Prophet

Since the temps have dropped, I notice the first few miles of highway driving have a bit of vibration in the rear. Once a mile or two goes by, it's gone. Only happens in sub 50 temps. Also can only fee it around 65-70mph and higher. I did some searching and found little to nothing on the subject. My guess is the diff is sticking till it has a chance to warm up from friction. Is this normal or something I need to see a dealer to fix?

RX8Soldier

iTrader: (24)

year/mileage/mods/service history.
c'mon...

Prophet

Sorry, guess that help.

Only had the car a little over a month.

'09 GT with manual
29K
all stock
No real service record I know of. Car was spotless when I got it and had a clean Carfax. Only once recorded service stop on it for basic stuff. I'm just about to my first oil change and have plug/wires planned for real soon. But getting snow tires first.

YaXMaN

Is it a thump or a constant vibration? Does the frequency of the vibration increase with speed?

I've got some Yokohama s.drive tires that thump for a minute if the car sits a day or two. Pisses me off.

monchie

Usually, the front vibrates because of the motor mounts. Never heard about a back vibrating? Maybe, the muffler bolts are loose and its vibrating when its cold.

Bladecutter

What brand/model/size of tires?
I'm betting its the tires that have flat-spotted after sitting all night in the cold.

Perfectly normal, depending on the tires.

If you were to switch to a different brand/bodel/size of tires, it would decrease, if not completely disappear.

You could try switching the front tires to the rear to see if the vibration follows the tires, or if you just can't feel the front tires doing the same thing the rear tires are doing.

BC.

Prophet

Dunlop sports, 225/45/18.

Never thought about the soft rubber flat spotting. Makes sence. Snow tires go on tomorrow, so if it still happens I will have to look more into it.

I know it's noting engine related as RPM has no effect. Only really feel it in the seat, so rear end. Once I feel it kick in around 65-70, it gets worse if I go faster. So, could be the tires as mentioned above. What ever it is, it's a rotating driveling part of some kind.

YaXMaN

Ya, man. I bet it disappears when you swap out to the snow tires. Maybe a rear tire was a little lower PSI than the other tires, but not low enough to trip the TPMS... gave it chance to flat spot a bit.

bazooki

I agree, it's the tires being cold and flatspotted. My other car (Spec V) does that too for the first couple of kms and then it goes away.