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swhunter's avatar
swhunter
Explorer
Jul 10, 2019

Which 19.5" tire to choose

I posted for the first time on here clear back in November of 2018. I was asking about upgrading to 19.5” wheels and tires for a 2000 Ford F350 SRW. I got a lot of good info from others here. I heard from some people about how hard it is to get wheels from Rickson. Well it seems that is the same case for me. All the correspondence I have had with Heather (she does the sales orders for Rickson) has been positive. But I never heard from the owner of the company or other personnel as far as getting my order for the wheels filled. I really wanted to buy wheels made here in the USA, but it didn’t seem like that was going to happen. So I ordered a set of Vision 19.5” wheels through a local Discount Tire store. The wheels came in within one week.

When my camper is fully loaded, I have 7850 lbs on the rear axle, or 3925 lbs per wheel. I am now researching tires through the Rickson website and also looking at tire manufacture websites. It looks like I could go with 245/70R-19.5” tires with load range H, rated at 4940 lbs, and a 33” diameter. These would give me a safety margin of around 1015 lbs. Or I could go with the 265/70R-19.5” tires with load range G, rated over 5000 lbs, and a 34” diameter. These would give me a safety margin of around 1100 lbs. I like the weight capacity and height gain of the 265s, but I am not sure if that is overkill. I also don’t want to cause other problems later on because of going with that big of a tire.

I don’t want a steer tire tread or straight highway tread tire. I need a good all-terrain tread that will be good when the ground is wet, whether in the mountains or the desert.

Heather did recommend the 265/R-19.5” Toyo M608 load range H, 16ply rated at 4940 lbs.

Anyone running 19.5” wheels on a SRW pickup, what tires do you prefer?

Thanks in advance for any information you can share.
swhunter
Truck Campers

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  • BigToe's avatar
    BigToe
    Explorer
    Jul 10, 2019
    2000 F-350 Single Rear wheel has a Rear GAWR of 6,830 lbs. (vs 7,850)

    Are you seeking to have a 1,000 lb "safety margin" on the tires, while at the same time overloading your rear axle by 1,000 lbs? Are rear axles immune to failure?

    Original LT265/75R16 tire diameter is 31.6" (vs 33" or 34" diameter).

    How will the taller tires affect your overloaded truck's grade climbing ability? Will you lose an entire gear at the top end, having to resort to second when you could otherwise be in third, having to resort to first when you could otherwise be in second? If diesel, will the taller tires lug your rpms, which will increase exhaust gas temperatures when climbing? If gas, will the taller tires put you out of peak horsepower range that is generally at higher rpms with gas engines?

    What effect will adding 50 to 75 more pounds per tire of unsprung weight have on the longevity of your suspension bushings? How often will you have to change dampeners? How punishing will the ride be?

    Is 4,940 + 4,940 = 9,880 lbs of tire capacity needed for a steer axle that is rated at 5,200 lbs? What will that ride be like?

    Can you air down steel corded sidewall tires below 80% of their minimum inflation rating (which for the Toyo M608 you are considering is 80 psi) without running the risk of overflexing the steel in the sidewall, which leads to catastrophic zipper failures when reinflated? Is that consistent with increasing your "safety margin"?

    You asked for "any information you can share." I strongly suggest reading the "safety" guidelines for 19.5" tires published by the Rubber Manufacturers Association, the Tire Industry Safety Council, and the tire manufacturers themselves, including Toyo, on the risks of running 19.5" tires below the minimum inflation pressures stated on the load inflation table indices.

    I've had 19.5" tires on my personal pickup for the last 20 years, btw.

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