[M Bay]

My intensin is to build a well handling street machine. I would like to know what are the widest tires and rims/backset that you have installed and fit on a stock height setup without rubbing? Suspension mods are OK.

[goatasaurus rex]

i had a pair of mickey thompson super softs in L-60-15 on 4 3/4 backspace 15X8 1/2 centerline auto/drag rims under my 69. really filled up the wheel wells. no alot of room for anything bigger. these measured 10 1/4 wide across the tread and were 27.65 tall.

[marauder]

295/50-15s in the back if you have a tight suspension. I have them on 15x8"x4.5 wheels

[Red Box Rebel]

1. I would not go bigger than the 60s on a 15 inch wheel.

2. The 60s will give you all the handling you need from a tire perspective. Quality and/or brand of tire is also very important.

3. I would add poly bushings to the control arms front and rear and add a rear sway bar.

4. Poly links up front attached to a larger than stock sway bar.

5. Think whole package when planning and completing this project.

[yakker]

I am going through this right now. My goal is to fit the widest tire that will not rub under any circumstances. I have done extensive measurements in the back of the car. I have determined that a 275/50-15 (BFG T/A Radial) will fit with minimum of 3/4" of clearance inside and out through the full range of suspension travel, if a wheel with perfect backspacing is used. I am using a 67 Chevelle 12 Bolt rearend, which is 1/2" narrower per side. The perfect backspacing for my application is 4 3/4" on a 15 X 8 wheel. On a stock GTO rearend, this would convert to about a 5 1/4" backspacing.

I have ordered custom offset American Racing Torque Thrust Classic CL205 wheels and tires from newstalgiawheel.com. These tires are 25.9 tall, 9" tread width, 11" section width on an 8" wide wheel. Some here have run a 295/50 tire with success, but that is cutting it close, as the section width is about 11.6" on an 8" rim, or 12.4" on a 10" rim.

I am confident in my calculations, but I would advise anyone to do their own measurements and determine what backspacing works on their car. My goal was NOT to do any wheel well lip trimming or other clearancing that would alter the car. When my wheels and tires get here (4 - 7 weeks! Sheesh!), I will post how it worked out.

Hope this helps.

[M Bay]

Thanks guys,

I got the 15X8 rims with 4" back spacing and a rear sway bar. Did not get the tires yet. Can you guys give me any ideas what I can get away with on the front of the car.

[yakker]

The 4 inch backspacing will really limit you. I received my new wheels that I mentioned above. I haven't installed the 12 bolt chevy differential yet, so I am running a stock width rearend for a 68/69 GTO/Lemans. With my 4 3/4" backspacing, the tires are offset toward the outer wheel opening. If my suspension compresses to the point that the widest part of the tire is right at the outer lip, it will have 1/4" clearance with my 275/50-15 tires.

With your 4" backspacing, this tire on your car would be interfering with the outer lip by 1/2". Not good. You will have to run a much narrower tire than me, unless you want to really raise the back of the car up. Or get rims with more backspacing. You should be running 5 1/4" backspacing with an 8" wide wheel to get it perfectly centered in the wheel house. You would need to make sure that the lower shock mounting hardware does not rub the rim on the inside. It should just clear. If not, use 5" backspacing. You could mount your 4" backspacing wheel and measure how much room you have between the rim and the shock and then determine if the ideal 5 1/4" backspacing would work.

Once I install the narrower 12 bolt Chevy, my rims will be perfectly centered.

Good luck!

[SGTGTO]

Im going to hijack this for a moment....

What is the limiting factor for a wider wheel/tire combo? Its cold out, and I don't want to look down there. Basically.. at which point will narrowing the rear not do any more good, and the wheels hit something else (ie. control arm, frame, shock)

[yakker]

Narrowing the rearend doesn't really gain you anything as long as you use a rim with the correct backspacing for the application. You can't narrow the rearend that much unless you relocate the shock mount inboard. As far as the tires go, they will either hit the outer wheel well lip or the inner wall of the wheel house if the wheel is not properly centered. The frame is right there as well.

P.S. It doesn't feel cold to me at all!

[BAW'D GOAT]

I currently run a set off 285/40/R18 with about 1/2"-5/8" clearance on either side. With 6 1/4" back spacing on a 12 bolt out of a 71 GP. No rubbing issues to date but am building a watts linkage for insurance. Should be interesting if it works.