Wheel (rim) Size Question

[Jeff1759]

2021 Ram 3500 SRW with a Bundutec Wild, comfortable in my payload capacity with 1,500 lbs to spare, drives very well on pavement and decent gravel roads, but feels a bit top heavy with roll when I think about taking some steep and very pot holed gravel hills where I recreate.
OEM wheels are 20x8" with 285/60R20E tires.
I think I have a better grasp on wheel/tire sizes, but looking for some clarification or some guidance.
My understanding is that smaller rim sizes allow for more sidewall, which translates to a better off road ride, especially if aired down when going off road. (installing onboard air soon)
Does this sound right?
If I were to go with a 17" AEV Salta https://www.aev-conversions.com/product/ram-salta-hd-wheel/
and wanted to run with a 35" tire, would this be a good first major investment in improving my off road capability? Not looking to rock crawl, but to be confident on forest service roads, ruts, potholes, creek crossings, etc..

 

[Vic Harder]

I hope JHanson jumps in here. I believe he has LOTS of relevant knowledge about this. For my $0.02, I think the smaller rim is the way to go for sure, depending on the availability of tires. For example, my truck uses 265/70r18 tires, but 275/70r18 is a more common size, that is what I will put on once mine need replacing.

Have you considered that you might need a fatter anti-roll bar? Since you won't be rock crawling the limits they put on articulation are well worth the handling benefits.

 

[fuzzymarindave]

..but feels a bit top heavy with roll when I think about taking some steep and very pot holed gravel hills where I recreate.
OEM wheels are 20x8" with 285/60R20E tires.

My initial thoughts are that if it feels like top heavy and rolls then high profile tires (ie. smaller rims ) are going in the wrong direction. Your roll feeling might be suspension related and not tire/wheel combo.

 

[Mighty Dodge Ram]

Be sure to check whether a smaller rim will fit; newer trucks have much larger brake calipers and discs. My initial reaction is that a 17” rim would not fit if the stock size is 20”. Maybe, just maybe, an 18” will work.

 

[Beach]

Go with a 17 or 18" rim there should be plenty of tire selection for either size. to accomplish what you want, you'll need load range E with a heavy/stiff sidewall. Tire pressure will also have a big effect on how much "roll" you feel when driving. Side note: 17 or 18" tires are generally less expensive than 20"

 

[Wango]

My 2 cents,
go down to 18 inch wheels, i feel this is a good overall fit with 35 inch tires. Looking for a sweet spot with sidewall.
Of course this can increase body roll/sway.
I went the hellwig swaybar route, and added stabilloads also. My leaf pack was made for my truck, so has progressive leaves.
This does limit articulation, but i have not found this to be an issue, while i do take mine on some pretty fun trails. I am not seriously rock-crawling. Ram powerwagons have had sway-bar disconnects in the past. Maybe this is an option also.
w

 

[JHanson]

Jumping in . . . With 20" wheels and the correspondingly shorter sidewalls of the tires I'm pretty sure the roll issues you mention are suspension related, as someone mentioned, rather than anything to do with sidewall squirm. It's difficult to say without driving your truck; the Bundutec is still a chunk of weight even on a one-ton truck if you have stock suspension. The roll you're feeling might be perfectly normal.

I also suspect, as someone else mentioned, that 17" wheels might very well not fit with the brake calipers on your truck, but that's easy to check through the dealer or factory.

You're correct that taller sidewalls contribute to a more pleasant ride, especially when aired down—and airing down also increases traction and flotation and reduces stress on the truck and on the trail. Then again, if you're planning to install 35" tires you'll have a decent amount of sidewall even with 20" wheels. I would consider saving money and trying that approach first. Alternately, since you don't plan on rock crawling I would consider compromising on the 18" option.

Just keep in mind that going from a 33" tire (the 285/60R20) to a heavier 35 will affect your braking, acceleration, and fuel economy negatively. Again, if you're not planning on rock crawling, but generally stick to forest service roads, I don't think you need the extra inch of ground clearance you'll gain.

 

[ntsqd]

17's seem to have the widest selection range, but fitting over the calipers could be the sticking point. I flat do not understand this fad of large OD wheels & low profile truck tires. Everything about it is wrong for the application. The rubber floor mat, hand crank windows version of your truck likely has the smallest rim size that will fit. Looking that up will tell you what will work and what likely won't. And if that doesn't get you there, then look up the OD of the front brake rotors. The rule of thumb is that the smallest wheel that will fit will be 3" larger than the rotor's OD, So for a 12" rotor the minimum size will be a 15" wheel, and for a 14" rotor OD the smallest wheel that will fit will be a 17"

Body roll doesn't bother me, but then I learned to drive in a Saab 96......

 

[JHanson]

"Body roll doesn't bother me, but then I learned to drive in a Saab 96......"

Now that is funny!

Agreed on the trend toward silly low-profile truck tires.

 

[fish more]

Low profile tires are for pavement pounders.

 

[Jeff1759]

Thanks for the replies. 17" do fit. Still not sure what route I will take, but there is no hurry. I plan on wearing out the OEM tires and that will give me more time to think about it.

 

[dennis 221]

Sure hope those stock tires are 10 ply e rated

 

[Beach]

Low profile truck tires are for the lookin cool/status crowd, nothing to do with what we at WW need/use them for.

 

[Jon R]

I feel the same about “leveling kits” that eliminate the rear suspension capacity to “level” the truck. I leveled my truck by installing a Grandby.

 

[zuber]

On my 2021 RAM, I went with 18x9 Method Race wheels, forged aluminum, just the right offset to easily clear 35's with stock suspension and 37's with 2 1/2-3" lift. These have a 4000# load rating, each. The ones with the extra ribs that act like a bead lock, but don't look like one.

Then went with 295/70-18 Cooper AT3, 34.5" dia, also with a 4000# load rating. The spare will 'just' fit under the bed. Makes a squeak when you squeeze it in there. I run 50 psi front and 35 psi back when empty. Rides very good, but I have a 2500 with coils and the Bilstens.

The stock RAM rims only have a 3500# rating, they are cast now and a little heavy.

 

[ramblinChet]

What you are experiencing are the affects of your center-of-gravity moving farther away from your system's roll-center. Since you are driving a 3500 and the Bundutec is only 1,650 lbs. it seems that everything is in order. You also mentioned that you have around 1,500 of additional payload to spare which makes me think you have an optimum load for your vehicle. It would be interesting to find the height of the Bundutec's center-of-gravity although I suspect it is acceptable since companies do their best to keep the heavy parts down low and towards the center.

What is interesting is that you mention everything feeling fine on normal roads. If you really had a significant roll problem I don't believe you would feel this way. Now off-road is another mode for the suspension to deal with and I too have experienced the back-and-forth rolling motion on uneven terrain. If you wish to smooth things out off road it seems like a front anti-sway bar disconnect would offer the most improvement. If you did opt for the AEV Salta HD 17x8.5 rims with 35" tires you could air them down to 15-20 psi off road which would slow your roll rate down also although not anything compared to disconnecting your front anti-sway bar (off-road only). BTW - AEV are the only rims sold by a manufacturer who has performed the necessary calculations for proper off-set, scrub radius, etc. relative to suspension lift, tire size, etc.

Although this does not seem necessary for RAMs with stock suspension, the only other way to reduce roll is to move the roll-center up closer to the new center-of-gravity. This is what AEV does with engineered panhard bar brackets for the front and rear axles. Of course, once the panhard rods are moved now the drag-link must be relocated also since those two items must remain parallel to eliminate bump-steer.

In closing, please do not permit any uneducated person to convince you to install a "torsion sway bar" which is simply a weaker front anti-roll bar which will immediately increase oversteer and place yourself and others at risk on the road.

 

[ntsqd]

CG can be measured and calculated, it is work, but it's not that hard to do.

For the whole vehicle you need separate front and rear axle weights. Then you need a third weight for either axle, but with the vehicle at as much of an angle fore/aft as you can manage and accurately measure. The difference in the flat weight and the "angled" weight with some trig will give you the height of the CG.

If you think that the side to side weight distribution isn't equal or close then you'll need L/R weights as well.