AP brakes soon - hooray!

[Andy Mcl]

Just a thought,
I made up a brake system using Willwood calipers on my old 360 16v
and kept the original diamer discs/(but vented) - god did it stop but again the improvements only were really felt when you pushed hard and warmed up the pad material.
It also meant I didn,t need oversiz wheels to get big enough brakes to make it stop.
Just a thought!

Cheers Andy

[basher]

for the 850 70 series, there is now a willwood kit which is 355mm vented discs with 6 pot calipers front and 330mm vented discs 4 pot calipers rear. Thats a bit mental and does need bigger wheels though, must look nuts.

[Bashy]

Hi

How much bigger??????

Regards

Martin Chadwick
Bashy
98 C70 GT T5

http://www.credit-busters.co.uk/C7TEA_small.jpg

[Andy]

FYI

http://forums.vptuning.com/viewtopic...llwood&start=0

Group buy was happening.

[Simon Linton]

Those are indeed monstrous brakes, but as one commentator said the pads do not sweep the entire disc area - a little pointless then.

Of course, the larger the disc diameter, the better the leverage, but the potential for differential heating on track days would be huge on those discs.

I notice that the user nearly had to fit spacers to clear the calipers - I've just got a sale-or-return set from Don in case my Volans have that problem with the APs.

This is apparently a factor of wheel tolerance; most Titans are fine with APs, but Volans and other wheels MAY clout the calipers.

And of course, if you fit spacers you have to lose your locking wheel nuts because the thread isn't long enough - does anyone know of a clip-on locking nut that works on alloys and is moderately secure?

[basher]

Simon,

I had the ap's with volans and they cleared fine, They definately will not clear the 7x17 comets on the s/v70R hovever they may clear the 7.5x17 comets as fitted to the c70??

Hope that helps

Hedley

P.s. The comets still didn't clear after 3mm spacers, as the discs offer a 2mm spacing thats a total 5mm which buggers the geometry and needs longer bolts, only managed to get 3 turns on the bolt

[Andy]

Simon

The AP kits fits behind my Volans no problem.

http://www.volvoclub.org.uk/photopos...cat=500&page=1

It was a very tight fit on Andrews gold C70, less than 1mm from memory. His car was at the first Power Engineering day.

Trust me your kit will never go back to Don once you've got it on :P

My Volvo locking wheel nuts fit fine.

I'm told big brake conversions for the rears is pointless due to brake bias problems(??).

I've seen recently a double callipered Willwood brake kit on a Volvo, some S60R concept or something and the pads only touch the outside half of the disc- pointless in my opinion but did look VERY cool.

[Simon J]

In relation to what wheel sizes are need for what brakes, the Volvo performance brake kit fits any Volvo 17" wheel. This being because it is a single piston 'fist' caliper similar to the standard one. And if you read some of the US threads about grinding the edge of the calipers or using spacers, well, words fail!

[Andy Mcl]

Simon,
I wasn't actually thinking of the S60R system everyone has seen.
I was thinking more modestly and keeping the original diameter brake disc.
The reason the S60 system pads doesn't sweep the disc track is beceause the caliper has not been sized to match the disc diameter.
On standard (280/302/320mm) discs the same problem does not apply.
The one thing you must remember is that pin sliding calipers (std single piston volvo calipers) flex when brake pressure is applied. The same problem is not the case for opposed piston calipers (AP/Willwood/Brembo etc). The flex causes loss of brake efficiency and you have to use them with ABS as once they rach maximum deflection - max flex - they snap shut.
Hence on some cars they lock their brakes or the abs cuts in rather early loosing brake power and more importantly, brake feel on the limit. Brake feel is in my opinion more important than absolute prake power cos if you can't control it extra brakes is useless.
You will always have more brake power when using opposed piston instead of sliding pin (single piston calipers) even if you use the same sized disc.
But as always pad material has to be considered very carefully and how and where you intend to use it.
Hope I am of help
Cheers

[Simon J]

All these 'Simons' and 'Andys' are very confusing!

A propos the standard single piston sliding calipers, while for sure the opposed piston AP, WIllwood or Brembo ones are potentially a better engineering solution with their alloy construction and different sized pistons, in anything but the most arduous conditions I would doubt if their benefits would be noticeable.

But I think we have all assumed that the AP, and other multi piston calipers offer greater hydraulic power - I know I certainly did until I started to look into this in detail as I was (and still am) not that impressed with my Volvo big brakes. The theory says that the force with which any caliper clamps the pads onto the disc is a function of both the hydraulic pressure applied and the effective area of the caliper pistons. The larger the effective area, the greater the force for any given hydraulic pressure.

The effective piston area of a single piston sliding caliper is twice the actual area of the piston, which, in the case of the Volvo caliper, works out at more or less the same as the total area of all four pistons in the AP caliper. So, for a given pedal pressure, the actual clamping force with which the pads grip the disc remains unchanged, whether we are using the standard Volvo caliper, the Volvo performance one or the AP caliper. So I wouldn't agree, therefore, that "You will always have more brake power when using opposed piston instead of sliding pin (single piston calipers) even if you use the same sized disc."

So it definitely seems to me as though the additional braking torque of the various big brake sets is due to the different pad characteristics and larger diameter discs, and not to any greater braking force from the larger calipers, whether single or multi piston. But I've only been able to get data on the Volvo and AP calipers and perhaps the Brembo and others do in fact have larger pistons. Does anyone actually know?

Interestingly enough, I happened to be parked next to a BMW 330 this morning and while personally I wouldn't be seen dead in one :P, I must admit that BMW have a well deserved reputation for engineering excellence. And it uses a single piston caliper! So I'm still inclined to the view that for road use a single piston caliper is probably quite sufficient.


Simon J