I tried this in the Wheel and Tire section and got some replies, but I want to make sure that everyone comes up with similar numbers.

For those gurus that KNOW how to convert...please do the following conversion from Offset to equal Backspacing.

20x8.5 with a +35mm Offset

20x10 with a -24mm Offset

Lets see the numbers. Ive had 3 different #'s and just want to compare what you all come up with.

Thanks.

 

20x8.5 w/ +35mm= 5.627" BS
20x10 w/ -24mm= 4.056" BS

thats what i figure anyways...

 

How do you get those #'s?

With the 20x8.5 Im told it would be somewhere around 6.1" of backspacing?

This is where Im getting confused...not that its bad...Im just looking for an accurate figure.

Here is one method I found:

TO CONVERT OFFSET TO BACKSPACING:

For positive offset wheels: (Wheel Width +1)/2 + (offset * .03937)

For negative offset wheels: (Wheel Width +1)/2 - (offset * .03937)

Thats from Mickey Thomsons site I believe.

 

this is how i figured:
offset is the distance from center so...
20x8.5
so center is 4.25"
+35mm= +1.377 inches
4.25+1.377= 5.62"

20x10
center is 5"
-24mm=-.944 inches
5-.944=4.056 inches

edit to add- i can see where they are getting 6.1" though- went and found your mickey t site, and did some reading...they are adding 1" due to the rim lip--- that rim lip varies from mfr to mfr- sooo...if i add .75" (i think 1" is alot) and then do the same math as listed above, the 20x8.5 has 6" BS
and the 20x10 has around 4.4-4.5" BS

 

Yeah, I noticed that...

Thanks for the help...whichever one is right...they will both work with the Rancho Lift Im getting anyways. If not...it will still work at stock height as well.

 

According to the chart on BigCustomRims.com the

20 x 8.5 with +35 = 155 mm or 6.1" backspace
20 x 10 with -24 = 115 mm or 4.5" backspace

So far all of the wheels that I have researched this chart has been dead on.

Good luck.

 

That sounds right...whats the site? I cant seem to get to it if thats the exact address.

 

Sorry about that, was kind of in a hurry. Try this address and go to the "Sizes Guide". Really a cool chart for figuring tire and wheel sizes along with back space and offset. Like I said before, it seems to be pretty accurate.

www.bigcustomwheels.com

 

Very useful and awsome site to use...that one is definately bookmarked. Thanks!!!