Tire & Wheel Weight Vs. MPG & Power
08-09-2009, 05:58 PM
#11
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Does anybody know with some degree of certainty what effect tire weight and wheel weight have on MPG's and ability of keep speed on the highway (power while towning especially?)
Would say Toyo MT's or Nitto Mud Grapplers at 90lbs plus a steel wheel have a noticable difference compared to say BFG's at 70lbs and aluminum wheels?
Am I worrying about nothing? I just don't want to shell out 10 grand for lift, wheels, tires, and gears only to find out I can't go over 55 mph on the highway with my trailer in the mountains here in Colorado.
Any physics majors out there?
Would say Toyo MT's or Nitto Mud Grapplers at 90lbs plus a steel wheel have a noticable difference compared to say BFG's at 70lbs and aluminum wheels?
Am I worrying about nothing? I just don't want to shell out 10 grand for lift, wheels, tires, and gears only to find out I can't go over 55 mph on the highway with my trailer in the mountains here in Colorado.
Any physics majors out there?
Your unloaded M416 trailer only weighs under 600 lbs. (with stock military tires).
I weighed my trailer last weekend with it loaded full of camping gear and a kayak on top, wth 37" Nitto MG's on the trailer and it weighed a little over 1,000lbs. The jeep still pulled it with no problems. I have a theory that with trailer being so short and close to the jeep that it drafts? Maybe I'm wrong.
I have changed the spark plugs (E3), have a hypertech programmer and run synthetic motor and gear oil. I also have a B&M Tranny cooler.
You would not notice a difference, if any, in gas mileage between a Nitto/Toyo vs BFG of the same size and width, on the SAME wheel.
Last edited by RAZORBACK; 08-10-2009 at 10:27 AM.
01-06-2010, 12:21 PM
#12
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01-06-2010, 01:36 PM
#14
JK Junkie
I've run some rough numbers before for 35s and 37s on 18" wheels before making some simplifications for the moment of inertia, but it should be easy to make them generic.
I'll post them when I get home if someone hasn't already done so already, but here is a real data point where the rubber meets the dyno from our friends at Ripp that I found interesting:
"Initial testing has found that in stock form the 3.8l only produces as little as 133 Wheel Horse Power (WHP) on stock wheels/tires and gears and as little as 108-123whp on up rated 35" tires."
rippmods.com/2007_2009_Jeep_Wrangler_JK_V_3_Si_Trim_Intercooled _p/0709jk-sds-01.htm
BTW, this page also indicates that the auto slushbox driveline sucks up about 16 HP over the manual. :what?
I'll post them when I get home if someone hasn't already done so already, but here is a real data point where the rubber meets the dyno from our friends at Ripp that I found interesting:
"Initial testing has found that in stock form the 3.8l only produces as little as 133 Wheel Horse Power (WHP) on stock wheels/tires and gears and as little as 108-123whp on up rated 35" tires."
rippmods.com/2007_2009_Jeep_Wrangler_JK_V_3_Si_Trim_Intercooled _p/0709jk-sds-01.htm
BTW, this page also indicates that the auto slushbox driveline sucks up about 16 HP over the manual. :what?
Last edited by wayoflife; 09-07-2010 at 09:50 AM.
01-06-2010, 02:02 PM
#15
JK Junkie
If you want to plug numbers the moment of inertia of a tire (and rim) can be calculated by breaking it down in two 3 components: 2 sidewalls (rings) and a tread (short cylinder) all rotating about the same axis.
I = 2 * [m(s) (R**2 - r**2) / 2] + m(t) R**2
I moment of inertia
m(s) = mass of sidewall
m(t) = mass of the tread
r = radius of the wheel
R = radius of the tire
Keep the units consistent
distances in ft
mass in lbm = lbf
I think I assumed 65% of the mass was in the tread.
You can use the same equation for the wheel with minor mods for 1 sidewall and the appropriate radius.
I = 2 * [m(s) (R**2 - r**2) / 2] + m(t) R**2
I moment of inertia
m(s) = mass of sidewall
m(t) = mass of the tread
r = radius of the wheel
R = radius of the tire
Keep the units consistent
distances in ft
mass in lbm = lbf
I think I assumed 65% of the mass was in the tread.
You can use the same equation for the wheel with minor mods for 1 sidewall and the appropriate radius.