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Downsizing from 20 to 18s- need some help with measurements

CMRoadster

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Right now I have the stock LT285/60R20 tires on my 2020 Ram Laramie 3500 SB SRW with the all black 20" rims that come with the night edition.

I tow a 15K fifth wheel and with my current truck/trailer setup I cannot get level- the front of the trailer sits high, requiring me to drive with it at "Alt Trailer height" which still does not bring it to level . I've lowered my hitch setup as low as it will go, and need to get another two inches to level the fiver and give me piece of mind and make the trailer axles and springs happier. The trailer has 15 inch wheels on two axles and I cannot size them up to 16 inch- not enough clearance under the trailer that could cause bigger wheels/tires to rub on the trailer underbelly if I hit bumps. It's a Vanleigh Pinecrest. The other problem is that the high front makes the rear levelling legs sit closer to the pavement and I have dragged them repeatedly on driveways and had the footpad pop off three times. And I cannot raise the levelers, they are mounted as high as they can go.

So my next step is to think about dropping tire/wheel sizes. I didn't ask for the 20s , they came on the truck as part of the total package. The tires are starting to show their age so with replacement in mind I am considering switching down to 18 inch rims and tires with the idea that I might gain an inch or two.

So for those of you who are towing trailers with your 3500 (and I run mine with about 400 lbs remaining payload capacity when hitched and loaded)...
If you have 18 inch tires and wheels what is the total height of tire and wheel? I'd like to compare to what I have now and see if it is an option worth looking into.
 

johanh13

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Just to be clear; you want to lower your truck (front & rear) by going to a smaller wheel and tire package so your trailer will sit level? If you dropped from your stock ~ 33" tires to 31", your truck would be 1" lower. Just my $0.05 worth, I would NEVER go to a smaller tire on these HUGE trucks. It would be much easier and better to raise the trailer by that same inch... anyhow, keep us posted on what you actually wind up doing! :)

By the way, my stock 18's are just over 33" tall, your stockers are less than a 1/4" taller overall, the difference in height of vehicle would be about 1/8"....
 

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Aketay

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33.2 inches tall for lt275/70-18 vs 33.46 for lt285/60-20. You don’t gain much. Are you sure it has 15” rims, most 8 lug wheels start at 16 inches.
 

RV_Goose

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My 2020 Tradesman 3500 dually has 17 inch wheels. Running LT235/80R17E stock Nexen tires. My 2008 WolfPack 295WP sits level at 6+ inches clearance.

Maybe Tradesman 17s instead of 18s?
 

Rockcrawlindude

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I believe the 3500 4x4 trucks have a factory lift block between the leafs and the axle. You can remove it to lower the rear of the truck a little. If you don’t want to buy new U bolts you can just move the block to the top of the spring pack and reuse the U bolts. Not sure if the air suspension trucks are the same but it wouldn’t cost you anything to do.
 
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Rockcrawlindude

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Quick search in the suspension subforum

 

RV_Goose

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I believe the 3500 4x4 trucks have a factory lift block between the leafs and the axle. You can remove it to lower the rear of the truck a little. If you don’t want to buy new U bolts you can just move the block to the top of the spring pack and reuse the U bolts. Not sure if the air suspension trucks are the same but it wouldn’t cost you anything to do.

Wouldn't someone also want to then lower the front the same amount?
 
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Rockcrawlindude

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Wouldn't someone also wantto then lower the front the same amount?

not necessarily, many people lift only the front of their truck to level the truck. I lifted my front 1”. Reverse level is also a thing where you just lower the rear

Taking 1” out of the rear wouldn’t level it, just remove some rake.
 

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