Mason

It's been cold here for the last week and I've had this strange loud noise twice now on the same drive. When I would get up to above 40mph or so I had a noise coming from the left rear tire which basically sounded like I was running on a flat tire. In fact, I was sure that's what it was so I stopped and the tire was fine. Went down the road again, got over 45 or so and it started again, sounded just like I was riding on a flat tire and it actually felt like it too. I could feel the rear tire 'hopping' until I slowed down.

I think it's my left rear strut is bad but how do I check it?

Lexmex

Mason,

Might be one of the rear 17mm alignment bolts back there. I have had the very same issue on that back tire. I not only tightened them, but also have been going to an alignment place that uses a Hunter alignment machine. Salimshah pointed this out in another thread and it really helps to align it back there instead of just teh front.

I don't rule out the struts, because I myself had bad ones for years until I replaced the shocks as you noticed a few weeks ago. Always same insane squeeking going on back there and it wasn't the lower support rubber pieces either. If you hear a clang, that is definitely one of the bolts. Squeaking and I would spray some WD-40 in the area of the lower rubber suspension piece.

What I worry about is a third thing that could be related to having a bad tire. One possibility is to briefly switch the rear tires to see if that confirms this or not.

TunedRX300

Check for a possible nail in the tire. Did you see any fluid coming out of the strut?

Mason

I guess I didn't mention, it's only happened twice and hasn't happened in three days.

I'll check for fluid coming out of the strut.

And the rear 17mm alignment bolts.

trhs75

A slapping noise like a flat tire happened to me with my daughter's older Volvo one time. I still can't believe I couldn't identify the noise. This sounds crazy, but bear with me. I was driving on the freeway, and I heard the rhythmic slap just like a flat tire. I pulled over, risking who knows what kind of injury, and carefully checked the tires and everything else I could think of. Everything looked fine. I started up again and the noise returned, stopped again, and couldn't find anything. This went on a few times, and I finally found the culprit. A loose rubber molding was flapping in the wind, hitting the car body. It fell back into place every time I stopped. This probably isn't your car's problem, but I thought I should throw it out as a possibility. At least it was easy to fix once I knew what the problem was. Can someone ride in the car and look at the wheel well area while you drive?

Mason

I actually checked that very thing but after really paying attention when it happens, you can feel the car hopping/shaking, like its in the tires or suspension system.

salimshah

How is the free roll?

Seems like unlikely in your case but:
Some times the auxiliary brakes tend to stick (more so in winter times) ... they typically fail to release and do not engage on their own at 40mph.


Salim

trhs75

Mason -- I wish it had been a loose piece of trim (for cost reasons!), but did you try LexMex's suggestion of switching tires between sides briefly to rule them out? (or maybe switch it with the spare if you don't mind getting it "used")