Towing tire confusion

[BigBlue2024]

Hello. New to the community and I am hoping someone can clear up some confusion on tires. I recently purchased a 2024 chevrolet 2500 hd custom with 20" wheels w/ 275/65/17 tires. In the towing section it says my current setup is rated at 12k for a bumper pull trailer. (I have a 16k equipment trailer, long story) However, if I switch to stock 17 inch wheels w/ 245/75 17. I can get 14.5k. If I go stock 18 inch w/ 275/70/18 mt tires, I can get 16k. And if i had the zr2 package, I would have 305/70/18 mt tires (bigger than what i have now) and able to tow 16k.

heres my dilemma: I want to get more towing capacity when I need it in a second set of wheels and tires. I understand that more sidewall helps (smaller wheel) and a less overall diameter helps (smaller tire).

Here's the question: I have a set of stock 17 inch wheels from a 2018 silverado hd. I've found a 295/70/17 BFG tire with a similar load index (125 vs 126 that I have). It has more side wall than I have now (over an inch) and smaller diameter but not enough to throw the speedo way out. (About 1.5 mph at 60mph).

Would this combo get me at least to the 14.5k? Or is this wishful thinking. The wheels were new take offs in really nice shape so, I'd like to use them if I can. 

Thanks!

[blt2ski]

BenK a past poster on here, possibly RIP as he was dealing with some BIG C issues. He helped design competition bicycles. He noted that the athletes would notice 1-2 ounces of less weight in a moving part, ie tire wheel combo, gears etc. vs it took 2 lbs to notice the reduction of weight in a non-moving part, ie the frame! So, a non-moving to moving part ration of 16-32 to one! 

Let's assume this ratio hold true in our trucks. If we reduce the tire and rim weight by 1 lbs, that is a saving of 16 to 32 lbs of weight equal in the bed. Two drive tires we have a total of 32-64 lbs saving equal. 4 tires on a dually, 64 to 128 lbs. 

Or as I did on my 05 DW DA combo, I kept the same tire size, a 215-85-16, went from a polyester sidewall tire, to a steel sidewall tire!  Toyo M55's to be exact. They were 10 lbs heavier than the typical steel tread, polyester sidewall tire. 40 lbs of tire, equals around 640 to 1280 lbs of non-moving weight! I lost around .5-1 mpg. To say at times I noticed this, I did, a lot of times no. Bryan who also used to post on here, noted the same difference in MPG when he did the same with his totally customized DW E350 ext van when he put Toyo M55's on his rig. He had a 6.8L V10 with a 4sp auto IIRC. 

BUT, mpg wise, I sure did. I did the same with my current 1500, went up an inch diam, but the tires are 10-12 lbs heavier being 10 ply 285-65-18 vs stock 265-64-18 XL tires. Ive lost 2-3 mpg depending upon driving conditions, and yes, my 285/305 4.3 V6 notices it a bit. BUT as also noted, I have a 6 sp auto, with 4.10 first gear, 3.42 rears, effective now a 3.23. I still out pull my BB 454's with TH 400 auto, 4.10 axle vs 2.48 first gear is tranny is taller than current setup. Along with three more gears to work with. 50 extra HP help, but down 80 lb ft of torque, but the gearing is an actual net torque multiplication, so easier to get the trailer at the same total weight going.  A bit easier with the stock 265 tires too. Next time around, I'm hoping I can find a 285 in an XL, or drop to a 275- 65-18. I can find these 2-3 lbs heavier than the stock tires. 

This is also one of the many reasons semi's are going with super singles. You can save 100-150 lbs total between the single 20" wide tire with aluminum rims, vs 4 10" tires on steel rims. Thats approx. 800-1200 lbs of unsprung weight gone! More payload, less HP needed to move the load!  For us driving 10-15000 miles a year, probably not worth it, but long haulers drive 80-120K miles a year, even local drivers can do 50-70000 miles a year. a .5 to 1 mpg increase, ie 8 to 9 mpg, pretty decent savings!

Choose your poison, I'll take the lighter tire setup frankly!

Also as far as GCWR goes, its a performance rating only! IF one chassis has a 12K lb rating, same chassis etc with a bigger motor, springs, tires, axle ratio, transmission is rated at 15K lbs. The 12K rated one will pull it safe and sanely, you will just be slower! OR, an equipment trailer vs RV TT, I got 1-2 mpg more, pulled 3-6% freeway grade faster and a gear taller at the same GCW! That was due to aerodynamics. Ea additional 3 sq ft of frontal area, is the same as adding/subtraction 1000 lbs to the vehicle total. I pulled upwards of 12K with my 96 6.5TD K3500, its rating was 12500, a BBV8 was highest at 20000 lbs. Other than HP, same torque with both, I'd go a bit slower with less hp.......

Many ways to look at how well your vehicle may tow!

Marty

[blt2ski]

Reality, put a smaller diam tire, your actual ratio will get lower numericly, making it easier to start a given load, you are running a few rpm more which equates to more HP at a give speed ....

From a manufactures warranty ratings standpoint, yes those tires can change the ratings. As a 2" smaller diam Ture will make a 3.73 effectively a 410. Like wise, a 2" diam larger tire will make a 4.10 effectively a 3.73.

Something you're not taking into account, tires with the same diam, say 31.5" iea 265-75-16 vs a 265-70-17 vs a 265-65-18. The 18" tires will be overall lighter assuming the same rim metal. As rubber tire part is heavier than aluminum. Steel rims it's the other way. The 18 will be slightly heavier. You need less HP to turn lighter rim tire combos, which gives you a higher trailer tow ability.

Also, a 65 series tire vs a 70, 75, series tire with leads sidewall, braking and acceleration are better due to less tire flex.

A 235-85-16 tire, vs a 265-75-16 tire. Same diam, same sidewall height, but one tire is an inch wider, has better handling than the narrower one. I had 235 snows, and 265 summer tires on two trucks. The 265 8 ply tires handled loads way better than the 235 10 ply tires. Both had 3000 lb capacities.

Reality, put whatever tire you want into on. A lighter overall combo, slightly wider has usually been better for me.

Tow ratings, are not enforceable from a cveo/Leo standpoint. Only axle ratings are used. You will NEVER hit the max to be consider over weight where you will have issues with an enforcement officer.

Marty

[valhalla360]

If you are drag racing, the weight of the tire and aluminum vs steel rims can make a difference as you have to accelerate that extra weight. Towing...technically it will make a difference but such a small one that it won't be detectable.

Larger diameter is likely the reason for the change in rating, though in the stock sizes mentioned by the OP, it's more like going from a 3.73 to a 3.95. Assuming the OP is towing mostly in flatlands, it won't be very noticeable other than with the 10speed transmission, it might pick a different gear and run at pretty close to the same RPM.  It's only in the edge cases where it might really make a difference. If you are loaded to the max, going up a steep grade and the transmission runs out of gears to drop down, it may eventually fail to get up the hill with the larger diameter tires but so long as it doesn't run out of gears, it will wind up running about the same speed & rpm.

This is different from the old days of 3 speed transmissions where huge change in gear ratio every time you dropped a gear and very quickly, you found yourself in 1st gear.  Also, the new 8/10speed transmissions, 1st gear is basically an extra deep granny gear, so you might be going slow but you will keep going.

What I don't understand is buying a truck with a 12/14.5k limit when you know you have a 16k trailer that you pull. 

[StirCrazy]

changing tires, won't increase your towing capacity.