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Discussion Starter · #1 · (Edited)
Hey all. Purchased my ST a little under a month ago. had 352 miles when I bought it (I wanted something specific so it had to be brought up from a few states down). Now has ~1500 miles

The issue is that the ride feels bumpy. I noticed it two days ago, before that everything was fine. I kept thinking well it does have a sportier suspension maybe I'm just now noticing it, but I took it to a freshly paved (less than 6 months) lot and went various speeds. The bumping was still there. I can feel it through the seat and the wheel. its not a huge bump, more of a wave. it feels like its coming from the rear. It came out of the blue and I have no idea if the car just doesnt ride well and I hadn't noticed how uncomfortable and annoying it was before or if something is messed up. Before I waste any time going to the dealer I want to get some ideas as to what it could be and attempt to diagnose it myself so when I do take it in I can tell them exactly what to look for. What should I look at specifically?

The ride feels like there are small bumps under the rear wheels even when their aren't any. There is nothing audible, just the bumpy feeling.

thanks in advance

edit: just took a vid going up my driveway slowly and it looks normal so Im not going to post it. Maybe I'm just a little stressed from work and I'm going crazy


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1. The tires may have been flat spotted from sitting on the lot. Nothing you can do to fix it other than driving it and hoping it goes away. (most likely will not go away)
2. You have a bent wheel.
3. You have tire separation starting.
4. Massively out of balance tire.
 
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Discussion Starter · #3 ·
Only plausible one would be number 4 I think. is it possible for tires to get out of balance after only 1500 miles and out of nowhere? Everything was 100% until two days ago


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Only plausible one would be number 4 I think. is it possible for tires to get out of balance after only 1500 miles and out of nowhere? Everything was 100% until two days ago


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A tire separation can come out of nowhere also, but it is not as likely. Wheel weights do fall off more often, however a vibration from a wheel weight usually won't start till at least 50 mph especially in the rear.

EDIT: What speed does it start at?
 

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Discussion Starter · #5 · (Edited)
Around 25 mph. its not a vibration, just feels like Im going over small bumps that don't exist. I have to get my winter tires mounted and balanced anyways so when I get that done I'll have this issue checked out too, unless someone comes up with an answer or it seems like a serious issue

I might be looking into it too much as well. Just seems strange that if it was always like that I didnt notice it till now.

edit: in my area, it suddenly got warmer than usual for this time of year yesterday and today. I began noticing the issue yesterday as well. Could a sudden temp change have something to do with it? I wouldnt think so, as I have the all seasons but I'm not sure.


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Around 25 mph. its not a vibration, just feels like Im going over small bumps that don't exist. I have to get my winter tires mounted and balanced anyways so when I get that done I'll have this issue checked out too, unless someone comes up with an answer or it seems like a serious issue

I might be looking into it too much as well. Just seems strange that if it was always like that I didnt notice it till now.


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Being that it is around 25mph I'd say it's either a separated tire or a bent wheel. You won't feel a balance issue at that slow of a speed. Easiest way to check is just to jack up the rear end and spin the tires in the air, you'll find the culprit real fast after that.
 

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Discussion Starter · #7 ·
Being that it is around 25mph I'd say it's either a separated tire or a bent wheel. You won't feel a balance issue at that slow of a speed. Easiest way to check is just to jack up the rear end and spin the tires in the air, you'll find the culprit real fast after that.
I'll try that tonight and report back


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Discussion Starter · #9 ·
Thanks

No bent rims. Psi is fine. Family went to dinner and I drove, they said it feels fine and noticed nothing. I hope I'm being paranoid but when I get my winters mounted and balanced I'll have them check my current setup


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Check your upper shock mount bolts. I bet one of them is missing. Reach up above the rear wheel and you should feel two bolts, one towards the front and one towards the back. Prolonged driving with a bolt missing will cause shock damage, I know this from experience.

Here's a pic of the bolt that replaced the one I was missing.
 

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I'm thinking it's the summer tires taking a set in cold weather. Any summer tire will temporarily flat spot in cold weather overnight. It will go away when they warm up again. Low speed wobble or bumpiness is a symptom of out of round tires, which is exactly what these temporary flat spots are. OP doesn't say where he lives or the weather, but that he has dedicated winter tires to mount makes me think it just got cold there.
 

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OP, my car does as you describe.

I have confirmed with a RoadForce balance that my tires have minor flat spots. This car sat on the dealer lot for over a year before I bought it. Mileage did not remove the spots, but they're not terrible.
 

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Discussion Starter · #13 · (Edited)
I'm thinking it's the summer tires taking a set in cold weather. Any summer tire will temporarily flat spot in cold weather overnight. It will go away when they warm up again. Low speed wobble or bumpiness is a symptom of out of round tires, which is exactly what these temporary flat spots are. OP doesn't say where he lives or the weather, but that he has dedicated winter tires to mount makes me think it just got cold there.
Pennsylvania near west chester. I have all seasons but I will be using winters because the snow is never the same year to year and you never know how much or when


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Discussion Starter · #14 ·
Check your upper shock mount bolts. I bet one of them is missing. Reach up above the rear wheel and you should feel two bolts, one towards the front and one towards the back. Prolonged driving with a bolt missing will cause shock damage, I know this from experience.

Here's a pic of the bolt that replaced the one I was missing.
All 4 are present, thanks for the suggestion.

I don't know how it would be a bald spot, I wouldve noticed it a long time ago


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new to the focusST site. 2016 ST1 purchased in April, western NY area. I was searching for a similar problem / or perceived problem and came across this thread.
So, I've a similar vibration , bumpy feeling in the car. best way i can describe it is that it feels like a tire is out of balance, or a vibration thru the body of the car felt thru the seat, not in the steering wheel. The condition happens at a similar to OPs speed, mostly above 35mph ish but under 60mph. It was hard to notice with the stock 18s and summer weather so i attributed the vibration to the suspension, tires, road combination. had the same ' i'm crazy' thoughts since i seamed to notice it sometimes but not others.... But once the cold weather came i put on factory focus 17" with new winter tires and the vibrations seam to be more noticeable
I haven't fully read thru the engine mount thread yet, not sure if something like this could be contributed to an engine mount.

Brian,
 
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