Limited rear droop travel

I noticed my rear droop travel was way too limited and suspected that could explain some of the rear inner wheel spin I have been troubled with.

My car is fitted with a Quaife ATB, and one of the "features" of the ATB compared to other LSDs is that if one wheel is completely unloaded, the ATB won't lock! So, when in roll while cornering hard, and the droop travel is too limited, the load on the inner wheel is reduced and the ATB is unlocked with inner wheel spin as a result.



More info about how the Quaife works

Here is a good article in Mark Ortiz Automotive CHASSIS NEWSLETTER describing what's happening when the droop travel is limited.

So now I have lowered the car with three complete turns on the spring platform on each damper.

I was at Mantorp (where else...) testing last week, and yes, the difference was obvious. No corner entry over-steer I've complained about last time, and the corner exits where a lot less dramatic. I think the inner wheel spin was reduced as well, but not completely. I've read on Blatchat that inner wheel spin is a common complaint on the ATB and what makes it not suitable for racing, and the solution is probably to change to a real LSD such as the Titan.

During the day I also experimented changing the rake to change the under/over-steer balance and found it to be a very easy and convenient way to quickly change the car characteristics in a few minutes. Just jack the front up and remove the hood and turn them with your hands. As little as an half turn each made a real difference. I made the car a little more tail happy and it did affect the lap times in a positive way.

But as usual...

That stupid plastic piece of tubing on the inlet was cracked, again. I tried to fix it with some isolation tape but it still leaked and sometimes the engine hesitatate at 6000 rpm as well as a notable lack of power. So no personal lap records today even if the chassis felt good.