New rattle/wobble

bngl3rt · 1 May 2014

So a few weeks ago I took a little off track excursion which thankfully did no damage to the car other than cracking one of my side skirts. Yesterday a new side skirt was painted and installed on the car. The body shop assures me they did not remove the wheels, and I can't see why you would need to to replace the side skirt.

Anyway, since I got the car back, there is a new wobble sensation through the steering while I'm driving on perfectly straight flat roads - it almost feels like the right front wheel is not round anymore. I did have to brake really hard on the way home from the shop on the highway - maybe it's as simple as a flat spot? I checked this AM that the wheels are all torqued down to spec and inflated to the correct pressure.

How could a side skirt replacement have caused this?

I also feel the engine idle through the steering wheel now even when the car is warm. It was always pretty shaky when cold but usually smoothed out once it warmed up. Again, coincidence? How do you fix this? Is it indicative of a collapsed motor mount? Something else?

B2FiNiTY · 1 May 2014

I'd check the wheel balance and get them rebalanced if needed. Then go from there.

silver2002 · 1 May 2014

Jack up car and spin front tire - look to see that rim is "true" and not bent.
Does wobble change with car speed?
Side Skirt completely unrelated - it's just a plastic piece-

bngl3rt · 1 May 2014

silver2002 said:
Does wobble change with car speed?

Doesn't seem to, no. I can notice it at parking lot speed.

JD Cross · 2 May 2014

I'm no expert but if you went off road hard enough to crack a side skirt you may have bent a suspension component or a wheel.
Silver 2002 has the right idea, jack up the car and if you have a dial indicator check for run-out.

bngl3rt · 2 May 2014

JD Cross said:
I'm no expert but if you went off road hard enough to crack a side skirt you may have bent a suspension component or a wheel.
Silver 2002 has the right idea, jack up the car and if you have a dial indicator check for run-out.

I had the alignment on the car checked immediately after the incident and everything looked fine...

Just went to the tire shop and they said both front wheels were about 1oz off balance. That's fixed and the car feels a little better now - the vibration that feels like it was coming through the wheels is gone.

However, the motor vibration remains. What can be done about that? Is the engine running rough, or are the mounts not doing their job of isolating the rest of the car from it?

JD Cross · 3 May 2014

bngl3rt said:
I had the alignment on the car checked immediately after the incident and everything looked fine...
Just went to the tire shop and they said both front wheels were about 1oz off balance. That's fixed and the car feels a little better now - the vibration that feels like it was coming through the wheels is gone.
However, the motor vibration remains. What can be done about that? Is the engine running rough, or are the mounts not doing their job of isolating the rest of the car from it?

If the wheels and suspension are now good, I'd get a knowledgeable engine person to take a look.
Hope it's nothing major

RYU · 3 May 2014

Hope the shop didn't take it for a joyride... then who knows what could have happened. dropped the clutch too hard > broke engine mount (or worse?)

bngl3rt · 5 May 2014

Ok, so the engine vibration was because I was a bit low on oil (it burns a bit of oil under hard i.e. track driving). Once I filled it all the way back up the engine ran as smooth as ever.

I'm still convinced I have some kind of problem in the passenger side front wheel though. If the tire were flat spotted would I be able to see it? I put the car up and spun both front tires and they don't appear to wobble at all or be bent... but that was just using the naked eye and I know how tiny things can magnify at speed. Could a wheel shop measure the rim and tell me for sure if it's bent or not?

silver2002 · 5 May 2014

even though the tread may be uni-directional, you can switch the front tires, just for a test, and see if the problem moves to the other side. [keep the speed down and no real cornering].

jwmelvin · 5 May 2014

silver2002 said:
keep the speed down and no real cornering.

Understand for wobble reasons but other than rain is there any significance to the direction of rotation?

JD Cross · 5 May 2014

As mentioned before you need to measure wheel runout to determine if your wheels/suspension are true.
Find a wheel shop that has a dial indicator and will measure your runout.
That will tell you if you have a bent wheel, a bent suspension arm etc.
Look under section 3-12 of your service manual for the runout limits of your wheels and brake disks (axles) and take that to the wheel shop for comparison to actual.

BTW I've never heard of low engine oil causing a vibration. If the engine was out of oil I could understand friction causing vibration but you would have major engine damage by then. However I'm not an expert and I'm sure another poster will have more experience on this

silver2002 · 5 May 2014

jwmelvin said:
Understand for wobble reasons but other than rain is there any significance to the direction of rotation?

I believe the tires are constructed to take the majority of cornering load from one direction
[and have directional tread].

jwmelvin · 5 May 2014

I'm not trying to start an argument but found this interesting:
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=188&

bngl3rt · 5 May 2014

JD Cross said:
BTW I've never heard of low engine oil causing a vibration. If the engine was out of oil I could understand friction causing vibration but you would have major engine damage by then. However I'm not an expert and I'm sure another poster will have more experience on this

It was more of just a slightly rougher idle. I've noticed the engine running slightly smoother and seeming rev-happier after oil changes even if it wasn't low before the change.

silver2002 · 5 May 2014

jwmelvin said:
I'm not trying to start an argument but found this interesting:
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=188&

Excellent read, thank you.

Dhalsim · 5 May 2014

silver2002 said:
Excellent read, thank you.

http://www.nsxprime.com/forum/showt...ctional-tires-backwards?p=1783324#post1783324

bngl3rt · 6 May 2014

I took it to a tire shop with a road force balancing machine. $50 of road force balancing on the two front wheels later and the car feels like it always did. Apparently one of the front tires had to be rotated on the rim.

Dhalsim · 6 May 2014

Huh? I don't understand. Why did the tire have to be rotated on the rim? And how did that fix the wobble?

JD Cross · 7 May 2014

bngl3rt said:
I took it to a tire shop with a road force balancing machine. $50 of road force balancing on the two front wheels later and the car feels like it always did. Apparently one of the front tires had to be rotated on the rim.

Did the shop check your wheel runout to see if you have a bent rim?

bngl3rt · 7 May 2014

Yes, the rims are fine. Both right tires were knocked off the rim during a slide at the track and then mounted back up again the same day with hand tools. I'm not surprised that it wasn't perfect...

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