Tire/Towing Advice

[bms44]

Hey all,

I have an 04 Ram with the 5.7 Hemi, 6.5 ft box, Quad Cab 4WD. The previous owner upgrade from the 245/70/R17 stock rims/tires to 295/60/R20 rims and tires. We tow a holiday trailer and I noticed that this thing crawls up the hills unless I give it some good gas, even mediocre climbs. Now the disappointing part is the trailer was only 3750ish pounds, which is well under the 7800ish pounds; the supposed towing capacity of this truck. It just seems that with the upgraded tires and rims this thing lacks overall torque/power.

Now my question, I am i the process going back closer to stock size tires and rims. If I go back to 17's does the tire size matter much or will the difference in rim size alone increase power/torque? Would I just be best to go back to stock size of 245/70/R17?

Any advice is appreciated, hoping to upgrade the trailer this year so want to make sure the truck is equipped with proper tires/rims to get the job done.

 

[xtremewlr]

To gain back the power and torque for towing, you would probably want to go back to the stock size. The other option would be to change the gear ratio in the axles to compensate for the larger tires.

The 295/60/20 are 33.9" tall, compared to 30.5" for the 245/70/17 tire. Because of the larger circumference of the 295/60/20, you effectively have a lower gear ratio and therefore, less towing power. Going to a shorter tire will get that back. The tradeoff will be in off-road performance, if you are worried about that. The taller tires provide you better ground clearance and make it easier to roll over obstacles.

Pricewise, it might be pretty close to have the gear ratio changed and keep the wheel/tire combo you have now. Just be aware that having 4wd, you have to have the gears changed in both front and rear differentials. As for the gearing, if you have 3.55 now, then you would want to go to 3.92 or 4.10 to get your power back. If you already have 3.92/4.10, then you would want to step up to 4.56.

 

[bms44]

Thanks for the info, my gear ratio is stock 3.55. I think at this point I will do what I was planning and just sell my current tires and rims and go back to stock 17 rims with

To gain back the power and torque for towing, you would probably want to go back to the stock size. The other option would be to change the gear ratio in the axles to compensate for the larger tires.

The 295/60/20 are 33.9" tall, compared to 30.5" for the 245/70/17 tire. Because of the larger circumference of the 295/60/20, you effectively have a lower gear ratio and therefore, less towing power. Going to a shorter tire will get that back. The tradeoff will be in off-road performance, if you are worried about that. The taller tires provide you better ground clearance and make it easier to roll over obstacles.

Pricewise, it might be pretty close to have the gear ratio changed and keep the wheel/tire combo you have now. Just be aware that having 4wd, you have to have the gears changed in both front and rear differentials. As for the gearing, if you have 3.55 now, then you would want to go to 3.92 or 4.10 to get your power back. If you already have 3.92/4.10, then you would want to step up to 4.56.

Thanks for the info. I think I will sell my current tires and go back to stock. Does it make a difference if the rims are 17 or 20" or is it just the total tire height that makes a difference here?

 

[xtremewlr]

Thanks for the info, my gear ratio is stock 3.55. I think at this point I will do what I was planning and just sell my current tires and rims and go back to stock 17 rims with


Thanks for the info. I think I will sell my current tires and go back to stock. Does it make a difference if the rims are 17 or 20" or is it just the total tire height that makes a difference here?

You can play with different tire sizes and keep the rims that you currently have. It helps to talk to a good tire shop too. Discount Tire, if you have them around, is pretty good about figuring out what tire size would work best for you. Another neat tool that you can play with online is this one: https://tiresize.com/comparison/

Just changing the sidewall height (295/60/20, the sidewall height is the 60, representing the percent of the width which is the 295), you could just swap tires to a 275/50/20 and be at a 30.8" tall tire and will have gained back a lot of your lost power. That could save you the hassle of selling your current rims and cost of buying new rims and tires.

Ultimately, the best option would be to get the gearing changed as 3.55 really isn't a very good towing gear choice. 3.92/4.10 would be much better overall for towing.

 

[bms44]

You can play with different tire sizes and keep the rims that you currently have. It helps to talk to a good tire shop too. Discount Tire, if you have them around, is pretty good about figuring out what tire size would work best for you. Another neat tool that you can play with online is this one: https://tiresize.com/comparison/

Just changing the sidewall height (295/60/20, the sidewall height is the 60, representing the percent of the width which is the 295), you could just swap tires to a 275/50/20 and be at a 30.8" tall tire and will have gained back a lot of your lost power. That could save you the hassle of selling your current rims and cost of buying new rims and tires.

Ultimately, the best option would be to get the gearing changed as 3.55 really isn't a very good towing gear choice. 3.92/4.10 would be much better overall for towing.

Not familiar with what's involved in changing the gears, sounds well over my head. I need new tires regardless so if the 20's won't make a difference then my best option may just be lower profile tires. I don't do any offroading so the extra tire size isn't needed.

Thanks for clearing this up, i'll likely just get some new tires and call it a day.