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

[Steve]

Compare the pad size of a 914-4 rear caliper to a 914-6 rear caliper. Not much of a difference. For me the 914-6 rear caliper is not worth the money. I used to have 911S aluminum front calipers and 914-6 rear calipers. I am now running Boxster brakes front and rear with a 911 parking brake. Much better braking for the money.

[zoomCat]

Compare the pad size of a 914-4 rear caliper to a 914-6 rear caliper. Not much of a difference. For me the 914-6 rear caliper is not worth the money. I used to have 911S aluminum front calipers and 914-6 rear calipers. I am now running Boxster brakes front and rear with a 911 parking brake. Much better braking for the money.

The /6 rear calipers have about 30% less more piston area than the /4, which results in a similar reduction increase in clamping force and braking effort. Most braking is done by the fronts, so it may not be noticeable in most situations. Porsche did a pretty good job balancing brake components, care should be taken when changing out individual bits. The 911 could be a good match for the /6 rears, and the Boxster stuff should balance appropriately since they were designed for a similar weight distribution. Big honking front calipers and stock /4 rears will be somewhat unbalanced, particularly on cold, wet pavement.

And then there’s the pressure regulator, but that’s another story.

[Superhawk996]

Compare the pad size of a 914-4 rear caliper to a 914-6 rear caliper. Not much of a difference. For me the 914-6 rear caliper is not worth the money. I used to have 911S aluminum front calipers and 914-6 rear calipers. I am now running Boxster brakes front and rear with a 911 parking brake. Much better braking for the money.

The /6 rear calipers have about 30% less piston area, which results in a similar reduction in clamping force and braking effort. Most braking is done by the fronts, so it may not be noticeable in most situations. Porsche did a pretty good job balancing brake components, care should be taken when changing out individual bits. The 911 could be a good match for the /6 rears, and the Boxster stuff should balance appropriately since they were designed for a similar weight distribution. Big honking front calipers and stock /4 rears will be somewhat unbalanced, particularly on cold, wet pavement.

And then there’s the pressure regulator, but that’s another story.

Not sure what you’re comparing to.

914/6 has larger rear pistons - 38mm vs 33mm on /4

914/6 has more rear lining area 106 cm^2 vs 80 cm^2 for /4

[zoomCat]

Compare the pad size of a 914-4 rear caliper to a 914-6 rear caliper. Not much of a difference. For me the 914-6 rear caliper is not worth the money. I used to have 911S aluminum front calipers and 914-6 rear calipers. I am now running Boxster brakes front and rear with a 911 parking brake. Much better braking for the money.

The /6 rear calipers have about 30% less piston area, which results in a similar reduction in clamping force and braking effort. Most braking is done by the fronts, so it may not be noticeable in most situations. Porsche did a pretty good job balancing brake components, care should be taken when changing out individual bits. The 911 could be a good match for the /6 rears, and the Boxster stuff should balance appropriately since they were designed for a similar weight distribution. Big honking front calipers and stock /4 rears will be somewhat unbalanced, particularly on cold, wet pavement.

And then there’s the pressure regulator, but that’s another story.

Not sure what you’re comparing to.

914/6 has larger rear pistons - 38mm vs 33mm on /4

914/6 has more rear lining area 106 cm^2 vs 80 cm^2 for /4

Sorry, I misspoke and got that backwards. The /6 has roughly 32% more piston area in the rear than the /4 (14.4 cm sq vs 10.9 cm sq)

[mepstein]

Compare the pad size of a 914-4 rear caliper to a 914-6 rear caliper. Not much of a difference. For me the 914-6 rear caliper is not worth the money. I used to have 911S aluminum front calipers and 914-6 rear calipers. I am now running Boxster brakes front and rear with a 911 parking brake. Much better braking for the money.

The /6 rear calipers have about 30% less piston area, which results in a similar reduction in clamping force and braking effort. Most braking is done by the fronts, so it may not be noticeable in most situations. Porsche did a pretty good job balancing brake components, care should be taken when changing out individual bits. The 911 could be a good match for the /6 rears, and the Boxster stuff should balance appropriately since they were designed for a similar weight distribution. Big honking front calipers and stock /4 rears will be somewhat unbalanced, particularly on cold, wet pavement.

And then there’s the pressure regulator, but that’s another story.

Not sure what you’re comparing to.

914/6 has larger rear pistons - 38mm vs 33mm on /4

914/6 has more rear lining area 106 cm^2 vs 80 cm^2 for /4

Sorry, I misspoke and got that backwards. The /6 has roughly 32% more piston area in the rear than the /4 (14.4 cm sq vs 10.9 cm sq)

Yes. 914-6 rear calipers are basically an M caliper with a handbrake.