I want to mintub my coupe, but keep the stock 18 polished wheels. I want to widen the wheel and fit a wider but maintain original tire height. Can this be done? Anyone know what tire size is needed? What is maximum wheel width that can be added on the inside? I have done a search but found little info.

 

Stock you can go 11.5" max w/ proper offset which may not be possible w/ widening the stock wheels.
w/ minitub you gain .5" to 12", everything else being equal.
I would deferred the minitub and run 305 35 18 on 11.5"

 

If your interest is cornering, your stock wheel width will dictate the width of the tread necessary for best "footprint", i.e. the most rubber on the road.
You can go up or down one size without problems, but more than that will require compromises in air pressure to maintain the proper footprint.
If you put a 345 series tire on your stock wheel and ran it at the recommended 30 psi, you can probably imagine how it would bulge out at the middle of the tread and you would only be effectively using the middle third of the tread for your tractive efforts. If you then reduced air pressure sufficient for a flat footprint (perhaps to 20 psi), the tire wood be dangerously unstable in vigorous cornering and would over heat at usual driving speeds.
If you are thinking of tires wide enough to require tubbing, you will undoubtedly need wider wheels. A good rule of thumb for most brands of tires is 1" of wheel width for 1" of tire tread width (not max cross section width).
Also remember to keep the diameter of the tires close to stock size and the diameter ratio of the front to rear tires approximately the same so as not to confuse the ABS.
As you go wider on the tires, the aspect ratio (40, 35, 30) will have to be reduced in order to maintain the proper diameter.
Roy


[Modified by 7.0sc SuperVette, 1:28 PM 7/3/2004]

 

I have been thinking along these lines as well. I dont really want to tub the car but I want to have the rear wheels widened. I think that since they can only be widened to the inside, that one of those adapter/spacers could be made to get the clearance/backspace needed. I know porshe did that on some of their cars so it seems a safe thing to do. I wanted to stay in the 11" to 11.5" width anyway. Now I need to find a company who widens wheels and find out if its a good idea to widen a forged wheel or not. Anybody know of any place thats good at widening wheels?

 

I looked into this as well for my Z06 wheels, since tubbing and a new set of wheels & tires gets expensive fast.

Most specialty wheel shops only widen steel wheels for non-performance use. Welded aluminum apparently becomes brittle, weak spots in the weld can't be seen without X-ray inspection, and the weld can fail without warning. Typically at an inconvenient moment. Shops don't want to see their extent of liability explained to them by your next of kin or their attorney.

 

I have 18x335-30 ( 13.1 in tread section ) on CCW with an 11.5 rim 8 1/2 offset and no problems. My track wheels are also CCW 11.5 in with a 9 in offset and I am using 18x335-30 hoosiers ( 13.6 in tread section )

I asked serveral ppl about the mini tub and they said put on longer lugs, a 1/2 in spacer then put the wheel on. This way the car has a wider rear stance and is more stable on high speed corners.

Tom

 

I was under the impression that the stock wheels were a one piece wheel. If that's true, I doubt that you will be able to widen the stock wheel.

I'm running a 335/30/18 on a 12 inch HRE wheel. Tire height is 26.2 inches which is very close to stock wheel height.

 

I went with 18X12's cause I wanted traction on the street.........I looked into doing the same as you, but the widening wouldn't allow a +74mm ( 9 3/8" BS) to keep my 345/35/18 street tires and 345/30/18 drs inside the fenders.........
Here is a link to old post:
http://forums.corvetteforum.com/show...ight=mini+tubs