Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - Taller tires for pickup?(do they increase mileage?)

aardvarcus · 06-10-2013, 10:34 AM

Regardless of who is right/wrong/nice/mean/etcetera why don't we try to get back on topic. Having some experience changing tire sizes on both big trucks and small cars, I figure I will try to assist from my experiences.

My first question is how low is your first gear? 10% taller means 10% lower cruising RPMs, but it also means over 10% harder on takeoff. It is something to consider, especially if your clutch is already worn, and may make you replace your clutch sooner both because it will wear a little faster and you will notice it is worn more. I am ok with the tradeoff in my Celica, but my 0-10mph take offs have definitely slowed down.

Second your cruising RPM’s aren’t that bad already. On my Celica sixth gear is 0.725, final drive is 4.529, and stock tires are 24”, thus at 65 MPH rpms are 2925 and at 80 RPMs are 3600, which are way out of the best RPMs for economy. That was a big driver in my change, but I think you are already in good shape on that front. On my trucks changing tire diameters on my truck from approx. 31.5” to 33” (5%) wasn’t really noticeable, as the differences in the other aspects of the tire overwhelmed changing my cruising RPMs when I was already at 2000ish.

Third, since you are already at a decent RPM choosing the correct tire tread pattern will have more to do with your fuel savings than the diameter. From my experience with a few different tires I would recommend Michelin M/S 2 for mainly street use, but they handle “light duty” off-roading fine as well, aka taking your 4x4 where you need it to go without getting stuck, but not dedicated offroading.

Fourth, weight of the tires matters too. Tire weight affects mileage more than regular on the car weight. It isn’t as important when you get up to speed, but if you get heavier tires expect to mash the gas harder or wait on the gas longer to get up to speed. Even highway driving has some speed up and slow down to it, so it still factors in a bit. On a truck going from a light tire to a heavy tire of the exact same diameter is noticeable on acceleration. (255/85R16 (light) vs 285/70R17 (heavy), both approx. 33” tires)

Fifth, I would let the prices of the tires help with choosing the size. On my car I knew I wanted Michelin Energy Savers, stock as 205/50R16 l and I wanted to do 205/60R16, but ended up with 205/65R16. The reason being at the time the 60’s were $120ish each and the 65’s were $75ish each.

06-10-2013, 10:34 AM	#51 (permalink)
aardvarcus Master EcoModder Join Date: Apr 2012 Location: Evensville, TN Posts: 676 Deep Blue - '94 GMC Suburban K2500 SLE 90 day: 23.75 mpg (US) Griffin (T4R) - '99 Toyota 4Runner SR5 90 day: 25.43 mpg (US) Thanks: 237 Thanked 580 Times in 322 Posts	Regardless of who is right/wrong/nice/mean/etcetera why don't we try to get back on topic. Having some experience changing tire sizes on both big trucks and small cars, I figure I will try to assist from my experiences. My first question is how low is your first gear? 10% taller means 10% lower cruising RPMs, but it also means over 10% harder on takeoff. It is something to consider, especially if your clutch is already worn, and may make you replace your clutch sooner both because it will wear a little faster and you will notice it is worn more. I am ok with the tradeoff in my Celica, but my 0-10mph take offs have definitely slowed down. Second your cruising RPM’s aren’t that bad already. On my Celica sixth gear is 0.725, final drive is 4.529, and stock tires are 24”, thus at 65 MPH rpms are 2925 and at 80 RPMs are 3600, which are way out of the best RPMs for economy. That was a big driver in my change, but I think you are already in good shape on that front. On my trucks changing tire diameters on my truck from approx. 31.5” to 33” (5%) wasn’t really noticeable, as the differences in the other aspects of the tire overwhelmed changing my cruising RPMs when I was already at 2000ish. Third, since you are already at a decent RPM choosing the correct tire tread pattern will have more to do with your fuel savings than the diameter. From my experience with a few different tires I would recommend Michelin M/S 2 for mainly street use, but they handle “light duty” off-roading fine as well, aka taking your 4x4 where you need it to go without getting stuck, but not dedicated offroading. Fourth, weight of the tires matters too. Tire weight affects mileage more than regular on the car weight. It isn’t as important when you get up to speed, but if you get heavier tires expect to mash the gas harder or wait on the gas longer to get up to speed. Even highway driving has some speed up and slow down to it, so it still factors in a bit. On a truck going from a light tire to a heavy tire of the exact same diameter is noticeable on acceleration. (255/85R16 (light) vs 285/70R17 (heavy), both approx. 33” tires) Fifth, I would let the prices of the tires help with choosing the size. On my car I knew I wanted Michelin Energy Savers, stock as 205/50R16 l and I wanted to do 205/60R16, but ended up with 205/65R16. The reason being at the time the 60’s were $120ish each and the 65’s were $75ish each.