Newbie ?: Why does BMW use a single piston brake?

[mpardun]

I apologize if this has been asked and answered...

I am far from an expert, but with all serious road and race cars using 4-6 piston brakes. It stands to reason that using a 1 piston brake setup may make sense for a mainstream production vehicle, but why would BMW choose a 1 piston option for it's supposed performance car?

Please something aside from cost (as all other German makers I am familiar with use multi-piston brakes).

Just curious...as I await my 2011 build and contemplate aftermarket wishlists.

[elh0102]

Well, cost is probably the biggest reason, like it or not. But, I wouldn't worry about it. Folks get too concerned about the number of pistons, but the quality and stiffness of the caliper is more important. The stopping effectiveness is mostly dependent on the rotor and pad sizes (swept area). And the fade resistence is mostly the determined by cooling, which is very related to the internal design of the rotor, as well as additional cooling ducts. Under extreme conditions, as in racing, multiple pistons should produce more evenly distributed pad pressure, resulting in less pad taper and probably longer dependable performance before fading. But with appropriate pads and fluid, the stock M3 brakes are very good, even for casual track use.

[rob612]

Originally Posted by elh0102

Well, cost is probably the biggest reason, like it or not. But, I wouldn't worry about it. Folks get too concerned about the number of pistons, but the quality and stiffness of the caliper is more important. The stopping effectiveness is mostly dependent on the rotor and pad sizes (swept area). And the fade resistence is mostly the determined by cooling, which is very related to the internal design of the rotor, as well as additional cooling ducts. Under extreme conditions, as in racing, multiple pistons should produce more evenly distributed pad pressure, resulting in less pad taper and probably longer dependable performance before fading. But with appropriate pads and fluid, the stock M3 brakes are very good, even for casual track use.

VERY well said!

[JCtx]

Only reason is cost; What else? They're not better than multi-piston calipers. And not nearly as sexy either . But they're 100% effective on the street. And somewhat effective on the track. And yes, better pads and fluid help with the latter.

[AP Racing - Chris_B]

Originally Posted by mpardun

I apologize if this has been asked and answered...

I am far from an expert, but with all serious road and race cars using 4-6 piston brakes. It stands to reason that using a 1 piston brake setup may make sense for a mainstream production vehicle, but why would BMW choose a 1 piston option for it's supposed performance car?

Please something aside from cost (as all other German makers I am familiar with use multi-piston brakes).

Just curious...as I await my 2011 build and contemplate aftermarket wishlists.

Like others have already said, it's the cost. I will say that Ate (Continental) makes about the stiffest and best sliding caliper production brakes you will find. In some cases, I prefer them to the low cost, OE-style fixed calipers like those found on many "value proposition" sportier cars. However, as good as they are compared to other sliders, they still do not compare to well-engineered multiple piston fixed calipers. All BMW Motorsport vehicles that I've seen come from the factory with fixed calipers (AP Racing).

Chris

[swamp2]

Originally Posted by elh0102

Well, cost is probably the biggest reason, like it or not. But, I wouldn't worry about it. Folks get too concerned about the number of pistons, but the quality and stiffness of the caliper is more important. The stopping effectiveness is mostly dependent on the rotor and pad sizes (swept area). And the fade resistence is mostly the determined by cooling, which is very related to the internal design of the rotor, as well as additional cooling ducts. Under extreme conditions, as in racing, multiple pistons should produce more evenly distributed pad pressure, resulting in less pad taper and probably longer dependable performance before fading. But with appropriate pads and fluid, the stock M3 brakes are very good, even for casual track use.

+2, very well said. I've posted similar comments over and over in many brake threads.

[AP Racing - Chris_B]

Originally Posted by swamp2

+2, very well said. I've posted similar comments over and over in many brake threads.

I also agree with much of elh1002's comments, IF one does not factor into the equation brake feel and driver confidence. Many drivers who like to experience the M3 for all that it is worth cannot easily do that. At the level the M3 represents, many drivers expect more from their brakes, regardless if the OE sliders can be band-aided to handle a bit more temperature or what the one-time panic 60-0 stopping distance is. Pads, tires, springs, dampers and their respective tuning can be worked in synergy to shorten stopping distances, if the driver is only concerned about numbers. If so, then the OE brakes are fine for many.

However, those that have really driven high-performance brake systems are typically not fully satisfied with BMW's selection due to its lack of feel and feedback at the limit of tire adhesion. For them, it is all about control. It is for those drivers that there are other choices out there, whether they seriously track the car or not.

Chris

[rzm3]

Well, we can soon say good bye to the sliders on M3 as the next gen M cars should all have fixed and multi piston calipers (as shown on the new M5 spy shots)

[jml]

Originally Posted by rldzhao

Well, we can soon say good bye to the sliders on M3 as the next gen M cars should all have fixed and multi piston calipers (as shown on the new M5 spy shots)

Gauging by the recent trends at ///M (turbos, 5000lb+ cars), that does not indicate better performance. Pretty, yes...