ZX rear disks are SOOO wimpy!

[Zvoiture]

Took these off my '79 parts car last night for a possible adition to my '71 project. I can't believe how wimpy these calipers are! The pads are, like, 2 square inches!!! and the caliper 'housing' is a big stamped piece of sheet metal!

I know this is a hotly debated topic, but I can't help but wondering how this could possibly be an upgrade over the stock drums with decent shoes. Is the raw physics of a disc brake that much better that this little thing would stop better than drums?

steve77

[Mike]

I know this is a hotly debated topic, but I can't help but wondering how this could possibly be an upgrade over the stock drums with decent shoes. Is the raw physics of a disc brake that much better that this little thing would stop better than drums?

Steve,

I was also amazed to discover this on my motorcycles. For instance, my Hayabusa has two huge 12" cross-drilled discs on the front while the back only has a single 6"-8" disc.

I've heard that the most important side is the front because it takes most of the force when you step on the brake. The rear is only applying enough force to keep you from going out of control.

Here is a totally cool site to find out more with braking systems:

http://www.howstuffworks.com/brake.htm

Watch out for that site. It's addictive. Especially to those of us who like to take things apart just to see how they work.

[2ManyZs]

The biggest advantage the ZX rear discs have over the stock drum brakes on a 240 is their ability to dissipate heat. The total brake swept area is actually smaller with the discs when compared to the drums, but the drums will not dissipate the heat. The biggest enemy of the drum brakes is heat, once they get hot they will not cool as efficiently as the discs.

Comparing the early 280ZX brakes to the later vented discs and the ZX brakes are a big loser.

The biggest problem with the 240's is that they don't even have a vented front disc. Once you get the solid rotor hot it keeps the heat for a long time, and transfers it to the pads and then to the caliper and fluid. The rear drums don't transfer the heat to the fluid like the front discs do, but the shoes and drums will disintegrate from the heat instead.

[Mike]

Your right about the heat dissipation. When the brakes get hot, it can can also affect the braking itself. And, poor braking isn't good when you're racing. I think they call it 'brake fade' or a similar term.

I have such a problem with drums. They are more complicated and the design itself is just wizz poor. Not sure why it was even invented. The howstuffworks site says something to the effect of easier maintenance with drums. But, I find that hard to believe. I always have difficulty working on my drums because they are either seized tight or the pads don't wear evenly.

I almost made the conversion to rear discs, but, I decided not to spend the extra money at the time. I was also scared to go disc because of the proportioning valve. I didn't want to cause a safety issue. Now that I found an adjustable proportioning valve, I might consider it.

[hmsports]

I found out quickly during my first year of racing just how important it is to keep the Z's brakes cool. I built some shrouds that helped a ton. I was able to keep my pads from deteriorating so quickly and the rotors/pads/calipers and brake fluid from staying so hot. There are also some easy ways to duct air into the rear drums to force more air on them. And yes, it is called brake-fade... almost as dangerous as brain-fade

BTW - 240Z club members get a 10% discount

[2ManyZs]

It is possible to have the rear shoes radius to match the drum better. If you notice when you change shoes typically only 1/2 to 2/3 of the shoe has been in contact with the drum. Many of the IT racers had theirs radiused to use more of the shoe. But then you build up more heat, so there you go with that problem again and trying to cool them.

Just put Z-32 dics all the way around and you won't have any more brake problems. :eek: That is if you want to spend that kind of money.

The biggest shortfall of the rear shoes is that they are a single piston design. If they had put on a dual piston design, where the top and bottom of the shoe moved outwards to meet the drum there would not be as much problem with not having as much contact area between the shoe and drum versus the shoe area.

In racing it was always a fine line between burning up shoes and pads and not using up rotors and drums like crazy. One set of pads might have great braking abilities and eat up a set of rotors in a weekend. Drums were the same way, you either overheated and cracked the drums or you had shoes that just burned up and disintegrated. Drums, rotors, pads and shoes were almost as expensive to keep up with as tires when I was racing. Todays shoes and pads are much better than they were 10 years ago.

[Zvoiture]

So how hard is it to put these vented fronts on a 240? I read alot about 4-pistons and Toyota calipers and whatnot, but I don't recall ever reading about switching a 240 to ZX venteds. The hub would have to be changed, no?

I know the rear is just a drilled plate to hold the calipers. I will probably be doing that.

steve77

[grommitz]

I'm not convinced this is worth it. A decent set of Porterfields or Green stuff can go a long ways--even in the heat.

[2ManyZs]

It's a lot of work to put the vented rotors on a 240, is it worth the effort? I don't know. I haven't done it and have not seen all that many cars that have had it done. I have seen pics of the Z-32 front rotors on a 240, I would imagin this would require quite a bit of machining in the hub, rotor hat area, and would therefore end up being rather expensive. For a street car the stock rotors should be plenty with the 4 piston calipers and a decent set of pads, you shouldn't have to worry about overheating them on the street or even in an autocross. Road racing is where the problems show themselves.

I'd have to disagree with the Porterfield brake pads though, especially the R-4's, they will eat up a rotor before you run out of pad. A better one to use might be the Carbotech's, they are a lot more "rotor friendly". I used the Porterfields when I raced, by the time one set of pads needed to be replaced, I had to turn the rotor once and after one turning there wasn't enough left to turn a second time. This was starting with brand new rotors.