Comparison of Rear Handbrake Calipers

[Dave Bilyk]

All
I have the standard Granada brakes on my Dax40, and am in the process of upgrading.
In doing so, I wanted to quantify the effect of putting larger brakes on the front, and to compare the available handbrake calipers at the back.
I found the results quite informative so wanted to share. Comments and observations welcome.

My observations are that the Hispec integrated handbrake caliper has a suitable piston area to give a useful improvement over the standard rear brakes;
That the Cosworth option has the smallest pad area (same as the standard Granada), and the Wilwood has the smallest piston area.
While I know that all these are being used successfully, I am just trying to make sure that my non-servo assisted arrangement will work efficiently, so I was being 'picky' about optimising balance, pedal effort and line pressures.
Aside from these few handbrake caliper choices, the world is our oyster if we choose to use a seperate handbrake caliper (or a hydraulic one).

I asked Wilwood (Rally Design) about the possibility of a larger handbrake caliper, and they said that they have been looking into it.
While the Hispec seems ok, I believe that the handbrake only applies pressure on one side, so although the caliper seems appropriate, I am not sure about the efficiency of the handbrake. Does anyone know if this is correct, or how well the handbrake works?

I know that Ian Anderson has a Saab front on the rear his 40, and would be interested to compare if I knew the piston diameter and pad size. Ian?

The caliper data and some bar charts in the attached pdf to avoid a cluttered thread.

Dave

 

[Brett James-McCall]

Dave,
Having read your PDF quickly, you need to update it. The Wilwood Powerlite handbrake caliper has 4 pistons. See the next Fortyfication issue. If you want to know more on the Hi Spec units, there's a guy called Chris who lives near me that has fitted them.

Brett

 

[Ian Anderson]

Dave

I can confirm the car stops well - although hard to quantify as it only has 200 miles on it and also has servos. and a pedal ratio that was almost enough to do without them (we chickened out on the not having themfor the SVA)

The problem I have at the moment is fuelling on EFI with a cam that works very well above 3000 rpm but not under it so a queue of traffic is a kangaroo session that is so vicious that I'm waiting for the gearbox to fall out!

The handbrake is also efficient (after the pads bedded in and cable was adjusted)

I'll see if I can find out what pistons etc the Saab uses

Ian

 

[Dave Bilyk]

Hi Brett, sorry for the confusion, the pdf is correct in that the number of pistons and the piston area is for one side of the caliper. It is done that way because the clamping force is the line pressure times the piston area on one side of the caliper, which makes the calculation the same for a 1 sided sliding caliper, and a normal caliper with pistons on both sides. You are right the Wilwood handbrake caliper is a Powerlite 4 pot. but all is correct in the maths.
I saw your pictures, looks good, is your conversion up and running now?

If Chris has any comments, would be pleased to hear them, esp on the handbrake efficiency if it only operates from one side.

Ian, do you know what Saab Model and year, as I think we can look up the piston size on the Brake Engineering Electronic Catalogue March 2005: Contact Sales on 01978 667800 site. btw I would be careful with your kangaroo, that kind of dynamic loading can induce high stresses in the gearbox shafting so I would fix that quickly if it is as bad as you seem to think.

Dave

 

[Dave Bilyk]

Brett,
I see there are some other typos in that pdf, including cells for piston diameter and inches getting merged into the piston area data.
so I will edit and resubmit that as well tonight.

Dave

 

[Dave Bilyk]

Brett,

apologies for some of the rubbish in the pdf when I copied over from the original spreadsheets. Here is issue 2 with the piston numbers changed, some explanatory notes, pad area inserted in table, and I noticed I had written Superlite instead of Powerlite. No changes to input data or answers which were all as intended.
I think its ok now, but then its always easy to understand ones own, so guys let me know if theres anything that isnt clear.

Dave

 

[Ian Anderson]

Dave

Better than that

Saap Part Number 10 789 4967 and 10 789 4975
Cost was £125.86 plus VAT each in 1991

Cheers
Ian

 

[Dave Bilyk]

Ian,
I ran these numbers past Brake Engineering on the phone, but they could not match the part numbers up. They said that they could maybe match casting numbers.

If you know the car Model and year, their website gives piston diameter.

I doubt that phoning a Saab agent would give the piston diameters, so I havent tried that avenue so far.

Dave

 

[Dave Bilyk]

Ian,
I ran these numbers past Brake Engineering on the phone, but they could not match the part numbers up. They said that they could maybe match casting numbers.

If you know the car Model and year, their website gives piston diameter.

I doubt that phoning a Saab agent would give the piston diameters, so I havent tried that avenue so far.

Dave