Ken,
Well cut my legs off and call me Shorty! That throws a different light on
the performance. What you have said makes sense to me and I have modified
the spread sheet accordingly. It would explain why Terry is so happy with
the 200B calipers performance!
Cheers
Feral Errol
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-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Ken Abraham
Sent: Saturday, January 06, 2001 5:23 PM
To: [EMAIL PROTECTED]
Subject: Brakes - Long
Errol, Terry, Trevor et. al.
Some Notes and questions about brakes resulting from my field trip to the
Wreckers,
(some of my recent posts on this have been rejected by the server, so I
don't know how much has already got through).
1. Sumitomo twin piston calipers
Readily available (i.e choose a good pair and don't pay more than $20 each)
on some Toyota Corona's and Mark 2's (6 cylinder sports coupe), all have
braided lines.
There are 3 main types, they differ in where the brake line attaches to the
caliper.
The Sumitomo caliper bolts straight onto an early 200b Strut, and I assume
it goes straight onto the 270mm brake-disc 240K struts.
2. Single piston versus twin piston, and four piston - IMPORTANT
Previously, we have calculated the effective piston area of a single piston
caliper as the area of the piston. However, actually the effective area is
slightly more than double the area of the piston since the force exerted on
the medial chamber wall (the inner face, opposite the piston) is used to
press the lateral (outside) pad against the disc.
With this new view, compare various calipers below...
(Note the greater the effective piston area - the greater the force on the
pads for a given brake line pressure, Pressure=Force/Area)
Porsche 993 Turbo caliper has 2x 44mm pistons and 2x 36mm pistons giving a
total area of 50.7681cm sq.
By my reckoning the stock 1600 caliper would have 2x 20.43cm sq. = 40.86cm
sq.
The big 200B caliper would have 45.80cm sq.
The poor old Sumitomo would have 36.19cm sq.
The Rover 3500/AP Twin pot would have 51.04cm sq.
Volvo & Hilux 4 spots 28.27cm sq.
As I see it there is no difference in the surface area to volume ratio ( i.e
caliper cooling ability) between 1, 2 or 4 or even 10 piston calipers.
Perhaps the advantage of 4 spots is that they distribute the clamping force
over the length of the pad better, hence reducing disc warp and pad hot
spots.
Perhaps single piston sliding calipers are more prone to flex and pad knock
off than the opposed-piston fixed type caliper.
3. Sources for brake mods and further research,
The Nissan Urvan has large single piston sliding calipers on vented rotors,
the calipers have the Datto 90mm bolt spacing, but with ~M20 (i.e large)
bolts, and would fit on Bluebird or R31 Struts with slight modification.
Approx piston size is 55mm, eff. area = 47.51cm sq.
BMW 3.0S calipers are 4 spot vented at the front and twin piston vented at
the rear have 90mm spacing and may fit on Datto 200b, 1600 etc... strut,
don't know what type of disc to use though. E28 also has 4 spots and twin
spots. E30 has twin spots up front.
4. Bluebirds/R31
The Bluebird is not an 'orphan' or black sheep as people have suggested,
parts from it can be good for swaps.
The disc brake rear (TRX, LX) is an early version of the R31 rear and the
calipers are interchangeable (internal handbrake on Bluey though), similarly
up front, the Bluebird brakes are just non-vented R31's
There are DBA sport rotors available for the R31.
The disc brake rear is basically what is fitted to the VN Commodore!
I would like to find a swap for the rear caliper though. I hoped to fit
Bluebird front calipers to the rear and fit a Mini pressure regulator,
however the bolt and pin spacing is different, any ideas?
5. I made a tactical decision and went for the R31 250mm vented front
struts, rather than the 270mm solid 240K struts, I'll just hang onto the
Sumitomo's until The brake issue is resolved.
I will have to change the spring seat though, or swap all the bits into my
Bluey struts.
BTW the R31 struts with vented rotors and finned calipers look SWEET.
What car did I get the struts from, it was an R31 skyline, but it was a
sports model in Two-tone grey - Not a GTS, they have 270mm discs. A
silhouette maybe?
Regards,
Nick
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