot!

Jeff

[Brandon J]

The front piston size for ALL e34s and the e31 single pistons are 60mm. It is stamped on the caliper. The rear of a non 540i or M5 piston is 38mm, and the 540i and M5 have 40mm rear pistons. Thus, most of the front braking increases with upgraded brakes come from the increase in scrub radius. The rear does make a difference if you upgrade to 540i/M5 rear calipers. Of course, if you are talking about heat build-up, the incresed thickness of the upgraded rotors also help.

All else the same, you should only feel a difference in pedal feel with a change in the rear calipers.