4 to 6 conversion: rear brakes Options

[bossboy302]

Collecting the bits for my project, (4 to 6) rear brake question...
Are the rear 4 rotors the same thickness as 6?
If so, can the 4 rear calipers (with their parking brake) be used?
I am doing the 5-lug.

Thanks in advance

[Chris914n6]

Rear rotor centers from the backside on the outer edge of the hub. There is a bit of rotational play but once the wheel is torqued down nothing moves. Not an issue.

The -6 vs -4 rotor diameter is 3mm diameter, or 1.5mm radius. Someone anal made the claim that it needs machined and it's been parroted since. Plenty of clearance on the -4 caliper for a -6 rotor.

-6 rotor securing bolts (available at Lowes etc) don't line up with -4 hubs.

[mepstein]

Rear rotor centers from the backside on the outer edge of the hub. There is a bit of rotational play but once the wheel is torqued down nothing moves. Not an issue.

The -6 vs -4 rotor diameter is 3mm diameter, or 1.5mm radius. Someone anal made the claim that it needs machined and it's been parroted since. Plenty of clearance on the -4 caliper for a -6 rotor.

-6 rotor securing bolts (available at Lowes etc) don't line up with -4 hubs.

Chris - I wish it was true that it always fit but that wasn’t the case for mine. It locked up until I asked my local mechanic to take off a couple mm. One he did, the rotor spun fine. So now I recommend people turn it down right off the bat.

Steve - you are really buying the six calipers for the bigger pistons to match the fronts. M calipers have small pads so they don’t last as long as later, larger calipers, but it’s the pistons that are doing the stopping. Once upon a time, six calipers weren’t so much money and since they were a bolt on upgrade, the swap made sense. Boxster calipers are great but by the time you buy the adaptors, calipers, 911 ebrakes and all the hardware, it’s not an inexpensive upgrade either.

But it’s good we have options.