Check my math, wheel/tire thing is driving me nuts

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Mudder

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So ok, I'm trying to figure what wheel and tire setup to go with on my truck. And so taking two sizes that seem very different but in actuality sit the same on the truck. Check my math, see if this is right.

So let's take a 17x8 0 offset wheel. And an 18x9 0 offset wheel. Both running 12.5" wide tires.

Backspacing on the 17x8 is 4.5. So if you add that to the split of the overhang of the tire (12.5-8=4.5/2=2.25) the sidewall of the tire sits 6.75" from the mounting point. Using the same formula, the outer edge of the sidewall sits 5.75" from the mounting point i.e. hub.

Backspacing on the 18x9 is 5. So if you add that to the split of the overhang of the tire (12.5-9=3.5/2=1.75) the sidewall of the tire sits 6.75" from the mounting point. Using the same formula, the outer edge of the sidewall sits 5.75" from the mounting point i.e. hub.

So essentially the two setups would sit exactly the same on the truck from a clearance perspective despite it seeming like you'd have more room with the 8" wheel having 4.5" backspacing.

What a confusing cluster this is turning into for me. And yes, I've been known to overthink things.


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Mudder

Mudder

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So essentially I think I've just described the whole offset thing versus backspacing. Any wheels with 0 offset using the same size tire will yield the same stance. What a confusing mess to someone who grew up with backspacing.


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dan1911

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So essentially I think I've just described the whole offset thing versus backspacing. Any wheels with 0 offset using the same size tire will yield the same stance. What a confusing mess to someone who grew up with backspacing.


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Ive always felt more comfortable with the offset measurements (+/- mm) rather than the backspacing. A -5 offset, for example, will always be a -5 despite wheel size and assuming the same tire. I know what a -5 looks like, so if i move up a wheel size ill already know exactly how it stands. Versus the backspacing (inches) that changes based on wheel size, always seemed to confuse me more.
What size diameter tire are you trying to fit, or did you already figure out what you needed? lol
 
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Mudder

Mudder

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It's more the stance thing. I'm wanting to run 35s but I want to tuck them as much as possible. It seems 0 offset is going to get me the closest without chancing UCA rub and still have some selection on wheels. If I go all the way up to an 18 offset then I'm right back to stock with the same issues width presents there. 12 you're flirting with rubbing it would seem. And 6 would be great but there are like 3 wheels with that offset. So 0 seems to be where I need to be looking.


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dan1911

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It's more the stance thing. I'm wanting to run 35s but I want to tuck them as much as possible. It seems 0 offset is going to get me the closest without chancing UCA rub and still have some selection on wheels. If I go all the way up to an 18 offset then I'm right back to stock with the same issues width presents there. 12 you're flirting with rubbing it would seem. And 6 would be great but there are like 3 wheels with that offset. So 0 seems to be where I need to be looking.


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I have a 17x8 with a zero offset and love how much it sticks out of the fenders, not crazy but enough to have a decently aggressive stance. Im running 34x11.50s Toyo AT2.

Personal note: I did a bunch of research about how wide i wanted my tires for the kind of off-roading I do and after having owned the 12.50s on my last truck I am STOKED with the slightly thinner wheel and how they perform (turning radius is a bonus lol)

I have zero problems with rubbing and not even close to anything when at full lock, so the extra 1/2in on either side and a 0 offset you will be just fine (keep in mind super luggy m/t tires could stick out the 12.50 mark and have to do some minor trimming
 
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Mudder

Mudder

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I'm leaning toward an 18x9 with a 305/70 tire. Little bit narrower than a full pledged 12.5 but should still look aggressive without being too crazy.


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dan1911

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Ya thats just under 35 and 12.00 wide so not much different than mine (about 0.1inches taller overall and 1/4 inch sticking out on either side).
It's gonna look great man
 
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Mudder

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Thanks. Gonna be a tough convincing to the wife. Bought truck last weekend. 10 week old baby boy. This may not fall under high priority right now. I will try my best to convince lol


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dan1911

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I went with "It seems unsafe to off road with the stock tires and if I blow one out I cant
resell it."
I got a 2013 a year ago with 30k miles and sold the stock tires for $300. That was about 1 whole brand new tire! And of course, the tires I wanted had to have a wider wheel to get within the operating range... so there's that too.
She ended up really digging the new look and I lucked out big time, but she also loves sitting shotgun when we go off roading
 
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Mudder

Mudder

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Good call on the argument there. My wife is all about the truck and mods and such, but the baby is currently holding sway over all decisions. Maybe in a few months when he starts talking I can rally him to the cause and get some ordered.


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dan1911

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Good call on the argument there. My wife is all about the truck and mods and such, but the baby is currently holding sway over all decisions. Maybe in a few months when he starts talking I can rally him to the cause and get some ordered.


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In my case, her dog loves when i drive through puddles and the passing branches when off roading.
Maybe the baby REALLY enjoys off roading too and makes him happy!
 

dan1911

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Meant to send this yesterday, but this is how far my tires stick out just for reference

276521269891608d78cb39e50b361df8.jpg



Sent via telepathy
 
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