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Fixed: Loose rear end (pulls right accelerating, left on regen)

Discussion in 'Model S: Driving Dynamics' started by zwede, Oct 28, 2019.

  1. zwede

    zwede 2013 P85+

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    TL;DR below

    I have a 2013 P85+ and the last few months I noticed what felt like rear steering. When accelerating the rear end would shift sideways and the car would pull right. During regen it would shift the other way and pull left. My suspicion was rear toe links. There's not much that can make a car steer with the rear wheels and toe links are top of that short list.

    So I figured I'd just pop the toe links out and inspect the bushings. Unfortunately Tesla makes that impossible by mounting the inner bolt that holds the link to the sub frame front-to- back. You can't pull it out as it hits the body of the car. The service manual solution: drop sub frame for access. Thanks, Tesla.

    Not feeling the fun in dropping the whole sub frame I went for the simpler solution of cutting the bolt and inserting the new one from the rear where there is plenty of room.

    So after some inspection and research I found several things.

    My old toe link was PN 1021420-00-A. The service replacement is 1021420-00-B. The difference is that the end of the bushings have little bumps on them now so they lock in place to the frame brackets. The original design with smooth ends will move no matter how much you tighten the bolts as there is quite a bit of play between the eccentric washers (for adjustment) and the frame brackets. I don't know when Tesla updated the part but if your car is newer than my 2013 you may already have the B part.

    Here's what my old link looks like. Notice the center of the left bushing has a flat appearance. This is the outer end that has never moved. The right is the inner and you can see the abrasion damage from sliding back and forth.

    toe link.png

    At this time I thought only the driver's side was moving so I bought one updated toe link 1021420-00-B and the eccentric bolt 2007061 from Tesla. Word of warning: Sellers on ebay want $120-$150 for used toe links but they're only $80 brand new from Tesla! The eccentric bolt was $8.80.

    As I had everything apart I also decided to fix the play between the eccentric and frame bracket by adding welds to the edge of the eccentric and then filing it down until it had a snug fit. This was surprisingly easy and quick to do. I put it back together and unfortunately it was better but not fixed. There was still a loose feeling to the rear. That meant the passenger side had the same problem.

    Before ordering another toe link and bolt I decided to just fix the slop in the eccentric by welding the edge. I could only do the rear eccentric as the bolt can't be removed without dropping the sub frame so that's all I did. Just got back from a test drive and it is now fixed. Rear end is perfectly stable. I'll drive it and see if it stays fixed. If it gets loose again I'll replace the passenger side toe link as well, but as of right now it seems fine.

    TL;DR: Problem is caused by slop in the adjustment eccentric bolt which allows the rear toe links to move. Updated toe link from Tesla ($80/side) fixes it. Alternatively you can weld the edge of the eccentric and file to fit to get rid of the slop instead of replacing the link.
     
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  2. bishoppeak

    bishoppeak Member

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    Clever guy!
     
  3. Ericunirolla

    Ericunirolla New Member

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    Zwede
    That’s some ingenuity if I’ve ever seen some! Do you happen to have some photos of where you welded? I am pretty sure that I am experiencing the same toe link slop you’ve described. I’ve been looking at diagrams trying to figure out where exactly you welded on the eccentric.
     
  4. zwede

    zwede 2013 P85+

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    Didn't take any pics of the eccentric, but I added weld to make it wider. If you look at the eccentric it contacts the frame bracket on two sides. One side towards the center of the car, the other facing outwards. I added weld to one of those contact areas to get rid of the play as the slot is machined too wide. So it's making it wider, not thicker.
     
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  5. linkster

    linkster Active Member

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    #5 linkster, Dec 24, 2019
    Last edited: Dec 24, 2019
    Thanks @zwede !

    I have noticed my jan 2013 delivery 90,000 mile P85 getting loose(r) this past year. I will mic the eccentric slot, add weld, and then file the weld bead accordingly for a zero clearance fit.

    Gosh, you and @lolachampcar are real lifesavers WRT to addressing the shortcomings of the rear suspension on our Ses. champs guidance has me now on *only* my second set of 21 Contis!

    You guys have saved me a buttload of money by significantly increasing my tire service life and I thank you both.
     
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  6. zwede

    zwede 2013 P85+

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    Update after 2+ months: I went ahead and replaced the second toe link for the b-revision as well. I figured it's only $90 with tax and I'll know it's all 100%. That said, I didn't notice any difference after replacing the link compared to the old link with welded eccentric so the eccentric weld is a valid repair even with the old toe link design.

    Car drives as it should, perfectly straight when hammering it.
     
    • Like x 1
  7. David99

    David99 Active Member

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    I had this issue 3 years ago after Tesla swapped a drive unit. I went in several times and they couldn't fix it. Now I understand why. They probably thought it was just not adjusted properly but the problem was really the play and movement under hard acceleration.

    I had the issue come back after I did some work on my suspension and I couldn't figure out what went wrong. Thanks a lot for explaining the issue and how to fix it.

    I have a few questions that might sound stupid but since English isn't my first language some of the terms are not clear to me. When you say you added a weld, do you mean you added material using a welder (electric or gas)? And to which part exactly did you do that. To the bracket on the subframe or to the little off-center piece that adjusts the toe angle?

    I don't have a welder. Would a flat piece of metal to fill the gap do the same?
     
  8. zwede

    zwede 2013 P85+

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    Yes, I used a MIG welder. A MIG welder is electric but uses a shielding gas. The bracket which is a part of the frame of the car is aluminum. I would not recommend welding on it. I welded on the eccentric (that you call 'off-center piece') which is made of steel.

    I don't think you'll have much luck with just adding a piece of metal in the gap without welding. I suspect it will fall out.
     
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  9. David99

    David99 Active Member

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    OK thanks. That makes sense. Why on earth would Tesla design the toe adjustment so flimsy. These cars have massive torque and the forces on the suspension are huge.
     
  10. zwede

    zwede 2013 P85+

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    Oh, don't get me started on using eccentrics instead of threaded rods. A friggin' Ford Taurus (econobox) has a threaded rod and balljoint for rear toe. But Tesla insists on cheap eccentrics.
     
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  11. Vthoma11

    Vthoma11 Member

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    Hello what are the Torque specs for the new links? Tesla wouldn't share with me
     
  12. zwede

    zwede 2013 P85+

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    Toe link to subframe: 80 Nm.
    Toe link to knuckle: 130 Nm.
     
  13. David99

    David99 Active Member

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    Totally! I couldn't believe when I saw this. And after Tesla realized the sliding issue the updated arms just have a few bumps on the contact area giving it more friction. That's a pretty poor 'fix'.
     
  14. ddawson

    ddawson Member

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    Is this zwede with a C3 too? If so Hi.
     
  15. zwede

    zwede 2013 P85+

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    Maybe....

    New springs.jpg
     
  16. Vthoma11

    Vthoma11 Member

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    Thank you!
     
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  17. mrjedistud

    mrjedistud Member

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    @zwede Thanks for this post. My 2013 P85 CPO was just diagnosed with this problem. Tesla wanted $700 for labor for each side (Rear L and R). My local repair guys who does deal with Teslas said to just buy the part and he can work on it. Fingers crossed that he can do it.

    Any specific tips you have other than what's listed above.

    Thanks again.
     
  18. zwede

    zwede 2013 P85+

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    That's a weird quote from Tesla for sure. The service manual wants you to remove the drive unit to gain access to the inner toe link bolt and removing the drive unit is like 90% of the job. So why $700/side? Once they have the drive unit out replacing the second toe link is a 10 minute job. They have to do an alignment regardless. Would make more sense if it was $700 for one side and $800 for both or something like that.

    Anyway, cutting the bolts like I did and turning them around is pretty easy. Your guy shouldn't have any trouble. Be sure to also get new eccentric bolts and that your new toe links have a B at the end of the part number.
     
  19. mrjedistud

    mrjedistud Member

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    Hi. Actually my part has a C at the end. See pic. Also does the drive unit have to come Out. I thought it could be done without removing it or the sub frame.
     

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  20. DukeJockey

    DukeJockey New Member

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    Slight segue to a similar issue with my '15 85D. It was side-swiped while parallel parked. The impact was just in front of the driver side rear wheel. The quarter panel at the front of the wheel well was crumpled, as was the rear door. This happened in a 25mph zone, so I'm guessing that's about how fast the other car was going. The driver didn't stick around to answer questions.

    The car was drivable but didn't go straight. I forget which way it pulled, but it took constant pressure on the steering wheel to keep the car in its lane. Now the bit that's relevant to this thread: The back end would also shift left under acceleration, and the car would take off to the right.

    Here's the work order for what was done to fix the suspension (the body work fills a small volume):

    Concern: Customer states that the vehicle is pulling to the right during acceleration. Please check and advise.

    Verified customer concern. Replaced Left/Right (Includes Alignment) Front Lower Fore Links. Replace LH/RH Aft Lower Front Suspension Links. Replaced LH ((Includes Alignment) Lower Rear Control Arm Assembly. Replaced RH (Includes Alignment) Lower Rear Control Arm Assembly. Verified Proper Operation.​

    No mention of toe links. Also no description of the condition of the old parts, which is now a bone of contention with my insurance. They think it's either normal wear & tear or subsequent damage unrelated to the original collision (per their claims critter: "a rear impact does not cause damage to the front suspension"). The service advisor told me the parts were bent, but didn't write that up in the description of work. The old parts were also picked up by the recycling service the same day the work was done, so I didn't have a chance to retain them.

    The car is now much better, but I think I'm still detecting a bit of shift/pull on acceleration. I need to drive it some more to really convince myself one way or the other. Since my 85D is a '15, it probably has the updated toe links with dimples. However, would a good, solid sideways wallop damage the dimples and allow the toe links to slide? I'm also so worn out by the ordeal of getting the car fixed (it's been 14 months so far), that I'm just about ready to live with it assuming it's not going to cause other damage or excessive tire wear.

    (If anyone's interested, I'll share my 14 month saga of delay, bungling, and incompetence in getting the car repaired. I'll have to tone it down, as I'm a new member and don't want to get banned before being allowed to upload my avatar image).
     

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