So I'm going to need to get new tires for the '91 F250 Diesel soon. I've found that it is equipped with 235/85R16, and I would like to get something maybe a little beefier. Not alot bigger mind you but just a little wider and a tough grip so if I want to I can get anywhere with it. I'm confused as to what I need to do about size differences and my speedo/odometer readings. I've read you just have to keep the overall diameter the same but then how is it that you can put 44" tires on then? So what do I do?

 

I have heard you can buy speedometer correctors for use when putting non stock size tires on your truck. Back in the cable driven days, which a 91 might still be.. idk, there was just a plastic? gear on the end of the cable that you could buy with several different tooth counts to help get your speedo accurate again. Better to get one off a parts truck instead of at the dealership... they wanted $42 for the last one i inquired about!!

 

I have heard of those as well.

 

Hmmm, interesting to say the least. I'll look into this; the father in law says hes pretty sure there should be a Gain control right on the transmission, ever heard of that?

 

Can't say I have ever heard of that.

Some tuners have adjustments for tire sizes but probably only for newer ones.

 

Does the 91 have a digital odometer like the 92-96 trucks?

 

My '88 F250 needed the little nylon driven gear replaced. A stock one was about C$25, but you can definitely find them on the net cheaper and with different tooth counts. I believe the stock one was pink with 21 teeth, but don't quote me on that.

Also, I'm also looking for different tires tires. My stock rims are 6" wide, which seems to mean (at least at tirerack.com) that a 235mm tire is the widest they will accept.