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Discussion Starter #1
So, I swapped out my summer tires for winter ones over Thanksgiving and since then I feel like the ride of my car has changed. Sometimes at around 55 or 60mph crusing on the highway I can kind of feel a rhythmic vibration underneath me. The weird thing is that I don't feel that at all in my steering wheel. My steering wheel doesn't wobble and stays perfectly calm. I only feel the vibration underneath my butt and my legs. I can't tell if it's just the road causing the car to kind of bump up and down (only at certain speeds though?), or if it has something to do with the new wheels or tires. I bought used stock wheels from another forum member and put a set of Michelin Pilot Alpin Pa3s on them. Should I get them checked out or am I just being paranoid? Sometimes I think I'm just being over-sensitive to it. Ideas anyone? Thanks!
 

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Were they ever balanced?
 

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My winter set is noisier and and not as smooth as the summers.
 

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I would check the balance of the tires, if it's one of the rear tires that is out of balance you wouldn't really feel it in the steering wheel.
 

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Discussion Starter #7
I had the tires balanced when they were first mounted, then balanced a second time when I thought something was wrong. I just came back from driving around the highway to see if I found any pattern and it doesn't seem to be super consistent. It's just kind of...bouncy but It's so subtle I think I'm imagining it half the time. It think it might just be the winter tires being a little less smooth than the stock F1s. If there were a wheel issue I'm going to guess any vibrations would be much more pronounced. I might just need to get out of my own head...
 

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Move the tires front to back and see if it changes anything. My guess is tire balance or tread separation. Could also be a bent wheel.
 

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I had the tires balanced when they were first mounted, then balanced a second time when I thought something was wrong. I just came back from driving around the highway to see if I found any pattern and it doesn't seem to be super consistent. It's just kind of...bouncy but It's so subtle I think I'm imagining it half the time. It think it might just be the winter tires being a little less smooth than the stock F1s. If there were a wheel issue I'm going to guess any vibrations would be much more pronounced. I might just need to get out of my own head...
Two things:

One, see how many weights are on your rims. Sometimes the tire guys will "chase weight" and add a lot of weights in lieu of spending the necessary time to balance them correctly. If you have a bunch of weights, take it back and tell them to do it right.

Two, it depends on what kind of tires you have. Some all seasons have a tendancy to flat spot pretty quickly. I have the cont extr contact, and when it's really cold they'll flat spot over night. This is worked out once they get a few miles on them and warm up. This might explain the inconsistency. If it only happens when you're first driving it but then goes away, this is probably your issue.

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Discussion Starter #10
Two things:

One, see how many weights are on your rims. Sometimes the tire guys will "chase weight" and add a lot of weights in lieu of spending the necessary time to balance them correctly. If you have a bunch of weights, take it back and tell them to do it right.

Two, it depends on what kind of tires you have. Some all seasons have a tendancy to flat spot pretty quickly. I have the cont extr contact, and when it's really cold they'll flat spot over night. This is worked out once they get a few miles on them and warm up. This might explain the inconsistency. If it only happens when you're first driving it but then goes away, this is probably your issue.

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How many weights would you consider "a lot?" Each wheel has like 4 or 5 weights on it which I feel like is pretty normal. I might try moving the tires around from front to back and see if that helps at all. Thanks for the help guys!
 

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Move the tires front to back and see if it changes anything. My guess is tire balance or tread separation. Could also be a bent wheel.
This! Vibration w/o feeling it in the wheel would probably indicate back tires out of alance/flatspot. See if you can feel something different in the steering wheel after moving the back tires up.
 

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Not sure if the ST has the same issue, but the Miata does. It is so common there is a name for it, 65 MPH Shimmy. It even takes a special machine to get it all out as 'normal' balancing machines aren't sensitive enough to get it all out. If you see a difference call around and find a Hunter Road Force machine have your tires balance on that.
 
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