: Vibration questions

02-22-11, 08:23 AM
So I have an odd vibration in the V, and wanted to get some feedback. I'm starting to think it could be motor or trans mount related...but I'm not sure.

First thing in the morning, get going about 60, the car has a significant vibration. The wheel shakes, and I can feel it in the rear as well. I can also just see the shifter shaking around quite a bit. After maybe 10 miles, the ride smooths out...and it's smooth at any speed. At first I wrote this off to flat-spotting of the low-profile tires as the car sat overnight, and I still think that's part of it, but I'm wondering if worn mounts are a component of how much of the vibration I'm feeling?

Is it worth replacing the motor or trans mounts for this? Or is there anything else I could do? I can live with this problem, but I'd really prefer not to.

02-22-11, 09:10 AM
Are you running Performance Summer Tires? My V shakes pretty badly until the tires warm up....about 10 mins at AutoBahn speeds. After they are warm...no shaking whatsoever.

You said the the ride smooths out after they warm up...do you still have some vibrations once warm?

BTW...I run Sumitomos and it's usually about 30-35 degrees ambient temp when the vibrations are the worse.....

I believe there is a pretty decent discussion in the +'09 CTS-V board about vibrations from running cold summer tires...

02-22-11, 12:15 PM
I have Bridgestone Potenza RE960AS tires installed. They're "all season" tires, but really, they're completely crap in the snow. It's a good thought, though, I guess I'll have to see how it does once the temperatures start warming up.

02-22-11, 01:20 PM
I ran RE960AS up until about a month ago and I can't say that they ever flat spotted so I'm not sure that's your issue. I will agree that they are horrible in snow so I ditched them for a set of Blizzak LM-22s for the remainder of the winter.

02-22-11, 02:22 PM
Yeah, I don't know if my parking on the second floor of a parking garage makes for them being colder or warmer than wherever you park, but I'd expect an A/S tire to not have issues with flat spotting. But then, who knows for sure. I've had three sets of tires on this car in the 4K miles I've owned, the run-flat's it came with, which where horrible and vibrated at any speed, the General Exclaim UHP's, which were decent (and then got stolen), but also seemed to vibrate when cold, and now the RE960's, which are probably the best I've had so far...

I had the tires road force balanced, and like I said, it rides nice and smooth at all speeds once warmed up. I still feel like I'm seeing the shifter shake more than I'd expect it to, so maybe I will have to get under there and take a closer look at all of the mounts to see what kind of condition they are in.

Next week is going to be my last chance to try and get fluids changed and the V cleaned up before I have to drop it off at the docks, so I'd like to get as much stuff done as I can.

02-22-11, 04:13 PM
Mine does this as well. Once the tires warm up, about 5 miles even in warmer months, the vibration goes away. I run Toyo Proxes T1R's.

02-22-11, 05:46 PM
:hmm: Hmmm, what air pressure are you guys running? Or should I say, what is the pressure at start-up.
:coffee: I was running my car in temperatures in the 30*s up until the last week in December and never had that problem.
:spin: I run Hankook Ventus V12s at higher than normal pressure. Approx. 37-42 psi. :vulcan:

02-22-11, 05:54 PM
I am running 30 cold all around...I've tried running higher pressures, but it does seem like it has a negative affect on the handling. I could give it a shot, just as an experiment.

02-22-11, 07:37 PM
For pressure, I figure a few psi over recommended (being 30) is probably ideal for non-runflats, since the sidewall is softer.

02-22-11, 08:45 PM
FWIW, when I had my RE960AS swapped out for the Blizzaks, the tire tech said I was way under inflated given the wear pattern he saw. I was running stock 30psi. He set the Blizzaks at 35psi.

02-23-11, 01:58 AM
I run 30 psi cold....if the ambient temp is about 30-35....the tires warm up to about 35-37 at Autobahn speeds (110-115 mph)...

02-23-11, 08:51 AM
I run 30 psi cold....if the ambient temp is about 30-35....the tires warm up to about 35-37 at Autobahn speeds (110-115 mph)...

Man, you keep rubbing our noses in that Autobahn thing. LOL

02-23-11, 09:28 AM
Man, you keep rubbing our noses in that Autobahn thing. LOL

Hahaha...sorry V-Guy....but if I just put 110-115mph...it'll probably draw more questions.....

BTW...if you ever head this way...let me know...there's a V waiting for you to test drive! Seriously...

02-23-11, 09:45 AM
there's a V waiting for you to test drive! Seriously...

Hey, be careful. I was in Munich on business last year, and I have an invitation to go back.

To avoid the appearance of a threadjack: I put nitrogen in my tires this year, which - as an inert gas - I thought would avoid the pressure fluctuations that I experienced with air. But I still see 4-5 psi swings as my tires warm up. I run my PS2's at 32 cold - but I see them hit 37 (on the plain ol' radar-infested American interstate). ;-)

Either I'm missing something or the guys at the Goodyear shop took my $20 and bought a pizza.

02-23-11, 11:25 AM
I run my tires at 32-36 psi cold on the street.