drewz06

i was just trying to reconcile the alleged cad drawings and noticed what looks to be dual rear calipers.

i got nothing more than my eyeballs and zoom to verify, just figured i'd throw this out there.

what looks to me that the larger calipers are positioned at the "front" position, while there appears to be something else covering the "rear" position.

downhil

Parking brake.

ByByBMW

That was my first thought.

stevebz06

I can't think of a single car that has used a separate caliper for a parking brake. This would seem to be not very efficient design if it is.

downhil

firebirdfan

It's common on high end braking systems. The main caliper is just braking and the other caliper is much smaller and used for parking.

MikeG37

Ford GT, Audi R8 also

NemesisC5

A good decision by the design team rather than using traditional parking brake shoes inside a drum.

RichieRich

Yup. Lots of mid engine cars it seems.

rgregory

My Gallardo has a separate parking brake. The rear brake caliper is the same as was used on some model Vipers in the front.

Yes less rotation mass, no drum to rotate too.

sammyv

My 01 viper had a parking brake caliper.

stevebz06

Well, learn something every day, but I don't see how this is an advance over using one caliper for both jobs.

63Corvette

Um..................................my 1958 Jaguar 3.4 sedan had four wheel disc brakes and the rear brakes had hydraulic calipers for stopping, and a pair of mechanical calipers for parking brake

NY09C6

I believe drums inside the rotors adds width to the car. It's not an issue when the motor is in the front but probably becomes an issue when it's in the rear.

ByByBMW

Somehow, this doesn't make sense to me. The engineers/designers will compensate somewhere to keep the width to what they want. Whether it be shorter drive shafts or whatever.
What I suspect is that the rotor doesn't need to be as beefy to support inside parking brake drums. The weight of the calipers would probably be less than the weight of the added mass for the inside drums, hence slightly less unsprung weight.

stevebz06

If Jaguar was doing it, then I would say that's a good argument against it. I'm just kidding. I love Jags, but I've never heard any compliments on them on how easy to maintain they are.

I just can't see where going to two calipers when years ago most cars were using one is considered progress. Calipers are heavy and the mounting hardware adds even more, especially when one of them isn't doing anything until the car is parked.

Maybe the engineers didn't want a heat soaked set of brake pads clamping down on the rotor, but that's where the internal brake drum probably worked fine or at least better than using the caliper.

Most of my work-life was spent flying medium to large jets and I'm sure none of those had separate parking brake calipers. The heat generated from a typical medium length runway landing makes what automobile brakes have to deal with seem like child's play. An engineer who suggested adding weight to a landing gear design just for the purpose of parking probably would have been fired.

I guess going to two calipers means that weight is not a super high priority these days.

Bill Dearborn

The problem is using one caliper to function as both a brake and a parking brake is fraught with reliability problems due to the mechanism required to operate it in the parking brake mode. The C4 Corvette had a setup like that from 1988 through 1994 and the 1988 GM B body cars had a similar setup until they stopped making that model. I believe the parking brake mechanism is required to be mechanical since I have never seen a hydraulic mechanism. The GM version used a complicated cable set up to push the piston in the caliper so the parking brake could be applied. Those mechanisms are subject to a lot of dirt and corrosion and tend to stick. When that happens usually the driver zings along fat, dumb and happy not realizing a sticking parking brake mechanism has slightly engaged one or both rear brakes thus boiling the fluid in the caliper. At some point the driver tries to apply the brakes and finds the brake pedal goes to the floor and there aren't any brakes.

Bill

stevebz06

That could be. Probably is a result of a Government standard, but my C5 seems to have a pretty reliable parking brake with one caliper. More reliable than my C4 with the brake drum in the rotor.

tooold2race

This is quite common on high performance cars. My Ferrari and Viper have that arrangement for the emergency/parking brakes. I had a Rolls Royce back in the '90's with that arrangement too. Back then the dealer said it was more effective because of the weight of the Royce. On modern hi-po cars, I'm guessing it's for simplicity, especially with a ME configuration.

firebirdfan

You realize the C5 and C6 use this method as well, right?