I recently purchased a '90 Dodge Dakota 4WD since I needed a truck. My '90 Civic hatch is great but just doesn't quite cut it when I need to haul much of anything. I didn't really want 4WD, but other than that it was everything I wanted - V6, manual transmission, 8' bed, and 2,000 pound payload package. After 6 months of serious searching I figured I wasn't going to do much better. At least it has 3.55 gears instead of 3.90s.
Anyhow, it needs tires. The current wheels have a silly offset, one is smashed, and I lucked into a set of factory aluminum wheels at a junkyard last weekend so I'm on my way. The stock tire size for this particular truck is 235/75R15. I think I am going to go with Michelin LTX M/S2 tires in the stock size but I thought I'd ask a couple of pretty open-ended questions here first in case anyone has some good insight
Really, I'd like to be running some narrower tires than 235s. My old Dakota had 205/75R15s and was a 2WD auto (yuck on the auto part). I knocked out 22-23 MPG at 65 MPH with 500-800 pounds in the bed with that truck, which was decent considering the trans. For my current truck, I would like to stay close to the same overall diameter so that I don't have to change out the speedometer gear. It's not difficult to change, just pricey for what it is.
The other issue caused by the smaller diameter from the 205 sizes is that they result in slightly higher engine speeds. Granted, it's not a lot, but a 205/75R15 would run about 2430 RPM at 70 MPH vs. 2280 RPM with the 235s. I wouldn't even be concerned about that for city driving (narrower would be obviously better if I never ran out of gears) but I plan on mainly doing highway travel in this truck. 70 MPH is the fastest I'd ever conceivably go.
The other big issue is that Michelin doesn't seem to make anything in the 205/75R15 size that would work. I've been happy with their tires so far and will continue to give them business as long as that remains true... or if someone else out there has a light truck tire that gets significantly better fuel economy.
Like I said, I'm pretty sure I'll just stick with the 235s but wasn't sure if anyone had any info regarding a similar tire sizing situation. I did see the link to the Car and Driver article (I'd link to it here, but I'm not allowed to as this is my first post) and noticed that the drop in fuel economy from 195/65R15s to 225/45R17s was 23.3 to 22.8 MPG. That's ballpark for my truck's MPG figures, although there may be a bit more increase in Cd since more of my tires would be exposed with the taller ground clearance. Granted, I'm not changing wheel size in this situation (stock 15x6s with either tire) but the width difference is similar.
Anyway, I'm definitely rambling at this point. Anybody have any suggestions or recommendations? Anybody able to stop me before I put 235s on and get stuck with them for 70K miles?