[dradernh]

Originally Posted by capt_and

It is going in for a cage and carbon fiber roof today! Should take up to 8 to 10 weeks to get it back. After that, we will install the MCS coilovers, SPL control arms, monoball and other solid bushings.

In terms of track performance, I did the first session on Saturday using the same beat up RS4s on the 9.5" wheels and was able to match my best time (haven't driven the car in awhile and it took some getting used to) that I set on the RE-71Rs. So I would say, all things being equal, the rear sway bar, custom engine mounts/differential bushings did help. The car went from an understeering cow to a tail happy monster. In terms of characteristics of the car, it is the polar opposite.

After the first session, we switched over to Hoosier A7s on 10.5" wheels. Lets just say I am not at all used to the grip level! There is a lot more grip there to exploit. We switched to a narrower R7 the next day and there was still a ton of grip. This is the first time I've ever been on a sticky tire so it was definitely a whole different experience. Lap times effectively dropped by 2 seconds BUT the theoretical times dropped by over 4 seconds. The theoretical and actual times for the street tires were within 0.3 seconds. Pretty obvious that I need to learn how to actually use the Hoosiers!

RS4: 1:24.01
Hoosier R7s: 1:22.04
Hoosier theoreticals: 1:19.7

Before: The car exhibited a lot of understeer throughout the whole corner, it was hard to move the rear unless all of the power was applied in the corners, and the car struggled to rotate.

After engine mounts, diff bushings, and rear sway: I almost lost it on the outlap because the tail of the car came out so quickly. If I had to choose between the two, I would take the tail happy version even though it is harder to control for me at this time. Why? There is a bit of a helpless feeling when the car is pushing and the only thing you can do is slow down. In contrast to oversteer where a little counter steer can bring everything back in line. I would venture to say that we could keep this bias as is because once the wing goes on, it should stabilize and balance everything out.

Also, fun note, there is gear whine from the diff bushings. So cool.... Major thank you to Texas Track Works for doing the tire test with me!

A7s / R7s...now we're talking!

Seriously, the R7s likely offer the minimum grip level required to get the most out of what you're building. An A7-level tire offers even more grip, but at the expense of a much shorter life at that grip level. If you ever decide to time trial, or even sprint race if the race is short enough, the A7 can work quite well.

"I almost lost it on the outlap because..."

Don't discount the fact that the tires were not yet up to temperature. That makes a much bigger difference with the stickier compounds, and if you're injudicious on the out lap with either the throttle or the brake when the tires are still cold, they can bite you...bigly.

It sounds like your build is really coming together. Thanks for sharing in such detail what you're doing - it's much appreciated!