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suspension problems - swerving after bumps in the road, with steering wheel straight

Discussion in 'Roadster: Technical' started by S-2000 Roadster, Jan 4, 2015.

  1. S-2000 Roadster

    Joined:
    Apr 10, 2009
    Messages:
    636
    I have a strange problem with my roadster suspension affecting steering.

    Recently, I had some suspension parts replaced with upgraded (stainless) Lotus parts, and then I had an alignment done. Now, my roadster swerves violently to the side whenever I hit a bump in the freeway that causes the suspension to bounce. Strangely, though, if the bump in the road is equal on the left and right side of the car, then there is no sideways travel - the car stays true. But, if there is a bump, dip, pothole, or road turtle on only one side of the car, the car will steer to the left or right after the bump as the suspension bounces. It's so bad that I can't travel on the freeway in the rain, because the car feels like it could easily lose traction or control.

    It's hard to be precise in my description, because the effect is more pronounced at highway speeds. I think that the unexpected steering occurs even with just an uneven road surface where one wheel articulates more than the rest as the suspension flexes to fit. It could be that the bumps are only causing the swerving when one wheel's control arms flex more than the others. Is it possible that some cross-linkage is loose or was left unattached during the recent work? The car has never performed like this before the recent service.

    Does anyone understand the Tesla / Lotus suspension well enough to say what could cause this? The alignment required adding shims, and the mechanic who upgraded to the Lotus parts has backed off on the shims to a setting in between the old and new, but I don't see how shims could make this much of a change. I drove the car for 2 years before this recent work, so I'm quite familiar with how the Roadster is supposed to handle bumps and uneven highway surfaces. I'm also taking the car to a different alignment shop that was recommended by a Lotus dealership here, so I assume everything will be worked out eventually

    I'm mostly wondering if there is any information available from Lotus or Tesla that would allow me to gain some understanding of the suspension. I guess I've been spoiled by Honda, who has detailed Service Manuals for all of this sort of thing, and where a few engineering drawings can make the geometry and settings fairly obvious. I interviewed the Lotus dealer extensively, but apparently there's just no information. I'm hoping someone here has a different answer.
     
  2. Doug_G

    Doug_G Lead Moderator

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    Are you certain the changes didn't affect suspension geometry? They are exact replacements dimensionally?
     
  3. wiztecy

    wiztecy Active Member

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    Santa Cruz, California, United States
    #3 wiztecy, Jan 4, 2015
    Last edited: Jan 4, 2015
    Whatever work they did they didn't know what they were doing. They made your "bump steer" worse. The Roadster inherited the bump steer problem from the Elise. And if something wasn't set right when they did the work, they aggravated the problem. Possibly if they did your alignment wrong, especially with the front that could amplify the issue. Something or someone changed the geometry of your suspension. As Doug mentioned if the part is not geometrically spec'd correctly that will definitely cause a problem.

    Bump Steer Explained - Circle Track Magazine

    What are these "some" parts you changed?
     
  4. S-2000 Roadster

    Joined:
    Apr 10, 2009
    Messages:
    636
    Thanks for the responses. The link was educational.

    I took my car to Tru-Line in Bellevue, as recommended by the Lotus dealership, and now the car is perfect. I'll do a writeup on the other alightment shops that did so poorly, but I'll save that for another thread.

    I'll be back here with some photos of the replacement parts, although it seems they were exact replacements after all, because she drives perfectly now!
     

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