Widening Inside Rear Steel Wheels

[EricPeterson]

I want more wheel width than the available 17" dually wheels offer.

I want more sidewall -- and tire aspect ratio -- than the available 20" dually wheels can offer.

I want a better ride than the 19.5" and 22.5" tires will likely give me. And I want to be able to service my tires at the local retail tire shop and not need to go to a truck stop.

I really want steel wheels.

Either take-offs or new replacement inner rear steel 5-slots just like the ones my truck came with are about a hundred bucks or a bit more. New replacements are easier to find. Getting them turned into 17x8 steels at Weldcraft in Livonia will cost me another $225 each.

So....

(1) Are there any strength concerns about the wheels when they're two inches wider? Oh, I'm not talking about the welds. I trust they'll be perfect. I mean with deflection in the hub and stresses in the joint between center and rim due to the larger offset loading. I can't imagine the factor of safety would be so low in the design that moving the centerline another inch from the mounting disk will hurt anything. I've found posts in four forums from four guys in fourteen years who have done this, and none posted any follow-ups about issues that I can find.

(2) Can I use them in all six positions, assuming I make appropriate choices, as necessary, for lug nuts and spacers?

(3) Anyone have concerns about the "rigorously tested" Chinese OEM knockoffs? Anyone have any experience with them, good or bad?

 

[KCJackson1]

Couple questions for you...
1 - what tire size are you planning to use on these new rims?
2 - Is Weldcraft just spreading the beads or do they need to add steel to create the new width?

Sounds like you could be adding a bit of unsprung weight which may put strain on other components, so that may need to be taken into consideration.

 

[EricPeterson]

Weldcraft is adding a 2" band on the concave side, turning the 5-slot 17x6 inside rear steel into a 17x8 ( or, more accurately, a 17x7.93 because we lose the width of the saw blade used to separate the two parts of the wheel ).

My spreadsheets are making me lean towards either a 295/70-17 or a 305/70-17, sizes guys generally run by throwing on a "leveling" or modest lift kit and 2" spacers between the stock wheels. I think the 305 makes things too tight both between the tires and between the inside tire and the spring, since my solution is fundamentally different than the typical squeeze-those-tires-down-onto-a-6"-rim approach.

I will be installing a BDS 3" front / 2" rear lift kit based on massively uprated trailing arms, an uprated and adjustable track bar third link, and replacement highly progressive replacement springs in front, and on small blocks and traction bars in back, since the axle already has a bad tendency to wind up the springs under load with the axle sitting on the springs. If that proves inadequate I may opt in the future for replacement spring packs. At first I'll be running single uprated shocks and a mid-range steering stabilizer, both of which might be upgraded in the future.

While I will no doubt be adding some unsprung weight, it's a fraction of the added mass that guys running 19.5 or 22.5 10-bolt conversions deal with. Those steel adapters are enormous, and likely contribute in no small way to the poor ride quality generally attributed to the high-ply-count truck tires. Added mass to the front axle will be relatively small. I've driven some SRW trucks with much larger tires -- larger than I'm planning -- and I know what to expect. It's not that big a hit in ride quality, but it can be a big hit to steering effort and feel. I expect I'm going to have to experiment with stabilizers and offset, using spacers. Not optimum, I know, but if I can't find good answers, I can always have a pair made with the proper offset for the front. Alternately, since the wheels will be steel, I can easily add permanent spacers to the fronts on the inside, if necessary.

Although I'd like to retain complete interchangeability of the six rims....



I've reached a point where there were just too many questions about the quality of the donor rims and the required spacing and clearances in both front and rear. I've had one new wheel sent to Weldcraft for widening. When I get it -- providing it passes his review up there -- I'll probably have one used tire mounted up and experiment with clearances front and rear. If everything looks good, I'll proceed.

 

[KCJackson1]

If you can live with the tire scrub during low-speed turns, your intended setup shouldn't be an issue. 305s would be about 3/8-inch closer between the duals than the 295s, not enough to cause concern about rubbing. 305s could present more of a problem up front, so you may need a spacer to move them further outboard to prevent contact with the suspension on turns.

 

[EricPeterson]

Yup, that's what I get. Spreadsheet displays a space between the duals for 305s at .92 and for the 295s, 1.32.

Which leads to a basic question. Or two. What is a good minimum spacing between the duals, unloaded? I know it's going to vary per tire size. The stock setup with the 235/80-17s is about an inch and three quarters.

And... along the same lines, what's a good minimum spacing between the tire and the spring pack, unloaded? Stock is about 2".

 

[nk14zp]

I'm running 315s on stock width rims and a 3" spacer between the rims on my 97.

 

[EricPeterson]

Yup, examples of owners running 305s or 315s pinched onto stock rims with spacers are everywhere. Not debating that. Seen 'em. Got friends with 'em. They look awesome! What I want to be able to do is run good pressures with a hefty trailer and not see accelerated center tread wear. I want the tire manufacturer to honor their treadwear warranty. I don't want to experience any of the "rolling sponge" effect from pinched tires running low pressures. Sure, there are ways around all the side-effects -- but not all at the same time.

 

[AnonEd]

Which leads to a basic question. Or two. What is a good minimum spacing between the duals, unloaded? I know it's going to vary per tire size. The stock setup with the 235/80-17s is about an inch and three quarters.

Tire data books should have dual spacing requirements by size in the specs. This is old but gives an idea...

 

[EricPeterson]

Should have thought of simply googling the question. Can't find anything for P-metric tires, but I did find a chart for typical 22.5 and 24.5 tire sizes....

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[AnonEd]

Yeah, I tried tirerack.com for your LT305/70R17 mentioned and the duals spacing didn't show up, but both tires appear approved since they list two load indexes. You might have to pick the tire first and get the dealer or manufacturer 800-HELP-ME to tell you what it is. Good luck!

 

[EricPeterson]

Not surprising. I suspect the stock spacing on the stock skinnies is extremely conservative and quite thoroughly lawyerproofed. Please no one take offense with that -- I've got three attorneys in the immediate family.

Consensus from those I've asked generally runs an inch to an inch and a half, which is the same range showing for the semi tires.

 

[EricPeterson]

Been a while. Figured I'd follow up rather than leave this hanging. This build is described in detail elsewhere, but the wheels are the planned Weldcraft customs with 2" steel inserts on the concave side. In front I recover offset and maintain clearances for the new suspension with off-the-shelf billet steel adapters. In back I had custom 2.4" billet steel adapters built with GMC Kodiak Class 4 studs whose spline engagement is better than twice what you see in the stock hubs front or rear. Detailed FEA predicts that these components will not fail before the wheels themselves do as long as all the lug nuts are properly torqued. The factor of safety is still greater than three for a significant overload on both axles. Yes, you can feel the increase in unsprung weight, but the tires are relatively modest and there's no out of spec loading of wheel bearings. Guys running wheelwell cutouts and 40s are placing substantially more stress on their bearings. Use of 2" adapter/spacers in front requires grinding off some of the unthreaded portion of the front studs, and the use of 2.4" rear adapter/spacers require no modifications to stock rear studs at all.

 

[EricPeterson]

I should also add that I tweaked the toe to as close to 0 as i can make it. The stock Nexens were showing some scuffing on the outside edges at 7500 miles. I've got that many miles on the build now and the MTs are showing no asym wear. Also added a Rough Country steering box stabilizer since the new adjustable drag link hits it with more offset loading. Yeah.. I know...it's only 3", but I want to be able to use those steel wheels.

The setup would work equally well with 305s... plenty of clearance to the spring pack in back ... but 305s are nominally "high flotation" and cannot be had in the E1 load range and the 80 psi nominal pressure. The 295 section width is the widest you can get in E1 and 80 psi.

While the wheel prototype was built from a Chinese wheel, I also picked up locally a well-used OEM steel. It was thicker and heavier -- a little. I found a utility body conversion shop in Illinois -- Rondo Truck & Trailer -- who had a stock of used OEM steels on ebay for less than the cost of new Chinese wheels. Bought a full set of seven and had them shipped the couple hundred miles directly to Weldcraft in Livonia. All eight wheels spin true and balance, but I asked the tire shop to rate them from best to worst and put the best two in front and the worst in the shop, and the second worst in the spare cradle. It's almost an arbitrary distinction. None of the wheels have any runout.

I've got no perceptible vibration. The horse-and-buggy suspension does, however, pass through just about any significant irregularity in the road surface....

 

[6V92TA]

Not surprising. I suspect the stock spacing on the stock skinnies is extremely conservative and quite thoroughly lawyerproofed. Please no one take offense with that -- I've got three attorneys in the immediate family.

Consensus from those I've asked generally runs an inch to an inch and a half, which is the same range showing for the semi tires.

figure them peeps in Detroit know a thing or two about wheels, durability, driveability and handling. LOL