Understanding BS and Offset

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Old 03-31-2011 | 04:46 PM
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Understanding BS and Offset

Pretty new to the site, proud owner of 11' FX4.

I thought I could get a thread going were you guys can explain BS and offset to us new guys. Theres alot of repeated posts about what size tires/wheels fit on stock 4x4 or 4x2 trucks with or with leveling kits. I for one would like to put 305/55/20 Nitto ATs on Ballistic Jesters 20 x 9 (4.52 BS, -12 Offset) Im not sure how far that setup will stick out. I kinda understand what BS is but im getting confused about the offset and what it effects.

thanks to all that help clarify this issue.

Also not sure how to make this a sticky?

joe
 
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Old 03-31-2011 | 05:12 PM
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Thanks for thread, and welcome to the site. First quick answer is only a moderator can make a thread sticky.

Offset and backspace essentially provide the same data, just in two different forms, you can calculate one from the other. Essentially offset is the position of the mounting surface of the wheel either forward (positive number), dead even (0), or behind (negative number) the center line of the wheel (outboard flange to inboard flange measurement / 2). The more positive the offset the less a tire will stick out. However, when running larger wider tires you often need a more negative offset to get the tires away from the suspension components for clearance, however at this time you need more lift on the truck to clear them.

The tires you are looking to get are basically 33x12.50, the wheels should stick out about 2.5" further than stock wheels (unless they have changed specs on the 11 model and of course if my math is wrong). Sticking out that far may require some trimming to get them to clear, I am not too sure about the newer trucks. Hope this helps.
 
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Old 03-31-2011 | 05:17 PM
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that was easy to understand - cool. That rim also is avail in 0 offset, if I understood correctly that would rub even worse? If it was your truck, what size tire would you recommend? I dont mind if i have to trim alittle bit of the valence.

thanks for your help
 
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Old 03-31-2011 | 05:19 PM
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one more thing - wouldn't the tires sticking out be less likely to rub on the CA's?
 
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Old 03-31-2011 | 05:24 PM
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I would go with the 0 over the -12, maybe the +12 if offered, UNLESS you plan on lifting in the future.... Here is a page with some +12 18" with 325 https://www.f150online.com/forums/wh...c-jesters.html. I think the 305 on the 0 would look great too.
 
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Old 03-31-2011 | 05:25 PM
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Originally Posted by BLUEforLIFE
one more thing - wouldn't the tires sticking out be less likely to rub on the CA's?
Yes, but more likely to hit your body. Thats why I said you would need more lift (and lifted truck with larger tires often run wheels with a more - offset.
 
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Old 03-31-2011 | 05:37 PM
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So to make it simple:

Backspacing- distance from inside rim edge to face/hub of rim
Offset- Distance face/hub of rim is from the center

Example 18x9 rim

0 offset = 5 inch bs - you have to had a 1/2 to the rim width to account for lip of rim

o offset = 5" bs
-12 offset = 4.53" bs
+18 offset = 5.68" bs
 
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Old 03-31-2011 | 05:37 PM
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Originally Posted by mdhawkin
I would go with the 0 over the -12, maybe the +12 if offered, UNLESS you plan on lifting in the future.... Here is a page with some +12 18" with 325 https://www.f150online.com/forums/wh...c-jesters.html. I think the 305 on the 0 would look great too.
very helpful, i see what you mean about the offset now. that looks perfect. what do you think about going with 0 and putting bushwackers on or would the bushwackers look ok with the +12. I dont want the bushwackers to overlap the tires, i hate that look. That guy should of went with the chrome ones, there so much hotter than the black!
 
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Old 03-31-2011 | 05:39 PM
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Originally Posted by rrozell
So to make it simple:

Backspacing- distance from inside rim edge to face/hub of rim
Offset- Distance face/hub of rim is from the center

Example 18x9 rim

0 offset = 5 inch bs - you have to had a 1/2 to the rim width to account for lip of rim

o offset = 5" bs
-12 offset = 4.53" bs
+18 offset = 5.68" bs
finally understand now! - thanks
 
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Old 03-31-2011 | 07:41 PM
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Originally Posted by BLUEforLIFE
very helpful, i see what you mean about the offset now. that looks perfect. what do you think about going with 0 and putting bushwackers on or would the bushwackers look ok with the +12. I dont want the bushwackers to overlap the tires, i hate that look. That guy should of went with the chrome ones, there so much hotter than the black!
If you want flares then yea you should prob do the +12 IMO, but I as mention earlier you may have to do some trimming. I would spend some time search the site and browsing albums to see what combo's others are running so you can get a visual example. I think spending a little time looking around before buying is always a smart idea.
 
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Old 04-01-2011 | 06:24 PM
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This is my truck with +12mm offset rims. Personally I wish I got something that stuck out a little further but I have zero rubbing issues with setup at all with no trimming so I'm not going to complain. The flares are aftermarket and just a bit bigger than the stock fx4's. I have more pictures in my gallery if your looking for an idea of what kind of spacing your going to get. Also, the tires are 305/65/18 and there is a 2" level.
 
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Old 04-01-2011 | 11:40 PM
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I put the ballistic jesters with -12 offset with 35x 12.5x18 trail grapplers on my 06 fx4 leveled and have bad rub on the back of the front wheel well. thought the - was better than factory backspace. looks sick but sounds awful at 3/4 turn. I guess I need to lift 6 or body lift 3 w level
 
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Old 04-03-2011 | 06:28 PM
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Originally Posted by jimme
I put the ballistic jesters with -12 offset with 35x 12.5x18 trail grapplers on my 06 fx4 leveled and have bad rub on the back of the front wheel well. thought the - was better than factory backspace. looks sick but sounds awful at 3/4 turn. I guess I need to lift 6 or body lift 3 w level
did you have the chrome or black ones. IM still debating what offset to get.
 
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Old 04-03-2011 | 06:35 PM
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Originally Posted by Trev18


This is my truck with +12mm offset rims. Personally I wish I got something that stuck out a little further but I have zero rubbing issues with setup at all with no trimming so I'm not going to complain. The flares are aftermarket and just a bit bigger than the stock fx4's. I have more pictures in my gallery if your looking for an idea of what kind of spacing your going to get. Also, the tires are 305/65/18 and there is a 2" level.
truck looks good, IM thinking the +12 tucks the tires in to far. I do like when they just clear the fenders. how close did your 34's come to rubbing the CA on full lock. Im leaning towards 305/55/20 with 0 offset. Im not planning on leveling it anytime soon, plus i want to try to keep the mpg up.
 
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Old 04-04-2011 | 09:04 AM
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I've had no rub issues whatsoever. Keep in mind the +12 rims do stick out about an inch I would guess with no flares on the truck. These flares are about 1.5 inches I think so it looks like they stick in a lot more than they do. If you have the stock f150 flares or no flares it will look like they stick out a fair amount. But I do agree, I wish mine stuck out another half an inch or so. All that being said, I'm pretty sure they would rub somewhere without the level. Theres no rubbing, but theres not a whole lot of room in there either
 



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