Gotta buy new skins this weekend.

I currently have 265x70x16 (30.61") tires on my Ram, with a 4.10 gear ratio. RPM's at 70mph with a .69 ratio OD are 2174, according to the calculator at Randy's ring and pinion.

I was wondering if going smaller would be harmful to the RPM's at 70-75mph. I know smaller tires would have less rotating mass, would raise the RPM's a bit, and may supply a bit more low end grunt. I was looking at a tire that was 29" or maybe even 28", but I don't know if 2294 or 2386 RPM's respectively are too high. Does anybody know if there is a "drop off point" where RPM's really take a nose dive MPG wise?

Any tire recommendations? This is just a DD 2wd, so no slicks or mudders going on it, and I'm fine with a smaller tire.

 

Put a 40 series tire on that bitch and bag it.

 

IMO, id go 245's since you have the 4.10 ratio...no smaller....I too have 265/75/16 with 4.10's...but my tires are 10 ply, and i switched from a 6ply 265, and i noticed a difference in take off...not as much power on take offs...but respectively, i lost no mpgs, nor had any change really in the rpms.

I run at about 1950 rpms at around 70mphs...so you'd be running maybe 2100-2200 rpms, with 245's and with rpms around 2200, it wont harm anything, nor take much more gas...maybe 1/4 mile per gallon. anything thats lower that 1600 rpms at running speed its making the tranny work much harder, and possibly cause it to overheat. so basically a potentially higher rpm will be better for the truck.

All in all i wouldnt go smaller then a 245, and you will probably see a .5 mile per gallon change, and a matter of about 200 rpms change...not a big deal....



sry, did a lot of thinking while writing, so i wrote alot of my thoughts, even tho some doesnt pertain to your question

 

Went with a 255/70/16, it's half an inch shorter, won't raise the RPMs too much, just a bit skinnier so it doesn't rub at full lock (the old ones did just a hair) and were a little cheaper to boot than the other sizes I was pondering.

 

You realize with those skinnier tires, it's going to be harder to aim4squirrels right?

 

Actually, I'll gain a little off the line, and should be able to catch them a little easier.