The custom auxiliary fuel tank project for our 2017 Ram/Cummins 2500 is underway! June 2019 I added two additional aluminum toolboxes aft-axle on my Hallmark Nevada Hillsboro flatbed camper outfit. My idea was to eventually remove one of the large, 30-inch-long front boxes and replace it with a fuel tank, preferably a commercially available aluminum saddle tank for a medium-duty truck.
The tank project was moved to the back burner and a year passed quickly. For a while I considered a much smaller 10 or 12-gallon tank, hoping to fit one under the chassis between the frame rails, and in front of the spare tire. Just 100 miles of additional range would be a game changer during long highway trips.
Evan a commercially available tank would have required custom mounts and modifications, and surely some compromises. After discussing the project with Chris at High Sierra Fabrication several weeks ago, we decided on a custom tank for my original under-bed location. The goal was to fabricate a tank that looks extremely similar to the toolbox that was removed, and the matching 30-inch box still on the passenger-side.
Custom costs more, takes time, and is never snag-free, but if you have the right business and people involved, the results can be fantastic.
A beautiful tank was constructed using 3/16-inch diamond plate aluminum. Then High Sierra Fabrication proceeded to drill and cut holes in the box, weld-in fittings, a sump, and clean-out port, etc. We are getting close, but still working on it.
After High Sierra Fabrication completes most of installation, I will still need to plumb and wire the external pump to transfer the auxiliary fuel into the 2017 Ram’s factory tank.
Cooper STT PRO 295/65R20 (35.4″), ready to winch under a 2017, fourth generation Ram/Cummins 2500.
Question: How much spare tire can you fit under your truck?
Answer: It depends.
This post is about squeezing a large (35.4-inches) tire into the stock location on a late-model, fourth-generation, Dodge Ram Cummins pickup.
Both my Ram 2500 trucks (2014 and 2017) have had the tailpipe heat shield removed to facilitate winching a much larger tire into the factory spot. Obviously a bigger tire sits closer to the tailpipe. Only you can decide if it’s too close for you and your application. This Cooper Tires STT PRO is only about one-inch from the tailpipe; close!
35.4″ Cooper STT PRO spare is close the factory tailpipe on this 2017 Ram/Cummins.
For several years I have carried oversized rubber in the factory location on my fourth-generation Ram/Cummins trucks, mostly tires that were 34.8-inches tall. The 295/65R20 Cooper Discoverer STT PRO is substantially taller.
This 2017 Ram has plenty of clearance for the rear-axle track bar.
My 2017 has less room overall than my 2014, as the factory trailer hitch receiver is still in place. (It was removed on the 2014.) There are also steel plates on the inside of the frame to mount the Hillsboro 2000-Series aluminum flatbed. The 3/8-inch plates, one on each side, consume 0.75-inches.
3/8-inch steel plates inside the frame are part of the flatbed mounting.
There are advantages to choosing 35-inch or smaller tires on late-model, heavy-duty trucks instead of the popular 37-inch versions, particularly if they will fit in the factory spare location. These include, but are not limited to, not needing an additional tire carrier or pushing a truck camper further aft to fit a spare in front of the camper (which increases rear-overhang, tail-swing, and impacts weight distribution). Unless your rig is geared low—and most new vehicles have tall gearing—the taller overall gearing that results from fitting larger diameter tires is often a negative, as it results in less torque at the wheels.
Many should ask themselves if they really need the extra clearance provided by 37-inch rubber, or are they just following the crowd, and potentially making unnecessary compromises. There are positives and negatives for nearly every modification and upgrade choice. Generally we need to give something to get something. Everyone should decide for themselves if the juice is worth the squeeze.
35.4″ Cooper STT PRO stuffed under a 2017 Ram/Cummins 2500.
When the Toyo Open Country C/T was initially introduced it was only available in Canada. A few years ago, when that changed, it moved to the top of my must try list. Commercial traction or hybrid designs are my favorite type of tread, and the C/T might be the best, slowest-wearing design I’ve used on any truck in several years; maybe ever.
The Toyo C/T has the severe snow, mountain snowflake rating.
Mount, balance, and tracking
Because the Open Country C/T is an on/off-road commercial-grade tire, there are fewer sizes offered than other Toyos like the Toyo A/ T II. However, there are still six 16-inch, seven 17-inch, five 18-inch, and seven 20-inch sizes available.
For this evaluation I mounted 35×12.50R17 on forged aluminum OEM Ram Power Wagon wheels. They required very little weight to balance, typical for Toyos, and ran smoothly down the highway at all speeds.
104-pounds on OEM 17″ forged aluminum Power Wagon wheel, needing only 1.25 ounces for a static balance.
Initially mounted my 2014 crew cab, which has an SPC offset right ball joint to counteract treads that pull to the right, the C/T would drift just slightly to the left after a few seconds with no hands on the steering wheel, depending on the road crown. (To be perfectly clear, this is because of the offset ball joint and caster settings, not a characteristic of the tires, the C/T does not appear to pull right or left, they are neutral.) On the 2017 Ram 2500 regular cab with Hallmark flatbed camper, the C/T track perfectly straight for several seconds on flat roadways. They were a great match for the outfit, and where I decided to keep them for this evaluation.
Almost all the miles logged have been with this 2017 Ram 2500 Hallmark flatbed camper outfit.
General traction and performance
The C/Ts saw a little of most terrains, including snow, packed dirt, gravel, rock and plenty of pavement. Deep off-highway mud, snow, and deep sand were not experienced; a 10,000-pound camper outfit is less happy on these surfaces, so I only drive on them when necessary. However, with the good void-ratio and siping this tread offers, I’m confident the C/T would perform as well or better than similar commercial-traction designs.
Many modern tires perform well in moderate on-highway or off-highway snow, and this was true with the C/T. However, the mountain snowflake severe winter rating provides extra assurance in wet conditions, and I would pick the C/T over many hybrid or all-terrain designs for winter service. Obviously they are unlikely to perform as well as a dedicated winter tire, but those designs are less versatile on heavily-loaded trucks and rarely offered in larger sizes.
Toyo C/T in a few inches of snow, pulling out of my shop.
The Open Country C/T is quiet for the void it offers, and no louder than the Toyo R/T or A/T II Xtreme with which I am familiar in similar sizes. I’ve recommended the C/T to many of my readers, including a professional photographer and adventurer who lives in Jackson, Wyoming. He has been impressed with their snow capabilities. Another guy lives full-time in his heavy truck camper and uses them.
Wear close-ups
You can see a small amount the feathering on the outer lug sipes. For nearly 6,000 miles without a rotation, this minor visible wear was impressive and not concerning. Appropriate rotations will true-up the tread.
Slow and even wear, 6,000 miles since the last rotation, most of it on highways.
Phenomenal Longevity
As my video assessment and testimonial enthusiastically shares, I am most impressed with the slow rate-of-wear on these Toyo Open Country C/T, better than any other tread in years, maybe ever.
17/32″ of tread depth remaining after 10,000 miles!
The 4,400 miles per 1/32 of depth is exceptional, particularly for such a heavily-loaded, diesel, truck camper outfit. Was the slow treadwear due to a higher than typical percentage of highway miles? Possibly, although my outfit is not a daily driver and routinely sees many more long-distance travel miles than city driving. Double the mileage of most tires I’ve run on diesel trucks, and still 50-percent more than other standouts is nothing short of phenomenal!
Absolutely love these Toyo C/T tires and would like to try them in a 295/65R20 size.
The C/Ts were removed from service only to begin another review, but I’d like to run them again soon, preferably in an 18-inch or 20-inch size with a higher load-index that’s better suited to my heavy camper. The 35×12.50R17 was chosen because I wanted a 35-inch size, and I already had the wheels. At the time I was adamantly against 20-inch tires because the shorter sidewalls offer less flex off-pavement. Though shorter, less flexible sidewalls can be a huge a positive for overall camper stability and handling. My opinion has softened, as long as the tire is tall enough that there’s adequate sidewall.
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James Langan
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My flatbed camper outfit works well, but I’m always tinkering, fine-tuning, and looking for small improvements. I’m still using and loving the TufTruck and Timbren springs, just also want to inflate these air springs again which have been sitting dormant for months.
Essentially the same Air Lift product has been on my 2006 4Runner for over a decade (they’ve been flawless, after another brand failed twice). Also on my 2014 Ram 2500 since new, including up to the Canadian Arctic Ocean a few years ago. That’s a good record, so I’ll give this one failure a pass.
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James Langan
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The questions and answers below were prompted by recent posts regarding auxiliary springs for my truck camper outfit.
Backgrounder
Iggy The Igloo asked about heavy-duty suspension setup and options. Iggy has a Fourth Generation Ram 3500 crew cab, long bed, with a flatbed Alaskan popup. His truck had Firestone air springs, including Daystar cradles to prevent limiting droop-travel, but he did not like how the airbags consumed inches of up-travel. His front axle has Thuren Fab 1.5-inch replacement coils.
Questions, Answers, and Comments
Q] Do you leave your camper mounted full-time?
A] The chassis is always loaded with my Hallmark flatbed camper, tools, and gear. I will remove the Hallmark occasionally to inspect things, but have not done so yet.
2014-and-newer Ram 2500s (like mine) have coils in the rear, so I couldn’t install extra leaf springs (add-a-leaf). My assessment from owning two coil-sprung, late-model Ram 2500s is that the OE rear coils work surprisingly well, even with maximum loads. However, for a big camper it seems nearly everyone (2500 & 3500, F250 & F350) wants or needs additional spring-rate for better all-around performance. Regardless of whether one uses air, rubber, or metal auxiliary springs, the goal is to support the load.
Excessive rear-overhang and tail-swing is popular these days… most of the camper is behind the rear axle. This nice FWC flatbed on a Ram 3500 was at Overland Expo West 2019.F-350/3500 pickups are arguably superior to F-250/2500 series trucks for maximum loads, yet this Ram 3500 with a massive aftermarket rear leaf-spring pack still employs auxiliary air springs for support.
If new or additional springs were not desirable for big weight, then those who rarely fill their trucks to capacity would complain loudly about heavy-duty pickup ride-quality. New trucks generally offer a more comfortable and softer ride these days, both with and without a load, though sometimes this includes compromises for heavy-hauling.
These good Old Man Emu/ARB Dakar springs were obviously flattened by a FWC Raven slide-in camper on a 2011 Toyota Tundra. Auxiliary support was added.
Replacement springs? Add-ons? Both?
Q] Why did you choose Timbren springs instead of an add-a-leaf?
A] My 2017 Ram 2500 uses something similar to an add-a-leaf in the form of beefier aftermarket rear coils from TufTruck. They were helpful, though they’re only designed for an additional 500-pounds. This is not enough, and I’m trying to convince TufTruck to make new coils with substantially more capacity.
The latest single-convoluted Timbrens and my other modifications (aftermarket sway/body-roll bars, shocks, and stout tires) have helped my flatbed outfit drive and handle impressively well for its size, weight, and height.
Aftermarket air springs seem to be the most common heavy-duty suspension upgrade, likely due to their cost, adjustability, and ease of installation. I’ve used air before, though some negatives can include leaks, failure in extreme cold temperatures, and a bouncy ride. Some choose replacement leaf packs, but if the weight is removed the extreme-duty replacements can be too stiff for an unladen truck.
Butt Sag
Q] How have your Timbrens changed the sag? Did the springs put you back up to stock ride height with your load, or do you still have some sag?
A] Neither my 2014 crew cab, which used to carry a Hallmark slide-in, nor my 2017 regular cab flatbed, has ever had a sagging, negative-rake stance. This was largely because I didn’t lift or level the front first. This is the opposite approach of many these days.
For my ’17 Ram 2500, I added the Hallmark Nevada flatbed, gear and other heavy accessories, while experimenting with auxiliary rear suspension options. Lighter-duty Air Lift 1000 springs inside the rear coils were used initially, then TufTruck replacement springs, and now the rubber Timbrens.
Butt low, negative rake stance was avoided by sorting rear load support first. This is after adding TufTruck TTC-1224 HD front (lift) springs.
While I respect companies like Thuren Fab and think their products are great, their parts are focused on a softer ride and/or going fast over rough terrain. Softer springs don’t add load support, and that’s typically the wrong direction for heavy, overland-style, backcountry camper outfits. There are numerous examples online of folks choosing to use softer go-fast springs (particularly on the rear axle) who after installation needed them to be reengineered or replaced because they were inappropriate for their load.
To their credit, I called and talked to Thuren Fab several months ago when shopping for front coils; I shared my measured axle weights and application specifics. They were direct and honest, stating that their front springs would not give the listed lift due to the weight on my front axle (winch bumper, camper, etc.), and they did not try to talk me out of using the higher-rate TufTrucks I was considering. They agreed that firmer springs were a good idea. As mentioned above, in many cases I think the rear springs from the go-faster companies are even less desirable than the fronts for heavy-duty applications; they’re not intended for the load support that heavy outfits need.
Only using products that added spring rate to the rear suspension helped me retain some of the factory-positive rake with my camper. I dislike a butt-low, negative rake. The front remained lower than the rear until I changed the front springs.
TufTruck’s heavy-duty front coils were installed May 2019. The TufTruck TTC-1224 gave me about 2.75-inches of lift, essentially leveling the chassis. Since adding the TTC-1224 I have been playing with the ride height, keeping the chassis either slightly higher in the rear, or level, depending on how I choose to adjust the rear suspension.
TufTruck TTC-1224 HD front coils for Ram 2500/3500s were installed above the front axle, providing both load support and inches of lift.
Compression Travel Loses?
Q] Do you think the Timbren’s inhibit your up-travel more than an add-a-leaf?
A] I have not tried to measure or document up-travel loses; supporting the load and overall handing has been the priority, while not limiting droop-travel. Coil-sprung axles have inherently better droop-travel, but they are generally inferior to leaf springs at controlling body-roll.
Air Lift plastic spring spacer (for lifted rear) droop-travel failure on 2011 Toyota Tundra. This prompted me to use Timbren rubber springs instead of traditional air springs for the FWC load.
In addition to firmer springs, my aftermarket heavy-duty sway/roll-bars limit travel; their performance benefits far outweigh any losses. While I enjoy superior off-pavement performance, I’m realistic about my outfit’s capabilities in the dirt. An empty full-size pickup can do much more, easily and safely, than one with a higher center-of-gravity that’s carrying tons of payload.
As an aside, I am not critical of your adding lift/leveling blocks in the rear. Near the end of my 2011 Tundra project with a Four Wheel Campers slide-in, I placed two-inch blocks under the rear springs and it was fine, loaded and not. Taller or different blocks don’t always cause axle-wrap or other problems.
Small, two-inch block added to the rear of a 2011 Tundra. There was not one before.
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James Langan
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