Are the Biggest Tires Possible Worth it on a Van?

[Muggydude]

Active member on the Transit USA forums, but I figure I might get better insight over here from more off-road oriented folks.

I'm currently building a 2020 High Roof, Extended Length, AWD, Ford Transit Camper Build.

I'm currently trying to decide if I want to put the absolute biggest tire that can be stuffed in the wheel wells without rubbing (for the most part), or go slightly smaller. I have put pretty much all the off-road upgrades I can on my van.

I currently run LT245/75R16 (9.5x30.5") Falken Wildpeak AT3W Tires on the Stock Steel 6.5", 98mm offset Ford Wheels. I want to upgrade the wheels to better support the tire sidewalls, gain stability from increase in vehicle width, add durability, and increase tire bead retention at low PSI (stock bead channel is not nearly as good as the Owl and Black Rhino Wheels), and better protect the face of the wheel and the wheel studs (studs currently stick out 27mm past the tire sidewalls on a stock wheel and 245/75r16 tires)

Basically, the biggest tire you can really squeeze into the wheel wells on a 2" Lifted AWD Transit, while still not rubbing through steering range of motion and suspension compression, is 31.9x10.7" when you have a slightly lower offset wheels than stock. 80mm is probably the sweet spot. It's still very tight, I'm guessing ~.5-.7" of clearance when turning after a lot of trimming, and you can't run splash guards.

The lower offset you go, the less clearance you have to the pinch weld (which must be folded over flat) at the rear of the wheel wells, so with a 60mm offset like the Black Rhino Sequoia Wheel, you have to go down in tire width and height to clear the pinch when turning. All the setups in the table below should work with only folding the pinch weld over and cutting plastic off the front bumper. More clearance overall with the 30.5" Tires.

The benefit of the taller tires is of course more ground clearance overall. The rear differential skidplate sits a lowly 7" off the ground with the 245/75r16 tires, so I could gain .7" all around going to the bigger tires. Of course the downsides are:

-Lower mpg (larger 17" tire/wheel combo weighs 10lbs more than the 16" combo)
-More stress on the drivetrain and worse accel (I may consider re-gearing to 4.10 in the rear with a truetrac diff eventually)
-Very little space for mud and snow/ice buildup
-Possibly a little bit of rubbing at extreme articulation angles
-Wheel face and lug studs/nuts are considerably more exposed to damage on the 80mm offset wheel.

So the question is - is the extra .7" of ground clearance worth the downsides? Would you stuff the biggest tire in there that can realistically fit, or go slightly smaller for the extra benefits and breathing room that brings?

Most off-road trucks and vehicles and even sprinters have much larger wheel wells to allow for some space between the tire and wheel during all circumstances. If only Ford had just added a couple of inches to the front wheel wells...



~30.5" Tire in Transit Wheel Wells:




My Van currently with 245/75R/16 (sitting higher in travel now than it eventually will). Plastic front bumper, Plastic in front of rear wheel, and front splashguard can be trimmed/removed to give .7" more space)



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~31.7" Tires in Ford Transit Wheel Wells:

 

[Muggydude]

Talon 17", 8" Wide, 80mm Offset Wheels:

245 (9.5" Wide) Tires



265 (10.7" Wide) Tires


30.5" Tires (Don't have one with the 32" Tall Tires)



Black Rhino Sequoia with 30.5x9.65" Tires:

 

[Muggydude]

TLDR - Only rear if you're interested in my build setup:

I estimate it will be 9500lbs finished. Been (very) slowly building it out. I'd guess it's 7500lbs currently. Can read more below about the build, but the general idea is to be able to get through pretty much any snow covered (maintained) roads and neighborhoods in the winter, and be able to get down most forest service roads and mild off-road trails to dispersed camping spots during warmer months. Obviously there's only so far you can (or should) push a 10,000lb unibody van off-road, but it's still fun to push it and get to cooler spots. The long rear overhang and crappy departure angle is the biggest limitation, but I've helped that tremendously with the steel rear skidplate bumper and the 3" lift+airbags. Can get the rear bumper up to 22.5" off the ground on command. The 11ft roof height is also a problem, but electric chainsaws and a ladder help haha (figure I'm doing free work for the forest service when there's a low hanging branch in the way).

-Ford Factory 9.75" LSD, 3.73 Rear Gears, 10 Speed Transmission, Ecoboost 3.5L Engine
-2" Front Van Compass Topo Lift (stiffer front red springs)
-3" Rear Van Compass Lift (1/2" extension Shackles + VC Mini Leaf Spring pack)
-(Rear end is currently about 4.5" Higher than Stock at 7500lbs, but I expect it to settle down ~1.5" with the next 2000lbs going in)
-Van Compass Front Intercooler Skidplate
-Van Compass Rear Differential Skidplate
-Quadvan Rear Shock Relocation brackets
-Falcon 3.3 Shocks in the Rear
-Airlift Ultimate 5000 Airbags with in-cab controls. I usually run them very low air pressure just to act as bounce stops, but they let me lift the rear end up to max height on-demand when I have steep departure angles (help rear-end dragging)
-Airbag 1.5" spacers and .5" Cradles
-Transit Off-Road Steel Rear Bumper (acts like big rear skidplate if the bumper drags)
-Extreme Outback Magnum Air Compressor and Tank under the Chassis for airbags and to air up.
-Diode Dynamics SS3 Max Fog Lights and SS3 Pro Auxilary High Beams/Driving Lights
-Will have 12,000Wh of lithium, 40 gallons fresh water, 600W solar, propane oven, gasoline air heater, hydronic water heater, starlink, etc when complete.

-Eventually I think I'm going to get the upgraded Falcon Front Struts when they release them, add a truetrac LSD in the rear (stock Ford LSD isn't impressing me and already seems like the clutch pack is going), and re-gear to 4.10. Probably add a steel or aluminum front bumper too.

It does surprisingly well off-road for such a big van. I haven't pushed it too much, but have gotten a few good camping trips in with mild off-road trails and forest service roads where I definitely needed the ground clearance, few friends with stock Jeeps (Cherokees) struggled a bit, although I'd probably chalk some of that up to driver skill. I use it driving up in Lake Tahoe and Colorado in the snow a lot and it's done awesome, one storm last year with about 2-3 feet unplowed in the neighborhoods and it trucked right on through.

Obviously not ever going to be a real overlanding rig. The AWD system has never really let me down yet but has its limits. It is a tank in snow and ice though (best snow vehicle I've ever driven). Especially with some extra weight in the rear, I've thrown 400lbs of sandbags in the past couple seasons. As long as I keep some momentum it keeps on trucking.

Only time I've ever gotten stuck was on some side roads trying to get around some fools who left their sedan in the middle of a rutted out snowy road. Got a little too far over on the shoulder trying to pass (through 1.5ft of snow) and the compacted snow base of the road dropped off so the van slipped down and grounded out the rear diff. Stupid to try I suppose. Was glad I had the diff skid plate and the steel rear bumper - got towed out from that.

The transits actually can get decent ground clearance (almost) everywhere even with a 2-3" Lift and the 30.5" Tires. Obviously they could be better haha.

Front Subframe: 10.75"
Front Bumper: 11"
Rear Diff Slid Plate: 7" (Sad)
Rear Quadvan shock Relocation brackets: 9"
Rear Swaybar 9.5"
Rear Axle: 12"
Spare Tire: 16"
Bottom of Transit Off-road Steel Rear Bumper: 20.5" (22.5" Max Extension with Airlift Bags fully extended)
Approach Angle: ~23-24 degrees
Max Departure Angle on Extended Length (Airbags fully inflated): 17 Degrees
Breakover Angle: ~24 degrees

 

[rruff]

-Lower mpg (larger 17" tire/wheel combo weighs 10lbs more than the 16" combo)
-More stress on the drivetrain and worse accel (I may consider re-gearing to 4.10 in the rear with a truetrac diff eventually)

Maybe on the mpg, but the weight won't be the reason. If the tire is larger that is more likely to reduce rolling resistance (same tire) rather than increase it. Aero drag due to more height might be noticeable... but they also stick out less. Should be very minor effects either way.

With 10 gears I don't expect acceleration will be an issue either except in 1st. Since you don't have a low range, low gearing is kinda important offroad. But the tire change is <5% so I wouldn't worry about that.

Ground clearance is an issue for these vans offroading, so I think it's a good idea. Did you raise your rear shock lower mounts 2" as well to match your 2" lift?

 

[Muggydude]

Yes, have the 2” raised Quadvan rear shock relocation brackets installed.

Good points for the mpg. May be a wash compared to the 245/75r16 I have in now.

It’s a bit frustrating Ford doesn’t allow the tire diameter to be increased past stock on these van, so you’re stuck with the factory shift points more or less. Regearing would help. 10% total change isn’t too bad though, although I will be approaching max GVWR

Just to clarify, I’m asking if .7” extra clearance of the 32” tires is worth the downsides over the 30.5” tires I have on it now.

 

[Farfrumwork]

In short, yes.

I don't have a transit, but I fit the largest tires I could (255/85/16, just under 33") on our 4x4 Sprinter without having to lift. The extra clearance under the pumpkin is nice, and they look sweet too. Bonus on our rig is that the 33" spare still 'fits' in the OEM location, which I wanted to maintain. What is the spare tire limitation on the Transit? (unless you already have a rear-mounted tire carrier)

Main downside is gearing change (mostly an issue accelerating from a stop), but the 10spd in the Transit shouldn't be as affected. We are also in CO, so the altitude is additive to this downside. I would like to get a locking rear diff in the near future which will allow me to re-gear and effectively cancel the 8-9% penalty.

 

[Muggydude]

I have an extended length transit, so I could fit a 35" spare under the chassis with room to spare, so good there.

I realized that with the Sequoia wheels, I'd have 9.5" Tires on an 8" wide rim. While I think that would help stability and handling a lot on-road, it definitely could limit my ability to air down off-road without worrying about losing a bead.

With a 10,000lb van, I doubt I'd ever go under 25/30psi regardless, but I don't know if a 10,000lb rig at 25PSI would be just as likely to lose a bead as a 5,000 truck at 10-15 PSI.

 

[whith]

Have you looked into a body lift for some extra clearance? My understanding is that Ford is doing a body lift from the factory on the new Transit Trails so should be doable in some capacity.

 

[Muggydude]

You can theoretically do a 2” Quigley spacer lift, plus a bilstein front strut (5/8” lift) and Van compass front strut spring (1.25” lift), to get a combined ~4” body lift. But it doesn’t really help much, because it does nothing to lift the front subframe up over the lift I have now, so it doesn’t actually increase ground clearance up front. It doesn’t really improve clearance for tires either, as the closest spot is directly behind the tire, so it won’t really give more room for larger tires.

And beyond that, the ground clearance on my van right now is 11” up front and 7-9” in the rear. So I’m really limited by the rear axle height regardless, a little extra body lift up front is a waste of $6000 over what I have now

 

[ZacSc]

The bigger the tires, the better the off-road capability of your car. Put on larger tires without hesitation if you plan to do more off-roading.

Hello everyone, this is my first post.

 

[whith]

The theory would be that the body lift would allow for clearance for larger tires, but if that is the cost for it and obviously if it doesn't allow for more tire clearance then....

 

[Muggydude]

With the transit the body lift past 2” doesn’t really get you much/any extra room for larger tires, because the clearance to the pinch weld area at the rear of the front wheel wells, and front of the rear wheel wells, is the issue (not vertical clearance), and a lift doesn’t help the clearance in front and behind the tires much, and certainly not under suspension compression. 32” is realistically the biggest that should ever be put on. Could maybe get away with 33s on RWD vans with a 5” lift (lift spindles) up front, but not an option on AWD vans

 

[LionZoo]

Counterpoint: I have a Quigley Transit with a locking rear diff and run moderate 4x4 trails (I use my Transit as about the equivalent of a stock 4x4 F-150 and run the same trails that I did when I had a GX460) and have decided to stick with 30.5 inch tires. The big issue with Transits and Sprinters is going to be the lack of articulation and (for AWD Transits as well as Sprinters outside of Iglhaut conversions) poor gear reduction. Clearance is on the okay-ish end. What this means is that most technical terrain will start to feel sketchy because your van is going to be lifting and jerking on its wheels before you run into the limits of clearance.

Going from stock size tires to a 30.5" on a Transit is relatively easy and yields decent gains. Going from 30.5" to 32" takes a lot more work and, in my opinion, is very much into the land of diminishing returns. A vehicle is a system, and the weakest links are the ones that should be addressed. I just feel that too many internet builds tend to focus on big lift numbers and big tires, probably because it looks cool, and neglect the actual items that are holding back the platform.

Now the one wrinkle in this is that yours is going to be a very heavy Extended. How much have you wheeled your current build and what is your impressions? Keep in mind that, once fully built out, wheel lifts and drops will feel even spookier since you're going to be adding 2,000 pounds (not insignificant!) and likely raising the center of gravity.

 

[Muggydude]

You raise some pretty good points. The ecoboost with the 10 speed isn’t too bad in first, I think regaearing to 4.1 gears and the rear truetrac will help too. I haven’t come close to not having enough torque yet though. I’d get a rear locker, but I drive so much in snow the truetrac would be a better choice. With 2000 lbs more it’ll be more laborious for sure though.

The lack of flex and articulation limitations on the transit is a good point. I’ve had a couple tippy situations where it’s teetered a bit on two wheels. Unfortunately, there’s not much to be done about it with the AWD. The front LCA can only take about .75-875” more droop than stock, which the Van Compass lift already does. That being said, I haven’t had any real problems with it yet on the trails I’ve been down. I’m pretty careful about picking my lines. As you mentioned though 2000lbs will shift the equation, but the good news is a lot of the weight will be low on the floor or under rhe chassis (water tanks, propane tank, compressor, lithium batteries). So the CG should hopefully stay decently low.

The rear overhang and overall length is still one of the biggest limitations for a lot of trails that are fine otherwise. I’ve done as much as I can to help that, other than possibly slightly bigger tires.

I did a lot of measuring and made a 3D computer model of the front wheel wells to see the clearance with different size tires and 31.7” x10.5” tires can fit with decent clearance without splash guards.

At this point just going to wait and see if I can sell my current wheels and tires, if I can then maybe I will go to bigger tires.

Ultimately there’s only so much the van will ever be able to do. If I could start over today I’d get a F350 chassis cab, a custom composite box, and put 37” tires on it and call it a day. Maybe one day.

 

[86scotty]

Ultimately there’s only so much the van will ever be able to do. If I could start over today I’d get a F350 chassis cab, a custom composite box, and put 37” tires on it and call it a day. Maybe one day.

But then you're opening yourself to other compromises. There is no perfect way. I've tried about everything. I'm still trying to live with a vehicle that will do most trails I want to do, fit comfortably in one standard parking space, not limit my life from overhead clearance issues (drive thru's, etc.), and most importantly one my wife can jump in and drive at any time without fear. For me that lands me back at a middle sized van.

I had a Transit 2wd a few years ago and upgraded to BFG KO2 E rated tires pretty quickly. This was before the advent of lift/suspension choices, wheels, etc. but other than the unfixable speedo problem I loved them. Dropped them to 20 psi for offroading many times. That's pretty much my go to off-pavement PSI for any van.

I don't want to contribute to your thread drifting from your tire size questions but you won't get the good mix of efficiency, comfort and all around livability out of an F350 with a box that you do with your van, especially if your travels include stretches of interstate. I'm in a butchy old 2011 E350 V10 on 35"s again and I like certain things about it a lot but highway comfort and modern amenities like the Transit is full of are things I greatly miss.

Personally I would not put any more money into your Transit quest. I'd use as it as long as the tool mostly does the job.