Good stuff Lance, keep it coming. I'm in the same dept as you, only phase II we'll call it. Got some stuff coming (well, que'd up) from the good doctor as well.....

Lance, would you be so kind as to share spring specs with us, please?
Will this require a shock re-valve?

I've spent a couple days driving the car around now and so far, I like it! The ride isn't bad at all, in fact it's better than when I bumped the compression in the rear shocks up to compensate for the too soft prior springs. I'm not sure I can accurately describe how the car feels on the road now, it's like it pivots or rides off the rear of the car instead of the front. I'm still getting used to how well it corners, rear grip has increased tremendously. I'm loving how I can drive it right up to the edge comfortably and it gets tight first instead of loose...with the rear staying under the car the whole time.

I still have the rear shock rebound and compression set at full soft (so I wouldn't freak out on the ride initially). I'll bump up the rebound to where I used to run it before for my first run at the race this Sunday and see what happens. :D

Doctor Ron said to put everything else back to where it was and run it. I've been thinking that it does seem to be tight once I race it, I can stiffen the rear sway bar up to loosen it up again. And I have plenty of adjustment available in the shocks as well if necessary.

My daily driver truck in on the lift now with the front steering knuckles off getting new upper and lower ball joints, idler and pitman arms...so I don't think I'll get to swapping the BFGs on before Sundays race. That test will have to wait until later.

Scott, I took out 250# springs and replaced with 600#s.

Lance, I could tell that they visually looked to be much higher rated. I'm amazed that you are experiencing a tight condition with these rear springs. Keep us posted sir!

Well, my first autocross with the new rear springs was educational. :D It started off pretty rough but with shock adjustments got much better by runs 3 and 4. The late roll thru to corner exit rear grip is vastly improved. I kept sneaking up on it not knowing what to expect and it never once surprised me which is a very good thing, I have fought that issue for over a year. It still needs more tuning though so I signed up for a bonus SCCA event happening in Topeka this Sunday. We should get a few extra runs and hopefully some fun runs after the event which will give me more time to tune on it.

I also mounted these up yesterday...

http://img.photobucket.com/albums/v3...psc5rz597s.jpg

http://img.photobucket.com/albums/v3...psjll7nsko.jpg

They look SO small...but they seem to be pretty grippy so far...

My runs from last Sunday...

Lance, any insight on theory/logic of increasing the rear spring grip so drastically to increase rear grip on exit? That is in the opposite direction of what my noob understanding would of thought. I'd love to learn why this works.

Also, did you notice an impact on the front end grip on corner entry and mid corner (which I would expect with such a jump in rear spring rate)?

Did you or Ron calculate spring frequencies or motion ratio in making the spring change?

Finally, you didn't get a chance to compare before/after on the same tire compound on a course, correct?

Thanks for being willing to share on this stuff.

Chad, I'm sure Ron will be along to explain it correctly when he gets caught up, he'll do a much better job of it than I will attempt to here.

The huge jump in rear spring rate is largely geared toward reducing rear roll rate (or increasing rear roll resistance, whichever way you want to look at it) without relying on a sway bar or help from the front in this manner. This in turn lets the inside rear tire stay planted and working in the roll thru or corner exit portion of the turn which is where my old setup was severely lacking. Ron did all of the calculations and has been trying to convince me to try this for about a year now.

With my rear roll center being so ridiculously high and no way to change that without adding more parts (watts link) this was the next logical step in making the car faster for us. The front was not affected at all, this thing still flat turns anytime I want it too, I can't remember the last time it pushed when not not induced by driver error.

I did not do any back to back tests on the same course...as we never run the same course twice...but my highway off ramp tests were done before and after the spring change with everything else the same including the tires. The rear grip change on long on\off ramps was drastically better with the new springs, application of throttle used to make it edgy loose, now the rear stays stuck while eventually the front will start to slide just a bit when adding throttle, just a light lift brings the front right back in. It is MUCH easier to drive fast this way. The autocross I ran last Sunday was pretty typical of a lot of the courses we run and I did it on my Falkens that I'm very used to so it was a good comparison as well.

What I did not know where to start with on race day was my rear shock settings... I initially had the same amount of rear rebound that I normally run, no rear compression and I hooked the new rear sway bar back up for my first run. Hence the huge drift slide in my very first turn... :D The car was super loose on corner entry, something I was not ready for. The inside rear shock just picked the right rear tire up under braking and turn in and all rear grip was gone after that. For each run after I kept taking rear rebound out and eventually started adding rear compression and I got the entry much better. Roll thru and corner exit were AWESOME, really felt good to not be afraid to push on the loud pedal with authority on corner exit. I only got 4 runs at it though, I believe with a few more driver mods and a click here or there more on the shock knobs can really tame down corner entry and it'll be a much easier car to drive fast on course as well.

Chad, go to about 3:00 in the video above and listen to my exit from the left hand sweeper. An application of throttle like that with my old setup would have spun the car out no doubt...it hardly even chirped the rear tires.

Thanks Lance. Explanation makes sense to me (again I'm a noob at this stuff).

Again I'm just looking to learn, but why did you want to not rely on a sway bar to accomplish the increase in rear roll resistance? In the back of my mind is Ron's soft spring big bar discussions.

With my rear roll center like it is, a stiffer rear sway bar just picks the inside rear tire up instead of limiting body roll. Disengaging the inside rear is one thing, carrying it 6" off the ground corner entry to roll thru zone is something much worse...

I'm not saying this is how it is for everyone, it is just how it is with my car right now.