Steering wheel shimmy |
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Steering wheel shimmy |
rbutler914 |
Jul 27 2023, 09:43 PM
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#1
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Newbie Group: Members Posts: 4 Joined: 5-June 14 From: Jackson, CA. Member No.: 17,439 Region Association: Northern California |
I’ve been doing a bit of freeway driving lately and I have a weird steering wheel shimmy, noticeable between 60-80 mph. The strange thing is it dissipates after about 5 seconds, the returns about 5 seconds later and continues like that. There is no accompanying wheel vibration or shaking, just the steering wheel. Any thoughts would be appreciated.
73, 1.7, all stock, slightly lowered by previous owner. |
rbutler914 |
Jul 30 2023, 02:00 PM
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#2
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Newbie Group: Members Posts: 4 Joined: 5-June 14 From: Jackson, CA. Member No.: 17,439 Region Association: Northern California |
Wow, thx for all the great suggestions. I’ve already tried balancing the fronts. Swapping with the rears will happen next. Btw Fuchs 2 liter wheels with 205/50 tires. I have a suspicion that front end geometry and/or worn components might be the issue, that’ll be next. The fact that it comes and goes and constant speed and road surface in puzzling though. I will definitely report back.
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Superhawk996 |
Jul 30 2023, 02:24 PM
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#3
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914 Guru Group: Members Posts: 5,891 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch |
The fact that it comes and goes and constant speed and road surface in puzzling though. The reason it comes and goes is because of phasing between the right and left wheels. The R1H component for right and left tire are not usually occurring at exactly the same place (in degrees of wheel rotation). The right and left tires will have slightly different diameters due to tire pressure and tread wear. This means they rotate close the same amount between the sides but not not exactly the same. Because of the slight difference in rotational speed between them, they will periodically align where both R1H forces occur at the same time - doubling the forces acting on the steering system. This is when the shimmy will be at its worst. Then due to the rotational speed difference, R1H forces will eventually go out of phase between right and left. The shimmy will dissipate for a bit. This pattern repeats over and over. Sometimes you can immediately break the shimmy if you are able to turn slightly. As you turn the right and left tires have to rotate at different speeds through the turn. Forcing that speed differential can move the R1H forces out of phase more quickly than it would naturally occur when travelling in a straight line. |
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