jwgroovin

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?!?!?

andyman

Can we see them?

tripsevn7

a 275/40/18 seems a little tall when i ran 18 on my gt i ran a 275/35/18 on all four corners and was perfect. have you tried dropping tire pressure to 30 35 might be a little much

delurker

275/40/18 is actually shorter than stock on an 05-06. The 285/40/18's on the rear of my 05 are a tenth of an inch or so shorter than stock. I'm running 255/45/18's on the front, and I don't have any squirliness issues.

05-06 Saleen models come with 275's all around, so I'm not sure what could be causing your issue, given that they're balanced and aligned properly.

jwgroovin

Sure

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jwgroovin

and some more...

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tripsevn7

did you try dropin your tire pressure. go to 28-30 psi and let me know what it feels like

Stoenr

Did you remove the retaining clip from around the stud, on the rotor. Used to keep rotor on while going down assembly line. Factory wheels allow room for these, aftermarket ones tend not to.
like the one in this picture on the stud in the 2 o'clock position. This has been known to cause vibration issues with aftermartket wheels

LS2_GTO

Are those the 9" wide rim??

If they are the 9" -- I would think the tire size you selected would be too wide, and would suggest a 245/40-18 (Great tire size for a 18x9 Rim) or a 255/45 -18

IMO the 275 is too wide of a tire for the 9' rim and will cause the symptoms you are describing. You are right though, it seems alot of "Newer type Mustang" owners like the 275 for some reason, that said, alot do complain of handling with that tire size too. I personally like the twisties, so I go with a 245/40 on my 9" wide rim.

Good luck, and let us know what you find.

jwgroovin

And removing them fixed it. thanks. I'll drive around all day today just to be sure, but I took off up to 80mph for a short run on a semi-smooth road, and not a shimmy to be seen. I'll keep you posted but I think this may have been the problem. You da man.

John