Multi-piston calipers!

[Wosby]

Con someone tell me why BMW doesn't offer multi-piston calipers on any of it's vehicles? Manufacturers like MB offer them as standard equipment on their AMG vehicles. ALL Porsches come with mulit-piston calipers. Nissan provides Brembo as an option. Do they have so much confidence in their single piston setup, that they dont feel it's necessary?

Wosby

[Wosby]

How come no one wants to touch this topic?

[Gary@Tirerack]

Perhaps it is because no one has a good answer to this question. I have heard that more pistons doesn't always equal more clamping force, so perhaps BMW is able to get what they want/need without resorting to more pistons. I've always been happy with the brakes on my 10+ yr old BMW, even compared to newer cars by other makes you've mentioned above.

[Wosby]

Perhaps it is because no one has a good answer to this question. I have heard that more pistons doesn't always equal more clamping force, so perhaps BMW is able to get what they want/need without resorting to more pistons. I've always been happy with the brakes on my 10+ yr old BMW, even compared to newer cars by other makes you've mentioned above.

I've also heard that more pistons dont necessarily equal more clamping force. But with mulitple pistons you get more evenly distributed force over a larger area, allowing you to use a larger pad, and a larger rotor, which should equal a larger heat sink with less fade. Dont you think?

[fuz]

Also increases weight, complexity, and price for only a marginal (if any) gain in performance.

A larger brake would cover up the venting in the brake disk, reducing cooling.

A larger brake surface also requires a lot more force to use, since you have to clamp just as hard, but over more area. A standard hydrauic system may not be able to exert the force needed to react fast. You suddenly have to rebuild and add more hardware to support this increased load.

Of course you could use multiple pistons on the same sized brake, but there seems little point in that.

For a sporting car, brake performance is important, but it needs to be considered with the trade-offs as well. The last thing you want to add wieght to is the dynamic wheel structure, decreasing the adaptability of the suspension.

[Brembo_RaceTech]

My first answer would have simply been price.

My second answer has to do with the fact that BMW has always had good results with the brake systems they currently use. This also becomes a factor that keeps them from wanting to change. While there can be major improvements in performance, the additional cost may not be worth the increase in performance that they would gain on an OEM platform.

[Brembo_RaceTech]

Also increases weight, complexity, and price for only a marginal (if any) gain in performance.

I don't know if I completely agree with that.
In most cases an aluminum, opposed piston caliper is lighter than a typical single piston sliding caliper.

Again, price is an issue, but if the time, cost and effort were directed towards designing a proper opposed piston system the performance would be considerable.

A larger brake would cover up the venting in the brake disk, reducing cooling.
Again, this is not really a factor since the cooling or venting of the disc comes from the center of the disc and out the top. The caliper will also be designed properly as to not inhibit the airflow from exiting the disc.

A larger brake surface also requires a lot more force to use, since you have to clamp just as hard, but over more area. A standard hydraulic system may not be able to exert the force needed to react fast. You suddenly have to rebuild and add more hardware to support this increased load.

Of course you could use multiple pistons on the same sized brake, but there seems little point in that.

For a sporting car, brake performance is important, but it needs to be considered with the trade-offs as well. The last thing you want to add weight to is the dynamic wheel structure, decreasing the adaptability of the suspension.

All of these are good concerns if we were talking about an amateur company wanting to design an aftermarket brake system to replace an OEM sliding caliper.
Fortunately there is allot of technology available for use during the design and development of an OEM brake system, opposed piston or not.
Allot of the issues you mentioned above are completely elementary and the simple mistakes that would cause these types of problems are not even a concern. Companies like Porsche and Ferrari fit their entire production line with multi piston opposed calipers. MBZ also does on their higher end AMG models. The fact that these types of systems are more typically found on the "cream of the crop" also leads us to believe that it's more of a cost issue than anything else.

Some automobile manufactures are more notorious that others for having inherient problems with brakes. Since BMW is not one of them I am not suprised that we have yet to see them introduce an opposed piston. It may come with time, but I would have to guess that there thinking right now is along the lines of "if it aint broke..."

While as enthusiasts, we know that it is possible to exceed the limits of any OEM brake systems, we are still a small percentage of the buyers market. Luckily we have lots of options for upgrades once we do pass the limits of what BMW provides as factory on their vehicles.

(my signature will serve as the smaless plug for the upgrades I mentioned)
=-)

[wolf6292]

four pots on the front and two pots in the rear of my 07 wrx has an amazing stopping power heat exchange is not really a factor or the weight. Willword, Brembo, Stoptech are good company's that are lighter, bigger pots and also can increase the number of pots. Also you can go slotted which help dissipate the heat. Most of the time it is a fitting issue as in bigger rims.

[Scany1980]

Check out the new 135i's brakes. There's multipiston for you. Remember though, everything is for a reason, though you might not know it yet :)