Offset for new wheels

[random882]

Ok so I keep reading that we need 5inch of backspace. However, a lot of wheels I look at are stated in offset. I know that offset tells you basically the same thing as back space just different verbiage. So basically if I am using a 1.5" adapter 6x5.5 what offset do we need? I know offset is technically different depending on wheel width. So I give you what i was looking at a 17x8 +25 offset with General Grabbers 265/70R17 will that work? If so will it stick out alot ..? Thanks ahead of time for info!

[Troutfisherman]

I found this thread helpful viewtopic.php?f=14&t=26

I'm in a similar situation trying to figure out if some 15x7 Cragar Soft 8s will fit on my TB. I know they have a backspacing of 4'' and the offset is 0. I will also be using a 1.5'' wheel adaptor to change 6x5 to 6x5.5. I really don't want my tires to stick too far out...

Here's how I calculated how far the tire will stick out (also mentioned in a previous thread):

1.5" from wheel adaptor + 2" of backspacing (stock is 6") + 0'' for rim width (stock is 7") = my rim will stick out 3.5'' farther than stock

I'm just a newbie... so input from others might be more helpful

[navigator]

Jon has it figured out. Once you understand it, it is no biggie.
Travess on an 8 inch rim, 0 offset is basically the middle or 4inches of backspace.
Since you have 25mm offset and there are 25.4 MM in an inch you have about 5 inches of backspace so your setup should stick out about 2.5 inches more than stock.

[HARDTRAILZ]

I'm in a similar situation trying to figure out if some 15x7 Cragar Soft 8s will fit on my TB. I know they have a backspacing of 4'' and the offset is 0. I will also be using a 1.5'' wheel adaptor to change 6x5 to 6x5.5. I really don't want my tires to stick too far out...

Too much backspacing for 15s. You wont get 15s without the tires sticking out due to that factor.

[HARDTRAILZ]

0 offset is basically the middle or 4inches of backspace.

Offset is the middle, but the wheel thickness lip edges could make it so it is not 4 inches of backspacing. As shown below 8 inch wheels can be actually 9 inches wide and the BS would be 4.5.




Found this nice explanation...
"Backspacing vs. Offset Explained(thought this might help some of us)

Wheel Offset
Offset is measured from the centerline of the barrel of the wheel to the hub mounting surface. If that hub mounting surface were in the exact center of the barrel of the wheel the offset would be “0". If the mounting surface is away from the center of the wheel the offset is measured in millimeters. There are 25.4 millimeters to an inch. So if the mounting surface is 12mm from the centerline of the wheel it has a 12mm offset. That would also mean that it is about ½ inch. If the mounting surface is moved away from the vehicle that is a positive offset. The picture shows a wheel with the positive offset. A positive offset will cause the wheel to set in or tuck into the vehicle. Originally you found positive offsets on just front wheel vehicles. Due to that some people refer to positive offset wheels as front wheel drive offsets. Currently there are many rear wheel drive cars and trucks with positive offsets. The higher the positive offset the less it sticks out from the vehicle and it will have a higher Backspace. If the mounting surface is moved in toward the vehicle past the centerline, that is a negative offset. A high negative offset will produce a lower Backspace. Once again the measurement in millimeters is how far away from the centerline the mounting surface is. A -24mm offset means that the mounting surface is located 24mm or 1 inch from the centerline toward the vehicle. The wheel will come out farther from the vehicle and will have that deep dish look.

Width
The width of a wheel is measured inside the beads which are usually ½ inches. If you measure on the outside of the beads an 8 inch wheel will measure 9 inches

Backspace
Back spacing is measured from the inner edge of the wheel to the hub mounting surface. It is a convenient measurement in that, as long as the back spacing remains the same, the clearance to the suspension also remains the same. If you know the width of the wheel and the offset you can compute the backspacing. For example if you have an 8 inch wheel with a +24mm offset. An 8 inch wheel is actually 9 inches wide so if the offset were 0 the mounting surface would be right on the centerline and the backspacing would be 4.5 inches. With a positive offset the mounting surface moves off center 24mm or 1 inch toward the outer edge of the wheel. This will make the inner edge go more inside which will result in a 5.5 inch backspacing.

Centerbore
This is the diameter of the center of the wheel. The centerbore must be equal to or larger than the hub of the vehicle for the wheel to seat. If the wheels centerbore is the same as the hub on the wheel then that wheel is hub-centric and uses the hub to center the wheels. If the centerbore is larger than the hub then the lugs will center the wheel and that is lug-centric. When using a lug-centric wheel be sure and snug the lugs up slowly and tighten them in an opposite or star pattern.

Bolt Pattern
A bolt pattern of 5x120 mm means it has 5 lugs and if there were a circle through the center of all the lugs the diameter of that circle would be 120 mm.
"

[navigator]

good catch Kyle.

[random882]

Jon has it figured out. Once you understand it, it is no biggie.
Travess on an 8 inch rim, 0 offset is basically the middle or 4inches of backspace.
Since you have 25mm offset and there are 25.4 MM in an inch you have about 5 inches of backspace so your setup should stick out about 2.5 inches more than stock.

Thanks for info those are probably what i am getting.

Just in case i want to look at others i want figure this out for our vehicle / lift with 1.5 spacers.

So by those calculations and the forum post http://forums.offroadtb.com/viewtopic.php?f=14&t=26, the stock rim has an back space of 6 inches on a 7 inch (width) rim. So 0 offset would be 3.5 inches of backspace. However, with 6inches of backspace (2.5 inches from center) that woudl be a +63.5 offset? That seems wrong!?

[HARDTRAILZ]

Our factory wheels are very high offset...just like fwd cars. That what high offset wheels were referred to as back in my day. Car rims.

[navigator]

So by those calculations and the forum post http://forums.offroadtb.com/viewtopic.php?f=14&t=26, the stock rim has an back space of 6 inches on a 7 inch (width) rim. So 0 offset would be 3.5 inches of backspace, but its ACTUAL offset is 2.5 inches from center. Which would be a +63.5 offset? That seems wrong!?

I looked here and couldn't find the chart that has been posted frequently, there is a chart on the following link that makes it easy to convert.

https://www.rsracing.com/tech-wheel.html

[random882]

I looked here and couldn't find the chart that has been posted frequently, there is a chart on the following link that makes it easy to convert.
https://www.rsracing.com/tech-wheel.html

Thanks again! That chart helps a lot.

TB's need Less than 5 inches of backspace to run bigger tires or you'll hit the Upper ball join correct?

If you're running the 1.5 wheel spacer you would want a backspace of around 5.5 (5.5 - 1.5 = 4), so you'll clear ball joint and stick out about 2 inches farther than stock?

However, you DON'T want to go too small of an offset / backspace or your tires will stick out ridiculously far?
~With a back space of no smaller than (with a spacer) like 4.0 inches ( 4.0 - 1.5 = 2.5), clear ball join, but have little more than 3 inches of tire sticking out)?

According to chart
~8 inch width rim +12 to +25 offset
~7 inch width rim +12 to +38 offset
These offsets would give you enough clearance and not too much stick out with spacers installed?!

I'm sorry, I am WAY overthinking this I'm sure of it! But, I am getting ready to drop a descent amount of money on wheels and tires! I don't want to get this wrong.

SO THANKS for your patience and your help is VERY MUCH appreciated!

[Opeth]

265/70-17 cooper discoverer STT 17x8 25mm offset 1.5" spacer



I stick out 1.5-2" beyond the fenders, trimming required of the fender liner.

[random882]

17x8 +25 mm offset with 265/70 17 General Grabber AT2 markmc 1.5 wheel adapter ..

I had to cut some fender liner out to keep from rubbing. Also had to pound a the screw heads back a bit.
After all that back and forth and worry. They fit well. They ride very nicely too.. So Thanks for all the help the wheel tire purchase went well!

http://forums.offroadtb.com/viewtopic.php?f=25&t=3742

[Darkrider_LS]

Ok I'm glad I found this thread before starting a new one. I'm looking at some 17x8 Ion alloy wheels that are in our stock bolt pattern and have a +10 offset. Will I require spacers to run P245/70R17s on these rims? Or am I better off running these tires on my stock rims with some 1.5" spacers? The tires in question are speced at 30.6"

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