rearend shimmy
 

Just bought a 370z used and tires look great on car...took them to have them roadforced balanced and they came out ok.....but i have a rearend shimmy at highway speeds around 60 to 70 ish that gets faster with speed. Anyone know if it would be in wheels tires or half shafts? Can a bent wheel still pass roadforce machine? need some help bad. thank you in advance.

would suggest trying a different wheel
the tire guys cant take a bent wheel and balance the tire on it to balance out the bent wheel

do you think the wheel machine would read 0 on the weights if it was bent but still cause issues? the reason im asking is because they balanced to zero

Had it aligned?

What would an alignment haveto do with a hum at highway speeds? Tires wearing perfect. Hums and vibration jacked up on rack too

Shimmy means shaking not humming... which a bad alignment and unbalanced tires could cause.

If you are hearing variable noise with speed it is either road noise off the tires or you could potentially have a bad wheel bearing. Could also be a problem with the rear diff.

Also I am curious to know how you could tell the tires wear perfect if you just bought the car. Just because the tires on it are good doesn't mean the alignment wasn't recently wacked out of spec (such as if someone sold a car that was lowered, put it back to stock and never had it realigned).

Ive swapped wheels tires........noise doesnt change when loading one side or other.....road forced tires wheels....car drives straight as an arrow....alignment bolts never touched....just had driveshaft replaced at dealer....no change....jacked car up and ran in first gear and both cv axles looked like had severe runout. So im wondering if both cv axles are bent....or differential trouble.....or bushings getting soft....also i can hear vibration noise with car off ground....so that rules out tire noise

Spacers ?

no spacers all stock

swapped wheels and tires? are they the same tires all around??

Yep brand new wheels tires.........just bolted em up and still same vibrations noise shimmy

Take it to the dealership