Tires Still Attached......

Use a hobby knife to cut them from the sprue, and then use 320 or 400 grit sandpaper, and sand lightly around the tire to remove the seam and make the tread look used. Go lightly, better to take longer than to remove too much. Hope this helps. Any other questions, email me.
Lee

I thought this was kinda cool...

There's a tip in Scale Auto from someone who uses a disposable razor to trim the flash off of tires. He likes the dual bladed razors. I wish I could remember the name to give credit.

As for cutting them off the tree...cut back from the tire a bit and whittle the sprue down. If you scuff them up as Lee said you may not even notice it.

Yep, this is one of those little things that unfortunately doesn't have a 'perfect' solution. Kits that have the tires seperate are the best, but sometimes they come molded on a sprue too. Personally, I use a very sharp xacto blade and cut as close to the tire as I can. This usually leaves a very small 'flat' spot on the tire, but this can be minimized with some sandpaper as already mentioned. It's likely best to sand the entire tread of the tire so that it is consistent.

M.

If you do get a flat spot, it can be mounted where it won't show.
Lee

I did'nt like the shine on new tires so i built a wheel sanding rig out of a 1/4 in X 1 1/2 in bolt. I took the protective cover off a spray can, the clear plastic that covers the spray nozzel on some paint cans, cut the end off to run the bolt through and now i can chuck it up in my cordless drill, put the tire on the plastic end and spin it on some medium grit sand paper. also read some where to rub the sidewalls on some denim as it takes the sheen off the side walls for a very realistic look, Modeling is always more fun when the wife is involved, sounds like you got a keeper.