Help finding a tire size OR help reprogramming F150-7700 speedo

Current tire size is 245/75-16. That is about 30.5". I want to go skinnier since any (minimal) off roading I do rarely requires flotation in mud or sand, but MPG, noise, and snow traction are higher priority. In the process, I would like to avoid going down in diameter because A) looks, and B) the speedo already reads fast; 65 indicated is actually 63 GPS and radar. My go-to truck size is 215/85-16, but that the same basic diameter as what I have at about 30.4"

235/85-16 jumps up to 31.7" which would correct the speedo nicely, but that is a LOT of tire. That size is usually HT, rib, and HD stuff and I think it might be too much. It also doesn't really cure my desire for a skinny tire, but it would be a nice compromise of skinny-enough for snow but fat enough for mud. It just seems like that monster tire would be overkill and may even look dumb.

I looked into 17", but two things are preventing me from that. First, most common 17" sizes are big for the looks of modern trucks; 285mm is pretty common. I can't find any skinny tires in 17" that make the right diameter. Second, this is a 7-lug truck, so there are no cheap 17" wheel options. The aftermarket has it covered, but it aint cheap.

WWGRMD? Get the 215s and reprogram the speedo? Get the 235s and suck it up?

I'd rock the pizza cutters, for the reasons you stated. And because I prefer anti bro-dozer.

I agree with pizza cutters. This:

is so much better than this:

You're pretty boned.

If 215 is your go to size, find a tall 215 tire. Those are all real high load ranges, though, same problem as your 235/85R16... 40lbs a tire! There goes your mpg benefit from going skinnier...

P range in a size that'll get you your diameter of choice will probably be just as efficient, and from the standpoint of us mortals, allow you to pick a tire with a tread design that's better in snow than the limited, narrower options. If you can deal with P rate. The higher ones are ~2,200 a tire. That's F-150 range for sure. 235/75R17 is going to be exactly what you need if you can find the wheels. I've got the Cooper AT/W, beautifully performing tire in the winter. Of course, if wheels are expensive, there goes any savings by changing tire size to get better mileage...

What year truck? Late model Ford's are really easy to reprogram at the dealer.

Edit; never mind, I misunderstood the question.

The reason I'm buying tires is because it currently has P tires on it. 7700 gvw plus 7500 lbs of trailer is nowhere near the capacity I need. I can't even put 10 sheets of drywall in the bed without the tires squishing all around and looking half flat.

The truck originally came with D-range which is all it needs, but no one makes a D-range anymore. Standard range LT would do the trick until I do the towing thing, and then the wimpy sidewalls make for tail-wag-the-dog situation.

and 40 lbs per tire only affects MPG during acceleration, and the narrower tread often makes up for the extra weight if highway is the primary travel. Suffice it to say that E-range is about my only choice. A standard LT would handle the weight by the numbers, but not be overly stable in towing.

Also in this size, you don't get many choices. There is a smattering of P-metric, a couple standard LT, and dozens of E-range.

gearheadmb wrote: What year truck? Late model Ford's are really easy to reprogram at the dealer. Edit; never mind, I misunderstood the question.

No, you understood. 2002. Correcting the speedo is something I want to do if I can't find the tire I need to correct it.

Dealer is not really an option for correction. First, they only have the factory flashes. So they would just reflash with what I already have and charge me $450. For instance, they plug in the tire size and axle ratio and it spits out a pre-digested data package that says 112 pulses per mile for 3.73s, 127 pulses if it has 4.10s, etc. There aren't any modifications you can really do outside of factory parameters. I need an aftermarket solution that lets you tell it 116 pulses (for example) to fine tune it to be correct.

235/85 all the way. Its plenty skinny for that pizza cutter look. In fact, I'd bet that's the tire size on that white Disco earlier in the thread.

curtis73 wrote: The reason I'm buying tires is because it currently has P tires on it. 7700 gvw plus 7500 lbs of trailer is nowhere near the capacity I need. I can't even put 10 sheets of drywall in the bed without the tires squishing all around and looking half flat.

Yeah, then you're screwed.

curtis73 wrote: and 40 lbs per tire only affects MPG during acceleration, and the narrower tread often makes up for the extra weight if highway is the primary travel.

...That's a bit of an exaggeration. Tire weight makes the biggest impact during acceleration (and deceleration), but once you're moving it's not some magic perpetual motion machine

curtis73 wrote: Also in this size, you don't get many choices. There is a smattering of P-metric, a couple standard LT, and dozens of E-range.

Yeah, you're hosed. For the tires.

Looks like this'll fix your speedo issue.

In reply to Osterkraut:

Thanks for the link. Looks like a workable solution.

And I wouldn't say "hosed" on tires. Just hosed on getting the perfect size that fits both my desire for "skinny" and "fix speedo".

D-range is a minimum on this truck, but since they don't make them anymore I just need to graduate to one of the 40 or so E-range options in this size and then fix the speedo with something like you linked.

thatsnowinnebago wrote: 235/85 all the way. Its plenty skinny for that pizza cutter look. In fact, I'd bet that's the tire size on that white Disco earlier in the thread.

Well, the forum website that hosts the picture says they're 215s, but they could be. They look tall enough to be 235/85.

i had 265/75r16 Treadwright's on my F250 light duty which is ~32" (since they are recaps they are a little bigger). They fit the truck pretty well, dont look to big.

but personally it seems like the difference between tires is splitting hairs. the 235 is only ~4.5% bigger, making your speedo only read ~2.5 mph faster then your actual speed. Also a 215 is only 2 centimeters narrower then a 235, that's only one centimeter added to each side of the tread. So if it was me I would just pick whichever one i could find with the tread pattern and load rating i wanted for the cheapest price.

Also if you dont plan on airing down for hardcore offroading (doesnt sound like you do) then i would look into Treadwright tires. they have the sizes you are looking for in AT and MT for decent prices. I have had them on 2 trucks now and they have been great.

What's the big deal ? 2/3 mph is pretty much the norm through the industry.

It's going to be really difficult to "correct" it with tires.

curtis73 wrote:

thatsnowinnebago wrote: 235/85 all the way. Its plenty skinny for that pizza cutter look. In fact, I'd bet that's the tire size on that white Disco earlier in the thread.

Well, the forum website that hosts the picture says they're 215s, but they could be. They look tall enough to be 235/85.

Guess I'd have lost that bet then

Tire Racks tire size availability listing

Look at the options for the tires that are in the range you want.

iceracer wrote: What's the big deal ? 2/3 mph is pretty much the norm through the industry. It's going to be really difficult to "correct" it with tires.

Its not a big deal, but its actually very easy to correct with tires. 235/85 should mathematically correct it to within 0.25 mph if I did my maths right... which is unlikely. (me and math have a rough history)

edizzle89 wrote: but personally it seems like the difference between tires is splitting hairs. the 235 is only ~4.5% bigger, making your speedo only read ~2.5 mph faster then your actual speed. Also a 215 is only 2 centimeters narrower then a 235, that's only one centimeter added to each side of the tread. So if it was me I would just pick whichever one i could find with the tread pattern and load rating i wanted for the cheapest price. Also if you dont plan on airing down for hardcore offroading (doesnt sound like you do) then i would look into Treadwright tires. they have the sizes you are looking for in AT and MT for decent prices. I have had them on 2 trucks now and they have been great.

Thanks for the pictures with your 265s. I have had 215/85 on an F150 before and loved the look, and I had 235/85 balloon-like HTs on a motorhome. I was just having trouble picturing what the 235s would look like. Seems like they would look just fine given how your 265s look.

No hardcore off road for me, but several times a year I do go to one of several camps which are tucked way back some roads that really require off-road capability; fording a couple streams, light mud, etc. No Moab crawling or anything.

THanks for the tip on Treadwrights

I'm used to running 235/75/15 when full size trucks had 15" wheels. 235/85/16 sounds good to me at least.