road suspension

[Mike]

Bob, that's a great suggestion. Can it be assumed that tire temps are a function of contact patch or are there other factors that might be considered? I have in the past just observed wear patterns and adjusted pressure while attempting to achieve even tread wear. My experience has been that most tires are over inflated.

 

[Dr. Bob Woods]

Mike,

If your tires are over inflated, then they will wear more in the middle, under inflated they will wear more at the sides. Looking at wear is a very long term indication of inflation. Get or borrow a tire pyrometer and know immediately.

Most passenger car tires tend to be under inflated since people don't check the tire pressures regularly. Of course tire pressure is also a function of temperature.

From the responses on this thread, I agree that GT40 tires are over inflated. The 32 psi recommendation for most passenger cars is for cars that weigh twice as much as a GT40.

Further if you do some spirited (but symmetric) driving and can take tire temperatures immediately the temperature pattern can also tell you about the camber. Measure the temperatures on the inner edge (or 1" in), the center, and the outer edge (1" from the outer edge). Ideally, you would like to have the same temperatures in all three places. If the inside temps are higher than the outside temps, then you have too much camber. If you are not going to adjust the camber, then strive for a uniform distribution across the three locations to determine the best pressure. In other words, if the center temp is much higher than the average of the edges, then the pressure is too high.

There is a lot more to tire temperature testing than this, but this is a quick start.

-Bob Woods

 

[Richard Carr]

Hi John,
I have heard great things about new springs and completly new shocks designed for the Superformance GT 40's by Randy Thomas & Performanceunlimited(dot com). I plan on going that route asap. As ride, rebound and most important compression issues are fully addressed for street and track..
All the best,
Richard Carr, SPF 2127

 

[Howard Jones]

The thing is this. There isn't anything you can buy at completely addresses setup on the road or track. Period. Setting up a car to behave on the track takes some time and the commitment to learning how to do it. It's not calculus, but some ability to think through a progressive set of steps and make small changes one at a time to improve the balance of the car is going to be necessary.

Good parts (not necessarily the most expensive) are helpful but frankly some of the worst handing cars I have every taken a ride in were the most expensive pile of mismatched parts possible. These cars all had one thing in common. BAD tire choice and WAY to much power.

So I would start with the parts that came on the car. Get tire pressures as close to optimized as possible after getting a basic alignment. Keep settings modest. 1/2 degree negative camber, about 5 degrees of caster, and street settings for toe and go from there. Then setup brake balance. Once the car stops as well as it can you can start thinking about antiroll bar adjustment, spring rates and, shock valve settings.

ONE THING AT A TIME! start shocks at full soft, then firm up 10-15% at a time (2-3 clicks out of 20 for example until it firms up just enough to control bumps. Now you can play with spring rates. It will depend on how much you want to spend on springs but I would start at about 300-350 and see how the car goes. If you change springs redo shock valve settings. The next thing is roll bars. Unless they are adjustable you will need to change them.

If you are going to spend money now's the time. Make or buy antiroll bars that can be adjusted. Cockpit adjustability isn't cost effective IMHO unless you are RACING but a series of holes on the ends will get you just as close in the end for a track day car, and a good balance will be just as beneficial on a street car.

My advice would be to avoid race setup settings such as really stiff spring rates or extreme chassis settings like big neg camber numbers in excess of -1 degree.

Have fun with this. It's all part of the rights of passage in the GT40 family!