piston sizes . calipers.

[Jim Cowden]

Hi.
Im looking at using 4 spot Brembos or AP's.
With duel master cylinders.
Before I start I thought I would ask the question.
(yes I have done a search).

I am looking for some recommended piston sizes for the calipers & masters.

If anyone can help me on this info it would be appreciated.

thanks. Jim C

 

[Gregg]

Jim, I would contact Fran Hall of RCR race cars here on the forum. I believe he may have a set of 4 piston AP calipers for sale. Best Gregg

 

[Jim Rosenthal]

I did some research into this looking for AP calipers for my GT40. The AP calipers used on the Mark V cars are AP 2270s and 2271s, which have four pistons of 1.75" each. They are a large diecast or forged caliper which was used on CanAm and Indy cars from what I am told. They also have stiffening plates, I think, and are a very old design by modern standards- they are cast or forged as one piece and then machined. They are not cheap- about a thousand apiece, but they generate huge clamping force. We could not find any modern equivalent that would fit and mount and function properly, and match up in other respects.

 

[Jim Cowden]

I think I should be a little more specific with my question.
The reason for chasing caliper piston sizes is i have a contact through a Porsche specialist (Brembos).

He can source calipers at an excellent price.
But if they are not suitable then it would not be worth the drama.
Making brackets ect is no problem.

And of course Robert logan does a package which I will check out.

Jim & Gregg thanks for that info.
I have time on my side at the moment so im doing some research before I get to that stage.
Thanks Jim Cowden.

 

[Jim Cowden]

Thinking about it if i get the brembos & piston sizes are not ideal i can vary master cylinder sizes.

 

[Julian West]

FWIW I'm using AP5200 four pot calipers front & rear.

Piston dia is 38.1mm

Front MC is a 0.625 inch

Rear MC is a .7 inch

once the car is road tested I'll fine tune with the balance bar & if required change the MC's.

 

[Howard Jones]

So if you had 34.9mm dia 4pot calipers front and rear what diameter masters would you recomend?

 

[Ross Nicol]

Jim C - Tilton have a formula for this that they supply with their dual pedal box.The formula is used to calculate master cylinder size, which in turn determines pedal pressure. What you need to plug into the formula are
1/ Caliper piston size
2/ Pedal Ratio
3/ Master cyl size
I maintain that there still remains some sujectivity though, as different drivers have varied views on what is and isn't acceptable pedal pressure.I have 3/4" master cylinders with AP 6spot front and AP 4 spot rear. If I want to lower the required pedal pressure for brake lock up I would replace the Master Cylinders for smaller units eg. 5/8". In other words Jim you were right in your previous post.Take the Brembos fit them and work out the required m/c sizes.
Ross

 

[Howard Jones]

Ross, I couldn't fine that formula on the tilton website. Would you mind posting it here?

Thanks HDJ

 

[Ross Nicol]

Howard I'll post it tomorrow I have it at work.

Ross