Testarossa suspension set up | FerrariChat

Testarossa suspension set up

Discussion in 'Boxers/TR/M' started by 66MK, May 29, 2021.

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  1. 66MK

    66MK Karting

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    #1 66MK, May 29, 2021
    Hi, I have an ‘85 Testarossa and have had to change the wheels from the metric standard ones to a reproduction 18” set that look pretty much identical. (No metric rears available) At the same time I had the entire suspension stripped down and rebuilt with all new bushes etc etc. Tyres are 295/30 on the back (should have been 35’s but there you go) and 225/40 on the front.
    Question is what do I set the Geo up for? At the moment I have very light steering around the 12 o’clock position but on a corner - even at roundabout speeds I suffer lots of front tyre screeching and slippage - seems as though it would much rather go straight on. So I dare not push it any harder in case it does. Confidence is low - the car should go round corners considerably better than it does!!
    Anyone got any ideas?

    Mark
     
  2. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #2 Steve Magnusson, May 29, 2021
    Your symptom description sounds more serious than just needing to tweak something a degree or two -- more like something was mis-assembled, and your front suspension geometry is not still adhering to the Ackerman Principle. Don't know if this is even possible to do wrong, but having an A-arm flipped over and/or mounted on the wrong side, etc. would be in that league.

    1. Are you sure the offset of your new front wheels is the same as the originals? (Although "offset" isn't such a clear thing on a knock-off wheel as it is on a 5-lug wheel.)

    2. Did the rebuilding shop provide you with the "after" camber, caster, toe-in alignment values, or did they just say "they are the stock values"?
     
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  3. 66MK

    66MK Karting

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    #3 66MK, May 29, 2021
    Hi Steve,

    Thanks for your reply. I’ve asked them for the figures and await their reply but won’t hear anything till Tuesday as it’s a holiday on Monday. The wheels were made specifically for this eventuality - exchange for the metric ones- so I have to assume their offset is correct. It hasn’t been back for a recheck yet as they asked me to do 100 miles to let all the new rubber bed in. Having never driven another one, I don’t have a frame of reference for how it should corner - but I’m pretty sure it should be better than this!! The suspension was shot when I got the car so it was the first thing I had done on it.
    Once I get the figures I’ll post them here.

    Mark
     
  4. turbo-joe

    turbo-joe F1 Veteran

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    romano schwabel
    #4 turbo-joe, May 29, 2021
    I agree with steve. there is something totally out of limit
    lift the car at the vront axle and try the steering how it works. it has to go all over from left to right and backwards with the same king of power. do this only to eliminate that it is a problem of the steering box
     
  5. 66MK

    66MK Karting

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    #5 66MK, Jun 7, 2021
    Latest: I can’t get the car in for another 6 week!! Annoyingly for me, I have to go to work!! But, these are the settings, from the manual that they have set the car to. Whether that’s what they are now is unknown until they get it back to measure and double check. The comment from the guy that runs the place was “I wouldn’t have set it up like that”.

    Anyone able to comment?

    Anyone able to describe how a testarossa should handle at way below its limit?

    Image Unavailable, Please Login

    I Cant wait to get to the bottom of this!!
     
  6. kartboy1234

    kartboy1234 Formula Junior

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    #6 kartboy1234, Jun 16, 2021
    Did they mount the ball joints backwards? Sounds stupid, but the upper ball joints fit both ways. I did that on one side when rebuilding mine. It looked correct when lifted, but was way off when at road height. That caused very light steering on center and it would pull hard left and right when you hit bumps. Just something to check.

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  7. ago car nut

    ago car nut F1 Veteran
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    #7 ago car nut, Jun 16, 2021
    Sounds like you have bump steer!
     
  8. 66MK

    66MK Karting

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    #8 66MK, Jun 17, 2021
    Hi Kartboy,

    That's a distinct possibility and I'll make sure that is checked out when I get it back to them. Thanks very much for the heads up on that. Is there any way to confirm which way round they do go?

    Mark


     
  9. kartboy1234

    kartboy1234 Formula Junior

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    #9 kartboy1234, Jun 17, 2021
    Sadly I don't have pictures that show it well. Basically when the car is sitting on it's wheels the ball joints will be at extreme angles, what you want is the ball joint to be roughly perpendicular to the ground. Basically when sitting on the ground, get a mirror and look at the top ball joints, if it looks like the ball is going to pop out of the socket then it's in wrong. You can post some pictures and we can give tips. I didn't recognize the problem, it was the alignment shop that did. Easy fix, replaced with new ones as the boots had torn. I'll see if I can find pics.

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  10. 66MK

    66MK Karting

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    #10 66MK, Jun 18, 2021
  11. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #11 Steve Magnusson, Jun 18, 2021
    Last edited: Jun 18, 2021
    Your front upper ball joints look spun around 180 deg from how they should be compared to the front suspension drawing Fig. 3 on page F7 of the TR WSM -- the ball joint mounting hole closest to the boot should be at the inboard position, not the outboard position as yours are. (Will need a serious alignment readjustment after correcting.)
     
  12. 66MK

    66MK Karting

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    #12 66MK, Jun 18, 2021
    Hi Steve,

    Thanks so much for that! I'm away at the moment but will have it checked out as soon as I get home (a few weeks sadly) and I'll drop you a line with the result.

    really appreciate your help, thanks.

    Mark
     
  13. 66MK

    66MK Karting

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    #13 66MK, Jun 18, 2021
    Hi, If you check back you'll see I found some photos....looks like you could well be spot on!

    Many thanks!

    Mark

     
  14. kartboy1234

    kartboy1234 Formula Junior

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    #14 kartboy1234, Jun 18, 2021
    Yep, it's the ball joint. That'll cause the problem. If they aren't damaged then just rotate them around 180 as Steve said. If they are damaged then just replace them.

    See, they look correct enough when the car is raised. That was my problem, made the car unmanageable and a pain in the ass to drive.

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  15. 66MK

    66MK Karting

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    #15 66MK, Jun 18, 2021
    Great News! At last I now have a fix rather than bumbling about in the dark! I intend to replace the ball joints anyway since they have to come off. Can't wait to get home and find out what its really like to drive! Did you stick with the standard geo set up?

    Thanks,

    Mark
     
  16. kartboy1234

    kartboy1234 Formula Junior

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    #16 kartboy1234, Jun 18, 2021
    Yea I stuck to the factory specs for alignment. The alignment shop I used was good and tried getting it as close as possible.

    The shop I used after my suspension rebuild sucked, only did the toe I think, didn't touch the rear. My mechanic even missed the ball joint issue when I paid them to go over it.

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  17. 66MK

    66MK Karting

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    #17 66MK, Jun 18, 2021
    Thanks for that.

    As I said before, I'm away for a few weeks, but I'll post back on here with the results!

    Cheers,

    Mark

     
  18. 66MK

    66MK Karting

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    #18 66MK, Aug 3, 2021
    Hi all,

    Still not home yet - should be soon but I was wondering if anyone had a photo similar to the one posted above that clearly shows that my top ball joint is in the wrong way around? I’m sure that it is as I bow to the much greater knowledge on the thread above, but I’m anticipating a bit of push back from the guys who rebuilt it and I’d really like a cast iron photo of one that’s in the right way around!! Trawled the net to no avail I’m afraid.
    Thanks,
    Mark
     

    Attached Files:

  19. 66MK

    66MK Karting

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    #19 66MK, Aug 3, 2021
    The photo attached is a grab from a pre rebuild video I took - should prove the point I think, but a better one would be much appreciated!
     
  20. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #20 Steve Magnusson, Aug 3, 2021
    The cross-section drawing of the TR front suspension on page F7 of the TR WSM confirms that your "fuzzy" picture shows the correct orientation of the upper ball joint (i.e. - the mounting hole of the ball joint closest to the boot should be at the inboard position):

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  21. 66MK

    66MK Karting

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    #21 66MK, Aug 3, 2021
    Thanks so much Steve,

    I’ve read many of your posts over the last few months of Testarossa ownership - I suspect there are very many grateful people like me out there whom you’ve helped!

    Thanks again,

    Mark
     
  22. Jay535

    Jay535 Karting

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    #22 Jay535, Aug 3, 2021
    Steve, can you please help me understand exactly what is backwards on Mark’s car in that diagram?

    Mark, can you please share more details on those wheels you bought?

    Thanks!!
     
  23. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #23 Steve Magnusson, Aug 3, 2021
    Last edited: Aug 3, 2021
    Look at Mark's photos in post #10 -- the upper ball joints are (incorrectly) spun 180 deg from how they should be.

    Mark's photo in post #18 has the upper ball joints oriented correctly (the top of the ball joint should be almost parallel with the top of the upper surface of the upper A-arm -- whereas, they are not in the post #10 photos).
     
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  24. Jay535

    Jay535 Karting

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    #24 Jay535, Aug 3, 2021
    Got it. Thanks!!
     
  25. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #25 Steve Magnusson, Aug 3, 2021
    It is a bit of a design screw-up to have something that you can assemble incorrectly, but still looks sort of OKish. It should be designed in such a way that it can only be assembled correctly, or, if there are multiple ways to assemble it, all are OK. The Japanese (Toyota formalized it in the 60s) call this concept poka-yoke ("mistake-proofing"), but it's always been part of "good design" IMO.
     
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