Rim Width to Tire Width Ratio - Heavy Vehicles

[Muggydude]

I have a 9500lb Camper Van (2020 Ford Transit AWD). I do a lot of snow and highway driving, but also take it down plenty of forest service and mild off-road trails to get to good dispersed campsites. Obviously no rock crawling, van is limited by its long rear overhang and height.

Currently has a 2.5” lift, and stock steelie 16” x 6.5J rims with 245/75r1 tires (30.5” x 9.5”). They have the goofy 101mm offset, so the wheel studs and wheel face stick out past the tire sidewall. I’d like to go to a lower offset wheel for rim protection and wider stance.

There are limited wheel options for the transit, with various widths and offsets.

8” rims seems too wide for a 9.5” wide tire like I currently have on. Probably would handle better on the highway, but I’d assume it would significantly hinder how low I can air down the tires without worrying about losing a bead? Does it matter if they have the little safety bead channel lip on the wheel like Owl, Black Rhino, and Method wheels have?

6” wide wheels sort of goes the other way, starts to get a little narrow for a 9.5” tire on a heavy vehicle. Could go 235/85r16 with those, but the narrower tires makes the wheel studs and rim face stick out even more.

Seems like 2.5”-3” wider is probably the sweet spot on a vehicle that’s approaching close to the load limit of the tires.

Any input is appreciated!

 

[MontySquareo]

Put bigger tires on the rims you have, they'll stick out more and protect the rims you have. 265/75/16 is a common size and is 31.5x10 i think

 

[LionZoo]

A 245/75 on an 8" wheel is a fairly common application and shouldn't be too wide. It might make the ride a bit stiffer, but shouldn't hinder airing down too much on a Transit, since built out Transits have so much weight that, coupled with their relatively smaller tires, they shouldn't be airing down to the same low pressures as a much lighter SUV. I currently run a 245/70-17 on a 17x8 and it's been fine, though I am planning to switch to a 245/75-16 on a 16x6.5 in the near future.

 

[Muggydude]

At this point I’m considering either 265/75/16 on stock 6.5” wheels or aftermarket 7” wheels with 15mm-20mm less offset.

Or maybe 265/70r17 on 17x8 rims.

Theres a small selection of LT265/70r16 tires I could use on the 16x8 60mm offset wheels, but no ground clearance advantage over 265/75r16 on 80mm offset wheels, and they both fit in the wheel wells

 

[Muggydude]

Anyone else have any input/experience with wide rims/narrow tires? On heavy vehicles?

I’m wondering if the safety bead lip is enough on the wheels to make slipping a bead much less of a concern.

Or maybe running higher air pressure (25-30psi) will keep the bead a lot more secure despite the van being much heavier (air pressure might have more affect than weight?)

 

[1stDeuce]

I've run 265/75R16's on stock 6.5" wide GM 2500 wheels on several heavy vehicles without issue. We put that size on a Sprinter van too and I'm sure those wheels are not wider than 6.5". No problems and they work well and wear well. There is no reason to need a wider wheel for the tire's sake, and factory wheels are your best bet for fitting bigger tires anyway. Going to less offset via spacers or an aftermarket wheel causes the steer tires to swing a bigger arc, which means you will need to a good bit of trimming and/or bashing, especially with a 265 size tire. Seems most people consider the 245 about the biggest tire that works well on a transit that has not been lifted and trimmed. Fits in the parking lot does not equate to fits when the going gets rough...

With a wider tire on a narrower rim, concerns of debeading are greatly reduced. In my opinion, concerns of debeading tires in general are greatly exaggerated on the internet... I've wheeled all my adult life, with pressures down to 4.5psi on the dunes and 10 or 12psi in the rocks of Moab on my Jeep and down to 15psi on 3/4 ton trucks on stock tires in the dunes and offroad in general and not once have I pushed a tire off the bead. Never had beadlocks, mostly stock wheels. All even inch size wheels have bead retention features (15, 16, 17...). Aftermarket wheels are not special. You really have to get unlucky with terrain or drive like you're on fire at pretty low pressures before you need to worry much from my experience.

For example, on my GMC K2500 loaded heavy with a truck camper, airing down to 30psi on the old 235/80R17's looked comparable to about 12psi in my Jeep on 255/85R16's. I only went that low when I had to, and I aired back up to 45psi or more as soon as possible. In baja I aired the truck down to 35psi on 265/70R17 for long sections of washboard and it was very effective, but probably lower than I needed to go. If things get REALLY soft, you may have to go quite low in an emergency, but you then drive accordingly and there is no problem. Air back up some when you are back on harder ground.

Finally, I've lately become a fan of the Goodyear Ultraterrain, which is probably about the best winter performance you'll get for a non-winter dedicated tire. They also have a very thick wheel protection bead that makes them look right at home on a narrow wheel.

 

[1stDeuce]

Re-reading, you asked about wide wheels/narrow tires but that's not what I would call a 265 on an 8" rim... With a 245, I think an 8" rim is wider than I would personally go, but Jeep had that combination on the TJ Rubicon's and it worked out fine.

Surf the web some... It looks to me like 265's are a squeeze on a Transit on stock rims with some lift and trimming. With no lift, it will require more trimming, as will non-factory wheels that move the tire centerline outboard. I don't know how much trimming is even possible, since I don't have a Transit, but the WWW will tell you... Good luck!!

 

[Muggydude]

sorry I maybe wasn’t very clear above.

My transit is lifted, and the pinch welds are folded to provide max wheel well clearance.

Im currently considering 245/75r16 tires on an 8” wheel with a safety lip on the under edge of the bead channel.

The lowest offset wheels (Black think Sequoia) I can run are 16x8j with a 60mm offset, and I can throw my LT245/75r16 Falken AT3Ws on them so I wouldn’t have to buy new tires.

But I’m concerned about the rim width to tire width ratio with a heavy van.

There are other wheel and tire combos where I could run wider and/or taller tires or narrower wheels than the 8j, but those are much more expensive at this point and don’t look as good or protect the wheel studs and rim as much. They also have less clearance in the wheel wells

 

[1stDeuce]

You'll be fine with a 245 on and 8" wheel. Yes, if you air way down, it will be "easier" to push off the bead than if the same tire was mounted on a 6.5" wheel, but if you are aired that far down, it is for an emergency situation, not for general offroad travel. With 30psi or more, you should not be able to debead a tire without doing really dumb stuff. Things will improve if you decide to go to 265's when your current tires wear out.
I wish the aftermarket would realize that wide wheels are not the hot thing, but they're all focusing on 20's and larger now too, so they really don't get it... Perhaps some day the practicality of a narrower tire and wheel combo will come back into style...

I wouldn't put too much priority on the bead safety lip hype gaining you much, or being worth the cost of new wheels... All 16" wheels have a bead retention feature, and making it much more prominent than normal would make the tire very difficult to seat on the bead in the first place. IMO, it really is not a concern unless you only hang out on internet forums...

Do be aware that going to less offset than your factory wheels will move them outboard, causing them to swing a larger arc. If your current tires just miss the fenders, you'll need to do more work with wheels that move the tires outboard farther... Just so you're aware...

 

[Metcalf]

3 wraps of Gorilla tape over the safety bead and about half way across the bead flat will get you a large difference in bead retention for about $30 if you have a tire shop that is willing to work with you or can do the mounting by yourself. Inside bead is pretty easy to get the tape to lay down smooth on the outer bead with 2" wide tape I usually do all the way around first and then cut slits in the tape to help it make the transition down into the valley of the wheel smoothly. Use a minimal amount of lube to seat the tire. I like 80 percent water and 20 percent dish soap in a little spray bottle.

 

[Muggydude]

Been going through various options still.

I think I’ve settled on an aftermarket 7” wide 16” diameter wheel.

Both LT235/85r16 and LT265/75r16 fit the wheel and wheel wells.

Question is do I go with the skinny tire or wide tire? Wide seems better for the extra load capacity (3400 lbs vs 3040 roughly) and overall vehicle width. Skinny gives a a bit of extra clearance, and less rolling resistance.

Would the skinny 235 (9.3” wide) tires or the wider 265 (10.5” wide) tires be best on the 7” rim?

 

[rruff]

My transit is lifted, and the pinch welds are folded to provide max wheel well clearance.

The lift really only prevents rubbing if it's at the top of the wheelwell. If it's fore-aft it will still rub.

A wheel or tire that sticks out farther will rub more fore-aft when turning... the outer edge of the tread as it sweeps.

If your offset is just enough for interior clearance, then you'll minimize what you need to do fore-aft.

 

[Muggydude]

OD is essentially the same between the two.

The 265 will give you the extra rim/wheel nut protection desired in post #1.

Tire load limits according to the TRA tables put the 265 about 10psi lower than the 235 (assuming LTs for both) for a similar load.
eg :
235, 3040lbs @ 80 psi. vs 256, 3105lbs @70psi
235, 2623lbs @ 65psi vs 265, 2625lbs @55psi

Lower required psi will prob give a smoother ride off highway.

Last vehicle I had with a 235/85R16 oem tire size (on a 6" rim btw) was a '91 F250 with a 8,600lb GVWR. The next MY they upgrades to a 265 (tho might have been also going with a 17" rim).

IMO, if you think you have a heavy rig, I'd go 265.

Yeah that’s the way I’m leaning.

@rruff I’m well aware of what does and doesn’t affect rub and clearance, and where. I’ve spent (too much) time carefully measuring the van and making some 3D computer models to figure out what clearance is possible with different tire and wheel setups. Overkill I know.

Stock wheels don’t work well with the 265/75r16 tires because the inner edge of the tread rubs the frame at max steering throw. 235/85r16 could work but clearance is still quite tight at max throw (less than 1/4”), and there’s no gain in van’s overall width or track width (which I’d like for stability reasons). And no extra protection for the wheel studs and wheel face.

Going to a wheel with 20mm less offset pulls the inner sidewall of the tire far enough away that 265/75r16 fits with about 1/4” clearance at max steering throw. Still gives 1/2” of clearance at the pinch welds when turning as well. Gains 2.7” of overall width over stock. At full bump it still has a little bit of space up top.

Same wheel with 235/85r16 gives more clearance in both places turning. About 1/2” max steering throw to the frame, and 3/4” to the pinch weld when slightly turned. Vehicle ends up being 1.5” wider than stock overall.

If the bigger tires still clear in all suspension and steering positions, seems like the benefits (stability, load capacity, wheel/stud protection, extra vehicle width) make it worth it. Main downside might be less clearance for ice buildup and a little extra weight, but in my experience it seems like ice and snow more or less builds up to the limits of the tire’s steering throw path regardless. Also less room for wheel well liners, but I’m sort of convinced at this point that ford’s crappy fitting front wheel well liners just allow road salt water and grime to get behind them and sit forever without being easily washed away. I’m going to probably just remove them and prep the wheel wells well before spraying truck bed liner to protect them.

 

[MontySquareo]

The 265 will be less mushy in highway corners. Kinda important for a tall van.

 

[rruff]

Question is do I go with the skinny tire or wide tire? Wide seems better for the extra load capacity (3400 lbs vs 3040 roughly) and overall vehicle width. Skinny gives a a bit of extra clearance, and less rolling resistance.

It's a common misconception that the skinny tires have less rolling resistance, but this isn't true... at least not on pavement. The wider tire has a shorter contact patch and less casing distortion, and less hysteresis from flexing the casing. The wider tire will also have more aero drag, so on the highway there probably isn't much difference in MPG.