As I've looked at lots of 2wd trucks in the 1992 - 1996 range, I've noticed that they have many different tire sizes, ranging from 235/75-15 up to 31 x 10.5/15.

I know that manufacturers offer a range of tire sizes as options, but does the transmission and/or axle gearing differ with each tire size?

In other words, if 31x10.5 tires were offered as factory equipment on a specific vehicle, and one installs that size tires later on, do you have to modify anything else to make everything match up? (I'm thinking specifically of speedometer and transmission shift points).

Russ

 

My '95 came from Ford with 235's. I later put on 31x10.50's and could hardly notice a difference with my I6 Manual with a 3.55 axle. I did some quick calculations and the difference in the diameters is about 6% which means that at 70MPH the speedometer is off about 5 MPH. There are ways to modify the speedometer readings to fix the problem, but I just remember that I'm going about 5 MPH too fast. With the 2wd's 31x10.50's rub when you crank the steering wheel all of the way, but this doesn't cause any problems. I wouldn't worry about the transmission if you have 3.55 or taller.

 

Hey Cowboy, how much are your tires too big for your truck. I am looking at putting 275/60/15 BF Goodrich Radial T/A's on mine and I am concerned about front clearance when turning. I haven't gotten under the truck lately due to the cold weather but as soon as I get a chance, I'll be checking. These are going to replace my summer set because in the winter time I go back to stock aluminum with Michelin's on them.

Have Fun & Keep on Truckin'
Dean

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1994 F-150 XLT Supercab, Long Box, 302 EFI, K&N FIPK, Bosch Platinum +4 Spark Plugs, Automatic, Single Catalytic converter, followed by a Raven Z-55 muffler and finished off with chrome tips (2 1/2" to 3"), Royal Blue in and out, Captain Chairs. Chrome Rims 15x8's, Michelin LTX M/S 105S 235/75R15 (Summer), OEM Aluminum Rims 15x8's, Michelin LTX M/S 108S (Winter), Lightly Tinted, Soft Tonneau Cover, Ford Receiver Hitch Cover & Lock, J&J Enterprises Stainless Steel AirDam with KC driving lights, Lund Supersteps, Lighted Grab Bars, VTech Slotted Taillight Covers, Alpine CDM-7829 Head Unit, PPI 4800 Amplifier, Kicker 10" Solo Baric Sub with Custom Box and Kicker Impulse 6.5 Mid & Tweets.

 

IzzyEddy-I'm assuming yours is a 2wd also. The 4wd's don't have a problem rubbing with 31x10.50's. The only way I can tell that my tires are rubbing is the signs on what I guess is the lower control arm (The lower black member running parallel with the frame). The width of the tire is causing the problem I think. The only time they could possibly rub is when I turn the steering wheel all of the way which is always at low speeds-hopefully. The 275x60's are about 0.3" wider than my tires, but about 3 inches smaller in diameter. I don't know if the reduced diameter will allow the wheel to be turned all the way or not. You may want to post a new message on this board and see if you could get someone elses attention. I don't think that you will have any problems though.