Any tire guys or hot rodders?

[testdepth]

I want to buy new rims for new tires I am placing on this hot rod truck. This truck was setup with a narrowed Ford 9" rear end. The truck currently has Hoosier 29 x 12.5 x 15 racing slicks. I am replacing this size tire with a 275 x 60 x 15 which is 2 inches more narrow in width. The new rims will be 15 x 10. I need to figure out what the offset and back space needs to be to get the tires to sit correctly on this truck. Ford 5 x 114.3 (4.5") lugs. How do I figure it out?

 

[fast306stang]

What size are the wheels on it now?

 

[fast306stang]

You can figure the backspace of your current wheels by laying a straightedge across the backside of the rim and measuring the distance down to the mounting pad.

 

[fast306stang]

This can help you figure offset once you've measured backspace.

http://www.gtsparkplugs.com/Backspace-Offset-Calculator.html

 

[Tony2X]

Judging by the amount of room those big tires have....and you are goin to a smaller tire....I would say zero backspace.
Just so it won't look stupid.

 

[rockyfatcat]

I would try removing the tire and place an unmounted tire of the new size on the ground and lower the vehicle till the axle is centered on the new tire.

With this sight picture, you can scoot the new tire inboard or outboard to achieve the proper clearances and the right look.

You might want to try this on both front and rear and verify enough offset compared to a stock size so the rim doesn't interfere with calipers. Unless you are ok with 'front only' and 'rear only' rims

The offset is the difference between the mounting surface and the center of the unmounted tire.

You could lay the new unmounted tire on the ground and lay a straight edge across the center of the tire. The distance from the ground to the bottom of the straight edge will give you a tire width and divided by two will give you the centerline measurement.

With the new tire posed in the opening. Measure from the mounting surface to a straight edge held across the center of the outer edge of your new tire. Subtract half of the thickness of your tire to adjust to the centerline because you are measuring to the outside edge and need to measure to the centerline.

Remember the offset is the difference between the mounting surface and the center of the unmounted tire.

 

[ARCman47]

20"s with nitto 420s

 

[greg vess]

You can also take a plumb bob and tape it to the inside of the fender in line with middle of the axle. Measure the distance from the mounting surface to the plumb and subtract the amount you want it to be from the inner wheel opening. That will give the distance from the mounting surface of the wheel to the exact point you want the wheel and tire to be when installed. They have charts to calculate that out so you get the proper dish depth.

 

[Comanche]

The Percy’s wheelrite tool is what you want.
You bolt it on and go through the simple motions of finding the fattest tire and backspacing that you can possibly get in there.

 

[Torn]

Was that pic taken at the Turkey Run in Daytona?