tape measure/wheel'n'tire tech

[porknbeaner]

Lets give this a try again. I guess I don't know how to post more than 1 pic at a time. So, give an old fart a break and let me post this whole tech thread before you start hacking it up. http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif

This has been covered by most of the major magazines at one time or another, but for the benifit of those who don't read them. How to figure out what tire'n'wheel combo will fit in your wheel wells.

Start at the starting place. the relationship of the rim to the sheet metal is set by two things, rim width, and back spacing. The relationship of the tire to the same is set by the relationship of the rim...

So how do to figure backspacing?

http://photo.starblvd.net/porknbeaner/3-1-1.jpg

Take a straight edge and lay it across the backside of the rim. Measure from the center flange of the wheel to the straight edge. That's your backspacing. This one's 33/4 inch.

[porknbeaner]

lets get to the hard part

http://photo.starblvd.net/porknbeaner/3-1-2.jpg

Remove the wheel and set the vehicle on a jackstand.

[porknbeaner]

Put a straight edge on the axle flange/brake. Measure the shortest distance from the frame or wheel tub. Remove 1 – 2 inches to allow for the tire sidewall and that's your max backspacing.

http://photo.starblvd.net/porknbeaner/3-1-3.jpg

[porknbeaner]

Measure from the axle flange/brake to the outer wheelhouse or inner fender. Note: look up to the radius, is your tire going to get into the sheet metal?

http://photo.starblvd.net/porknbeaner/3-1-4.jpg

[porknbeaner]

Measure from the backside of the wheel tub to the outer side. Look up for a radius or other obstacle on either side. This will give you your max tire width, given that you are trying to keep everything inside the fender well.

http://photo.starblvd.net/porknbeaner/3-1-5.jpg

[porknbeaner]

Measure from the lowest point on the tub to the axle center. Think about it; how tall can the tire be without getting into the sheet metal?

http://photo.starblvd.net/porknbeaner/3-2-1.jpg

Now get your calculater out. You know how wide the fenderwell is, and how tall, and how much backspacing you can get away with.
So you know how wide a wheel is going to fit, and how much tire room you got to go with that wheel.
To figure tire dia, you are using the measurement you took as a radius, so what ever will fit between the top of the fenderwell and the canter of the axle times two.

Whats left is to go to the tire shop with your tape measure and start measureing. or maybe FatHack has good info to post on tire section width. http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif

OK I'm done. http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif