Hey all, just picked up a 2012 Ram 2500 5.7L 4x4 Crew/long box 3.73 gears. It has 265/70/17's I want to put some aftermarket wheels on the truck as i did with my 1500. I was thinking of going as big as 35inch rubber. I had 33.5 inch rubber on the 1500 with a 3.92 gearing and noticed little change. Does anyone have any comment or experience with 35'' tires and how it will effect my towing ?Thanks in advance.

Larger diameter tires will essentially reduce the gear ratio numerically. You will lose some pulling power.I personally wouldn't see any benefit in the change but some obviously do. They sell lots of aftermarket tires and wheels.Make sure whatever you buy has a load range equal to or higher than original.

Larger circumference tires raises the gear ratio which reduces towing power.

By going from 265/70/17 (31.8") to 35" tires you're are essentially reducing your rear axle ratio by 10%. From 3.73 to 3.38. Looking at Rams towing chart going with a 3.73 tow rating of 10,350 to 4.10's increases it to 13,350. Assuming that reducing 3.73's by 10% your new tow rating would be 7,350lbs. If you tow less than that then all will be good. JMO but I can't imagine a 2500 5.7 with 3.38 gears. Your mpg would take a big hit and towing power would be sluggish. Remember too that your 1500 weighed considerably less than a 2500. And you already started out better with 3.92's over 3.73's. If you had 4.10's in the 2500 it would be better.

Your existing tires are apx 31.6 inches tall, so the 35" tires will make a very noticeable diff in towing performance.Jerry

In addition to affecting towing performance, the taller tires will negatively affect braking performance as well. The taller tire is a bigger "lever" acting upon the braking surface of the disk/drums. Taller sidewalls are also going to have more flex so you may experience more swaying as you pull. While taller tires can make a truck look better and do make it perform better off road they otherwise hinder a truck's performance. Don't forget that when you raise the truck, you'll now need a longer drop on your hitch which places more strain on the receiver hitch.

Advice needed with wheel size and gear ratios. | Good Sam Community

L_R_G
Explorer
Mar 28, 2014
I'd say go with the 4.10's at least, maybe even take a look at 4.56's. Depends on the balance you want between towing power, fuel economy, and RPM at a given speed. Something like 4.56's will make a big difference in towing performance but you'll sacrifice fuel economy at highway speed since the engine will be spinning faster.
OBX-GL
Explorer
Mar 30, 2014
Yeah, i guess i knew how your answers would go. Guess i was looking to be surprised by the 6sp. transmission as i've noticed as the # of gears on these newer trucks increase the 3.92's and 4.10's are disappearing. Looks like i'll go no bigger than 33's, my trailer is far from the trucks towing limits so i'm thinking some towing loss is doable.

Clarification - When not towing, bigger wheels achieves better hwy milage, less torque ?
APT
Explorer
Mar 30, 2014
"Clarification - When not towing, bigger wheels achieves better hwy milage, less torque ?"

Not in my experience. I had heavy 33" tires on my last F-150. I replaced them after towing one season with lighter 32" tires and noticed a slight power improvement. Maybe a diesel if you have enough torque lower effective gearing could improve FE non-towing. The problem is wheel/tire weight is higher.

Also, the towing power it takes to pull an 8x8' wall through the air at 65mph is high, thus why we all get 8-10mph towing. Decreasing power (increasing rotational weight, reducing gearing) will always be noticable.

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Advice needed with wheel size and gear ratios.

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