I just put on some 27X12X12 (rear) 27X10X12 (front) Swamplites with new rims on my Forman 450. It starts to shake at 25 mph until 35 mph on hard ground. It shakes enough to make the handlebars wobble (not too bad). The rims are not warped, but the tires wobble like they are. Jacked up the rear on blocks, the tires wobble ¼ to 3/8 of an inch. The stock tires spun true. Wanted to know if this is normal.

 

Also, if you read your IM, make sure your lugs are EXACTLY to specs, or it will shake worse, and warp your rims. You need a torque wrench for this.

 

I had a set of Swamplites with a crooked tread pattern to them. If they're on the rear, have someone follow and see if it seems the rim is bent. The best way to tell is to jack it up and spin the tires fast. Mine were WAY out of wack.
Buck