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what's bent on my car?

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#1
ptk

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A few weeks ago, at the regional Watkins Glen race, I went off track and hit the tire wall outside of turn 6 (right side of car) during the last session of the STL race Saturday.  I limped the car back to the paddock with the steering wheel angle off left about 20 deg.  I looked for things that were bent and saw nothing obvious (tie rod, control arms, knuckle, frame, brackets) beyond sheet metal.  I measured the alignment and had gone from -3.4 deg camber to -2.6 deg, and from 0 toe to 1.5" toe out!

I looked again at what could be bent and called over some other Miata folks to look also.  The new alignment made it seem like the LCA would have bent to pull the bottom of the wheel in and lose camber and add toe out, but the arm looks solid - no broken paint, no kinks in the flange, etc.  Pulled the control arms off the car, and things still looked ok (UCA bolt came out straight, bushings look good, cam bolts are good). I ended up realigning the car back to approx -3.4 camber and 0 toe, shook it down, and ran on Sunday very tentatively at first and with more confidence as things felt better and better.  I ended up running my fastest lap of the weekend later Sunday (still slow compared to competitive racers). 

Clearly, something is not the way it was originally - suggestions on what to look for? 

Thanks

 

 



#2
Steve Scheifler

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Sounds like the impact rotated a cam bolt. Did you have their position marked and check it after impact? From what you know about the car before and how much more camber you can still get, does it seem likely that you would still be able to get -3.4 after losing .8 to a bent part?

As for spotting a bent LCA, it doesn’t take much to lose that much camber, but it could also be the sub-frame. But a hit that hard at an angle to bend arm or sub-frame would seem likely to bend a tie rod as well.
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#3
FTodaro

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Unless i am missing something you are getting back to the same pre crash numbers, I would think your ok, if something is bent its not much. However, i would put some toe out up front, there is an argument that with that much camber in the front you need toe out to let it roll free.


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#4
davew

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You probably did one of two things, or both.

 

Bent the lower control arm at the rear bushing or bent the subframe at the same point.

 

The best way is to measure everything on that corner and see what is bent. I have a set of jigs that can measure every suspension component and the subframe. First, put the car on stands. Lay on your back and using one hand on each side feel the control arms and subframe mounts. It is kind of ZEN like. Close your eyes and by feeling both sides at the same time you will feel small differences. You will feel silly doing it, but it works.

 

Inspect the wheel bearing/hub, many people report broken hubs after contact. Lower ball joint studs also can bend in an impact.

 

You did not mention caster readings, that can also help diagnose what happened.

 

Think logicly, before tearing anything apart. Since you lost camber you either pulled the upper ball joint outboard (not very logical) or moved the lower ball joint inward (makes sense). Since the toe went dramticly out, the logical thought would be the rear lower arm mount was moved inward (the wheel then pivots off the outer tie rod end). Had you measured caster, you probably would have found a loss of caster on that side as the lower ball joint would be moved rearward.

 

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#5
Steve Scheifler

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Dave, not everyone gets the cam bolts tight, and they can move on impact. It probably doesn’t happen often because to move very much they also have to turn, but just the slop often present in the excentric washers (between the pads and on the bolt for the outer one) allow for a significant amount of movement. As I noted above, I agree with the obvious possibilities but I also know that it could be simpler than that.

One thing about doing all your own setup and being consistent in how you do it, you will know without doubt whether something has bent vs. just moved. At a minimum, each time your setup is changed mark the adjusters. Not that you can use them to reliably get back to some known exact quantity, there’s too much slop for that unless you are extremely careful and consistent in how you set them, but you will know at a glance if they have moved for some reason.
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#6
ptk

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Thanks for the thoughts and recommendations.
I don't think the cam bolts rotated - I have not adjusted it since I got the car last year, but the marks looked lined up - but if there really is that much slop between the bolt and the bushing sleeve, it might have slipped without rotating.  The cam bolts on both sides were pretty much eccentric hole at bottom dead center - so I had 90 deg of rotation available to go inboard or outboard.

I had also wiggled the wheel, and the bearing felt ok, but I will look closer at that and look closer at the ball joint studs.  There is probably a better method to inspect the wheel bearing, but I haven't searched the forum to find it yet.

I also like the idea of feeling underneath the car.  I just need a good mantra to chant while I'm doing it.  I hope to post an update in the next few days for closure, and let you know what I find.

And thanks also for the tip on toe out - I will try a little there for next time out.



#7
Tom Sager

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Thanks for the thoughts and recommendations.
I don't think the cam bolts rotated - I have not adjusted it since I got the car last year, but the marks looked lined up - but if there really is that much slop between the bolt and the bushing sleeve, it might have slipped without rotating.  The cam bolts on both sides were pretty much eccentric hole at bottom dead center - so I had 90 deg of rotation available to go inboard or outboard.

I had also wiggled the wheel, and the bearing felt ok, but I will look closer at that and look closer at the ball joint studs.  There is probably a better method to inspect the wheel bearing, but I haven't searched the forum to find it yet.

I also like the idea of feeling underneath the car.  I just need a good mantra to chant while I'm doing it.  I hope to post an update in the next few days for closure, and let you know what I find.

And thanks also for the tip on toe out - I will try a little there for next time out.

 

ooga ooga ooga chaka    

 

Works every time. 


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#8
ptk

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I realized I forgot to close out this thread.  The answer was the lower control arm was bent.  After it was off the car and comparing it to a spare that I had, the arm was slightly bent through the middle section near where the stabilizer bar attaches.  New arm, new ball joint (just in case), and I should be ready.
Thanks again for the suggestions






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