40's vs 37's. What's the reality while daily driving?


New member
I'm looking at buying a used 3500 Cummins with the AEV lift and 40's on it, basically a Prospector XL. I definitely don't need 40" tires, but was planning on buying a truck with 37" tires, since I think they look good/proportionate on the truck and I do use it for backcountry driving. My question is that if I go with the truck with 40" tires, am I going to regret it since it will be my daily driver? I live in a very rural area and don't spend a lot of time parallel parking or stuff like that. Thoughts?
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With a truck built to run 40’s, you’ll be fine, don’t expect maneuverability in tight spaces, don’t expect great braking, don’t expect a truck easy to get into and out of, or a cheap repair bill for your next set of tires.

I tow, haul and Daly drive a truck on 37’s... no issues or complaints.


Also, what sway bar does it have, what size wheels, and does it have a steering box brace or steering stabilizer?

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New member
Right, I'll take that into account. But, back to the original question, in terms of day to day driving do folks have an opinion whether 40's just make no sense at all unless I'm planning to do a lot of off road?


Hillbilly of Leisure
I suppose it depends on how comfortable you like your daily driver to be. Larger tires equal worsened mileage, loss of power, more drivetrain wear and tear, higher replacement costs, an even more filthy rig, longer braking, and worse steering performance on rutted pavement (the great majority of pavement where I live).

My Jeep had 35s for a year. I changed to 33s and it made a huge difference for the better. Of course the Jeep doesn't have the long wheel base or horsepower of your rig.

In short, yes, you will notice a difference between 37s and 40s. Everything that is generally considered to be undesirable in a truck (for comfort and drivability) will be amplified. You might be able to mitigate the negatives with 5 - 10 grand worth of suspension work though. Not sure of the cost to upgrade...but it will be considerable.

Would you regret it? Maybe not. I still have bigger tires on two of my rigs. They are fun and cool! It's nice to know that you can probably roll over most terrain without worry.

When I have a long road trip or the roads are really crappy I leave both big wheels at home at drive a car with factory-size tires on it.

Different strokes though. ;)


New member
When I went from 37s to 40s on my ram there wasn’t a whole lot of down sides. Obviously power dropped a little bit, braking feels about the same, steering reaction changed a little bit. Ride quality improved major, stability changed just slightly, although I don’t have swaybars installed. All

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