[rammertide07]

I have a 3" body lift that the previous owner installed and 315-75-16 tires. First time I drove my truck back from GA, I was pulling an empty 18' box trailer. Going through some decent hills my truck had a really hard time making it up the hills. Also, my dad bought an stock 01 F250 with the exact same body style as mine, auto, 4x4. His truck is way faster than mine, I barely pull on him with my chip on the high performance tunes. I'm thinking it may be my tire size causing the lack of power and 180* transmission temps running empty?? I hardly every go off road, I just like the idea of 4x4 because my 96 2x4 would get stuck in damp grass. So I'm thinking the next time I need new tires, getting rid of the body lift and going with a tire size between 265 and 285. How does one remove the body lift? Also I would like comments on whether my current size tires would cause that much of a power difference?

[ticopowell]

Yes large tires like that will cause a large drop in performance. I put 315's on my F-150, then added a gryphon and I was maybe as fast as I was before, but I think I was a little slower. Those tranny temps seem very high for not towing anything, but that will probably be lower with different tires. The body lift might be pretty tough to remove, but I would think the easiest way to do it is to go to a local shop and ask them how much they charge. Also the body lift will be ok with smaller tires, but it will add drag so you will get worse gas mileage with it installed. The other option is to change the gears in the differentials, it is ex*****ve ($1500-$2000 from what I have heard), but it will put the tranny back in the right gearing range, and give you more power to the tires.
On another note, the 315, 265, 285, is just the width of the tire, it has nothing to do with the actual diameter. The difference is going to be in the second number. It is a ratio of the width to the height, so you could have a 265/70R17 and a 275/65R17 and the diameter will be very very similar, or a 275/70R16 would also be close. I have 35"ish tires (they are for sale) that were 315/70R17, and total diameter was 34.5", while yours are total diameter of 34.6". , In your case where you drive on damp grass I think the wider, 285s, will work better and get you stuck less, but on snow they will be slippier so be careful of that too. Sorry if I got off topic a little, just thought you might want more info than what you asked for lol

[rammertide07]

Thanks man. I'd rather go to a CHEAPER tire to buy (and less maintenance) rather than putting MORE money into re-gearing. I think 265/75/16 is stock size for our trucks. I think my dad went 285 on his.

[JackandJanet]

Originally Posted by rammertide07

Thanks man. I'd rather go to a CHEAPER tire to buy (and less maintenance) rather than putting MORE money into re-gearing. I think 265/75/16 is stock size for our trucks. I think my dad went 285 on his.

I think 265/75/16s sound good. They are 31.6" in diameter. My OEM tires are about 32" (on 18" rims). By using the larger 34.6" tires, you are losing about 10% of the effective force your engine is capable of exerting on the road to get you moving and keep you moving.

- Jack

[rammertide07]

I just measured my tires and they are 33.5" and my dads 285-75-16 tires are 32". Why does the height of the tire change when the only difference in the tire size (as indicated by the side wall) is the width of the wheel.

[ticopowell]

You are correct in that the difference in the sidewall size is the width of the wheel, but the second number denotes the height of the side wall as a percentage of the width, so even though the number is the same, the sidewall is larger because the tire is wider.
Does that make more sense now?

[rammertide07]

Hahaha....Yes it does. I found the formulas to figure everything up on tirerack.com. I think by trying to set a world standard they made it confusing for some people...like me Thanks again

[ticopowell]

Glad we could help