New Tires for Dakota
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Joined: Jun 2011
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New Tires for Dakota
I have a 2000 club cab dakota with 255/65-15 rims. I had to get new tires and my tire guy told me they stopped making them so I got 255/70-15s on his recommendation.
It feels like I have to give it more gas to go. I am not a tire expert, but is this going to effect my gas mileage, speedometer reading, etc?
He sold me Grand Ams btw.
It feels like I have to give it more gas to go. I am not a tire expert, but is this going to effect my gas mileage, speedometer reading, etc?
He sold me Grand Ams btw.
Professional
Joined: Mar 2008
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I have a 2000 club cab dakota with 255/65-15 rims. I had to get new tires and my tire guy told me they stopped making them so I got 255/70-15s on his recommendation.
It feels like I have to give it more gas to go. I am not a tire expert, but is this going to effect my gas mileage, speedometer reading, etc?
He sold me Grand Ams btw.
It feels like I have to give it more gas to go. I am not a tire expert, but is this going to effect my gas mileage, speedometer reading, etc?
He sold me Grand Ams btw.
Not sure you can do much about it, at this point. The tires are already on the truck. What I would have suggested before this is to look for some aftermarket rims in a different rim diameter (16"-18" perhaps) and try to match the combination of the rim and tire diameter to meet your original OEM specs. Your configuration would not change and you would spiff up your ride a bit. Plus, if you bought a lighter rim, like a forged alloy, you'd be reducing some unsprung weight; thus increasing torque, throttle response and (potentially) gas mileage.
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Joined: Feb 2012
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From: Missouri
I've got the stock alloy rims on mine, and I'm currently using 235/75/15s. I tried the 70 profile and I noticed that my gas mileage and traction were negatively affected. I honestly don't know much about tires, but I do know that I did NOT like 70 profile tires as they aren't as....touchy as the 75s. You won't notice a speedometer difference on profile as much as you will on...diameter? The "235" or the "255" in your case.
Registered User
Joined: Jan 2012
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From: Sheridan, WY
Tire nomenclature as it applies to your setup:
255 = tread width in millimeters
65 or 70 = aspect ratio: the height of the sidewall expressed as a percentage of the tread width
15 = diameter of the rim
What this means is that your original tires were approximately 10 inches wide and the sidewalls were 6 1/2 inches tall. Overall height of the tire was approximately 28 inches.
The new tires are 10 inches wide, sidewalls 7 inches, and overall height is about 29 inches.
The extra inch in height increases the circumference from about 88 inches to 91 inches or about 3.5% So your speedo will be off about 2 mph at 60 mph.
Shouldn't be a dramatic falloff in performance due to the minor difference in tire height (about like a 7 HP loss to a 200 HP engine), but it is possible the replacement tires are substantially heavier than the old ones. More mass takes more effort to accelerate and stop, so heavy wheel/tire combos can hurt performance more than you might think. Different tire construction can have a dramatic impact on tire weight, even among similarly sized rolling stock.
As for fuel economy, you may actually notice a slight increase while cruising at steady speeds due to the engine turning fewer RPMs at a given mph than the shorter tires.
An alternative in the future is to get tires that are wider, but lower profile. You will end up with tires the same height as the originals, but with better handling characteristics. (Fuel economy may suffer some due to the increased rolling resistance and air resistance). A 275/60-15 would be almost exactly the same height as your original 255/65s.
255 = tread width in millimeters
65 or 70 = aspect ratio: the height of the sidewall expressed as a percentage of the tread width
15 = diameter of the rim
What this means is that your original tires were approximately 10 inches wide and the sidewalls were 6 1/2 inches tall. Overall height of the tire was approximately 28 inches.
The new tires are 10 inches wide, sidewalls 7 inches, and overall height is about 29 inches.
The extra inch in height increases the circumference from about 88 inches to 91 inches or about 3.5% So your speedo will be off about 2 mph at 60 mph.
Shouldn't be a dramatic falloff in performance due to the minor difference in tire height (about like a 7 HP loss to a 200 HP engine), but it is possible the replacement tires are substantially heavier than the old ones. More mass takes more effort to accelerate and stop, so heavy wheel/tire combos can hurt performance more than you might think. Different tire construction can have a dramatic impact on tire weight, even among similarly sized rolling stock.
As for fuel economy, you may actually notice a slight increase while cruising at steady speeds due to the engine turning fewer RPMs at a given mph than the shorter tires.
An alternative in the future is to get tires that are wider, but lower profile. You will end up with tires the same height as the originals, but with better handling characteristics. (Fuel economy may suffer some due to the increased rolling resistance and air resistance). A 275/60-15 would be almost exactly the same height as your original 255/65s.