What causes this brake issue?

[jgkurz]

Yes, but I'm lazy and will likely just replace the suspect caliper under warranty so I don't have to bleed twice. : )

 

Correction: my calipers cannot be moved between sides. They are left/right specific... Not sure why I thought they were interchangeable.

[Zmanco]

BTW, shouldn't my rear brakes have locked also if the car was setup correctly? My assumption is that the rear brake bias should be slightly less than the front. Correct?

I have the same setup as you on my 240z and found that even with the prop valve all the way open I was always locking the fronts first. So I went with a more agressive pad in the rear (higher coefficient of friction) and now the prop valve actually makes a difference. I will say that I had always read that the fronts do most of the braking so was very pleasantly surprised how much harder I could brake when I had the rears properly set up.

 

The 280z weighs more than the 240 so I'm not sure how the balance f/r is affected, but once you solve the issue of the right front locking, I'd suggest you find a safe place to gradually add more rear brake and see if you can ever get the rears to lock first. I suspect you'll find that you can't.

[jgkurz]

I have the same setup as you on my 240z and found that even with the prop valve all the way open I was always locking the fronts first. So I went with a more agressive pad in the rear (higher coefficient of friction) and now the prop valve actually makes a difference. I will say that I had always read that the fronts do most of the braking so was very pleasantly surprised how much harder I could brake when I had the rears properly set up.

 

The 280z weighs more than the 240 so I'm not sure how the balance f/r is affected, but once you solve the issue of the right front locking, I'd suggest you find a safe place to gradually add more rear brake and see if you can ever get the rears to lock first. I suspect you'll find that you can't.

 

 

Excellent post. Thank you. I will be switching out the front left caliper soon to fix the unequal braking behavior but the bias is also a concern. My hunch matches your suspicion. I don't think I could ever lock the rear brakes with my current setup. I use the Porterfield R4S pads which are the most aggressive street compound I know that don't require a warm-up. What pads do you use in the rear that would provide a higher coefficient of friction?

[Zmanco]

I'm running Beck/Arnley Axxis XBG Semi Metallic #088-1383M for '84 300zx in the front and Hawk HP+ in the rear. The Axxis isn't anything special, it's just what I started with at both ends, and then later tried the Hawks in the rear. I'd really prefer to run the Hawks in the front and run something even more aggressive in the rear, but it's hard to find coefficient of friction charts for a lot of pads.

 

The good news is that this setup is very good on the street, yet I have never experienced any fade with it. At Pueblo Motorsports in CO which is reasonably hard on brakes, I was fine (seeing about 115 at the end of the straight before braking to 80 for a sweeper) while the stock 350Zs, even with high temp fluid, would have major fade issue within 10-15 minutes.

 

FYI, the 300zx pads have a tab on the backing plate that you have to grind off. But look at pads for that car - it gives you a lot more choices in pad materials than looking at Toyota 4x4s.