6 vs 4 caliper piston area

[vette427sbc]

Why is it that most 6 piston calipers have a smaller piston area? The wilwood SL6 calipers have a 4.04 sq inch area and the SL4's have a 5.18 sq inch area. Does more surface area always mean more clamping force? It seems like this caliper would have far less area than say the SL4's, yet these are supposed to be a big upgrade. http://www.vividracing.com/catalog/...iston-caliper-chevrolet-corvette-p-93758.html
The calipers Im looking at are Porsche 955 (cayenne) front and rear calipers (monoblocks ) The fronts use 30/34/38mm pistons equaling a total of 2750mm^2 or 4.26in^2
Would/could this be fixed or remedied by using a different size master cylinder?
Im still a brake system noob so forgive me... I cant seem to find any decent reading material about this kind of stuff online

 

[Twin_Turbo]

The more pistons do ahve a smaller area but the smaller bores make for a stiffer caliper. Also, a differential bore setup has a much more uniform pad&rotor temperature profile over the contact area when compared to a typical 4 piston.

Most people buy the 6,8 or even more piston calipers because it looks cool.

What would need fixing on the brembos?

 

[vette427sbc]

I guess I worded that a little funny... I havent found a specific set yet. By "fixing", I was referring to the less piston area and clamping force possibly being less than ideal, and changing that by using a different bore master cylinder (is that possible? And is piston area directly related to clamping force?) Aside from being lighter, stronger, and less prone to heating up would these calipers have better or at least equal clamping force as the stock calipers?

I have to admit, one of the reasons I want to use these calipers is because they are big 6 pots (what car doesnt look bad ass with some big red brembos behind the wheels). But more so because you can find these CHEAP (for a brembo caliper) - They are also used on Volkswagen Touaregs and Audi Q7s but arent painted and dont look like anything special to the local pick-a-part guy. Plus, I like to keep myself busy at school with some engineering projects on the side.

 

[BBShark]

What would you use for rear calipers? If you use the stock Corvette rears you will have problems. Most cars, if not all, have a smaller rear piston diameter than the front. Keeping the stock rear will reverse this. I think that is why some people who use C5 calipers on the front only, reverse the lines to the master.

Also, are you going to use the stock front rotor?

 

[vette427sbc]

Im planning on using the front and rear Porsche calipers; and some kind of mechanical spot caliper for the parking brake.
I really want to use the Wilwood 12 bolt hats and 13" rotors, but it looks like the brake pads are too tall to fit on a 13" rotor with such a large hat. I may end up using a Mercedes or BMW rotor. I did a test fit out of cardboard and it looks like these monster calipers will just fit in my TT2 wheels on a 13 inch rotor.

BBShark: Is it you that made the Brembo and MB rotor setup for your car? Thats my main inspiration for designing a BBK myself

 

[BBShark]

BBShark: Is it you that made the Brembo and MB rotor setup for your car? Thats my main inspiration for designing a BBK myself

Yes, I did the Brembo setup and the biggest challenge was the rear caliper. The offset trailing arms I have really limit the amount of room you have to mount the calipers and I am using radial mount Brembo.

Are the rear calipers you are using radial or lug mount?

REAR (back):



REAR (front):

 

[vette427sbc]

Very cool :thumbs:
The calipers are lug mount. What model MB are the rotors from? S500?

 

[BBShark]

That's the catch. In order to fit the caliper and spot brake, I had to use a rotor that is bigger than the S500 (on the rear). I used a CL600 front rotor on the rear, 345mm.

 

[vette427sbc]

Ill have to get creative with my parking brake then since I only plan on running a 330mm rotor on the rear so I can fit inside my 17" wheels.

 

[mrvette]

Ill have to get creative with my parking brake then since I only plan on running a 330mm rotor on the rear so I can fit inside my 17" wheels.

:harhar: What you going to do? drag a 2x4 over top of the tires??:trumpet::yahoo::bonkers:

 

[vette427sbc]

Just an update....
I found a set of rear calipers for $190 :bounce: Picking them up Tuesday. Im going to try to use 12.8"x1.1" wilwood GT rotors on the rear with the 12 bolt aluminum hats. Its going to be really tight trying to fit a spot caliper in there as well, but I'll see what I can work out.
Fronts will be tight as well with 13.1" rotors and the massive 6 pot front calipers inside my TT2's. Still on the hunt for those though... Im trying to have all 4 calipers for under $450.
Any objections using the wilwood hats and GT rotors? Is there a cheaper alternative? (Id like to stay with a 2 piece) Its going to be over $1300 for the rotors and hats on summit racing.

 

[BBShark]

You probably won't find any two piece rotors for less than the Wilwoods. Have you looked at the iron hats they have to solve your parking caliper issue?

What is the inside diameter of the 17" TT2's?

 

[vette427sbc]

Yeah I saw the iron parking brake hats... I will probably end up using those, but Im going to try to see if I can fit the spot caliper anyway. I was going to print out a 3D model of the spot caliper to check for fitment (or lack of).
I dont remember what I got for an inside diameter for the TT2's, but I did a rough cardboard mock-up of a 13" rotor with the front caliper and it looks like it will fit. The spokes look like they will be the area of most concern. Im hoping the 2" offset hats will be enough.

 

[BBShark]

Yeah I saw the iron parking brake hats... I will probably end up using those, but Im going to try to see if I can fit the spot caliper anyway. I was going to print out a 3D model of the spot caliper to check for fitment (or lack of).
I dont remember what I got for an inside diameter for the TT2's, but I did a rough cardboard mock-up of a 13" rotor with the front caliper and it looks like it will fit. The spokes look like they will be the area of most concern. Im hoping the 2" offset hats will be enough.

I may have a layout of the setup I did. I'll see if I can find it.

 

[BBShark]

Here is a layout of a 345mm rear rotor (black line) with an offset trailing arm in position. You can see there is limited room above the arm for the caliper and park brake. Something I considered is mounting the caliper on the bottom half of the rotor and the park brake up top.

 

[vette427sbc]

Thanks for the drawing... I like the idea of mounting on the lower half of the rotor. Any reason you wouldnt leave the caliper in the stock location and put the parking brake on the bottom?

 

[BBShark]

Thanks for the drawing... I like the idea of mounting on the lower half of the rotor. Any reason you wouldnt leave the caliper in the stock location and put the parking brake on the bottom?

If I put the park caliper on the bottom I would have to route the cable through a pulley at an angle. The top was a straight shot. Also the park caliper floats on pins so I didn't want the cable to bias the caliper in either direction.

 

[vette427sbc]

Thanks for the drawing... I like the idea of mounting on the lower half of the rotor. Any reason you wouldnt leave the caliper in the stock location and put the parking brake on the bottom?

If I put the park caliper on the bottom I would have to route the cable through a pulley at an angle. The top was a straight shot. Also the park caliper floats on pins so I didn't want the cable to bias the caliper in either direction.

Is that the brembo/viper spot caliper you used? That one looks fairly big compared to the other spot calipers available. I was looking at using something like the wilwood, HiSpec, or some other company that makes them for panteras. HiSpec seems to be the cheapest out of all of them (wilwoods would have to be modified since they dont accept 1.1" wide disks.) The Mr. Parker by revolution brake is right up there with the brembo/viper and the pantera price wise. It looks like HiSpec doesnt do anything in the US either, so I may see what wilwood thinks about machining a spacer to put inbetween the two halfs.

Heres the Mr. Parker:

HiSpec SVA:

And the Ipsco Pantera:

Also... I picked up the calipers this morning. They are feather-weights compared to the stockers. Couldnt weigh more than 7lbs each.