First I wanted to say hello to everyone out there. I am new to the forum and am going to be starting a 92 Extended Cab project hopefully in the next 2 weeks. I have been researching nonstop for the past week and got caught up on backspacing and offset numbers. just couldnt quite get a grasp on them. read on a few build threads about different offsets and backspacings, this kinda gave me an idea of what i needed but i still wasnt 100% sure about it all so i continued my researching and came across this guide and it has helped me out. Im not sure if its been brought up here before but I figured I'd put it up in case it helps anyone like it has helped me Wheel Offset - Wheel Backspacing - Bolt Pattern - Mini Truckin' Magazine Hope this may help anyone else out there.
was just trying to see what offset id need on some 15"-17" rims that are 9" wide with the rim just sitting barely tucked under the fender. found out id need a 4.5" backspace but couldnt figure out the offset because all the different rims i was looking at on different sites would put the offset in different "terms", i guess is the word im looking for, and couldnt make sense of it all so that link i found helped me a bit. at least i feel like it did
so what i did because i too had the same question about offset i used this website Online Wheel & Tyre Fitment calculator. Offset, Tyre stretch and Rolling Radius calculator i used to have 14x7 -7mm. but i wanted to fill up the wheel well more so i pretty much got a rough measurement of how much i wanted to fill and started plugging numbers in on the website. it came really handy because im now running 15x8 -19mm but i plan on going bigger and wider. heres a pic..
oh wow sweet! that'll come in handy too. thanks for the additional info there and your truck looks super clean. this is jyaortead's truck (pulled from his build thread here http://www.toyotaminis.com/forum/build-up-project-threads-25/%24500-xtra-cab-6701/index12.html )and basically the exact image i had in my head when i decided to get my yota. he put the info about the rims he picked up(17"x 9" with a 4.5" backspace which should be a -12 offset) but of course ill be needing to know how to figure out the numbers when i figure out which set of rims i want.
I found back spacing to offset conversion and vice versa. Don't know if this is what you're looking for. Offset to backspacing conversion
If you have a 9" wide wheel with 4.5" backspacing, it should be a 0 offset wheel. Wheel width minus backspacing equals offset. Have to convert to metric, though.... No?
thats what i originally had thought but all these charts seem to say other wise. so i keep getting mixed info about it with that general thought and then all these sites seem to be saying otherwise
No. The advertised width of a wheel is from inner bead to inner bead. The bead flange is generallly about 1/2" thick so you need to add 1" to the advertised wheel width to get the actual physical width. So a 15 X 9 wheel is actually 10 inches wide so a 0mm offset will have a 5inch backspace. A 4.5" backspace is thus about -12mm. The 1/2" is not exact and will differ with different manufacturers, forged vs. cast, and whether it is a J or JJ style bead but it is close enough, until you are trying to shave that last 1 or 2 mm... In which case, you should take out a ruler and actually measure it.
Yup. Measuring from the inside bead to inside bead is the standard way to measure and advertise wheel width.
The section width (195, 205, 215, etc.) is measured at the sidewalls of the tire. I don't know if it is measured internally or externally at the sidewalls. I've never seen that question raised and I've always assumed it is the outside. It should be noted that the sidewall width is for a specific size wheel, usually called the "design wheel width". If you use a wheel wider than the design wheel width, the section (sidewall) width will increase as well. IIRC, in general, the section width will increase 0.1" for every 1" increase in the wheel width. There is a limit, of course on how much the sidewall will increase and soon the bead area becomes wider than the sidewall (like stretching 195s on a 10inch wheel). Sometimes you can find the design wheel width for a tire on most tire manufacturers' websites. There are usually tables with the recommended range of wheel sizes as well as the design width.
