As Beau said, every car will be slightly different here based on tire width and frame-to-frame variances. We initially setup my car to not rub at all on the fender liner and that wasn't enough travel because I was bottoming out and getting understeer. So we eliminated the spacer and replaced it with packers. That worked well at about 30mm of drop. Now I'm dropped another ~7mm AND running softer springs. It was bottoming again so I chopped 10mm off the bump stops. However, it's definitely chewing away at the fender liners. I also chopped 15mm off the rear bump stops since there's so much travel available in the rear before the tire contacts the body. See pics below of ground down fender liners with 225/45-17 tires

I'll have to re-measure travel but it's between 1.5-2" front and rear.

 

Why not flare the front fenders and run more aggressive offset. That will give you plenty of outside clearance, and also if running a 225, will fix your front shock tower support clearance issues as well.

As Beau said, every car will be slightly different here based on tire width and frame-to-frame variances. We initially setup my car to not rub at all on the fender liner and that wasn't enough travel because I was bottoming out and getting understeer. So we eliminated the spacer and replaced it with packers. That worked well at about 30mm of drop. Now I'm dropped another ~7mm AND running softer springs. It was bottoming again so I chopped 10mm off the bump stops. However, it's definitely chewing away at the fender liners. I also chopped 15mm off the rear bump stops since there's so much travel available in the rear before the tire contacts the body. See pics below of ground down fender liners with 225/45-17 tires

I'll have to re-measure travel but it's between 1.5-2" front and rear.



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Looks like they increased droop travel in the front over mine.

Will, so just to be clear, you're running a 30mm stop with no packers and no delrin spacer?

 

I was running +45 17x8 RPF1s and a 7mm spacer. I would need longer studs to run a bigger spacer but I prefer to have the wheel tucked under the fender for aero and potential contact reasons.


I think these have the same droop in front as yours. Might just be the angle of the pic. I'm running 30mm stop, 2 packers, and no spacer.

Come to think of it, I think I was getting a touch of push coming out of the corkscrew so it probably would have helped to remove a packer or 2 from the left side. Left side also has more clearance then the right.

 

This is my front damper at full droop, you're running helpers or tenders and I'm not.
I'm running a 30mm stop and the delrin spacer, I'm amazed you can utilize a whole inch of travel over my tire and wheel setup.

 

I think the main difference is skinny 225 tires and that I "clearanced" the frame up front with a dead-blow hammer. When I take off the fender liners I'll take a pic.

 

Ah ok, didn't realize you did that.
Not sure if I can do that, a 255/35 would be nice

 

Just an update on the Ohlins TTX and setup for auto-x use...

Current Settings:
-Ohlins TTX, 2 way adjustable (shortened rears)
-700/500 springs f/r
-12.75"/12.0" ride height (approx hub center to fender)
-Gendron 1.25" Hollow FSB with BB mounts(set 1/6, "full soft")
-Gendron 1" x 0.125" hollow bar with BB mounts(set 1/5 "full soft")
-17x9+60mm wheels with 255/40/17 Dunlop Star Spec Tires (36/34 psi f/r)
-Alignment: -3/-2.5 camber f/r, 0 toe front, 3/8 toe-in rear, 7' caster front.
-OS Giken 1.5 way clutch type differential (softened unlock)

The 2011 Solo National Championships was the first big event where we used these shocks. The rear shocks ended up too long to allow for the ride height we wanted. No matter the settings on the bars and shocks, the car was very unstable for National style autocross courses. 2012 has been a year of progress and changes on at a time. We sent PSI the rears shocks to be rebuilt/shortened. Installed a OS Giken diff, custom rear sway bar kit, modified front sway bar, lowered ride height (more in rear), modified alignment #s, fought with lousy computer tunes and electrical issues, etc, etc. Each time we made changes and felt comfortable with it at local events, the car felt terrible a at the National events. We ended up driving the car cautiously this season and had little confidence pushing it to it's limits. The break-through for us was adding rear toe and lowering the rear at the Blytheville National Tour. I was so fed up at this point, I lowered the rear and added rear toe using plates. With 1" total toe in and a 11.75" rear ride height, the car finally wouldn't spin out every time we tried to power out of turns. There has been plenty of room for shock travel and no bottoming out.

How does this all relate to the shocks? I have felt the car was the problem from the beginning and not the shocks. Running the shocks full soft on both rebound and compression seemed to allow for the best handling. Auto-x usually runs on bumpy lots and involves a bunch of aggressive transitions. Running to much low speed compression or rebound usually make the cars I drive pushy or undriveable at the limit. Once the rears were rebuilt and shortened, there were no more excuses. All our modifications and changes were done over time. No matter how we adjusted the shocks, they would only mask or intensify the underlying problem. That problem was overall grip. Initial bite and rear stability were key for me to drive aggressively. Softening the front sway bar made huge changes to the car's turn-in. That cause the rear to become unstable. Firming front compression and rear rebound made the biggest changes to this. After getting the car stable, Our settings are still really low. In the front, we are running compression at 6/22 or 16 clicks from soft. For rebound we are the same, 6/22 or 16 clicks from soft. In the rear, we are 1 click from full soft (so not to crank the dial all the way). While I'm no shock expert, my impressions is that these are valved too stiff for my needs. The small street tires offer little grip and are the biggest factor here. Unfortunately we can run anything bigger or softer for STR.

With National a couple weeks out, I'm not changing anything. After Nationals, I may try and raising the ride height f/r .5" to make driving around, bumps, putting on trailer, etc. better. After that (assuming handling remains the same) We may try softer sway bars and springs (since we are full soft on most our settings) in hopes of finding a happy median with the adjustable hardware. I would like to get these shocks to a point where we can have room for adjustment. I'm sure there is plenty of other changes we can make that may help. With limited time, money and resources, I wonder if anyone has input to add?

-Marc

 

Nice post Marc, lots of interesting info in there.

Are you sure you're not hitting the bumpstops? You probably have quite a bit of suspension travel with that low spring rates/sway bar rates/damping.

 

One other thing...I've seen those plots, and I highly doubt you want to soften them further. At full soft they're firmly in the territory of shocks you'd find on for example a toyota corolla.