How nice is your car? There is a trick with a baseball bat that works real nice. I would never
do it on my car. I would do it in a second on a pals camaro. On a nice car its much better to move
the rubber around by backspacing and spring work. Don't mess up the metal. You can tap the inside lip of the fender up out of the way a little with body working tools. If this hasn't been done yet
to your car I would not do it now. It is rare to put your hand on that lip and find the original shape still. my two cents.
Don't cut or grind them down. I use a body hammer and small strokes.
Don't try to go fast, take your time. Put your hand on the outside of
the fender so you can feel what your doing. If you use a razor blade
and make a cut in the paint about 1/8" in from the lip, it will stop
the paint from chipping into the area that shows. After your done
treat the area so it won't rust. There is a lip rolling tool out there
but it is $60.00 and only does the first half of the job. Take your
time and don't hit it too hard. If the fender has any bondo on it
you may want to have a shop do it for you.
My project 65 X-tremestang fastback is being built primarily for track racing and as such, I need all the tire/wheel clearance I can get. To that end, I very carefully folded in the wheel lip by using my rotary diecut grinder cutting notches in the lip approximately every 1/2 inch. Then, using a good body hammer and with a piece of 2 x 4 soft pine under the fender edge, gently tapped them in to complete blend into the inner fender contour. In this way, you have no lip whatsoever but you still have the strength of a double-metal edge. I am running 255/60R15 on Torque Thrust Ds out back (my nine each was narrowed about an inch to acheive this clearance) and 225/60R15 on the same wheels up front. Progress on my car can be viewed at my website http://www.bossman-motorsports.com
Keep in mind that my fastback is a garden variety C-code 289 2 barrel and wouldn't encourage this on a factory GT car or K-code.....
The fender bending tool is called a Jimmy or Chicane. A company in California(Torrance I think) makes those and they go for $60. I don't think the tool is worth that. Its just a curved block with a groove in it and a handle on the end. It leaves the outer half of the fender lip intact and only bends up the inside half which is good for about a 1/2 inch of extra clearance. You still have to tap the lip up after using the tool.
I've been trying to find somebody who bought one, used it, doesn't need it any more and wants some of their money back on it. I need to bend my rear fender lips up after which I would probably sell it to the next person that needs one. No luck on that so far.