Advice: Tie rod lengths

"InfinityAero" (infinityaero) 07/12/2016 at 17:04 • Filed to: None

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I’m installing new tie rods and the stock center link/steering column alignment results in the wheels being off by about a third of a turn of the steering wheel when the tie rods are set to equal lengths. By shortening one and lengthening the other so they’re about 1/2" different in length I can get the wheel center-aligned. Will this cause problems with bump steer?

If so, I’m guessing I should set them to equal lengths and then try to find a way to adjust the center link or steering column...

TheTurbochargedSquirrel > InfinityAero 07/12/2016 at 17:11

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Set them to equal lengths and then take the wheel off and resinstall it so that it is straight.

RamblinRover Luxury-Yacht > InfinityAero 07/12/2016 at 17:16

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Adjusting the center link would be best, but may not be possible. It depends on the setup of the suspension, of course, but if you have a flat tracking tie rod that climbs (let’s say) 10 degrees in a bump, then it “shortens” by about a percent and a half. Let’s say a longer rod makes it swing only seven degrees on one side *as well as* being longer. Okay. That’ll be .8%. Assuming (wildly) that your tie rods are about 10" long, hitting the bump will give you one rod at 9.85" long and the other at 10.4", or a *shift* of difference between the two links of at most ~.05". This is *not* very significant. This is a wheel twitch of around half a degree.

LOREM IPSUM > InfinityAero 07/12/2016 at 19:34

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Tow it to an alignment shop and let them deal with it. It’s gonna need an alignment anyway.

(Fwiw, I aligned the front end of my e38 with a plumb bob taped to the center of the roundel and a tape measure. Car drives straight and still on the same front tires two years later, wearing equally, somehow. I wouldn’t recommend others do the same however.)

Ideally, next time, before you remove the tie rod ends, count how many exposed threads you see and make a note of it. Then reinstall the new new with the same number of exposed threads.

InfinityAero > LOREM IPSUM 07/12/2016 at 21:36

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Alignment shop was actually my first step after I bought the car. They weren’t able to get the camber within spec and didn’t want to mess with it after that. The camber is highly dependent on the bushings for this car, so a front suspension rebuild was in order. All upper and lower A-arms, springs, shocks, bump stops and tie rods. The thrust angle was off for the rear axle by about a degree as well, so I decided to rebuild the rear suspension with new shocks, springs, long trailing arms and a new panhard rod. All is installed other than the rear shocks and springs; which I hope to have done this week.

The tie rods were ancient— original I’m sure, and totally siezed to the centerlink. Needed a tie rod press. I pulled off both tie rods and visually compared them— they were off by about .5" I split the difference in length before reinstall... but that leaves the steering wheel off center.

I’ll be at least checking the alignment after all is said and done. Based on the other advice I’m going to set them to equal lengths, straighten the tires, align it like that, and then deal with adjust the steering wheel or center link afterwards. I know I can get it in alignment for driving straight, but I’m thinking a half degree of toe in or out is the difference between neutrally stable and unstable mid-apex, so I may as well do it right and get the tie rods as close to equal length as possible.

Not familiar with the plumb bomb technique— I used string wrapped around the 4 tires last time I set the toe on a car. Will look into that.

InfinityAero > TheTurbochargedSquirrel 07/12/2016 at 21:37

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I think this may work, the manual shows just a single bolt holding on the steering wheel— doesn’t mention it being indexed. Thanks for the convo below guys, great info.

InfinityAero > RamblinRover Luxury-Yacht 07/12/2016 at 21:48

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Thanks for the math! You had me pulling out SohCahToa and drawing triangles... checks out (sheepish face for overthinking it) and yeah, I think I’ll just deal with the tie rods being slightly unequal... I am not nearly good enough of a driver to notice a .05-.1" difference...