I need tire help!!

[banjovi34]

I have some questions about new tires. I have 2006 Dodge Quad cab 2500 5.9 cummins 4x4.

I currently have Goodyear Silent Armour tires and want to get another set. My current tires have 97k miles, and prob still have another 20k left. I do about 90% hwy driving with empty load.

Here's my questions:
1. I would like a slightly larger tire (have 265 now). Either 275 or 285. Will I get better or worse MPG? Im currently getting about 24.5 on hwy at 70mph.

2. I noticed Goodyear Silent Armours dont come in E rated at sizes 275 or 285. Will I see an increase in wear as compared to my current E rated tires? I belive the 275 and 285 come in C and D rated.

3. If I get a larger tire, how do I adjust the speedometer to read my correct speed? I dont have any chips and dont really want any either...

Any help would be greatly appreciated!!!

[SundayMoney]

Originally Posted by banjovi34

I have some questions about new tires. I have 2006 Dodge Quad cab 2500 5.9 cummins 4x4.

I currently have Goodyear Silent Armour tires and want to get another set. My current tires have 97k miles, and prob still have another 20k left. I do about 90% hwy driving with empty load.

Here's my questions:
1. I would like a slightly larger tire (have 265 now). Either 275 or 285. Will I get better or worse MPG? Im currently getting about 24.5 on hwy at 70mph.

2. I noticed Goodyear Silent Armours dont come in E rated at sizes 275 or 285. Will I see an increase in wear as compared to my current E rated tires? I belive the 275 and 285 come in C and D rated.

3. If I get a larger tire, how do I adjust the speedometer to read my correct speed? I dont have any chips and dont really want any either...

Any help would be greatly appreciated!!!

1. The fuel mileage will likely be worse with bigger tires.

2. Its been my experience,that D rated tires won't last as long as E rated tires.

3. I'm running about 2mph fast with 285s. I checked it with a GPS after the switch. I didn't correct the speedo. I just rememebr that I'm 2 mph fast. When I'm figuring mileage,I just figure in the 3% I'm off.

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2007 3500 SRW Quad cab,long bed,Bighorn edition.
4x4,5.9,6spd,3.73s
Patriot Blue

[catti05]

Sundaymoney is right...ur mileage will prolly go down...but nothing extreme...like 1 or 2 mpg...I had 285 on my 04.5 5.9 and I was getting around 23mph...but they were not D load tires..so not much help...but anyways it shouldn;t hurt ur mileage too much.

[banjovi34]

Thanks for your responses.

But Im curious, Ive seen in other posts that people went from 35's to 37's and got better mileage. Im talking about going from 265 to 285. Would I not expect to see mileage gains from this size increase as well?

90% of my driving is hwy, and with an empty load...

[SundayMoney]

Originally Posted by banjovi34

Thanks for your responses.

But Im curious, Ive seen in other posts that people went from 35's to 37's and got better mileage. Im talking about going from 265 to 285. Would I not expect to see mileage gains from this size increase as well?

90% of my driving is hwy, and with an empty load...

IMO, you need to take alot of these mileage claims with a grain of salt. I read some of this stuff and just have to shake my head. People post alot of stuff that defies the laws of physics.

If you were going to a taller,narrower, tire that was less agressive than what you're running now,you might see a small increase.

Typically thats not whats happening. Taller tires are usually heavier,wider,and have more rolling resistance.

Reducing the rpms because of the taller tire doesn't automatically mean more mpg.

__________________
2007 3500 SRW Quad cab,long bed,Bighorn edition.
4x4,5.9,6spd,3.73s
Patriot Blue

[banjovi34]

Ok. That makes sense. This is my first diesel so I was thinking (hoping) that the torque from the diesel could overcome that extra weight from a slightly larger tire. Thanks for the help!!

[totalloser]

The theory behind a taller tire overcoming loss from rolling resistance is that it is like having a taller axle ratio. I didn't do better with my setup, but took nowhere near the loss I expected. The key to better fuel efficiency with what you are trying to do is to use a narrow tire. The reason the E rated tire will often do better is that with the same tire pressure, the tire will be stiffer. This makes a smaller contact patch on the pavement, and thus less rolling resistance.

Another thing to consider other than loss from rolling resistance is the poor aerodynamics of a larger tire, and the sticky compound used on offroad tires. Choose a taller skinnier e rated and air it up all the way, and you might find no penalty. I don't think I took more than 2mpg in mine, but I did major fuel efficiency improving mods at the same time as the tires, so I don't really know.

My best before exhaust/injectors/tires was 16.5 mpg. My best currently on biodiesel is just shy of 19 mpg on a tank

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01 24v 100hp tips, 4"ss BDbrake &steering brace PSCpump 1.5"dom steering tapped box 1.5"ram manual CAD switch dual carters 3.55's LSD, big shaft nv5600/241HD 6 35's inners pulled in (no spacer) Ugly black and thrashed!