I have a 2008 F-250 6.4L. Came with 265-70-17". I am looking to do the 2.5" lift in the front (with new shocks) and a 2" block in the back.

I need to step up my tire size- I'm looking at 315x70x17" tires on new 17x8.5 rims. Does anyone know if these will fit with the lift kit? How about without the lift kit?

 

Ugghhh...I'm gonna sound like a broken record on this particular topic, kind of the way I do when it comes to tuning. Anyway, here goes...

Do NOT put 12.5 tires on a stock (8 inch wide) wheel. They are NOT the proper size, period. It doesn't matter how many people do it, that doesn't mean they're the right fit...sorry.

Just about every tire manufacturer has a "recommended rim/wheel width" specification on their website, and I couldn't fit a single one that recommended a 12.5 inch tire, never mind a 13.5 inch tire (?!?!?!) for an 8 inch rim.

Why does it matter? You may get it to fit (as obviously a whole lot of people here have) and it may look right, but you don't need to be a tire engineer to figure out you're putting a whole lot of sidewall stress on the tire by fitting it on a wheel that's too narrow. And if you tow (as I do with my '10 F250) you could be asking for all sorts of trouble.

That's definitely trouble I don't need, and although it seems a whole lot of tire shops don't seem to mind that they're fitting the wrong size tire on a rim they sure would care if there was a catastrophic malfunction/failure followed by a wreck...or worse...

That's when the "I read it was OK to do it on the internet" excuse would fall real short in a court, etc.

What will work? For stock 18s the Toyo Open Country A/T 285/75 R18 which, coincidentally, are double marked as 35x11.5 R18. The Open Country M/Ts are also available in the same size, and both tires are Load Range E rated, as they should be. I would not recommend a Load Range D tire on these trucks. That's a step down from stock and will give you all sorts of squirm with load. Not cool.

If you want a legit, unbiased, thoroughly researched and "court defensible" (!) answer to your question, call Tire Rack tech support @ 888-541-1777. They'll tell you exactly what you can (or can't use)...

Hope this helps...

 

Does anyone know if you need a lift to clear 35" on an 04? I'm not sure if the wheel wells are the same size. It seems like I need a 4", does that sound right? I'm thinking of getting Toyo Open country m/ts 35/12.5/17. How much back spacing would I need with a 17x8.5?

 

I'm running 37x13.50R22 with a 2-1/2" kit in front, 350 blocks in the rear. Occasional rub.

 

Ronin is right 12.5" wide tires on an 8" rim is not the correct match and not recommended. Even more so with a 20" rim vs. an 18" rim. Having said all that, I was not going to shell out and additional 2K plus for new rims and I like the stock aluminium rims so my combo is 35 x 12.5"x 20" Pro Comp Extreme all terrains on stock 8" x 20" rims and a 2.5" Ikon levelling kit, Firestone aribags and Torklift camper spring extensions in the rear.

I fit a 3000 lb. camper and tow a 7500 lb. boat on this rig and so far it has handled very well. No sway, some pretty rough terrain and tough roads in the wilds of B.C. and I am pretty happy with the results. They may not be the optimal (i.e. 10" wide rim with 12.5" tires), but it isn't far from optimal.