Adjusting the adjustable suspension

[kgb]

Some guys there were running with racing slicks. My tires were street legal. I think the fastest time was 65 seconds. I fell in the middle of the pack. But the important thing is: I was invited by my brother-in-law who does this ALL THE TIME. The dance at the end of my lap was because I beat his best time by .06 seconds. :wink::biggrin:

June 5, 2011 Autocross Results

 

[Webbie]

Looks to me like you did pretty well. You brought your times down in every run, and wound up with a respectable time for street tires.
We could check with Roger, but I don't think your tire pressures are high for street tires. He may set low because he's running R tires.
If you are still getting some understeer, you could try more pressure in front. Often, the understeer is because the front tires are rolling
over onto their edges. You can mark them with chalk to check that. If the chalk is wearing off, you need more pressure.

I campaigned a Tesla Sport last year with shocks set at 6 front 8 rear and stock tires pressures at 30 and 40. Later I set the fronts higher and had less understeer.
I won my class with a 4th (on snow tires!) a third, two seconds and a first, and finished about middle of the pack overall -- maybe 30th out of 70, mostly BMWs.
We compare with PAX numbers, and the Tesla is heavily penalized by having a Super Stock PAX.

 

[S-2000 Roadster]

What are the torque settings when tightening all of these adjustable suspension nuts and bolts?

 

[richkae]

Have you had a wheel alignment done?
I'm going to be taking my car to an autocross sized track next week, I've been there 4 or 5 times before, but next week will be the first time since getting my alignment done.
( It will also be my first time on R compound tires and with better brake pads, I'm hoping for a huge improvement in my lap times )
The old ( factory ) alignment had massive amounts of toe-in and not enough negative camber in the front.
I'm not an expert, but my new alignment makes the car feel much more ready to turn - but it also feels a little less stable on the highway, the bad pavement and ruts make it drift around a little more, requiring more tiny corrections.
It seems likely that all the drag caused by the toe-in was designed to keep the car going straight.

 

[S-2000 Roadster]

Good question, richkae.

Could someone post alignment specs, both OEM and 'track'?

For my S-2000, I learned that Honda UK took the car around the track until they dialed in the alignment - to reduce bump steer among other things - and those alignment specs were published online. After a year or so with the default Honda US default alignment, I switched to the UK alignment and really enjoyed the car even more.

Sorry for the long story, but I am hoping that we can get similar public sharing of knowledge here. With the adjustable sport suspension, there are obviously more figures to track than mere alignment. So far, we seem to be accumulating great information on the adjustable suspension, so I'm hoping we can add alignment specs as well.

 

[richkae]

My car before the wheel alignment was done ( as it came from the factory plus almost 2 years of driving wiggling things ):

Left Front:
Camber:-0.55 deg
Caster: 4.58 deg
Toe: -2.6mm

Right Front:
Camber: 0.09 deg
Caster: 3.78 deg
To: 6.1mm

Left Rear:
Camber: -2.03 deg
Toe: 3.9mm

Right Rear:
Camber: -1.61 deg
Toe: 6.1mm


New specs ( I told him I wanted to make it perform on the track and still be good on the street, and that I weigh 180 pounds - its a left hand drive car ):

Left Front:
Camber: -0.85 deg
Caster: 4.52 deg
Toe: 0.1mm

Right Front:
Camber: -0.85 deg
Caster: 4.36 deg
Toe: 0.2mm

Left Rear:
Camber: -2.19 deg
Toe: 1.9mm

Right Rear:
Camber: -2.19 deg
Toe: 2.1mm

I don't yet have feedback to give on how it performs when pushed hard, and since I changed two other variables ( tires and brake pads ) it will be difficult to isolate improvements.

 

[Roger Reid]

Well, we took the adjustible suspension to the next level. I sent the shocks off to Bilstein for revalving. Blair just finished testing the new setup in the Winnemucca autocross (the other thread). So now the shocks are stiffer and slow the roll rate a little. We are still rinning the rear sway bar at full stiff and the front at full soft to balance the understeer. With modified shocks we are running the rear at setting 10 and the front at 6. Blair wants to try 8 on the front but my opinion is it will bring back some understeer.
If anyone is interested in the address of Bilstein in SoCal, let me know.

 

[Lloyd]

Sounds like a bigger bar on the rear would help, and possibly allow a better ballance of the front. Likely cheaper than custom bilstein's.

 

[Roger Reid]

Sounds like a bigger bar on the rear would help, and possibly allow a better ballance of the front. Likely cheaper than custom bilstein's.

Not within the SCCA rules for the SS class. Also the stock springs must be retained.

 

[Lloyd]

ah, yes, but would this be a better performance option for the 'street speedster' ?

 

[Doug_G]

My Tesla Ranger recommended shocks 7 front, 8 rear, roll bar outer (loose) front and middle rear. It looks like the factory setting for my car was 4/4/4/4 and middle/middle.

I just dialed in his recommended settings and took the car for a spin. Wow, it's quite a difference. Should have done this a year ago.

One thing I wasn't expecting - the steering feels lighter, especially at low speeds. Should I have expected that?

 

[speedy99]

Now my turn to play with settings. I am using the EU spec sheet as a guide (Thanks!). My 2.5 settings from the factory were as specified on the sheet (for AD07 tires - which I have) - Shocks 4-Front, 5-Rear, Anti-roll bar in center on front and rear. The shocks are TRIVIAL to adjust, once you know what to look/feel for. I had the benefit of looking at a Tesla on a rack a week ago at the Menlo Park store - so I could see the orientation of the shocks. You can peek through the ends of the car to see what setting they are on, then reach around and "click click" to adjust, and double-check the numbers when done. All I needed was a flashlight and about 10 minutes.

I have dialed in the "Factory Sport settings for AD07 tires" as a first step - cause I am lazy. This means no change to sways (slightly harder to adjust), but Front/Rear shocks at 7/8 instead of 4/5. I plan to do a bit of driving today (got the day off), to see the difference.

My second test will be to adjust the anti-roll bars. I'll look at loosening the front (move to hole on the "outside edge" of the bar), instead of stiffening the rear (per the spec sheet), since this mod seems easy, and is getting good reviews here.

For full disclosure, I am using the Tesla as a "daily driver", and I've done several dozen open track days in other cars, but fewer autocrosses, so I am looking for more mid-high speed stability, excellent turn-in, but with some comfort. As a "comfort" benchmark, I've had a few M3s (stock and modified suspensions) and a 911 with PSS9 setup, so "comfort" to me is relative. I like my suspension "confident", but not "rock hard". I could certainly stand for better turn-in and less understeer, and a bit more "confidence" on the shocks.

 

[Jaff]

I had Mark emulate your settings on my car...noticed a big difference right away...the car corners much better now!

My Tesla Ranger recommended shocks 7 front, 8 rear, roll bar outer (loose) front and middle rear. It looks like the factory setting for my car was 4/4/4/4 and middle/middle.

I just dialed in his recommended settings and took the car for a spin. Wow, it's quite a difference. Should have done this a year ago.

One thing I wasn't expecting - the steering feels lighter, especially at low speeds. Should I have expected that?

 

[speedy99]

This means no change to sways (slightly harder to adjust), but Front/Rear shocks at 7/8 instead of 4/5. I plan to do a bit of driving today (got the day off), to see the difference.

My second test will be to adjust the anti-roll bars. I'll look at loosening the front (move to hole on the "outside edge" of the bar), instead of stiffening the rear (per the spec sheet), since this mod seems easy, and is getting good reviews here.

The shock setting change had very little impact - as could be guessed based on previous posts. If anything, it is a bit smoother (ironic). This is because on freeways, the front end can get a bit bouncy over old expansion joints. The slightly stiffer settings seemed to have settled down the car a bit. I suspect this is because the springs are a bit stiff, so the suspension is a better match on the sport setting.

The tips on anti-roll bar (17MM (deep) socket and wrench) are spot-on. Really easy to crank the wheels over, and adjust the front sways from the rear side of the wheel. I just changed to loose setting for front (keeping middle for rear), and it is time for another test drive. I suspect this will make a bigger difference in handling.

As an aside, making the front bar looser, or making the rear bar tighter technically should have a similar effect. Since I am not worried about the car leaning when cornering, the front-loose option is a better/easier one for me...

I'll update again after the second test drive! Fun!

 

[Doug_G]

The shock setting change had very little impact - as could be guessed based on previous posts.

Yes, the effect of dialing the shocks is fairly subtle.

The tips on anti-roll bar (17MM (deep) socket and wrench) are spot-on. Really easy to crank the wheels over, and adjust the front sways from the rear side of the wheel. I just changed to loose setting for front (keeping middle for rear), and it is time for another test drive. I suspect this will make a bigger difference in handling.

Unless you are willing to jack the car up and remove the wheel, it is far easier to adjust the front. I can't comment on the relative effects of the front and back sway bars, but adjusting the front has a very noticeable effect.

Has anyone here tried adjusting both the back and front sway bars?

 

[Roger Reid]

My suggestions for the 2.0 or 2.5 with adjustible suspension is to start out with the front sway bar set at loose (outside holes).

The rear sway bar set to firm (inside holes).

Set the shocks up at 5 front and rear.

Set the tire pressure at the recommended street pressures (example 35 psi all 4 tires).

In general whatever you do to the left front, do also to the right front. The same goes for the rear.

In general whichever end you stiffen up, it will push more.

Stiffining up the rear will shift the balance of the car towards more oversteer whether done with the sway bar, shock, or tire pressure. Softening the rear has the opposite effect.

Stiffining up the front will shift the balance of the car towards understeer. Softening the front has the opposite effect.

Now go out and mark out a 60 foot radius skid pad in a safe empty parking lot where you won't get anybody mad at you. Enter the skid pad and start increasing your speed until you reach the maximum speed you can maintain. Either you will find out that the front end pushes (understeer) or the rear wants to spin out (oversteer). Go both directions to even out the tire wear and temperatures of the tires.

If in the case of understeer (most likely) you will want to stiffen the rear shocks 2 clicks at a time (remember both left and right) then test on the skid pad again. If you reach full stiff on the rear shocks, next soften the front shocks 2 clicks at a time then hit the skid pad again. If you still have understeer after changing front and rear shock settings, increase the rear tire pressure 2-3 psi then skidpad test again (6 psi max difference front to rear). Something to remember is that the heat generated by working the tires on the skid pad will increase the pressure in all tires until the tires cool off. If it still pushes, decrease the front tire pressure 2-3 psi.

If in the case of oversteer (not likely), do the opposite by adjusting the shocks first, tire pressure second (6psi max difference front to rear psi), then sway bar adjustments.

I hope this helps.

 

[speedy99]

I just changed to loose setting for front (keeping middle for rear), and it is time for another test drive. I suspect this will make a bigger difference in handling.

OK, front bar adjust is the "fix" that makes the most sense. Hard to believe what a difference such a small adjustment makes, but WOW!! Just got back from a nice "Skyline" drive. A few low speed (20-30) corners, and lots of sweeping mid-speed (40-60) twisties. The car is MUCH more neutral than before. I can get it to "set" in corners, and adjust with the throttle (I left TC on). Still a (slight) tendency to understeer, but not nearly as much as before. For me, this is a good thing. If I was doing competition/autox, I might be more extreme, but for my daily driver with occasional detours into the local hills driving at 8/10, I'd say this setup is just about perfect. It feels just as "comfortable" as before (tested on those pesky freeway expansion joints), but the handling is MUCH MUCH better.

To complete the picture/recap, I am also running the "sport" tire pressures (30F/40R), and have the AD07 Tires. Front shocks at 7, Rear shocks at 8. Anti-roll bar front at full soft (outer-most hole), and rear anti-roll bar at the middle setting. This is a 2.5 sport model with less than 1000 miles on it. Now that I've upped the fun factor, I am sure I'll be hanging out on the tire thread sooner than I expected...

Enjoy!

 

[Doug_G]

I hope this helps.

Indeed, very useful information. I'll have to see if I can find a place to use as a skid pad.

I did find by trial-and-error that I had to reduce the pressure in my fronts by a few psi. Otherwise the car would really plow in the corners. That was after the loose/middle and 7/8 adjustment. It made a huge difference.

Do you readjust your sway bars back to mild understeer when you aren't autocrossing? I've seen a comment elsewhere that balanced settings might make a car a little twitchy for street driving. After all it's one thing to mow down cones...

 

[SByer]

Darn! Now I really have to get the suspension upgrade!

And, if you 'Skyline' Sunday mornings at all, watch out for me so you don't wreck me and my other carbon fiber beauty. I'll be in the Chrome kit, so you'll know it's me. ;-)

 

[Roger Reid]

Doug

I dont change the sway bar settings between autocross and street driving. If anything I just soften the shocks.

Roger