Verify backspace calculation

[Jimmy Sean]

I’m getting ready to order my wheels and would like someone to verify that my math is correct.
The wheels are 18x9.5 ET20. Do you come up with a backspace of 6.04”?

Thanks

[Ranaexcavating]

6.023622 to be exact!

Check this link out and plug your numbers in ....... http://www.rims-n-tires.com/rt_specs.jsp?item=Wheel-Tire%20size%20comparer&showRim1=1&showTire1=1&sw1=235&ar1=60&bd1=15&rd1=15&rw1=7.0&et1=1&showRim2=1&showTire2=1&sw2=275&ar2=40&bd2=18&rd2=18&rw2=8.0&et2=13&text1=&text2=

[Jimmy Sean]

Thanks!

[ProdigyCustoms]

Whch car? the Firebird is different from the Camaro is different from the Chevelle

[Jimmy Sean]

Whch car? the Firebird is different from the Camaro is different from the Chevelle

Sorry, Firebird. I knew that the backspacing should be 5.5 inches for a Camaro or Firebird. My Firebird has a 1971 Chevelle 12 bolt rear end in it. I believe that rear end is 1 or 1.25 inches wider than a Camaro/Firebird.

I probably should have rephrased the question. What I was trying to figure out was, what the distance was from mounting surface to the back edge of the wheel. I figured it to be 6.04 inches and wanted to verify that my math was correct.

9.5*25.4 = 241.3 mm
241.3mm/2 = 120.65mm
120.65mm + 20mm(ET) + 12.7mm (1/2 inch for the lip converted into mm) = 153.35mm
153.35mm/25.4 = 6.0374 inches