tire size affecting mpg??
#1
02-09-2007, 12:22 PM
tire size affecting mpg??
Howdy...................first off I'd like to say that I'm very new to the group and I'm sure there are lots of threads on mpg. However, I don't really have the time to go through them all because in a little while I am going tire shopping.
My main question is this..............the guy that sold me the truck, ('01 Ram 1500 QC Sport 5.9L) put on Bridgestone Dueler APT LT285/75R16 tires. I know that the taller tires throw off the speedo but are they also affecting my mileage in a negative way? From the few things I've found on-line this will indeed affect mileage.
I like the way the taller tires look on the truck, but they also make the truck handle stiffer and ride rougher. I won't necessarily buy new tires just to get a smoother ride, but if it will also help my mpg I think that I'd be money ahead in the long run.
I've also got a '05 1500 Ram QC with the 4.7L in it and I consistently get 15-16 mpg with that. My first check with the '01 running the 360 was about 10.5 mpg. I was hoping to get more toward that 15 to 16 mpg range. Am I just dreaming, or is this possible?
The previous owner told me that he always got around 15 mpg unless he was on a long trip then he would see upwards of 17 to 18 mpg. This of course was before he installed the new tires. Is he correct, or was he blowing smoke up my butt??
So...............have any of you experienced anything like this or do any of you have any input on the matter? If this is a dumbassed question go ahead and tell me, I've got pretty thick skin! ;-)
Bartman
My main question is this..............the guy that sold me the truck, ('01 Ram 1500 QC Sport 5.9L) put on Bridgestone Dueler APT LT285/75R16 tires. I know that the taller tires throw off the speedo but are they also affecting my mileage in a negative way? From the few things I've found on-line this will indeed affect mileage.
I like the way the taller tires look on the truck, but they also make the truck handle stiffer and ride rougher. I won't necessarily buy new tires just to get a smoother ride, but if it will also help my mpg I think that I'd be money ahead in the long run.
I've also got a '05 1500 Ram QC with the 4.7L in it and I consistently get 15-16 mpg with that. My first check with the '01 running the 360 was about 10.5 mpg. I was hoping to get more toward that 15 to 16 mpg range. Am I just dreaming, or is this possible?
The previous owner told me that he always got around 15 mpg unless he was on a long trip then he would see upwards of 17 to 18 mpg. This of course was before he installed the new tires. Is he correct, or was he blowing smoke up my butt??
So...............have any of you experienced anything like this or do any of you have any input on the matter? If this is a dumbassed question go ahead and tell me, I've got pretty thick skin! ;-)
Bartman
#3
02-09-2007, 01:06 PM
RE: tire size affecting mpg??
I believe stock size is 265/75/16.
If you go with a bigger size, be sure to have your computer reprogramed to correct the speedo, odo, and shift points. If you don't your mpg calcs will be thrown off, among other things.
My experience with larger than stock tires is slightly worse mpg in town and slightly better on the highway. If you think about it that makes sense. It takes more effort to turn the bigger tires from a dead stop, kind of like it takes more effort to swing a long ball bat than a kid size ball bat. Bad analogy, but you get my point...it's pure physics...the force moment is greater on the larger diameter tire. Likewise, once in motion the larger circumference tire covers more distance per rotation of the axle.
The key word is slightly. Neither difference is huge, so i would make my decision on whether you need or want the larger tires, not on the mpg.
If you go with a bigger size, be sure to have your computer reprogramed to correct the speedo, odo, and shift points. If you don't your mpg calcs will be thrown off, among other things.
My experience with larger than stock tires is slightly worse mpg in town and slightly better on the highway. If you think about it that makes sense. It takes more effort to turn the bigger tires from a dead stop, kind of like it takes more effort to swing a long ball bat than a kid size ball bat. Bad analogy, but you get my point...it's pure physics...the force moment is greater on the larger diameter tire. Likewise, once in motion the larger circumference tire covers more distance per rotation of the axle.
The key word is slightly. Neither difference is huge, so i would make my decision on whether you need or want the larger tires, not on the mpg.
#5
02-09-2007, 01:22 PM
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RE: tire size affecting mpg??
yea, the stock size was 245/75R16 on these trucks. the 265/75 were an option on the SLT and on the Sport models. If the sticker says you had 245/75, then thats what was original equipment. So unless the previous owner had the computer recalibrated for the speedo, you will be way off on your mileage.
a 245/75R16 is only a 30.5 inch tall tire, a 285/75R16 is 32.5. Since the odometer directly relates to the speedo, if you speedo says your doing 70, when in reality you would be doing 76, its going to say you travel less distance than you really do, meaning you use more gas to go fewer miles, at least according to the odometer. So simply your calculations are off, this could throw you off 3-4mpg per tank. So dont worry too much about that, just have the speedo recalibrated, takes like 2 minutes.
another thing to consider, 245/75R16 tires are only 9.5 inches wide, with tread width of about 6-7, depending on the brand. 285/75R16 tires are 11.5 inches wide, with a tread of 8-10 again depending on the brand. THIS is what hurts mileage. it more rolling resistance to get them going and takes more to keep them going. this will lower your mpg just a little, but no more than 1 mpg or so.
the only other thing that will affect mileage in regards to tire, other than properly inflating them, is gearing...if you go too big, you will lose low end grunt and it will take more to get them going, wont matter a ton on the highway, more noticeable in the city.
now that thats taken care of, you want my opinion.....get the 285s. they look better, if you inflate them properly, you wont notice a difference in ride too much, and you drive a giant brick. you didnt buy it for mileage, and when you are only goign to get 13-15 at best in it, whats another 2 or 3 mpg less...who cares, go for the big ones, way cooler then little pizza cutters!
a 245/75R16 is only a 30.5 inch tall tire, a 285/75R16 is 32.5. Since the odometer directly relates to the speedo, if you speedo says your doing 70, when in reality you would be doing 76, its going to say you travel less distance than you really do, meaning you use more gas to go fewer miles, at least according to the odometer. So simply your calculations are off, this could throw you off 3-4mpg per tank. So dont worry too much about that, just have the speedo recalibrated, takes like 2 minutes.
another thing to consider, 245/75R16 tires are only 9.5 inches wide, with tread width of about 6-7, depending on the brand. 285/75R16 tires are 11.5 inches wide, with a tread of 8-10 again depending on the brand. THIS is what hurts mileage. it more rolling resistance to get them going and takes more to keep them going. this will lower your mpg just a little, but no more than 1 mpg or so.
the only other thing that will affect mileage in regards to tire, other than properly inflating them, is gearing...if you go too big, you will lose low end grunt and it will take more to get them going, wont matter a ton on the highway, more noticeable in the city.
now that thats taken care of, you want my opinion.....get the 285s. they look better, if you inflate them properly, you wont notice a difference in ride too much, and you drive a giant brick. you didnt buy it for mileage, and when you are only goign to get 13-15 at best in it, whats another 2 or 3 mpg less...who cares, go for the big ones, way cooler then little pizza cutters!
#7
02-09-2007, 05:28 PM
RE: tire size affecting mpg??
Thanks to all of you that responded so far! I'm still learning I guess and the tire guy confirmed what you guys stated about the tire size. Even though the door says that they are 245's, he explained that with the off road or sport package that they used the 265's. He says that Dodge is the only one to do this.
Who says you're too old to learn?? ;-)
Thnx again!
Who says you're too old to learn?? ;-)
Thnx again!
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#8
02-09-2007, 06:24 PM
Professional
RE: tire size affecting mpg??
I have the factory 20" wheels and tires on mine, actually I have the factory tiresize for the 3rd Gen 4x4 Rams (275/60R20), which is a 34" diameter tire. I was seeing around 15 in the city and 19/20 on the highway, 21 even on really long extended cruises (IE, across West Texas). My tranny needs to be rebuilt though, it has over 300,000 miles on it now and it is starting to slip, so I've seen that come down about a mile or two in the past months... If you do alot of in-city driving, the bigger wheels and tires will lower your gas mileage and wear your brakes a little faster. If you do mostly highway driving, you should see an improvement in MPG, although don't look for anything too major either way. 1 or 2 mpg at the most...
#9
02-09-2007, 10:22 PM
RE: tire size affecting mpg??
from the FAQ:
---
TIRE CHOICES for BETTER MPG
Increasing the air pressure in your tires, and picking a narrow 'rib tread'
commercial delivery truck type tire that has low rolling resistance
definitely will help MPG.
Raising the air pressure by 15 psi to the max 70 psi in Goodyear Wrangler
HT 235/85R16E tires increased my mpg by +1 in a 311 mile
test run - but the ride was bone jarring. A narrow, highway rib tire like the
HT gives the lowest rolling resistance. Wide, aggressive tread tires can be
three times harder to roll. It might pay to have a 4 tire set for the weekday
commute, and a weekend mudder wide tire set.
Several Cummins Diesel Ram owners have reported that buying special
wheels and converting to 19.5 Commercial truck tire designs have
improved both MPG and tire tread life - but these tires are generally
heavier. RicksonTruck is one such special wheel seller:
http://www.ricksontruck.com/
Note that the new 2007 Ram 3500 Cab-Chassis with the 6.7 Cummins and Aisin 6 speed automatic transmission also comes standard with 19.5 wheels and tires.
Consumers Reports is the only organization I know of that tests for rolling
resistance of tires but even they do not report the Crr number.
Quote from CR:
" Fuel mileage at a price. Some tires roll with less drag than others. The
lower a tire's rolling resistance, the more fuel you can save. Those savings
can be significant. {Pickup and SUV} Tires with the lowest rolling resistance
delivered nearly 2 mpg more at a steady 65 mph in our highway tests {2003
four-wheel-drive Ford Explorer XLT 4x4} than those with the highest rolling
resistance. The catch: While some high-scoring tires had low rolling
resistance, most tires with the lowest rolling resistance also had lower
overall scores."
In their 11/2004 Pickup & SUV tire test CR the
lowest rolling resistance tires rated 'excellent' were the:
Bridgestone Dueler H/T (D684)
Michelin Cross Terrain
Continental ContiTrac
BF Goodrich Radial Long Trail T/A
The Pickup & SUV tires with the worst rolling resistance were the:
Pirelli Scorpion STA
Kelly Safari Signature
Yokohama Geolander H/T-SG051
A tire with a 'very good' rolling resistance and high scores in other handling
and braking tests was the Hankook DynaPro AS RH03
Hankook recently announced that they had spent $10 million developing a
tire called the fx-Optimo that has even lower rolling resistance and can
give up to a 3% MPG improvement:
http://www.moderntiredealer.com/t_in...p;storyID=5961
In another test of "All Season" tires in November 2005,
CR rated these tires as 'excellent' for low rolling resistance:
Michelin X Radial DT
Michelin Agility Touring
Michelin Harmony
Hankook Mileage Plus GT H707
Kumho Touring 795 A/S
Toyo 800 Ultra
Sumitomo HTR T4
In the same November 2005 issue
'All Terrain' tires were also tested
but only the
Continental ContiTrac TR
got an excellent rating for low rolling resistance in this group.
The California Air Resources board is pressing the tire companies to make
rolling resistance measurements on tires freely available to the public by
2008, one of the few reasonable things CARB has ever done in my opinion
The lower profile 17 and 20 inch tire designs used on the 2003-2005
5.7Hemi Rams have a 'sticker' tire tread and higher rolling resistance than
earlier year Rams. It is probable that if a manufacturer makes available a
235 85 R17 tire in Load Range E it would be lower rolling resistance
than the stock tires and might improve MPG by 1-2 at 70 mph.
The 2006 Ram press release says the new model will have 'low rolling
resistance tires.'
In April 2006 the "independent and non-partisan" US National Academy
of Sciences completed a report on the rolling resistance of tires and how
MPG for the entire country might be easily improved if tire makers
increased their research into how to make tires roll even easier.
The 'meat' of this report starts about page 50 at this weblink:
http://www.trb.org/publications/sr/sr286.pdf
---
TIRE CHOICES for BETTER MPG
Increasing the air pressure in your tires, and picking a narrow 'rib tread'
commercial delivery truck type tire that has low rolling resistance
definitely will help MPG.
Raising the air pressure by 15 psi to the max 70 psi in Goodyear Wrangler
HT 235/85R16E tires increased my mpg by +1 in a 311 mile
test run - but the ride was bone jarring. A narrow, highway rib tire like the
HT gives the lowest rolling resistance. Wide, aggressive tread tires can be
three times harder to roll. It might pay to have a 4 tire set for the weekday
commute, and a weekend mudder wide tire set.
Several Cummins Diesel Ram owners have reported that buying special
wheels and converting to 19.5 Commercial truck tire designs have
improved both MPG and tire tread life - but these tires are generally
heavier. RicksonTruck is one such special wheel seller:
http://www.ricksontruck.com/
Note that the new 2007 Ram 3500 Cab-Chassis with the 6.7 Cummins and Aisin 6 speed automatic transmission also comes standard with 19.5 wheels and tires.
Consumers Reports is the only organization I know of that tests for rolling
resistance of tires but even they do not report the Crr number.
Quote from CR:
" Fuel mileage at a price. Some tires roll with less drag than others. The
lower a tire's rolling resistance, the more fuel you can save. Those savings
can be significant. {Pickup and SUV} Tires with the lowest rolling resistance
delivered nearly 2 mpg more at a steady 65 mph in our highway tests {2003
four-wheel-drive Ford Explorer XLT 4x4} than those with the highest rolling
resistance. The catch: While some high-scoring tires had low rolling
resistance, most tires with the lowest rolling resistance also had lower
overall scores."
In their 11/2004 Pickup & SUV tire test CR the
lowest rolling resistance tires rated 'excellent' were the:
Bridgestone Dueler H/T (D684)
Michelin Cross Terrain
Continental ContiTrac
BF Goodrich Radial Long Trail T/A
The Pickup & SUV tires with the worst rolling resistance were the:
Pirelli Scorpion STA
Kelly Safari Signature
Yokohama Geolander H/T-SG051
A tire with a 'very good' rolling resistance and high scores in other handling
and braking tests was the Hankook DynaPro AS RH03
Hankook recently announced that they had spent $10 million developing a
tire called the fx-Optimo that has even lower rolling resistance and can
give up to a 3% MPG improvement:
http://www.moderntiredealer.com/t_in...p;storyID=5961
In another test of "All Season" tires in November 2005,
CR rated these tires as 'excellent' for low rolling resistance:
Michelin X Radial DT
Michelin Agility Touring
Michelin Harmony
Hankook Mileage Plus GT H707
Kumho Touring 795 A/S
Toyo 800 Ultra
Sumitomo HTR T4
In the same November 2005 issue
'All Terrain' tires were also tested
but only the
Continental ContiTrac TR
got an excellent rating for low rolling resistance in this group.
The California Air Resources board is pressing the tire companies to make
rolling resistance measurements on tires freely available to the public by
2008, one of the few reasonable things CARB has ever done in my opinion
The lower profile 17 and 20 inch tire designs used on the 2003-2005
5.7Hemi Rams have a 'sticker' tire tread and higher rolling resistance than
earlier year Rams. It is probable that if a manufacturer makes available a
235 85 R17 tire in Load Range E it would be lower rolling resistance
than the stock tires and might improve MPG by 1-2 at 70 mph.
The 2006 Ram press release says the new model will have 'low rolling
resistance tires.'
In April 2006 the "independent and non-partisan" US National Academy
of Sciences completed a report on the rolling resistance of tires and how
MPG for the entire country might be easily improved if tire makers
increased their research into how to make tires roll even easier.
The 'meat' of this report starts about page 50 at this weblink:
http://www.trb.org/publications/sr/sr286.pdf
#10
02-09-2007, 10:38 PM
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RE: tire size affecting mpg??
I was just thinking about this today. Since I put my lift and 35" tires on the truck, my gas milage has been horrible. I used to get about 12 mpg in the city now I am only getting 7 mpg!!!! I can only go about 200 miles on a tank of gas. I am running 3.55 gears right now and plan to re-gear lower - but I would like to have my speedo accurate as well. My milage may not be as bad as I think it is because the tire size is messing up the accuracy of the odometer. My question is, where can you get the speedo re-callibrated? Can a Dodge dealership or local repair shop do this?