Supercar rear brakes x 2?

[andy_mk3]

My Dad's V8 Vantage has the same thing on the rear.

 

[tigerstyle]

first time I've seen chrome brake discs in a while

 

[burns]

So, if somebody knows...in a caliper with an intergrated handbrake, the piston that is used for the handbrake must be seperate from the main hydraulic system. I'm assuming, please correct me if I'm wrong. Also, what "performance" cars have an intergrated parking brake that have over 2 primary pistons?

Perhaps it's because a conventional 2 piston (or 4 or 6 etc) caliper will take up the same space (and weight) as the intergrated caliper, but offer the obvious braking benefits of having two pistons for service braking in comparison to one? Maybe that's why the extra handbrake caliper is usually seen on a performance car...wasting pots in the primary caliper is unacceptable due to braking demand.

Miles off?

edit: The answer would be to build a 10-pot rear caliper with an intergrated handbrake, so cost must factor into this.

I'm not aware of any cars that have more than a single caliper on the rear brakes and have the handbrake built into the caliper. Even the wilwood only rear caliper with a handbrake on it I can find has a single caliper.

The usual way to have a handbrake on the rear caliper as you probably know is to have a screw thread down the middle of the caliper which winds it out when you pull a lever on the back of the caliper. Without a sliding caliper you need to move at least one piston on either side of the caliper. Even on a two pot sliding caliper you still need to turn two screws which increases the complexity massively.

I guess it's so that they can used a fixed mount caliper rather than sliding, and a spot caliper is just cheaper and easier to engineer than the drum type?

 

[Dogbreath]

Wilwood make fast road and track calipers with the handbrake, but Brembo don't, instead offering the spot caliper. I don't know what the weight of the drum and shoes would be, so can't compare it to the 2kg Brembo.

The Willwood four pot handbrake callipers are virtually useless IME. They can just about hold a lightweight kit car, but it would never be a useful solution for a production car. They aren't self adjusting either.

So, if somebody knows...in a caliper with an intergrated handbrake, the piston that is used for the handbrake must be seperate from the main hydraulic system.

The same piston is used to push the pads, but the mechansim used to push the piston is completely mechanical, not hydraulic.

IMO the reason for separate handbrake calliper is primarily down to the difficulty of integrating a usable and reliable handbrake mechanism into an opposed piston calliper.

It's not going to greatly help the handbrake loosening if applied with a hot disk; in fact it might even make things worse since with a conventional handbrake calliper the disk and calliper will both get hot, and therefore both contract as they cool. A separate handbrake calliper will always be running cooler, so won't contract as much as the disc.

 

[Fett]

I'm not aware of any cars that have more than a single caliper on the rear brakes and have the handbrake built into the caliper. Even the wilwood only rear caliper with a handbrake on it I can find has a single caliper.

Wilwood do a 4 pot Powerlite caliper with intergrated handbrake for lightweight (Atom, Caterham etc) applications. Apart from that, everything else seems to be a single pot affair.

The usual way to have a handbrake on the rear caliper as you probably know is to have a screw thread down the middle of the caliper which winds it out when you pull a lever on the back of the caliper. Without a sliding caliper you need to move at least one piston on either side of the caliper. Even on a two pot sliding caliper you still need to turn two screws which increases the complexity massively.

So Audi have a choice:

A single pot, sliding caliper with integral handbrake. I would have thought this to be the least attractive option due to obvious reasons on a R8.
A multi-pot, fixed caliper with drum assembly. VAG don't do drum handbrakes, no idea why (reliabiltiy, ease of servicing, cost?)
A multi-pot, fixed caliper with handbrake caliper. I'd guess at extra unsprung weight being the disadvantage. Cheaper as well maybe, rather than engineer a drum into the assembly. Maybe it's something to do with wheel / hub design or track width.

Traction and stability control systems perhaps play a part as well. The systems that use the rear brakes, at a guess, wouldn't want to be reliant on a floating caliper.

I guess it's so that they can used a fixed mount caliper rather than sliding, and a spot caliper is just cheaper and easier to engineer than the drum type?

At a guess, you are probably right.

IMO the reason for separate handbrake calliper is primarily down to the difficulty of integrating a usable and reliable handbrake mechanism into an opposed piston calliper.

This makes more sense to me than the heat issue, primarily because the drum design is perfectly adequate and addresses the issue (if it was, in fact, an issue). If it were the main reason, then I'd have to ask why any manufacturer would incorporate a sliding caliper with integrated handbrake into their braking system in the first place.