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I guess I've always had a very slight off/on steering shimmy, but it was so slight and off/on I never worried about it and it didn't bother me. I've recently upgraded to a Saleen BBK and it has gotten worse, much worse, about 1/4' shimmy now. I've had the front tires rebalanced twice now. They are the same front tires and rims before/after the upgrade. The rotors/calipers are new so I don't see how they could be the problem, so I assumed it was the balance.
Before the 1st rebalance (after the BBK install) I got the shimmy from about 40-50 mph, then smoothed out for the most part. I had the fronts rebalanced and got it at 50-60 mph, then mostly smoothed out. I just had them rebalanced again using the Road Force system and it's smooth as glass (smoother than both the other rebalances) up to about 58 mph, then smooths a little (shimmies worse than other rebalance though). When they did the Road Force they did say they had to rotate one tire on the rim 90 degrees and the other they had to rotate 180 degrees.
The BBK upgraded the rotors to 14" slotted rotors and the calipers are 4 piston StopTech ST-40's. There's about 5 Ibs more weight at each front corner now, which I assumed was making the shimmy more noticeable. I also upgraded the rears to the stock size Roush slotted rotors (both Roush and Saleen use the same ST-40 calipers, but the Roush kit uses 2 piece rotors, the Roush rears match both) that use the stock calipers. I put Hawk HPS pads out back with the new rear rotors. Everything installed fairly smooth, except for compressing those rear caliper pistons was a PITA. I had to rent a caliper tool from Autozone for those and it was still a bear getting those rotated/compressed.
The front tires are Nitto 555's and the rims are American Racing Razors 20x9. I don't notice any play in my steering in the car so I assume the tie rod ends are ok, but I haven't actually gotten under the car and had someone move the steering wheel to check them visually. The car is lowered with Steeda Sport springs and I have the Steeda upper strut mounts to adj. camber. I do notice a slight shimmy when braking, if I barely put my foot on the brake, but once I apply more pressure it stops.
Do you still think it's the tires/balance or something else...?
Before the 1st rebalance (after the BBK install) I got the shimmy from about 40-50 mph, then smoothed out for the most part. I had the fronts rebalanced and got it at 50-60 mph, then mostly smoothed out. I just had them rebalanced again using the Road Force system and it's smooth as glass (smoother than both the other rebalances) up to about 58 mph, then smooths a little (shimmies worse than other rebalance though). When they did the Road Force they did say they had to rotate one tire on the rim 90 degrees and the other they had to rotate 180 degrees.
The BBK upgraded the rotors to 14" slotted rotors and the calipers are 4 piston StopTech ST-40's. There's about 5 Ibs more weight at each front corner now, which I assumed was making the shimmy more noticeable. I also upgraded the rears to the stock size Roush slotted rotors (both Roush and Saleen use the same ST-40 calipers, but the Roush kit uses 2 piece rotors, the Roush rears match both) that use the stock calipers. I put Hawk HPS pads out back with the new rear rotors. Everything installed fairly smooth, except for compressing those rear caliper pistons was a PITA. I had to rent a caliper tool from Autozone for those and it was still a bear getting those rotated/compressed.
The front tires are Nitto 555's and the rims are American Racing Razors 20x9. I don't notice any play in my steering in the car so I assume the tie rod ends are ok, but I haven't actually gotten under the car and had someone move the steering wheel to check them visually. The car is lowered with Steeda Sport springs and I have the Steeda upper strut mounts to adj. camber. I do notice a slight shimmy when braking, if I barely put my foot on the brake, but once I apply more pressure it stops.
Do you still think it's the tires/balance or something else...?
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