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Wheel diameter

flyfishing48
Explorer
Explorer
I thought this would already be a topic on this forum, but my search netted “0”. Specking out a new truck to tow a fifth wheel. Standard wheels are 18 inch. Wondering about going to 20 inch, any advantage to doing that?
With my current set up, raising the hitch higher off the ground with larger wheels would be a negative for towing level. I can’t go any lower with my hitch.
Thoughts. I might add GM is lowering the sides of the new trucks.
Gloria & Tom::R
Chevy 2500 Crew Cab Duramax
Cougar 24 RDS
B&W Companion Hitch
24 REPLIES 24

Super_Dave
Explorer
Explorer
My 06 Dodge came stock with 16" wheels. I've always hated the gapping space between the tires and the wheel wells. I haven't gone to bigger or taller because of torque loss. But I still hate how it looks. lol
Truck: 2006 Dodge 3500 Dually
Rig: 2018 Big Country 3155 RLK
Boat: 21' North River Seahawk

Grit_dog
Nomad III
Nomad III
"What is MOST important is the PROFILE ! For a truck, I would want at least a 70 series profile tire. Big difference in ride quality."

Says someone who is either being stubborn for the sake of trying to right, or hasn't driven too many newer trucks, or just plain don't understand.

You bring your 265-70-17s over (what was OE on our ole Dodge), heck bring a set of 285s as well and we can compare them to the 60 and 65 series 20" tires I have for the truck currently. $20 says at the same or equivalent pressures, you cannot tell the difference.

There was once a saying....something about an old dog and new tricks. Trying to remember it....dang
2016 Ram 2500, MotorOps.ca EFIlive tuned, 5” turbo back, 6" lift on 37s
2017 Heartland Torque T29 - Sold.
Couple of Arctic Fox TCs - Sold

flyfishing48
Explorer
Explorer
Thanks everyone for the input. I personally don’t see where it would matter too much. But wanted to see if I might be over looking something.
I think I’ll stay with the 18 inch with no extra cost. It’s been working out fine on two different trucks now since 2005. If it ain’t broke ".........
Gloria & Tom::R
Chevy 2500 Crew Cab Duramax
Cougar 24 RDS
B&W Companion Hitch

ksss
Explorer
Explorer
theoldwizard1 wrote:
wanderingbob wrote:
I am always amused by these discussions , What difference can it make , it is just a tire on a truck .

What is MOST important is the PROFILE ! For a truck, I would want at least a 70 series profile tire. Big difference in ride quality.



I am of the same belief.
2020 Chevy 3500 CC 4X4 DRW D/A
2013 Fuzion 342
2011 RZR Desert Tan
2012 Sea Doo GTX 155
2018 Chevy 3500HD CC LB SRW 4X4 D/A
2015 Chevy Camaro ZL1

theoldwizard1
Explorer
Explorer
wanderingbob wrote:
I am always amused by these discussions , What difference can it make , it is just a tire on a truck .

What is MOST important is the PROFILE ! For a truck, I would want at least a 70 series profile tire. Big difference in ride quality.

Lynnmor
Explorer
Explorer
wanderingbob wrote:
I am always amused by these discussions , What difference can it make , it is just a tire on a truck .


Some would rather educate themselves than stay ignorant of the facts. For example, Ford uses 18 & 20 tires on some models that are about 7% different in diameter and so they actually install a different gear ratio that is also about 7% different unless the customer knows what to order. Those in the know, can decide on tire sizes and gear ratios using worthwhile knowledge.

"Where ignorance is bliss, 'tis folly to be wise."

Me_Again
Explorer II
Explorer II
twodownzero wrote:
In the size I use, a 20" costs a lot more than a 17". I've thought of changing for years, but not at $400 per tire. No thanks. If money is no object, 20" all the way. Less sidewall is better for towing, but not so drastically so that it'd be worth the marginal cost for me.


I tow a 16K 5th wheel at a combined weight of 24,500 with SRW 3500 and LT275/70R18E's, and have no stability issues. I did not want 20" because of replacement cost, and the wheels that the
RAM 20" tires come on.
2021 F150 2.7 Ecoboost - Summer Home 2017 Bighorn 3575el. Can Am Spyder RT-L Chrome, Kawasaki KRX1000. Retired and enjoying it! RIP DW 07-05-2021

twodownzero
Explorer
Explorer
In the size I use, a 20" costs a lot more than a 17". I've thought of changing for years, but not at $400 per tire. No thanks. If money is no object, 20" all the way. Less sidewall is better for towing, but not so drastically so that it'd be worth the marginal cost for me.

p220sigman
Explorer
Explorer
One other thing to consider is what the weight difference there is between the two for the tire/wheel combinations. I'm guessing the 18's will be lighter.

ib516
Explorer
Explorer
20" are usually more expensive to replace. Overall diameter is about the same.
Prev: 2010 Cougar 322QBS (junk)
02 Dodge 2500 4x4 5.9L CTD 3.55
07 Dodge 3500 4x4 SRW Mega 5.9L CTD 3.73
14 Ram 2500 4x4 Crew 6.4L Hemi 4.10
06 Chevy 1500 4x4 E-Cab 3.73 5.3L
07 Dodge 1500 5.7L Hemi 3.55 / 2010 Jayco 17z
All above are sold, no longer own an RV

Grit_dog
Nomad III
Nomad III
Durb you're right, I was comparing different height tires, so the cost is skewed more in favor of the 18s and the load cap is closer to being the same for same diameter tires 18 vs 20.

Overall the point is, many still believe that somehow 20s are low profile race car tires that don't belong on big trucks when that is absotivley not the case. The difference is almost negligible and should not be a primary consideration when picking out a truck. Especially since you could swap 1 size wheel for the other for pretty much even money. Many OE wheels for sale as new or almost new takeoffs.
2016 Ram 2500, MotorOps.ca EFIlive tuned, 5” turbo back, 6" lift on 37s
2017 Heartland Torque T29 - Sold.
Couple of Arctic Fox TCs - Sold

ppine
Explorer II
Explorer II
I have 16 inch wheels on a one ton truck. They are the stock size, easy to get and the tires are the diameter the designer intended.

I don't get all the attention for bigger wheels. You may be able to buy a low profile tire that is the same diameter as the stock tire. But why go to that trouble? What is the point? If your tire is a larger diameter, then your effective rear axle ratio will be lower.

Learjet
Explorer
Explorer
wanderingbob wrote:
I am always amused by these discussions , What difference can it make , it is just a tire on a truck .


I'm always amazed by people who take time to post something like this ^^^ 🙂
2017 Ram Big Horn, DRW Long Box, 4x4, Cummins, Aisin, 3.73
2022 Jayco Pinnacle 32RLTS, Onan 5500, Disc Brakes, 17.5" tires
B&W Ram Companion

Me_Again
Explorer II
Explorer II
Durb wrote:
Doing ther math, 285/75R18 has a diameter of 34.83". The 285/60R20 has a diameter of 33.46". The difference is 4%. Theoretically, the 20" tires should accelerate better and stop better. The 18" tires might allow for better fuel economy. Your truck should sit 5/8" lower with the 20s, if all other things are equal. I trust Grit Dog that these are the sizes offered.


RAMs I believe still uses LT275/70R18E that are the same diameter as the LT285/60R20E ones they use.

Michelin list the LT275/70R18E Defender at 33.1" and the LT285/60R20 as 33.0". 627 revolutions per mile for the 18s and 630 for the 20s.

I went with 18", as the Laramie 18" wheels are the best looking of the lot. Chris
2021 F150 2.7 Ecoboost - Summer Home 2017 Bighorn 3575el. Can Am Spyder RT-L Chrome, Kawasaki KRX1000. Retired and enjoying it! RIP DW 07-05-2021