WOAH!!! HPA 4 Piston calipers

[chachacha28]

http://hpashop.com/HPA-BMW-Brembo-4-...ke-Upgrade.htm

anybody know anything about these? It says they will work on E8x/E9x. what size rotor (dia. and thickness) will these run? Any word on how long pad development will take, or what the options will be? What is the weight of our stock caliper (the 5lb savings is compared to the E9x single pistons)

Hopefully HPA chimes in here, this looks great (if pricey)!

[Focusedintntions]

Look nice, but I've never seen anybody post anything on here about them.

[MilehighM3]

They won't fit a 135 unless you buy 1M/E9x M3 steering knuckles. Our calipers bolt on differently than those do. So they will only fit non 135 E8x vehicles.

[chachacha28]

boo. oh well, saves me a few pennies.

[ZIPNBYE]

They're using a BMW caliper, and yet the 135i already uses a 6-piston caliper... Upgrade for a 128i perhaps...

[Zeros and ones]

not to sure about this.... Looks promising but I think for everything the price is a bit high. Why wouldn't I want to get the BMW Performance BBK for my car at $1485?

[Focusedintntions]

B/c for people that track their cars on a regular basis this is a better caliper and will take the heat better. If you search on this section of the forum you'll find that there are a lot of us that have destroy piston tops and melted seals on the bmw bbk. It's great aesthetically, but not designed for serious abuse of a track.

[MilehighM3]

Not to mention the BMWP kit for the F30 is 370mm. That's way bigger than a 135 kit. Even stock E90 335 rotors are larger in diameter than our 135s are.

[pixelblue]

this is all true but don't forget the pads on our brembos are huge compared to the 1M/M3 pads and in my opinion it makes for stronger stops minus the heat dissipation issues for for our smaller rotors

[robert @ eas]

Pixelblue is correct -the pad area is considerably larger on the E8x 135



Below is comparison showing both max pad area along with measured pad/ rotor
contact area with new pad (w/ consideration for chamfers in the pad face);
Rotor contact area will increase with wear on all three but at slightly
different rates based on chamfer geometry.



E8X 135i * - * Max area 87.1 cm2 ; rotor contact-67.3 cm2

F30 335i * - Max area 67.9 cm2; rotor contact 46.9 cm2

E9x 335i/M3 & E8x 1M - Max area 56.6 cm2; rotor contact 44.7 cm2

[GaryS]

Bigger caliper piston surface area increases clamping power so it increases torque, and bigger rotor diameter increases leverage against the axle so it increases torque. I'm guessing that in this case the difference in piston surface area is more than the difference in rotor diameter.

[MilehighM3]

Originally Posted by robert @ eas

Pixelblue is correct -the pad area is considerably larger on the E8x 135



Below is comparison showing both max pad area along with measured pad/ rotor
contact area with new pad (w/ consideration for chamfers in the pad face);
Rotor contact area will increase with wear on all three but at slightly
different rates based on chamfer geometry.



E8X 135i * - * Max area 87.1 cm2 ; rotor contact-67.3 cm2

F30 335i * - Max area 67.9 cm2; rotor contact 46.9 cm2

E9x 335i/M3 & E8x 1M - Max area 56.6 cm2; rotor contact 44.7 cm2

Yet an E9x M3 stops considerably better than a 135. Anyone who has driven both cars on the street, especially on a track will agree there. I'd love to swap M brakes on to my 135. The rotor diameter makes a huge difference in stopping leverage on the M. Plus the 135 brakes get so damn hot!