StopTech E39 4-Wheel brake kit details - The Unofficial BMW M5 Messageboard (m5board.com)

DZeckhausen · 1st February 2003, 06:41

I know a bunch of you have expressed interest in a 4-wheel kit for your E39 M5 and I promised to provide details as soon as I found out. I received the details this evening from StopTech.

StopTech plans to have their 4-wheel kit finished in the middle of this month. I don't have an exact ship date yet, but I do have part numbers and prices up on my web site.

The good news is that pricing will be a relatively low $4995 for the complete kit which consists of 4-piston calipers and 355mm rotors at all four corners of the car, plus stainless braided Teflon lines. The parking brake will function exactly the same as it does now, with the rear rotor hats doubling as drums for the parking brake. This is how the Mov'it rear system works on my wife's 2001 540i/6; however, installation will be vastly simpler since the larger rotor will move the caliper away from critical components and grinding of aluminum mounting ears and lower control arm won't be required. Except for some possible trimming of the backing plate, this installation may be no harder than swapping your rear rotors and replacing a brake line. I'll let you know after I've installed the first one.

Extensive grinding will not be required as it was for the Mov'it system

For those of you who already have front kits and would like to add a rear kit, you will need to replace your front calipers first. This could not be avoided because the massive 355mm rear rotors, combined with the smallest piston sized calipers currently available to StopTech, still generated substantially more brake torque than the stock rear brakes. If you were to add the rear kit to your existing StopTech front set-up or to your stock brakes, the result would be unacceptabe rear bias and the car would not be stable under braking with ABS turned off. With ABS turned on, the result would be longer braking distances. Thus, StopTech needed to switch to front calipers with bigger pistons to compensate for the more powerful rear brakes and maintain an optimum balance for stable braking and shortest possible stopping distance.

If you have a front kit and plan to switch to a 4-wheel kit, your easiest solution may be to sell your existing front kit and buy the new 4-wheel kit. If you did this, you could take the new front brackets, rotors, pads, and lines out of the 4-wheel kit and combine them with your old calipers to make it more atttractive to a potential buyer. Essentially they would be getting a new kit, but with old calipers. That's just an idea. Alternatively, you could order just the rear kit plus two new front calipers, but then you're stuck with your old calipers.

If you have any questions about this kit that I haven't answered, feel free to call me or, even better, post your questions here. If you have a question, the odds are good that other people have the same question. I'll do my best to answer them.

tfung · 1st February 2003, 06:57

hey Dave,
we discussed briefly over email about the new Brembo rear brake kit.. would there be a problem with that and require a front caliper change like the stoptech ones?

DZeckhausen · 1st February 2003, 07:16

Quote:

Originally posted by tfung
hey Dave,
we discussed briefly over email about the new Brembo rear brake kit.. would there be a problem with that and require a front caliper change like the stoptech ones?

No. Unlike the StopTech front kit, which closely matches the stock brake torque, the Brembo front kit is heavily front biased. The new Brembo rear kit, which is expected at the end of February, will use a new 345mm rotor and a new caliper. (These new parts are what is holding up release of the Brembo kit.)

I don't yet know what the piston sizes are for this new Brembo caliper, but I am fairly certain it will generate more brake torque than the stock rear brakes. Unless Brembo overdoes the rear brake torque, which I don't expect, the new rear kit should help provide better balance than the front kit alone. We'll know more in about a month, at which time I'll provide more details.

These are the same new parts we are eagerly awaiting to provide some balance to the BMW X5 8-piston kit that was recently released.

tfung · 1st February 2003, 07:48

that's good to hear.... I'm suprised that no-one has wanted to put the 380mm kit on a M5 yet... :p

DZeckhausen · 1st February 2003, 08:09

Quote:

Originally posted by tfung
that's good to hear.... I'm suprised that no-one has wanted to put the 380mm kit on a M5 yet... :p

That's what Apples has on his Nowak M5. He has the Mov'it 380mm front kit and the Mov'it 322mm rear kit.

In the meantime, I'm thinking it might be time for me to switch from the current 4-wheel Mov'it system to the 4-wheel StopTech system. It will work with my Style 66M summer wheels, but it won't even come close to working with my 17" Style 71 winter wheels. I suppose I could sell the wheels and my Mov'it kit to make up some of the difference.

Anyone want a 4-wheel Mov'it kit? And no, I'm NOT going to install the rear brakes for you!!! You can follow the instructions on my web site. After doing that installation twice, I vowed never again.

I'll also have a set of these wheels for sale with snows:

Style 71

They fit over the 322mm Mov'it brakes without spacers but they won't clear the StopTech, Brembo, or M5 brakes.

leederek · 1st February 2003, 19:45

Dave,

Is there performance data for the Front kit vs. 4 wheel kit? I'm debating the next upgrade was leaning towards a quaiffe differential when you posted the 4 wheel info.

Paul S · 1st February 2003, 21:25

is this more show than go? (or stop..

)
the front stoptech setup works extremely well, on the track i've been out for 4 hours in one day in 100+ temp and experienced no fade and short stopping distances. and i hammer the brakes!
will i notice any improvement?

i can't imagine anyone but a racer needing anything more.

TriflowM5+M3 · 1st February 2003, 22:14

Just when I thought I had all my M5 spending thought out...here comes something new. Now I dont know if the rear brakes are going to help greatly for street driving but they certainly would look hot under my new rims

Need4Spd · 2nd February 2003, 00:36

I'm sure the STOCK brakes are fine for street driving, and even if you track the car, I'd bet the stock rears are ok, too, but it sure looks cool to have a matching set of super calipers.

DZeckhausen · 2nd February 2003, 02:40

Quote:

Originally posted by germansedanfan
is this more show than go? (or stop.. )
the front stoptech setup works extremely well, on the track i've been out for 4 hours in one day in 100+ temp and experienced no fade and short stopping distances. and i hammer the brakes!
will i notice any improvement? i can't imagine anyone but a racer needing anything more.

To answer leederek's and Germansedanfan's questions and to affirm TriflowM5's comment, I would have to say this rear upgrade is mostly cosmetic. Having gone through a similar upgrade process with the front and then, several months later, the rear Mov'it brake kits, I can do a good job of setting your expectations.

If you've been running the StopTech front brakes on your E39 and have had no problems with rear pad fade or soft pedal due to boiling of fluid in the rear calipers, this upgrade will not make much of a difference for you at the track. You will feel a slightly firmer, and taller brake pedal because you'll have eliminated another pair of heavy, iron, floating calipers which are nowhere near as stiff as the StopTechs. That will make heel/toe shifts slightly easier, but most of the gains in this department have been achieved already with the front brake upgrade.

Your rear rotor temperature will probably be several hundred degrees lower at the track, making fluid fade a non issue and pad life longer. If you've been running Pagid blacks in the rear, you could probably switch to Pagid Orange.

The balance will be virtually identical to the front-only kit, since StopTech is using DIFFERENT front calipers with the 4-wheel kit to balance the higher rear brake torque. However, since the overall brake torque (front and rear) will be higher, you will notice more mechanical advantage (less pedal effort for a given amount of braking) and may find it easier to modulate the brakes at higher speeds.

Changing the front calipers to larger pistons will result in slightly longer pedal throw. However, this may be offset by the ultra-stiff, StopTech rear caliper, to the point that pedal travel may be the same or even less than it was before. When I installed the rear Mov'it system, the total effective piston area was greater than the stock rear brakes, yet pedal travel was reduced slightly. This seemingly contradictory effect is due to the 4-piston caliper not being as flexible and the pads themselves not flexing because of the more even distribution of pressure from all those pistons.

Finally, you will be able to use the same pads at all four corners of the car, so swapping track pads for street pads is as simple as removing two retaining screws, popping off the bridge, and yanking out the old pads. This is simpler and faster than removing the entire caliper, which is what is requred to change pads on the stock M5 rear brakes. And you don't have to worry about finding a brake pad manufacturer who makes a specific compound to match the front StopTech and rear M5 calipers because all four corners will use the same pad. (It's a Porsche 993TT rear pad, by the way.)

The bottom line is that you will be able to get by without the rear brake upgrade if your primary goal is to go fast on the track. If you've got a limited track budget, your "go fast" money would be better spent on a Stage III suspension or, if you've got a 540i, a Quaiffe limited slip differential. But if, like me, you are doing it because you like the way it feels and the way it looks (and in my case, because I wanted the adventure of installing it) then this is a pretty neat upgrade.