Questions on Tire size, RPM's, and MPG's
#1
Questions on Tire size, RPM's, and MPG's
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.
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.
#3
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
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
#4