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Adjusting the adjustable suspension

Discussion in 'Roadster: Performance' started by Tdave, Oct 29, 2009.

  1. Tdave

    Tdave Member

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    #1 Tdave, Oct 29, 2009
    Last edited: Mar 26, 2010
    Has anybody done adjustments to the suspension in the Sport model, or the regular model for that matter? This is something I've been very interested in doing. I was going to have a race shop tune it, but have just started doing it myself by experimenting...

    Coilover shocks: Set them all to the most firm. This is how I had Tesla set them from the factory, so I haven't compared this to any other setting. Car does feel nice and firm, and reminds me of the feel of my former 3rd gen Mazda RX-7. I'm happy with the firm setting. I'm just assuming this makes a worthwhile difference in handling.

    Sway Bar: Loosened the front. Adjustable sway bar has three settings. Car comes from the factory using the middle setting front and rear. I changed the front sway bar to the loose setting and left the rear in the middle. Goal was to reduce the extreme understeer that the car has. I'm quite happy with the result. Car is more balanced, understeer lessened but still present (for safety). The extreme understeer seems to be gone.

    I need to gain more experience driving with the sway bar change. The rear weight bias will mean the rear will be twitchy near the limit. I'm guessing that's why Tesla ships with some rather extreme understeer. Frankly, I found the understeer as it comes from the factory so extreme that I actually consider it unsafe, at least for the way I drive the car. I have enough track experience to be able to balance the oversteer if it starts to come on. At least I think so. I've been told by a Tesla rep that the extreme torque of the electric drive, if driven with TC turned off, can induce sudden rear wheel spin and near instant oversteer (spin out). With the sway bar change, this danger will be increased. I'll play with this in a safe place to see what I experience.

    Anyone else?
     
  2. Palpatine

    Palpatine Banned

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    My Tesla Sport is current getting serviced, so I just sent an email asking the local Tesla server manager to do exactly the same with mine.

    I am not sure what setting it had from the factory. I will ask and report back on the changes.
     
  3. Tdave

    Tdave Member

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    Just took it out for another drive to gauge the sway bar change. Nice! Really nice! Traffic circles make for good makeshift skid pads. I'd say about half (maybe more) of the understeer is removed by loosening the front sway bar. Now it handles much more like how a sports car should handle. And the gobs of power available coming out of the turn is far more useful when it's applied starting with a more neutral balanced car.

    I definitely recommend the sway bar adjustment.

    You could probably remove the rest of the understeer by tightening the rear sway bar. That may be useful for autocrossing, but probably too much for safe street driving. Sometime later I may try it to see its effect.
     
  4. Roger Reid

    Roger Reid Old but effective

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    Tdave

    What is your definition of loosening the sway bar? Moving the link to the outer hole of the bar?

    Thanks, Roger
     
  5. Tdave

    Tdave Member

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    Yes, moving the link to the outer, rear-most, hole of the bar. When I say rear-most, that applies to the sway bar for the front tires. The front sway bar is much easier to access than the one for the rear. You can easily see the link and the holes by looking through the front wheels and just under the brake rotor.
     
  6. doug

    doug Administrator / Head Moderator

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    This thread could use some photos.
     
  7. Roger Reid

    Roger Reid Old but effective

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  8. DaveF

    DaveF Member

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    Photos and results

    I have a couple of photos of the front bar being re-adjusted. The first is of the Driver's side front bar after the link has been disconnected - showing the 3 adjustment holes. The second is shot from the Driver's side showing the passenger side. The nut to be removed and the washer behind it are in the center of the photo.

    Changing the front was easy without removing the wheels or jacking the car up. Turn the steering wheel to the right to do the driver's side and vice versa.
    You will need 2 17mm wrenches or one wrench (open end) and a 17mm socket and ratchet. One wrench (or the ratchet) loosens the nut, the other wrench goes between the rubber boot and the sway bar to fit over the flats on the stud that is part of the swaybar link.

    The rear is tougher to get to. I backed up onto 2 homemade ramps made of 2 2x6 boards stacked on top of each other. One is 2 feet long the other 1 foot. The ends are beveled to allow the car to drive up on them. It ends up with the rear raised about 3 1/2 inches (due to undersizing of US lumber). Otherwise the same as the front. Jacking up the car will not work, unless perhaps you have 2 floor jacks to jack up both sides at once. This is because you will put the bar in a bind if you jack one side up and then you cannot get the link out of the bar (trust me on this!).

    Results follow from track testing at the MotorSport Ranch 1.7 mile track. First I did a baseline with the stock middle bar settings F/R. Best lap 1:32.7. Then I set the front bar to soft - using the hole at the end of the bar. Huge improvement with a best lap of 1:29.8. Then I stiffened the rear bar by moving the link in the opposite direction - further away from the end of the bar. The change was less dramatic than softening the front bar. Some bonehead pulled out of the pits in front of the Porsche I was following and ruined my planned hot lap. Since it was late in my track day I was only able to run a 2 to 3 laps before getting into reduced power mode and other traffic made a clean lap impossible - 1:30.8 best time. The next time I can run the 1.7 mile track CCW is next weekend. I'll try a couple of sessions then and decide whether to leave it as-is or soften the rear. The car felt much better after the first adjustment and some better after the second - but I want hard data before deciding. I'll also get tire temps and decide on the best tire pressures for the track and likely dial in a bit of camber depending on the temp readings - probably a street/track compromise. Then play with the shocks... Then some Hoosiers... Then figure out how to keep this baby cool for a 30 minute session.
     

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  9. Tdave

    Tdave Member

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    Thanks for the detailed writeup, DaveF. Please update us if you have more insight on settings, including the coilover settings. What were shock settings during the lap tests you did?
     
  10. DaveF

    DaveF Member

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    Stock settings - 5 on all corners for my car. 40 psi rear/30 front. I did check tire temps this weekend and on a track run in the CCW direction, the cold pressures to give a flat temp profile across the tread looked to be about 30RF, 30.5LF, 31RR and 31 LR. I think the rear pressures were too low at that level given the rear weight and want to do some more testing to decide. The RF tire was badly in need of more camber with a 50 degree F hotter outside temp than inside.

    I have not duplicated my 1:29s lap time and plan to put the rear bar back to the middle position with 40 psi rear/30 front to see if I improve from the 1:30s or if the variability is just my inconsistency. I have several hundred laps at this track mostly in a Viper but also in a Spec Racer Ford so I'd like to think I can run within less than a second per lap but I could be wrong - a pro I am not.

    After the above test, I'll put the car on our alignment system and see where stock settings are on my car. I'll then fiddle with shock settings but my hunch is there will be more benefit in softer front springs.

    Your original change to a softer front sway bar has been the single most positive change so far.

    Regardless of the results, this is really fun! I have some cooling ideas to give me more than 3 hot laps before reduced power mode kicks in. With colder weather here, that issue may improve without intervention.
     
  11. doug

    doug Administrator / Head Moderator

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    DaveF, could you repost your photos? I have no idea why they're so tiny.
     
  12. DaveF

    DaveF Member

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    Help

    I will but I am (obviously) photo challanged. They are on my iPhone. What do I do to post them?
     
  13. DrTaras

    DrTaras R254->R725->S1364-->X769

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    Totally a novice here, but I am greatly interested in understeer as I have been the victim of it in the past. When you buy the Roadster Sport they told me the suspension settings were set to "5" out of "10" and that you were entitled to one FREE change. When they change the settings do you know what they are referring to as it applies to the original post? Just shocks, or sway bar, etc? :frown:
     
  14. Tdave

    Tdave Member

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    That's just the adjustable coilover shocks setting. That's not the only part of the adjustable suspension. They should realize there's more to the suspension than just the shocks. I'm sure they'd adjust the sway bar as well for you. For you, and anyone really, the adjustment of loosening the front sway bar is a safe and worthwhile change. I highly recommend it. Just be more careful if you turn off traction control, as it's easier to induce oversteer with power when driving near the limit.

    DaveF is still yet to play with his shock settings. I'm anxiously awaiting his findings. Right now his are all set to 5. And mine are all set to 1 (as I requested from the factory). Neither one of us have tried settings other than those.
     
  15. DrTaras

    DrTaras R254->R725->S1364-->X769

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    Shock setting 1 is stiffer or softer? It obviously affects ride comfort, but does it affect over/under steer?
     
  16. Tdave

    Tdave Member

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    Tesla set mine at 1 when I told them to deliver my car with the stiffest setting. I questioned whether that was right when it didn't feel as stiff as my 3rd gen RX-7 R1. I couldn't find anything online to verify. I'd love someone to verify this for me or confirm. Right now I'm just trusting that Tesla was right and 1 is the stiffest setting.
     
  17. Palpatine

    Palpatine Banned

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    #17 Palpatine, Dec 4, 2009
    Last edited: Dec 4, 2009
    My Tesla Sport came with the factory setting of 5.
    When it was recently in the Seattle service center, I asked Carl to dial it into the firmest setting possible.

    WOW !!!

    The car feels so damn good driving compared to before. It was a nice sports car before, but now I feel like I am driving a fighter jet. This car is so damn tight driving through turns and around other cars in traffic.

    Anyone with a Tesla Sport should do this.

    I don't have enough experience with performance sports cars to describe what is actually happening with any technical details. All I do know is that my Tesla Sport feels amazing. I drove 4,400 miles with the factory setting before the adjustment. So I really can tell something different with the car now. And is a MUCH better feel on the road.
     
  18. Tdave

    Tdave Member

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    So James, can you check what settings your shocks now have? Did they change the setting to 1?

    And have you loosened the front sway bar yet?
     
  19. DaveF

    DaveF Member

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    Adjustable Shock Details

    Correction to my earlier post: my shocks were factory set to 1 front and 10 rear. I thought they were all at 5 because the number facing out at each corner was 5. However, the shocks are read at the inboard side of the shock on my car. I say my car because they can easily have the bottom shock eye rotated 180 degrees. How to tell? On the fronts there is a very small red dot on the side of the mounting eye where the reading is taken - I have not had the rears off and can see no dot when they are mounted on the car. Another way to tell is to cycle the adjusting ring through the full cycle. That is a bit tricky if each shock is full against one of the stops as mine was delivered.

    Second: 1 is the softest, not firmest setting. 10 is the firmest. I felt this was true through internet research (our shocks appear to be the PSS10 model) and verified it on my shock dyno (high quality Roehrig).

    Third and most disturbing was that there was a post on another forum regarding a PSS9 Bilstein (9 position instead of 10) about a dyno test that showed the adjuster was close to useless with 8 settings the same for all practical purposes and only the firmest setting of 9 having any significant effect. I also saw a similar post on a PSS10 Porsche shock that showed complete and proper adjuster response. Unfortunately my dyno results were similar to the former PSS9 test . Settings 1 through 8 were virtually indistiguishable (tested at 4, 6 and 9 inches/second). Setting 9 increased rebound slightly and setting 10 made what I would consider a proper amount of change in rebound. Compression was changed very slightly but insignificantly at setting 10.

    The shock force seemed quite high overall (which is why high speed bumps like traffic lane markers, potholes and other abrupt pavement irregularities are so harsh). I did not take the time to rate the spring but will in due time.
     
  20. Webbie

    Webbie Rather Senior

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    Just got finished with the suspension settings. Front shocks now at 6 (were at 4), rears at 7 (were at 5). Both sway bars have been set to 3 (were at 2). Ride is a little harsh which doesn't bother me. Dramatic difference. Turn in is much smoother and more predictable. Balance is much better. Feels very flat and settled.
    I recommend this if handling is more important to you than ride.
     

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