my dad doesnt want me to sell my stock rims/tires cause if i need to get trany work or ne thing he says my extended War. will be voided any truth to this this size tire comes stock on fx4's so im thinking they couldnt do ****.

 

All depends on your dealer and your problem. True, 31's do come stock on a Level II, but they didn't come stock on your truck. Your truck's computer will still think you have the smaller tires on and will not compensate for the larger diameter tire. Speedo,shift points, and abs will all be effected to some degree. If the dealer really wants to be an *** they may use that against you, or they may never notice it.

 

Most likely you will keep your stock tires if you get 31s. So you have two choices. Either keep your stock tires in the garage and switch em on during problems, OR go to like a junkyard or wherever you'd find old used tires. Find 4 tires that fit your truck that have like 1% tread left AND DON'T have serious defections(so they won't pop on ya or somethin) and drive in on those badboys.

Aaron

 

my transmission is getting fixed under warranty and i have 32s

 

you could get the 31s and keep your old rims/tires and if for some reason you have to take in your truck, just switch them back

 

you could get 31" tires and have the control module adjusted
not sure what your rear axle ratio is but if not at 4.10 your 3.0 might have a hard time with 31" tires

 

you can get 31s and not worry about it cause I highly doubt they are gonna affect anything but speedo

 

doesnt the stock tires come out to something like 30.2"? most 31s are about that size so tell them that...in fact sarahs tires come out to the same size as my old 31 bfg ATs...

 

30.2" == 31??? 31" tires (ie 31x10.5) are 31" across, hence the name!

Just as an interjection, some FX4 LII owners I know have had problems w/ warranty service on their 100% STOCK trucks because the service departments have blamed the problems on their 'big aftermarket' tires.. Were you to encounter such a dealer it would be hard to counter that UNLESS you had an FX4..

 

[QUOTE=NHBubba]30.2" == 31??? 31" tires (ie 31x10.5) are 31" across, hence the name!
QUOTE]


30.7=31's but whos counting anyways

 

Yes, I had a service writer try to deny me warranty coverage because of my tires, wheels and Level II shifters (all stock). He got spanked.

Despite what logic might suggest, 31's are actually approximately 30.5~30.7" diameter (when new) for most brands including the BFG ATs on the Level IIs. When someone told me that, it seemed so ridiculous that I had to go measure mine before I allowed myself to believe it.

As a matter of fact, the 245/75R16's found on many other stock Rangers are almost exactly the same diameter as the 31's on the Level II's.

 

i dont think you will have any problems but the best thing to do is to ask the dealer, you never know they may say that is fine because you are being up front about it.

here is a calculator for tires, bob is right on the tire size.

http://www.zabeard.com/info.htm

 

I must have a broken ruler. I measured 31" within a 1/4" myself when I had the wheel off the truck for a rotation one time, properly inflated, unloaded. Although YOU are saying 30.7, which is close to the 30.75-31.25" I measured.. Whatever..
Mine has yet to give me static about the tires/wheels, but I did get it over the shifter. Tried to deny me service on my tcase indicator because of my 'aftermarket' shifter package! .. That was before I unloaded on him over the telephone!

..That still pisses me off just thinking about it! Every time I pull into a Ford garage I get at least a dozen comments like "Whoa! We make a Ranger like that!" You'd think product training would be part of the job..

 

across? across what? the height? ERR DOES NOT COMPLY...im saying the 31x10.50x15 tire and stock ranger tires are so close to the same height u can argue the same.

 

Across means from one side to the other. I too was told that imperial sized tires are not acutally the size they advertise, so I went to measure. I had the tire off the truck and w/ it lying face up on the ground I measured from one edge of the tread to the other, making sure my tape measure laid across the middle of the wheel. W/ the ATs it was fairly easy as there is a very pronounced and squared lip to the side of the tread. I forget exactly what I measured, but it was within 1/4" of the specified 31".. A noticible increase over the ~30.1" I calculate the 255/70R16 tires the base FX4 ships w/.
Tell that to your truck's computer & spedometer.. Besides, which 'stock' are you comparing to? The ORP/FX4, or the 4x2, 3.0 powered Edge the OP drives?

I see your argument as it pertains to added stress and wear, and I agree. But it will effect the mileage and speedo indicators. My calculations show a 30.1" tire (like the 255/70R16 the FX4 ships w/) would require ~670 rev/mile while a 30.7" tire would require ~656. A non-trivial (at least in my mind) 2% difference.. My '99 XL Sport 4x2 came w/ 225/70R15's. I caculate those were ~27.4" across and made for 736 rev/mile, or a 12% difference over a 30.7" '31x10.5'..

 

well i have 235's so there 28.9" and the 31's ill be putting on are 31 exactly ( i got lucky lol.

 

Many people measure either by eye estimation of where the tape crosses the edge of the tread, or foolishly wrap the measuring tape down to the edge of the tire, down around the bulge of the sidewall, making it seem effectively LARGER.

To do it right, you would need two flat pieces that are laid flat on the tread and extending out to where they can be measured. Even then, it would be difficult to get an exact measurement.

What you need, is a really big caliper. Short of that, ALL your measurements are approximate and if the manufacturers data says 30.4, and you measure 31, your measurments are probably in error, and you didn't get "lucky", lol.

 

whatever the edges come with, 255/75/16? hell i dont know but i measured it off the truck with 2 rulers at each edge and across like u mentioned...as long as u see what im saying i made my point.

 

As long as YOU understand that if the manufacturer says it isn't 31" as you measured, then your measurements are probably in error. All measurements are approximations, just some are more "approximate" than others.

 

or john you can measure circumfrence then calculate the radius no need for calipers.

 

[/QUOTE]or john you can measure circumfrence then calculate the radius no need for calipers[QUOTE]

 

Depends on model and year. The 2005 FX4 Off Road ships with 255/70R16 but years 2003 and 2004 FX4 Off Road were equipped with 245/75R16 as were many other years/models of 4x4s, Edges and Trailheads.

BFG lists the 31x10.50R15 ATs as 30.7" and most manufacturers list a 245/75R16 as 30.5~30.6" - in this case, a trivial difference of about 0.3~0.7%.

But there are many tire swaps that don't show such a small error. It matters not only where you are going to but also where you've come from. Ford generally offers 4 diameters of tires and 3 axles ratios on Rangers. It is not correct to say that a switch to 31's on any Ranger is without significance.

 

Actually, it doesn't matter much at all. My point is that people saying "my tires are exactly..." are standing on thin ice, in terms of measurement. Being in manufacturing, and dealing with this issue all the time, makes me a measurement ****. Ignore it if it bothers you -- but most "simple, easy" measurements are neither, lol.

There are more errors you can get measuring the diameter as well. Make 3 measurements: inner outer and middle edge under proper inflation and you will get possible 3 different readings. Average them and calculate. You also need to ensure the correct tension on the tape to ensure compliance, and check to make sure you are measuring a true diameter with no tape skew.

The way tires are molded and finished, there is very little variation in their diameter. When in doubt, consult the manufacturers tables and that is the "real" diameter of your tire, no matter what you measure. Your methods will be suspect without good procedure, and even then, you need to make many measurements and average out any non-systematic errors.

 

Ah, we're splitting hairs here.. But..

I did a halfassed measurement w/ the tire off the truck, unloaded, as I decribed earlier. I just slapped a tape measure down on the tire, lined it up to intersect the center hub knock out on the wheel, and eyeballed from there. I got pretty damned close to 31" and called it a 1/4" margin from there. Not the most technically perfect manner of measurement in the least, but close enough for my purposes. I'm more than willing to call it 30.7" though..

And I hadn't realized the '03 FX4s shipped w/ larger tires than the '05s. That certianly reduces the difference. So yeah, if you have an '03 FX4 and swap tires for a set of 31x10.5 tires you shouldn't have any problems whatsoever. And the Ford shop is just being an a$$ if they give you a hard time. Whip out the calculator and/or go to another shop, whichever works best for you..

However, if you're running a 3.0L or smaller 4x2 Ranger w/ the 7.5" rear and a set of 225/70-something or others stock and want to swap for the same 31x10.5's, expect some trouble. If not from wear or warranty issues certianly from speedo inaccuracies..

 

Or just give them a "dope slap"...dealers understand that.