Rear wheel/tire math problem, 69 Dart...

[dusterdoug]

69 Dart...

255/60/15 Drag Radials
7" wheel with 4.625 of back space.
Tire has a 10.1" section width.
That results in +/- 1" of sidewall to quarter lip clearance.

So if wheel and tire combo was switched to:
295/55/15 Drag Radials
Tire has a 12.2" section width.
10" wheel with 6.625 back space.
That results in ______" of sidewall to quarter lip clearance.

LOL...three of us come up with different answers depending on the math used.

What says the FABO?

PS: Don't worry about leaf spring or tub clearance; we got that!

 

[69_340_GTS]

NOTE: THIS IS WRONG >>> Both wheels have exactly 2.25" offset, so your tire centerline does not change. The 295 is 1.05" wider per side, so you have 1.05" less clearance.

 

[diymirage]

Both wheels have exactly 2.25" offset, so your tire centerline does not change. The 295 is 1.05" wider per side, so you have 1.05" less clearance.

I don't think so
Your adding 3 Inches to the overall width of the drag radial wheel, but your adding 2 inches of backspacing, which is half and inch more then half the 3 inch increase, which means it moves the centerline one quarter of an inch...i think

 

[69_340_GTS]

Well, instead of doing "math" I just drew a picture of it. According to this, you lost about 1/2" clearance on the outside. Not sure where my math went wrong. If I needed an exact answer I'd make a CAD drawing of it.

 

[72bluNblu]

From my favorite wheel calculator. Ignore the 305 tire size, I did that to get the section width to match closer as it was suggesting a narrower section width for a 295. About a 1/2" lost to the outside according to the math, it underestimates the 255 too so it should be close...

Calculator is here if you want to mess with it, just pay attention to the section widths as they can vary. Custom wheels, rim tire packages

 

[dusterdoug]

Winner winner, chicken dinner! Didn’t even think to look for such a program...Thank you.

Best part is I was right, or closest to it at my estimated .4 of an inch. Other best part is that I can get the wheels made up to 6 7/8 backspace, so I’ll add some insurance. Again, THANK YOU!

 

[72bluNblu]

Winner winner, chicken dinner! Didn’t even think to look for such a program...Thank you.

Best part is I was right, or closest to it at my estimated .4 of an inch. Other best part is that I can get the wheels made up to 6 7/8 backspace, so I’ll add some insurance. Again, THANK YOU!

No problem!

Yeah if you’ve got room to the inside I’d go with a little more backspace, you want at least a half inch to the quarters to keep things from rubbing with body roll, tire deflection, etc.