I recently swapped out the stock 17" rims and 235/55R17 tires with 18" AFS Mach 1 wheels and 275/40R18 Goodyear Eagle F1 GS-D3 tires--that's all the way around, by the way. The new tire wheel combo was balanced to zero before mounting. These are unidirectional tires, by the way, and filled to 35 pounds.
I've got a few issues. One, on light to moderate acceleration, the wheel begins to vibrate/shimmy around 50mph and continues up through 75mph or so. It's most noticible when cruising at a constant speed in between that range. The wheels/tires were removed and checked for balance, and they all balance to zero and no noticable out of round problems. The tires were then swapped back to front, and the exact same vibration was noticable under the same conditions. The front suspension was checked and it's tight with nothing loose.
Second, the tire/wheel combo has made the car really squirrelly under hard acceleration and the car wants to dart all over except in a straight line. It's like my old turbo Eclipse! Under controlled hard cornering it's like the car is on rails but from a standing start I have to struggle to keep it under control. I am not taking it to the track at this point!
On glass smooth surfaces the car doesn't drift left or right, but I am having the alignment checked at the dealer asap. But the shimmy isn't indicative of misalignment, nor is the hard acceleration issue.
I know several tuners use 275 series tires all the way around, and I don't think it's the width. Would lowering help? I have the Steeda springs but am worried about making the issue worse.
Any ideas?!?!?
I've got a few issues. One, on light to moderate acceleration, the wheel begins to vibrate/shimmy around 50mph and continues up through 75mph or so. It's most noticible when cruising at a constant speed in between that range. The wheels/tires were removed and checked for balance, and they all balance to zero and no noticable out of round problems. The tires were then swapped back to front, and the exact same vibration was noticable under the same conditions. The front suspension was checked and it's tight with nothing loose.
Second, the tire/wheel combo has made the car really squirrelly under hard acceleration and the car wants to dart all over except in a straight line. It's like my old turbo Eclipse! Under controlled hard cornering it's like the car is on rails but from a standing start I have to struggle to keep it under control. I am not taking it to the track at this point!
On glass smooth surfaces the car doesn't drift left or right, but I am having the alignment checked at the dealer asap. But the shimmy isn't indicative of misalignment, nor is the hard acceleration issue.
I know several tuners use 275 series tires all the way around, and I don't think it's the width. Would lowering help? I have the Steeda springs but am worried about making the issue worse.
Any ideas?!?!?