295/70 or 305/70 on stock 18s - Dodge Cummins Diesel Forum
4th Gen Tire and wheel Discussion of tire and wheel options

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post #1 of 9 (permalink) Old 09-02-2019, 10:20 AM Thread Starter
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295/70 or 305/70 on stock 18s

I need new tires and am debating on 295/70/18 or 305/70/18. The 295 have a higher load rating (129 vs 126). Iím looking at the Yokohama Geolandar MT G003. I donít tow heavy, mainly just my utility tractor and my UTV.

Discounts website shows the 305s at 34.8Ē and the 295s at 34.4Ē. 305s should be about 12Ē wide and the 295s about 11.5Ē wide.

Will the 305/70 rub on stock 18 inch wheels with stock suspension? Iím pretty sure the 295s will not rub.

Price is a little higher on 305s but still much cheaper than most other tires even in 295 series.

Truck is a 2017 2500 4x4 crewcab short bed.

Thanks guys.


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post #2 of 9 (permalink) Old 09-17-2019, 11:08 AM
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I put 295s on mine and really like them. Any wider and the wheel will be way narrower than the tire tread.
The 295s are taller than stock and noticeably change the gear ratio. 6th bogs even worse than stock! So I went with 4.10 gears and fixed the problem. Now, the tires fill the wheel wells better and the new 6th gear, with the 295s and the 4.10s, is slightly higher than the stock 5th was, with the 275s and the 3.42 gears. It just runs better and it steers just as good as stock. I went with Michelin Defenders and they are very nice.
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post #3 of 9 (permalink) Old 09-17-2019, 08:09 PM Thread Starter
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Thanks for the input. Iím going to go 295s. Too bad about the gearing on these trucks, but Iíll just use 5th when towing. Iím sure 6th will still be fine unloaded. Our speed limits are 75 mph and I usually run 78-80 mph so Iím reluctant to go 4.10s due to loss of high speed economy.


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post #4 of 9 (permalink) Old 09-17-2019, 08:55 PM
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What makes you think you'll lose "high speed economy" with 4.10s? Have you ever tested the theory? High speed and economy are incompatible, regardless of gearing. At speed, a little faster means much more wind resistance, as it's an exponential relationship. And, do you only drive at 78-80? Never at 65, or around town, or tow, or at any other speed anytime? ONLY 78-80? How do you get up to that speed from a stop. The logic escapes me?

In order to make the truck drive very well with 3.42 gears and 295s, 6th must be locked out a lot of the time, which means you are using a gear that is lower than 6th with 4.10s. So, if you think only higher gears get reasonable mileage, what will happen as you drive around in 5th?

And the truck is slower in all the lower gears with 295s and 3.42 gears. So the truck accelerates worse, starts out worse with a load and while towing. This means worse performance, more torque converter slipping, more heat and waste.

Unfortunately, it's not always correct or useful to simply say you'll get better mileage with taller gears.

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post #5 of 9 (permalink) Old 09-18-2019, 07:18 PM Thread Starter
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Thanks for the thoughts. I understand what you are saying and I mostly agree. I understand that 78 mph is not ideal for MPGs. Slowing down to even 70 mph is a big improvement but you get ran over here at those speeds.

If my math is correct 4.10s in 6th with 35Ē tires at 75 mph would be very similar to using 5th with 3.42s and 33Ē tires. My MPGs go down significantly unloaded when I lock out 6th and run in 5th, (Iíve tested just for grins)1650 rpm in 6th vs 2100 rpm 5th. I live in the country and spend the vast majority of my time unloaded at speeds above 75 mph. Just the nature of where I live. If I was in an area where I spent more time below 70 mph or towing heavy I think it would be much more tempting. 3.73s would be ideal but I canít stomach the high cost to just jump a small amount in gearing. Thatís the beauty of the 6 speeds, at least you can compensate for loading conditions.

Who knows, maybe after all this talk Iíll stick with the stock size. I like the look of the bigger tires but it is counterproductive for everything else mechanically speaking. Again thanks for taking the time to provide your input, I do value input.


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post #6 of 9 (permalink) Old 09-18-2019, 11:58 PM
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With the 295s and 4.10s, I'm running about 1750 at 75 or so. It's the perfect RPM because it can build boost and is still not running too fast. Plus there is very little downshifting on grades and reasonable throttle response.

Mileage is more based on the amount of work being done, and the efficiency of the engine at that speed, than it is on RPM. It has to make enough power to do the job. And it has to be nice to drive and not lugging all the time.

6th with 295s and 4.10s, is half way between 5th and 6th with 3.42.

I got totally burned out on having no power in 6th, even unloaded. My mileage, not hand calced, will settle in at about 19-19.5 with normal driving on highways with a 60 mph limit. If I drive at 75 with my trailer, it goes down, again, not hand called, but averaged over a few hundred miles, to about 13.

These days, with speed limits of up to 80 as the posted limit, I'm slower than a lot of traffic because I will not tow at that speed. 70-75 max.

I recently drove home from Salt Lake, across Utah and Nevada to near Reno. The limit was 80 a lot of the way and it was 600 miles. It felt weird droning along at 80 MPH, hour after hour.

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post #7 of 9 (permalink) Old 09-21-2019, 04:39 PM Thread Starter
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Thatís not bad. Iíd be happy at 1750 rpms at 75 mph. I need to go back and check my math because I was way off think Iíd be at 2000 rpm. Guess I just need to save a couple grand for gears too!


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post #8 of 9 (permalink) Old 09-21-2019, 06:25 PM
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Quote:
Originally Posted by Raspy View Post
I recently drove home from Salt Lake, across Utah and Nevada to near Reno. The limit was 80 a lot of the way and it was 600 miles. It felt weird droning along at 80 MPH, hour after hour.
So did I, except in the opposite direction. And I kept it at around 85.
That's stock size tires on a DRW and with 3.73s, so 2,000 rpm or better. My engine really likes it there.

Maybe if we start telling people that the brain is an app, they will start using it?

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post #9 of 9 (permalink) Old 09-22-2019, 01:00 PM
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So did I, except in the opposite direction. And I kept it at around 85.
That's stock size tires on a DRW and with 3.73s, so 2,000 rpm or better. My engine really likes it there.
Yeah, at about 2,000 RPM we get instant throttle response and lots of power. Love it. That low RPM feeling of lugging, bogging, no torque, is annoying. But get the revs up a bit and the power is great. That's why I love my 4.10 gears.
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