DanielB

As others said, toe will change. But it's not hard to reset in your garage with a few boards and tape measures.

DavidNJ

That sounds like a very nice, well thought out suspension setup!

Some questions:

On suspension: Karcepts has different torsion tubes for their bars, which ones are you using. How did you modify to allow for more camber and how much camber are you running? Did you use lowering blocks (i.e. roll center adjusters) to get the additional camber? Which piston did you use in the Penske shocks (linear/linear, digressive/digressive, etc.)? Was any additional low speed bleed added? What are the reference points for you ride height measurement? Penske told me the 7500DA didn't have a lot of room for lowering.

On brakes; Are you using front brake ducts? Did you consider using the Girodisc or other two-piece floating front rotors, since the car now has 2-piece rear rotors?

On tires: Do the +45 rims rub the fenders? Why did you chose them over the +60s often used with 9" rims? Are you running under rules that limit your car to 9" rims or was there a different reason for not using wider rims and tires (e.g. a 265/35-18 or 275/35-18 on a 10" rim which would have about 1" more tread width)?

DanielB

While we're discussing ride heights, what is the consensus if it should be set with the driver (or equivalent weight) in the seat? I made some basic assumptions about where the driver's center of gravity would be relative to left/right and front/rear and it seems that for me (~180 lbs driving weight) that I add ~40 lbs more weight over the left rear wheel than the right (I'm assuming the left/right spit to be 1/3 to the right, 2/3 to the left) and the same front to rear. With 11kg/mm springs that would mean the left rear was compressed ~2 mm more than the right. Does this make much of a difference? My instincts say no, but curious if anyone has tried both approaches and can share if there were noticeable differences on the track.

s2000Junky

The answer is corner balance the car. Yes it makes a difference. In order to get a proper balance, you need to have driver weight in the seat. The driver side of the car will typically have a slightly higher ride height then the passenger side as a result.

DavidNJ

To approximate the driver, I take the wheel weights with the driver in the car, then place dumbells in the driver's seat and the floor in front of the seat until the scales read the same.

Note that ride height and wheel weight are closely related. Making a ride height adjustment by itself will most likely put add wedge in the suspension.

DanielB

Great point that I hadn't thought about. I've been debating buying a set of scales vs. having a local race shop do a corner balance. I'm leaning towards the latter as I have my doubts that the stands I've created to do alignment in my garage are within 1 mm of each other in height. I leveled them with a long construction level but 1 mm (or even a bit more) is within the tolerance for reading the bubble over the width of the car. And with 11k springs, being 1 mm off means 22 lbs off - all else equal.

DavidNJ

The scales need to be level. They sell expensive leveling pads for the scales, some with a roll-on, roll-off to remove any reload from the adjustment which often requires raising the car to reach the shock barrel. Some include ramps. I just use a combination of Masonite sheet I cut into squares and thinner vinyl tile sheets. To check level I originally used a large diameter clear plastic tube filled with colored water attached to shock stands. These day I use a laser level. Once the shims needed are determined, the position in the garage can be marked and the shims just thrown in to place each time the car is weighed.

With oval racing bias ply tires and stagger, scaling the car was a weekly event. With radial tires that may be less important, although tire wear may affect ride height and wedge.

Typically, ride was measured from the frame rail to the ground rather than a reference on the bodywork. In autocross, SCCA specifies the shock length as the ride height measurement.

This pictures shows a scale leveler attached to a platform, a raised stand that lets the tuner work under the car, two different hub stands that take the tire out of the picture giving a consistent reading and allowing more suspension access, and a stand with a roll-on, roll-off provision. There are also plates that let the stand slide to relieve preset. Not shown are a wide variety of ride height measurement tools that slide under the car to reach the frame rails.