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Cost: $4-500
Difficulty: |
BMW E32
535i with Wilwood calliper and 850 rotors
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The BMW E34 brakes fast... But I
wanted something unique for the race car, and something cheap,
so I developed some brackets so I could use some cheap used
wilwood 4 pistons calipers.
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I am working on a set of brackets to
install wilwood type calipers 4 pistons on the front of the
car.
Front rotor size will be: 324x30. The rotor size
334x32 will need different brackets and might not fit all the
17" rims.
Rear rotors size will be: 328x20, but I have some
issues locating the caliper.
Front setup:Rotors: OEM BMW 324x30 p/n:
34-11-6-756-087 (21.5lb) or 34-11-1-159-895 (22.9lb)
Calipers: Wilwood Superlite
1.75" pistons will create a tad more braking power.
Other
calipers will work as long as they have the same pad location
and mounting points.
Bracket: Racingking.ca design,
steel.
Calculations: Piston area= 2Ap for
single piston and 4Ap for 4 pistonsMaster cylinder
diameter = 25mm
The target is a brake ratio of 70:30
| Ft Piston diam |
Piston Area |
Rr Piston diam |
Piston area |
Brake Ratio |
| 1x60mm (850i) |
5,655 sqmm |
1x40mm (M5) |
2,513 sqmm |
69 : 31 |
| 1.75" wilwood x4 |
6,207 sqmm |
1.38" wilwood x4 |
3,848 sqmm |
61 : 38 |
| 1.62" wilwood x4 |
5,319 sqmm |
1.00" wilwood x4 |
2,027 sqmm |
68 : 32 |
| 1.75" x2 - 1.62" x2 |
5,763 sqmm |
1.12" wilwood x4 |
2,533 sqmm |
69.5 : 30.5 |
| Corvette 2x40mm |
5,027 sqmm |
Corvette 1x1.75" |
3,104 sqmm |
62 : 38 |
Finding the right caliper piston
size:1- A bigger master cylinder means less pressure, and
therefore higher pedal effort.
2- A bigger master cylinder
means less pedal movement.
3- Sliding calipers act like
they have twice their actual piston area.
4- Bigger pistons
in the calipers mean more force and, therefore, less pedal
effort.
5- Bigger pistons in the calipers mean more pedal
movement.
6- Bigger rotors generate more brake torque,
which makes the pedal effort feel lighter without affecting
pedal travel.
Calculations:Area: PI x
Radius^2
Master cylinder stroke= Caliper piston
stroke/(Master Area/Caliper piston area)
The E34 and
upgraded E28/E24 have a 25mm master cylinder, the idea is to
keep the stock master cylinder (at least on the E34 and
upgrade to the E32 one for the E28/E24)
My setup right
now is 1.38" pistons at the front and 40mm 540i calipers for
the rear, the brake pedal feel is same as stock 635csi
brakes.
I still want to install some 4 pot calipers at the
back, and will try different front piston diameter calipers to
get a similar pedal feel.
Brake booster for the E28 and
E24:If you have a 535i E28 or a 635csi, and like me you
are tired of the old brake booster setup with the brake bomb,
the valve and the hydraulic booster, you can replace all that
with the following:
- Brake booster from an E34 525i Wagon
(with master cylinder, vacuum hose and reservoir)
- Power
steering hoses, power steering cooler and reservoir from an
E34 535i.
I decided to install the power steering
cooler considering that the volume of ATF in the system is
greatly reduced compared to the old system.
The brake lines
going to the ABS pump need to be bent down a little bit to
make enough room for the new brake booster.
So far the
brakes are running great with this new setup but I need to
test them more on the race
track. |
(Thanks to )  |
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