I thought I'd post this here too because this section gets more action and some of you may have experienced the same issue.

My 2006 GT came with 17" wheels and I didn't like the look of them. Without seeking advice, I bought 20" x 8.5"Driv GT wheels with Falken fk452 - 255/35/20 tires. Although the "on-line" package included balancing, I had them re-balanced in an attempt to get rid of a shimy in my steering wheel. Although it's a little better, I still get some steering wheel shimy aroung 70 MPH. Is something wrong or is this to be expected with the larger, 20" wheels?

Thank you for your "informed" help on this.

A second question - I'd also like to lower my car for a personally preferred appearance. I lost some of the ride comfort by adding the 20" wheels so I'm a little afraid to add the FR Handling Package for fear it will ride like a buckboard. Can I lower only the back end by an inch or so or must I lower the front also? I guess I'll need new shocks in either case. Is there a brand out there that does the trick but has a little softer ride?

Thanks again.

 

I have 20s and Steeda sport springs. I have a little steering wheel shake at highway speeds. I'm assuming it's the 20s. It only appears to happen on the rough highway roads, the smoother roads have very little shake.

With the above setup, the car rode like a real mustang horse. I recently installed Tokico D spec shocks/struts from the recommendations on this board and it has helped the ride quality considerably. I'm told the adjustable LCA brackets will help some more, so I'm doing that next. If I'm still not satisfied, I'll be moving to 18" wheels.

 

I have 20" wheels on the stock Saleen setup (saleen wheels, racecraft suspension, etc.) and no steering wheel shake at all, even at speeds over 120.

I think when there is a substantially greater amount of rotating mass and a wider path of contact with the ground, slight imperfections in wheel balance or treadwear are amplified when compared to smaller tire/wheel combos. This is based on my prior experience in upgrading the wheels/tires on my '95 GT to substantially taller/wider wheels (245s in front, 275s in the back), I noticed steering wheel shake if the wheels were not perfectly balanced. I also noticed that lower quality (Goodyear) tires seemed to cause vibration that went away when I installed better (Michelin) tires.

My $.02.

 

I've got your answer!! It may sound silly, but I had the same problem and found an answer on here. Remove the clips that hold the rotors on. When the car is on the factory floor, they put a little clip on one of the studs to keep the rotor from falling off while they get the pads on there. There's another thread on here and I'll get you a link to it. I just did it Saturday and it nearly eliminated my higher speed shimmy with my newly mounted 20s.

post #19 of this thread https://mustangforums.com/m_2044381/tm.htm. this may or may not be your problem, but it certainly made the difference for me!!!

 

I'm running 20" Saleen's on my V6 Pony and it runs fine and much better than the stock tires. Maybe you had them mounted wrong or something?

 

+1 on the rotor retaining clip. Some aftermarket wheel manufacturers do not have enough clearance to fully clear the retaining clip, so the wheel is very slightly out of 'sync' with the hub and at certian speeds can cause vibrations.

 

I had the same problem, but cannot tell you which one fixed it. Thewheels and tireswere in fact out of balance, and I had them take off the washer/clip at the same time, but no vibration or wheel shimmy since. This issue was discussed in an earlier thread and there are pictures of the washer/clip in case you need to see what were talking about. Just run a search and you should find it.

 

I had the same problem and just removed the clips and all fixed.

 

check that the wheels and tires are balance properly if they arent it can lead to all sorts of problems. like piled up wheel bearings, uneven wear on pads and rotors that will cause a shimmy when breaking, not to meantion the extra wear and tear on the suspension

 

Same problem, I've already balanced my wheels three times and the alignment is good. I got the same advice on here last week to remove the clips. Now wouldn't you think that if the dealer put the rims on, that they would know to take the clips off? *sigh* Looks like I'm off to the dealer this weekend to get that fixed. Will let ya guys know how it goes.