Suspension and brakes on a budget...

[93anthracite]

I'm building my 73 240z to be used primarily for road course / time trial purposes, but it will also see autoX and some street driving. Currently powered by the stock L24, hoping to eventually run with an L28ET and SR20DET in the future, probably never more than 350 hp in any case, no matter what engine I have in it. Please give input on the brake selection I'm going with and recommendations for suspension. I have searched a lot and read the FAQs, this thread is for input on my selections and help picking a good economy-minded suspension.

 

Brakes:

280zx front calipers, freshly rebuilt, with 300zx front rotors, and aggressive pads (Carbotech XP8 for track, Carbotech AX6 for street and autoX)

 

240sx rear caliper conversion, freshly rebuilt, with 300zx rear rotors, and aggressive pads (Carbotech AX6)

 

All hard lines will be replaced, ATE Super Blue or Ford Heavy Duty brake fluids, and new Teflon/Stainless braid hose to the calipers with AN fittings.

 

My biggest question at this point is about my Master Cylinder. The true budget route is a rebuilt 280zx master cylinder with a prop valve, however I am tempted to go with a dual master/balance bar application. This is new, unfamiliar territory for me and I want some input from other road racers on the necessity of this and recommendations on doing it inexpensively.

 

Can I get some input on my decisions here and a master cylinder recommendation?

[JMortensen]

Did you search this topic? I had a good thread on modifying the stock pedal box to use dual masters, that would be my suggestion. Alternatively you can buy a modified box from http://www.betamotorsports.com which is really slick but fairly expensive, or buy a Tilton or Wilwood pedal assy and adapt it into your car, which is going to require fabrication. All options were discussed in my thread.

[z-ya]

If you plan on running the L24 for a while, just get the stock brakes in good working condition. DOT4 or better fluid, Porterfield R4S or Hawk HP-Plus pads will give you a good bite on the track, but not too aggressive for the street. In the rear OEM Nissan shoes work quite well on the track. You can also get the R4S compound on 240Z shoes.

 

Another option is to upgrade the front to a vented setup using 300ZX rotors, Toyota calipers, and the correct spacers for your hubs. I'm running this setup along with drums in the rear, and it is a great track setup. I'm using the stock MC, but I shoe-horned a 280Z booster in there for more power assist. Swapping the booster is a lot of work BTW. I'm using Porterfield R4 shoes and pads, and the stock prop valve.

 

Of course the more track days you do, the less you will use the brakes. As you learn to carry more and more speed into a turn, you will rely less on the brakes. Yes, a road course is tough on brakes, but as you gain more experience, you will be surprised how easy you can be on your brakes. I've got well over 2000 track miles on my R4 pads in the front, and they still have over 50% pad left.

[93anthracite]

Hey Jon, I did search, but I must not have been putting in the correct terms . Thanks for the referral to the BMC thread.

 

I was also posting up here to get feedback on whether I would need the more advanced setup, or if the simple 280zx MC would be all I needed, considering the brake upgrades I was planning.

Thanks for the evaluation Pete. I actually was recently privvy to a ride on track in a 260z with stock brakes and it was quite adequate with better pads and brake fluid. I realized that I probably could just use what I have, but I don't trust them and would have pull everything off and rebuild it, and figured I might as well put better parts on.

I figured the S13 rear setup would offer me something I am more familiar with (I've owned 4 different S13s) and easier maintenance, even though the actual performance would probably not be much more. I chose the 280zx fronts b/c the Toyota calipers seem soooo heavy and I was trying to reduce my increase in unsprung weight from this mod. You're absolutely right that the more you drive the less you use your brakes (getting on the gas sooner and shrinking brake zones are constant goals), and it definitely helps that our cars are so lightweight to begin with.

[blueovalz]

One advantage which stood out for me on the S130/Z31 front set-up was that it would work with just about any wheel combination without spacers, and work well. The only reason a larger MC would be needed would be to keep the OEM pedal feel (keeping the MC/SC ratio the same) with the larger diameter S130 caliper piston.

 

Confusion:

As you learn to carry more and more speed into a turn, you will rely less on the brakes

 

Perhaps I'm not understanding the statement. It tells me that brakes become less important the more speed you carry into a corner. My experience shows the opposite. The faster I enter the turn (later braking), the harder I must apply the brakes. Yes, it will be for a shorter period, but total energy expended by the brakes is more. The only way that I got away with less braking (after a good line was found) was with better tires or set-up on the chassis.

[e_racer1999]

terry, from what i understand, short/focused brake application is much better for the durability of the brake system. at least that's what i read in a thread on here...

[93anthracite]

Terry, do you think the S130 15/16" MC will be sufficient for giving good pedal modulation and brake feel (a little play is OK, but I don't want a lot of slop), or is a dual master setup going to be necessary for my application?

 

I took it to mean that with more experience, you'll find turns where throttle modulation can replace brake application and you'll compress your brake zones to the point that you aren't using them for as long of a period of time.

"Using brakes as much" is a very subjective term which, as shown here, can be taken two ways. The length of time will decrease, but the amount of work being performed during that time is increasing dramatically b/c the entire system is being used more efficiently.

[z-ya]

My point it simple, if you can carry more speed in the turn, you have to slow down less on your entry into the corner. The less you have to slow down, the easier it is on the brakes. Also, the more speed you can carry through the turn, the higher the top speed at the end of the straight.

[blueovalz]

The larger MC will decrease the pedal travel, and stiffen it up just a tad. IMHO, the smaller MC provides better modulation because it takes a little more stroke for the same brake pressure. For me, this allows me to ride on the edge of lockup more predictably. With that said, your choice of brake pad will provide a lot of this as well, but I've not played with enough differnent compounds to recommend a specific application.