Three-wheelin'I have an S13 hatchback with D2 coilovers, 255/40-17 Falken Azenis RT615s on all corners and an S15 helical limited-slip differential. At my last track day, I had problems with the inside rear tire lifting during cornering, which causes the helical limited-slip to just spin the inside tire. Obviously, this was killing my exit speed.
This just started happening because I went down in spring rates in the front from 9kg/mm (500lb/in.) to 7kg/mm (390lb/in.)-I have 7kg/mm springs in the rear. I did this because I was having a hard time keeping the front tires on the ground when things got a little bumpy.
I've tried removing my rear anti-roll bar since then in hopes of keeping both the rear tires on the ground, but to no avail. Now I am awaiting a pair of 5k springs for the rear. I'm hoping this will help/cure the problem.
Have you ever had problems lifting the inside rear tires on your S13? I am looking into a new set of dampers (with a longer stroke and softer springs (preferably 6kg/mm (335lb/in.) up front and 5kg/mm (280lb/in) in the rear coupled with Progress anti-roll bars).
Are there any dampers that you would recommend for road racing and a little bit of autocross? Rob EvansUndisclosed location
From the problem you describe, it's not clear that you necessarily need new dampers, you just need to adjust things a little smarter.
My first guess is that your rear spring doesn't have enough droop travel. A 7kg/mm spring rate converts to 390lb/in. With about 600 pounds on each rear tire, the spring is only compressed 1.5 inches when the car is sitting on it. So if you have enough body roll to make the inboard suspension droop a mere 1.5 inches, the wheel will have nothing pushing down on it. Sure, the shock might allow the wheel to droop farther once the spring falls off the perch, but with no spring pushing it down, there is no grip.
Now, if you've been misled into thinking you need to 'pre-load' the spring, you might be in an even worse situation. The D2 coilovers have threaded spring perches and threaded shock bodies, allowing you to adjust the spring position and damper position separately. Many people will tell you to adjust the spring perches so the springs are slightly compressed when the suspension is at full droop and then adjust ride height by adjusting the damper position.
Say you did this, and pre-loaded the spring by half an inch. Now you have only one inch of droop travel before the wheel comes off the ground. Nice job.
First, you need big anti-roll bars on an S13. Get the Progress bars now. Less body roll means you'll use up less droop travel with body roll. Second, install the softer rear springs you already ordered: 5kg/mm, or 280lb/in. gives you 2.2 inches of droop travel. Not exactly SCORE territory, but a big improvement, especially if you reduce your body roll.
I run 6kg/mm up front and five in the rear and never lift the inside rear tire.
Do the spring and bar adjustments I suggested before tossing those dampers.
If, with this setup, you still can't get the damping behavior you want, then you can look for other dampers.
In terms of a recommendation, all I can offer is the opportunity to blindly follow my blind lead. I'm working on setting up another S13 for street and track and I had to work up a custom-built set-up to get the results I want. Ground Control is building new strut housings to hold Koni Sport inserts and 350lb/in. springs in front.
In the rear, it's 300lb/in. springs and Koni Sport dampers for a Z32 300ZX. The Z dampers are needed to match my Z rear uprights, though 240SX Konis will work if you still have cast iron back there. Progress anti-roll bars and a helical Quaife diff round it out.
My experience with Konis tells me this should give good ride and good body control on the track, but nothing is installed yet, so at this point it's just my well-honed gut telling me this will work.