offset and backspacing question
 

Iam looking at putting 18x9 rims with a 35x12.5 tire.I leveled my h3 and i know this will work, but the question i cant find an answer to is what backpacing and offset range i should be looking at.Stock backspacing is 5.5" and has a 30mm offset.A 10mm offset would equal a 5.4 " backspace it would be .2 " closer to the brake components and tire would stick out 1.8" further.Anybody with this setup i would appreciate a response

Don't get hung up on the Offset number. It changes with wheel width.

The important number is Backspace. As long as it's less than 5.5" then you will be OK.
So if your new wheels have 5.4" Backspace, they should be fine.

Attachment 12787



The only other thing to confirm is that the center bore is larger than 100mm diameter.
It has to be that big to clear the center hub.

I went all the way down to a 0mm offset and it sticks out the perfect amount (bet 1 and 2 inches..id have to measure exactly).

Once again, Offset means NOTHING. It's different with each wheel width.
Offset is a result of wheel width and Backspace.
No 2 wheel models are exactly alike. So you CANNOT rely on Offset to get wheel clearance right.
Backspace is a fixed number regardless of wheel width.

You need 5.5" Backspace or less to clear H3 rotors & calipers.
The smaller the Backspace number, the further your tires will stick out.
Rim width will affect how much the tires stick out too.

It would have been better if you took a lok at this before posting in the FAQ section. ;)

https://www.hummerforums.com/forum/h...section-19461/

Finally!
 

I knew what backspace was but couldn't get the offset right. from bungers info I went to a tire site and got a picture of offset,bungers right,not very important. backspace pretty much tells It all,but,
"You need 5.5" Backspace or less to clear H3 rotors & calipers." is not quite right. the 5.5 is right,my finger just cleared the upper control arm,"just!" but the rotors/caliper are neatly inside the wheel, it could only hit the control arm if it was over 5.5.
in the rear , nothing is close.

Btw,when I was putting some fat rubber on an old car years ago I ordered wheels made to fit from California?. Not knowing the terminology I gave them the exact measurements from the mounting flange to the inner/outer fender and,THEY still got it wrong! by the thickness of the wheel bolt flange. I had to "adjust" the fender to fit them.

'
How to Measure Wheel BackSpace



https://www.rsracing.com/images/tech-wheelfit1.gif Measuring Wheel Offset

To calculate offset you'll need the following measurements:
https://www.rsracing.com/_themes/rstheme1/abstrbu1.gifWheel backspacehttps://www.rsracing.com/_themes/rstheme1/abstrbu1.gifWheel Widthhttps://www.rsracing.com/_themes/rstheme1/abstrbu1.gifWheel Center line (outboard flange to inboard flange measurement / 2) Subtract:
https://www.rsracing.com/_themes/rstheme1/abstrbu1.gifWheel center line from Wheel backspace to get offset. https://www.rsracing.com/_themes/rstheme1/abstrbu2.gifIf backspace is less than the wheel centerline the offset is negativehttps://www.rsracing.com/_themes/rstheme1/abstrbu2.gifIf backspace is greater than the wheel centerline the offset is positive Tip:
https://www.rsracing.com/_themes/rstheme1/abstrbu1.gifTo convert from inches to mm multiply by 25.4https://www.rsracing.com/_themes/rstheme1/abstrbu1.gifTo convert from mm to inches divide

thanks bunger I went to order 18x9 wheels and they wanted the offset .When you change the offset the backspacing changes.So they work together The big question was what backspacing and offset would work best. if you take the same rim a 0 offset =5" B.S. a 10mm offset = 5.4" backspace. so I should stay close to the 5.5 " B.S. thank you sorry doc olds i didnt realize i was in the FAQ section

duffy,if you need to do something now,ill say what I think bunger will tell you,
FORGET the word offset. you must have 5.5 backspace,regardless of the wheel size,or less. more will hit the control arm. go out and put your finger in there and see how close it is.

backspace determines that other word that you don't need.
im guessing that bigger tires will hit inside sooner with more backspace so less is better anyway.
just get a guarantee that they do it right.

I run a 4.5" backspacing on mine 18s

Clearance to a control arm is going to change with wheel diameter. An 18" will clear the control arm more than the stock 16". What size wheel do you have?

Method Wheels that are 18x9 come with two available back spaces, 4.5" and 5.75". Method says both fit the H3 but the -12 is used with the biggest tires so you don't rub turning all the way to lock tire wise.

If a 16" with 5.5" just clears, then an 18" has the rim an inch further out and should clear a bit more. Anyone disagree? I prefer to not have the tires sticking out as much.