How much sidewall

[fifty]

I am running an F-350, with a not so light 7.3 up front. I dont do any crawling per say... Just lots of dirt roads...a couple water crossings if its in the way...Although I am becoming more adventurous as the wife gets more comfortable... Its simply for back country excursions and camping.

I am almost done with my newest evolution with my truck...the coilovers/4 link lift etc...So I can run 37's to get a little more clearance and all.

Now for day to day operations on street, I have a set of 20's on 37's. Thats 8.5 inches of side wall. (Theoretically the same as a set of 18's with 35's)

I am wondering if there is going to be any advantage to invest in a set of 17's to get an extra 1.5 inches of sidewall? Am I gaining enough to offset the extra $2500 in wheels and tires that are just there to run when I go on vacations?

 

[Buliwyf]

As I look at tires for my 17" wheels, I find that 18" wheels offer a better variety of tires with greater load capacity. If I ever buy another set of wheels I'm going to go with 18" steel wheels close to the factory backspacing and close to factory width.

17" will be better for rock crawling and general offroading that is probally beyond your goals.

Nothing really wrong with 20" wheels and 37" tires, except that tires for 20" wheels appear to be a small fortune.

 

[911regular]

Really depends on if your gonna air down or not.

 

[redthies]

If I ever buy another set of wheels I'm going to go with 18" steel wheels close to the factory backspacing and close to factory width.

Nothing really wrong with 20" wheels and 37" tires, except that tires for 20" wheels appear to be a small fortune.

I've found the opposite. Lots of 17s, not so many 18s. Cost on 18s is also a significant amount more. 20s should be fine with a 37, as long as you are not airing down a lot... As stated above.

 

[fifty]

I run 50 psi street. I imagine I would go down to 35/40 for general fire roads etc. If I hit deep loose sand maybe less. I haven't had too much chance to experiment yet.

 

[Redline]

You obviously have a good handle on the fact that it's only the bottom half of the sidewall that matters. If you are going to run 50 PSI on the street, 40 doesn't seem low enough to gain much benefit. Seems like your 35 PSI (or lower) would be my preference, but you'll have to experiment as you know. I have zero experience with 20" wheels. Though I like having multiple sets of wheels & tires, I would guess it's probably not worth it to have a set of 17-inch tires/wheels just for vacations unless you really need them.

Do you plan to carry a full-size spare? Or at least one that is close? I'd assume carrying a 37" spare would be a challenge, surely you can fit a 33" spare, and maybe a 35", in the stock location depending on the year and set up of your truck. Do you plan to regear? Manual or auto tranny? I've considered 35s for my 7.3L a few times but stayed with 33s thus far. I'm not sure I would like the performance with 37s, even with my 4.10 gears.

I initially wrote a longer reply, possibly more than you want… I'm going to use my extra ideas on my blog.

Good luck with your decisions and share some pictures of that 7.3L

 

[redthies]

Redline- Your thoughts are correct on 37s with your 7.3. A friend of mine is running 37s on his truck (identical to yours, assuming you refer to your white F350), and I ran 35s on mine, (also identical, but 7.5). The power from his low mile 7.3 is adequate to turn the 37s, but it is not what you would call "zippy".

 

[BigAl]

A new set of wheels and tires for that beast has got to be 2K plus. I would live with the existing set up. Sounds great as is.