'71 240 upgrade to 4 piston calipers????

[DavidB]

The car has always weak brakes. The Booster appears to be working. Just replaced MC and booster hoses and check valve, new fluid and bled lines. Still poor braking. A mechanic who has lots of experience with 240's is urging me to replace the stock front 2-piston calipers with 4-piston. He says they will most likely dramatically improve braking on the car. Has anyone used the Motorsports 4-piston brake upgrade kit(about $400)?

Another option I'm considering would be to go in an completely rebuild both of the stock front disc brakes(new calipers pads etc), but the same machanic feels that would be waste of money, saying they are working fine. My dad bought this car new, and the brakes have always been an issue.

In a recent emergency stop going down a slight hill, I stomped the brakes hard and then rear brakes locked up, but the fronts did not.

[mperdue]

Do a search for "S12-8" on this site and you'll find info on a bolt in 4-piston upgrade. Much cheaper than MSA. If you want to take it a step further the S12-W allow for vented rotors but require a spacer. These are Toyota calipers by the way.

Michael

[dogma420]

Your front brakes in good condition should work better than what you're describing. They aren't perfect, but they should work better than that.

[zguitar71]

The stock brake system should be fine for your car. The weak area on the 240 brakes is their tendancy to over heat. You should not be having that problem if you are driving on the street. I have been auto crossing with the stock (I do have stainless lines, but that only affects the feel of the brakes not the power) system in F prepared for 2 years and have not had a problem, I have even turned the rotors blue and not had a problem with the power of the brakes. The stopping distances I experience between the race tires and street tires is very big. That difference is not the power of the brakes but the difference in traction of the tires I use for the track and the street. If you are not able to get enough power in your system to lock up the front brakes first then there is something wrong with the brake system. You might try looking at the proporing valve. With my stock system I can lock the brakes (front) with either tire type I am running, to stop well I have to modulate the brakes to keep them from locking. Before you spend a bunch of money on everything try a better set of pads, something made for low heat friction (street driving/autocrossing, NOT ROAD RACING). The larger surface area of the 4 piston caliper pads can acually make too much heat for the stock rotor to disipate. So if you are dead set on going to a 4 piston set up then the vented rotor type might be better. I do not think you will be able to stop any shorter with them (4 piston) than a properly working stock system though. Your brakes are only as powerful (with a properly running system) as the grip of the tires you are running. When you add braking force in the front you will upset the front to rear brake balance so you will need an adjustable proportioning valve or some other type of brake biasing system to restore your braking system's balance. Make sure the machanic bleeds the Master cylinder befor the rest of the system. If there is a small amount of air in the MC then the system will work but be very weak and spongy. There could be air in the front chamber of the MC and not in the rear, that would upset the brake biase to lock the rears and not the front. A properly running system should not lock the rear first, that is a very dangerous problem.

[240ZMan]

I have a 73 and did the 4 piston swap last year myself instead of using the MSA kit. I've been very happy with the results once I put Axxis Metal Master pads in. I have the stock rotors too. The improvements were much easier modulation at the limit of brake lockup on the fronts, and a slight improvement in fade resistance, but that's probably more a function of better pads as I didn't change the discs.

BUT...

my system was functioning properly before I did the swap. In your case I think you need to determine why you're not getting lockup in the fronts before the rears before you do any swaps. Many people claim that a properly functioning stock system is just as good at stopping the car as the 4 piston swap. (go to hybridz.org for some very heated discussions on this topic.) I will also say that if you want to buy more performance oriented pads, there are more choices for the stock calipers than the 4 piston. Keep in mind that the 4 piston calipers come from a 4x4 truck and hence the pads offered are oriented towards a truck.

Again, the improvement for me was in the ease of controlling or modulating the brakes. You really don't get any significant improvement in fade resistance.

Now if you do the 300zx vented rotor swap and go with the wider 4 piston calipers as suggested above, then you'll get a significant improvement in fade resistance as well. I wanted to do that, but didn't have enough clearance with my current wheels and didn't want to get new ones. At least not right now

Good luck!

[Marty Rogan]

The car has always weak brakes. The Booster appears to be working. Just replaced MC and booster hoses and check valve, new fluid and bled lines. Still poor braking. A mechanic who has lots of experience with 240's is urging me to replace the stock front 2-piston calipers with 4-piston. He says they will most likely dramatically improve braking on the car. Has anyone used the Motorsports 4-piston brake upgrade kit(about $400)?

Another option I'm considering would be to go in an completely rebuild both of the stock front disc brakes(new calipers pads etc), but the same machanic feels that would be waste of money, saying they are working fine. My dad bought this car new, and the brakes have always been an issue.

In a recent emergency stop going down a slight hill, I stomped the brakes hard and then rear brakes locked up, but the fronts did not.

Here are a few thoughts on things to check out:

1) Make sure the Master Cylinder is competely bled.

2) If the MC has been replaced, make sure the reaction disk behind the MC push rod, inside the booster has not fallen inside the booster.

3) Make sure the calipers are installed on the correct sides. If the bleeder valve is on the bottom, you will never get the brakes bled completely.

4) Replace the rubber hoses at the front with braided hoses. It will give better feel to the brakes (takes out spongyness).

5) If in fact you are going to replace the calipers, I would replace them with the 4 piston type. Be prepared though, from my experieince with these, they are even harder to bleed correctly. They may not fit under your wheels either.

Good luck,

Marty

[auxilary]

I have the same setup as MM kit. S12W calipers, 300zx vented rotors, 1/2" spacers. I bought it from www.outlaw-brakes.com, but it looks like they no longer manufacture Z parts. I paid 450 for the kit with rebuilt calipers, 300zx rotors, spacers, bolts, +60 bucks for earl's SS braided lines (4 of them) from MSA.

For what it's worth, you can do a quick add up on the parts separately:

-remanufactured '88 toyota 4runner s12w calipers from napa - $80 each, 160 total (if you can turn your old calipers in for a core charge, you'd get about 40 bucks back)

-cheapie napa '84 300zx NA vented rotor - 45 each, 90 total

-machined spacers (40mm thick, I think?) I'll have to measure them on my car, probably 100 bucks for the pair?

-bolts for the spacers, 6 bucks

-decent front brake pads, semi metallic. 50 bucks

so you're looking at roughly 400 bucks for the vented conversion.

The MSA conversion for 380 bucks is a rip off. You can piece that set yourself for 200 bucks at most, not counting braided steel brake lines. And that doesn't even include front rotors. New rotors are about 65 bucks from napa, 130 for the pair. STILL cheaper than the MSA kit,

Here's what the vented setup looks like:

I'd also advise to get a 15/16 master cylinder from a 280 for the bigger pistons

[DavidB]

Thanks for all of the advice. I replaced the rear brake pads yesterday, as one side was worn...and alos discovered a leaking rt rear brake cylinder. Planning to re-bleed everything today. How much play should occur in the brake pedal before feeling pressure? Mine goes +- 1 inch and then is very stiff..yet little braking.

[71_240Z]

Do the spacers that come in these kits have a lip on them so that the rotor touches the hub? If there is air between the rotor and the hub, a lot of sheering force is on the bolts. Kind of dangerous if you ask me.

I did this conversion last week, but I got a machinist to make me a "collar" to take up the space between the rotor and my axle hub. That takes all the pressure off the bolts.

[Miles]

I have two 72 240zs. One is stock and the other has a 350 sbc in it. I replaced all brake components in both cars and the brakes always sucked. No matter how much I maintained the stock brakes thay were always weak and faded easily. They just seem to be under designed for ther car.

A month ago I replaced the stock front calipers with the basic Toyota 4 piston calipers (Napa $80.00) and installed a new 79 280 zx MC (MSA $100.00) in my stock 240z.

You will need to adjust the booster push rod out a bit. I adjusted mine to where it just touched bottom as the MC mated up to the booster. BTW I bought two boosters from Autozone and there was no reaction disk in either one of them which relieved my paranoia about loosing the disk when I had to grab the push rod and adjust it. The push rod adjustment can be done with the lines hooked up to the MC. Just unbolt the MC from the booster and push the MC out and away from the booster. It took about 3 or 4 tries of adjusting the push rod, bolting the MC back onto the booster and driving the car until I got it just right. Just don't adjust the rod too far out.

The four spot calipers made a major difference in brake performance. No more brake fade and the car hauls down fast. The most time consuming part of the upgrade was bending the bridge tubes (new ones) to fit the Toyota calipers. I practiced bending the old bridge tubes before I bent the new ones.

Last weekend I replaced the springs (Arizona Z) and shocks (KYB) and decided to use the MSA SS brake hoses they sell for their Toyota brake upgrade in place of my bent bridge tubes thinking it would be easier to reinstall the lines. However, the MSA bajo fittings leak no matter how tight you make them. This is due to the fact that the Toyota caliper was not machined for banjo fittings. This was an oversite on my part, but MSA should advise people to file or machine the banjo fitting mating surface on the caliper before installing the SS banjo lines. I put my old bridge tubes back on and the brakes are fine.

Paint the new calipers before installing them or they will rust and look like crap if you have rims with open areas.

With the the new shocks, springs and the four spot calipers the car rides and handles well.

For a daily driver the Toyota conversion is an improvement over the stock brakes based on driving my V8 240z and my stock 240z for the last three years. For the V8 Z I would go with the vented rotors.

Miles

[71_240Z]

Miles, did you do a rotor conversion too?

[240ZMan]

However, the MSA bajo fittings leak no matter how tight you make them. This is due to the fact that the Toyota caliper was not machined for banjo fittings.

I experienced the same thing unti I realized I had forgotten to put the metal washer on the fitting before threading it in. Once I did that it sealed perfectly. The SS lines give a very nice firm pedal.