To start, I do like the performance of the current brakes on the Z. We are running the StopTech Sport Slotted Cryo Rotors and Hawk Performance DC-60 brake pads. However, since this is an arms race, improvements are always the goal. With that in mind, there are two items that I would like to improve the brakes.
The first upgrade is to get an increase in brake pad longevity. Currently, when we run the car for the 7-8 hr we are going through about 60% of the Hawk DC-60 front brakes. This means we replace pads after every major stint. Looking around, I have been able to find and believe we can upgrade to a mixed version of 350z rotors and caliper setup "with a little bit of help with an A-daptor kit". The router and pads are the same material, so this should increase pad and rotor size by ~15% and keep the desired performance. Even as the car evolution continues, and we get faster, this increase in brake size should see brake wear get below the 45% per stint and allows for one set of brakes per weekend.
The front brake change will exacerbate the second issue. The brakes are too sensitive and lacks the preferred fidelity. The cause of this we believe is the bore size of the master cylinder. We have examined the unit, and it is stated to be a 17/16", Torch measured it and the bore size is really only an 1". This has proven to be a consistent problem as I have sourced Master other OEM cylinder from three other manufactures and all were found to be 1". Thus, upgrading to the 350z brakes, we will then really have a hot mess.
Normally the solution is to increase bore size. Since we are have such trouble with this, I am thinking of going to a Wilwood Master Cylinder setup. They have 17/16" and 9/8" bore size options. Now the question is just changing bore size be enough?
To answer that question, we need to look into braking pressure. I don't know the peddle's ratio, so this will be all a guess from a 7:1 @ 100 lbs peddle pressure chart I found (shown below). From this, my guess is that we want to drop 200-300 psi to give us some better feel. Then, moving forward with the proposed 350z break system, if I assume a linear increase of brake size to pressure, a 15% increase in brake size could result in a relative increase brake pressure of 250-300psi. Looking at those combined number, we are looking at a 450-600 psi brake pressure drop. Bore size change is not going to cover that, so our attention turns to the brake boosters.
Looking at the brake booster, the 300z and the 350z diaphragms are similar in size, so no help. This had me look, at the Nissan's 240SX single 9.55" booster. The booster did have the same mount points as the Z, except the studs were about an 1" short. No trouble. With some welding by Torch, we had some stud extension, and it fit right in. So now, I estimate that we get a brake pressure reduction of about -225 psi. This might be enough reduction to give us better brake sensitivity in our current setup. We will find out in about 4 weeks.
Then, when we move to the 350Z brake system, I would propose changing the master cylinder from the current 1" to the Wilwood 9/8" bore. The referenced chart indicate that we would get a brake pressure change of ~ -320 psi, and with hope matches the 350z brake increase.
How could any of this cause a problem?
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