Ok guys, I am looking at some 18" wheels that have 5.02" backspaceing and -12mm offset. I would like to get Toyo MT's 35x12.5/18's tires....Does anyone know if this is the correct backspaceing and offset for these size of tires? I have a 2.5" leveling kit and F-350 4" rear blocks for my lift on an '02 F-250 PSD. I am just wondering if there is a designated backspacing and offset that I should get for this setup.

Thanks

 

Just for reference, I'm running 4 1/2" of backspacing and -25mm offset on my '02. Tires are 325/60r20 which is close to 36" tall and 13" wide.

 

Thanks Pocket,

Well I am assuming that everything should clear but I just wanted to double check before I order anything.


BTW Pocket, Nice truck!

 

Just so you know, you only need to know backspacing or offset. They're basically the same thing, measured differently; when discussing the same width wheel. An 8" wheel with 4.5" backspacing will always be 0mm offset, so as an example, you wouldn't have to say you're looking at a 8" wheel with 4.5 backspacing and 0mm offset. However, if you're looking at an 8" wheel, a 9" wheel and a 10" wheel then it would be different of course, but you could always say a 9" wheel with 4.5" backspacing, or a 10" wheel with 4.5" backspacing and they would all have a different offset, but stick in or out the same amount (4.5" backspacing is the same, is the same, is the same, regardless of the width of the wheel).

 

this has helped me alot...

http://www.rims-n-tires.com/rt_specs.jsp

and it seems your dead on with the backspacing/offset... its still gonna stick out a good 1.5" or so... maybe more...

Joey

 

Thanks, Yeah the wheels I am looking at are 18x10's with 5.02 BS and -12 offset. They are the Diamo Karat D17's(black), I just cant seem to find a fitment guid but I will try that link. thanks

 

when I compared it to my 285/75/16's on my stock 16x7's and the tire/wheel combo you mentioned, apparently you would be at the same spot I am right now on the inside (meaning you probably won't hit the leaf springs)... it seems like a good amount of backspace to offset the width of the wheel... FYI, OEM offset is +7mm, IIRC...

Joey

 

The way I see it is that 5" of backspacing and a 12.5" tire have a good chance of rubbing the leafs. I have 35X12.50R18 on factory wheels that if I remember right have 4.80" backspacing. My tires just rub the leafs, so 5" of backspacing would put the tire farther in and cause more of a rub. But 4.5" of backspacing should bring the tire out just enough that there would be a good chance it will not rub.

 

doesnt matter how wide the wheel is, the tire is 12.5" wide and that would be the first thing to touch any suspension part... yeah, I had a hard time wrapping my head around it as well... put in the figures for your tire/wheel package and then the one he mentioned... THEN you'll see what I mean

Joey

 

I agree the tire is the first thing to touch and the wheel width does not matter when it comes to backspacing, but if you use a wheel with 5" of backspacing the wheel and tire both will be closer to the leafs to begin with. This is why 4.5" backspacing is ideal.

As for the wheel width not making a difference, well I have to disagree when you are talking about the limited clearence there is between the tire and the leafs.

For every .5" change in rim width there is approximately .20" difference in mounted tire width. Take the same exact tire, for example a 35X12.50R18 and mount it on a 8" wide rim and it measures 12.50" overall width. Now take the same exact tire and put it on a 10" rim and the overall mounted width of the tire will be closer to 13.25".

 

hmmm... which do you think physically moves the tire closer to the springs? a 17x8 with 4.5" of backspacing or a 17x9 with 5" of backspacing? granted the tire might be 1/4" wider with the wider wheel, but leaving that aside... and I don't meant to argue, btw

Joey

 

I am not trying to be argumentative either as I know this to be a subject with many variables to consider and I have test fit many of them.

But anyway the 17X9 with 5" will put the tire closer to the leafs by a 1/2" over the 17X8 with 4.5". You have to remember the larger the backspacing number the closer the backside of the wheel will be to the leafs.