20" vs 17" tires ?

[penner]

I currently have 8 ply 275/55/20" KO2's on my truck. Considering swapping out my 20's for 17's and going for a less aggressive tire. I do next to no off roading ,a lot of backroad driving and mostly highway driving since the truck is my daily driver. Couple of questions. 1- Would there be much /any difference in the ride with the higher sidewall ?? 2- If I do the swap, any recommendations for tires? Maybe it's just me , but the KO2's seem to throw a lot of gravel. Our truck is a 2017 Z71 Silverado 1500 with a 2018 ATC Ocelot shell (72"wide) with a few mods. Thanks. Glen.

 

[Wandering Sagebrush]

Glenn, I think you would get a slightly softer ride (maybe). I like Cooper Discoverer AT/3s. I have them on my F350 and as of this morning, on my Ranger. Somewhere on ExPo there is a tire thread, I believe it was by Jonathan Hansen, that did a tire comparison. The Cooper was deemed the best tire for back country and road.

WS

 

[klahanie]

Given the same overall diameter and tire type I'd expect with a 20" rim less "roll" or sideways flex when cornering on pavement. And with a 17" a softer ride on irregular surfaces. If you air down for gravel I think the 17, having more sidewall height to compress, could give noticeably more dampening.

 

[Wandering Sagebrush]

Found the review...

https://expeditionportal.com/where-the-rubber-meets-the-road/

 

[smlobx]

First, let me say that I have a high regard for the Cooper tire. We used it in Africa earlier last year and in driving over 2000 miles off-road in some very rough terrain our convoy of four Land Cruisers only suffered 2 flats. The Acacia thorns are very tough!

In the article mentioned above they left out one very important consideration and that is the weight of the truck fully loaded. It's one thing to test tires on a 5000 pound Jeep and a whole other beast to test it on a 8-10,000 pound truck camper.

IMHO when you are in that weight range you need tires with very robust sidewalls and E rated tires are almost mandatory. Our truck came with Michelin LTX AT2 and for a general tire used as described by the OP I would say that this should be considered. I recently upgraded to Toyo AT2 tires that were about 20mm wider than stock that allowed which also gave me more carrying capacity and perhaps better off-road grip. Time will tell.

I will also agree with above that if you plan on airing down 17" tires allow you more flexibility. Have you considered 18" wheels? There seems to be more E rated tires in that wheel size and might be a good compromise...

 

[Taku]

Have an 05 Tundra with an Ocelot. Ran Michelin LTX AT2's for almost 60K and no problems. Switched to KO2's for the beefier sidewall and different tread pattern. They definitely pick up more gravel and are noisier. Traction is very good even driving Teton Pass in the winter. If you are going to use for a daily driver with the camper on I would go for the E rated Michelin's.

 

[Ace!]

I would definitely check tire sizes of several good brands in several sizes or ranges of sizes you might use, then determine what size wheel works best.

Here's how it works, reiterating other posts above, the smaller the wheel the taller the sidewall for the same overall tire height. Sidewall allows for more flex, which on the road translates to more roll when cornering. Taller sidewalls "feel" less responsive when cornering. They also allow for more flex when going over "bumps" in the roadway, which translates to more cushioning effect.

The reverse is true as you go up in wheel size/less sidewall height. So, if you feel like you need more responsive cornering you'll want to stay with 20" wheels, but you'll feel more of the road while driving, both seat of the pants and through the steering wheel.

Generally, if the overall tire height is the same, the taller sidewall will ride better but be less responsive.

 

[iowahiker]

We have LT245/75R/17 load range E tires from the factory for 110,000 miles, BF Goodrich AT's (not KO2's). We are on our second set and obviously satisfied. The first set were replaced after 75,000 miles and were in good condition (we wanted deeper tread). Our loaded and wet weight is around 7500 pounds and handling/ride is perfect (unleashing the 5.0 liter double overhead cam V-8 on a curvy mountain climb got a thumbs up from the motor cycle following us at the top, with the camper on). The door tire pressures are 60 psi rear and 55 psi front and we like the loaded ride while the empty ride is harsh at these pressures. Picking up rocks is not a problem. My brother-in-law's truck came with similar LT tires but no payload package and his door sticker tire pressures were 35 psi at all four corners.

The P rated BF Goodrich AT's (not KO2's) had groves in the outer tread races while the LT rated AT's outer tread races are almost solid. Those solid outer tread races increase tire life and handling and reduce noise at the expense of some traction. My opinion is a truck with LT 75 profile tires (stiff sidewall), solid outer tread races, a solid rear axle, a heavy duty spring pack (we have the payload package), and sufficient air in the tires handles well (whats left to move sideways?).

 

[penner]

Thanks for the replies. My camper is only on the truck for 4-6 weeks a year and they are high mileage trips. I'll have to see what I can get for my tires and rims , that will help make my decision easier. Have a good day.

 

[XJINTX]

Following... timly post for me. I am running 20" BFG KO2's on my F250 with a Hawk. NO COMPLAINTS actually second set of BFG's KO and now KO2. I am moving downsize this summer. I ride with others with same size setups and "most" are running 17's. When we air down they are at a big advantage and each love their setups. Unless convinced different I am looking at 17's with new BFG's

 

[Advmoto18]

Wheel sizes...
As others have posted, the smaller the wheel, the more sidewall the tire caucus will have thus allowing you to air down to a lower psi without damaging the sidewall as long as you pay attention to gross weight.

Why are we seeing 20" wheels on trucks?
Easy/quick answer-less rolling mass thus better fuel economy. All truck manufacturers are trying to get the last .1 of a mile in fuel ratings.

20" wheel are not optimum in the least for overland and work pickup trucks. Why we still see 18" wheels the norm except in the more expensive submodels.

I have 16" wheels on my 1988 Toyota Land Cruiser. I can air down to less than 1 Bar and get a super comfortable ride on the harshest terrain.

Axle hub/drum, brake rotor/caliper will determine the minimum size wheel your truck can accommodate.

Generally, you want to stick to even numbers, 16, 18, 20 as these tire diameters are more common with greatest offerings.

Start with the smallest wheel your truck can accommodate, then work through the tires. You will want to set the spare up the same way if you change tire diameters. Using a spare of different outside diameter will put stress on your axle bearings, cause the gears to overheat and created problems for a limited slip rear end if you have to travel more than a few miles to a shop. This doesn't mean you must use the same wheel diameter for a spare, but rather, you must select a spare tire with the same outside diameter as your other 4 tires.

If you're stuck more then ~25 miles from a repair shop, and using a dissimilar diameter spare, put the spare up front. Front end parts will be cheaper and easier to replace/repair than the rear.

Having a spare set up identical to the other 4 wheels/tires gives you the ability to perform a 5 tire rotation which adds longevity to all 5 tires.

 

[Mighty Dodge Ram]

This: “Axle hub/drum, brake rotor/caliper will determine the minimum size wheel your truck can accommodate.” Also, if you use tire chains on a larger than stock tire, be sure they will clear brake lines, etc. Here in CA, I carry them by law but never use them. If I ever had to...

I ran KO2s E rated on my Dodge. Great tire offroad, nothing stopped them. But I found that the treadwear was very low compared to others. YMMV

 

[klahanie]

Thanks for the replies. My camper is only on the truck for 4-6 weeks a year and they are high mileage trips. I'll have to see what I can get for my tires and rims , that will help make my decision easier. Have a good day.

Sounds like our road trips. Lots of highway. We usually do a good bit of gravel on those trips too. I read you also use yours as a DD. Don't really need an aggressive tire for any of that.

FWIW we ran the oem Continental AT tire for 3 years and it did everything we asked of it off highway and on, prob helped by our vehicle weight. Think tread pattern was like this

I reckon you can find a quality tire with more of a highway tread that would noticeably improve your pavement ride over current and might be quieter, last longer and use less fuel. I'd talk to a few tire shops too, so many choices available and I know they get customer feedback. Not sure why you want to buy different wheels tho ...lower tire cost maybe ?

True, 55 is low profile and 17" would be better for airing down off highway but that might be moot for you, IDK. I like to air down for gravel, but our truck has extra stiff spring rates and I tend to drive faster than some, so I want all the cushion I can get. Good Luck !

 

[penner]

The reason I was thinking of the 17" rims is that I thought the extra sidewall might smooth the ride a bit. Also the extra sidewall might handle the HUGE potholes I I tried to avoid in Baja and Nfld last year.

 

[klahanie]

Also the extra sidewall might handle the HUGE potholes I I tried to avoid in Baja and Nfld last year.

In this case, for sure. Another benefit could be reduced inflation pressures required even before "airing down" with a different tire size. eg. using LT275/55R20 (~31.9" OD) as a base, a LT265/70R17 (~31.7) is rated to a max load of ~8% higher for a given PSI and a LT275/70R17 (~32.2) is rated ~13% higher.

So if you had been running at 35PSI (1750# max load rating at that PSI x 2 tires = 3400# for an axle wt) you could safely do the same at ~32 and ~30.5 PSI respectively with the tire size listed above. Per the TRA Load and Inflation Tables.

Might not sound like a lot but coupled with the taller sidewall it will make a difference in ride quality when on irregular road surfaces.

 

[Advmoto18]

The reason I was thinking of the 17" rims is that I thought the extra sidewall might smooth the ride a bit. Also the extra sidewall might handle the HUGE potholes I I tried to avoid in Baja and Nfld last year.

If 17" is as small as you can go, and you can find the tires to suit your needs, then such is a worthy consideration.
Just realize those 17" tires you find and like may not always be available due to low demand.

Personally, if 17" was the smallest my truck could handle, I would step up to 18". Yes, the 18" sidewall is not as tall and the ride many be a bit harsher when aired down, but, the sheer number of tires available in 18" would make the decision easy for me.

Indeed the roads in Baja can be rough in places. Yet, plenty of RVs, truck/campers, even towed travel trailers, head up and down MEX 1 all the time without much of an issue. Don't get distracted while driving and never drive at night and I think you will be fine regardless if wheel/tire choice.