22'5 Semi Wheel upgrade?

[NIsaacs]

Hey Big, do you remember back in the day, the Camper Special 12:00x16.5's the RV guys used with their 4x2 trucks? They were a small super single

I dang sure don't like them on a big truck, they just don't look right Give me the standard duals.

Nick

 

[BIGNASTY]

At work they ran the super-singles, on Semi's I really didn't care much. But on a Truck & Trailer it got REALLY SQUIRRELLY when I was dropping off Whitewater Grade East bound and the turntable tire blew with a SS on it. It took a few minuets for me to let go of the seat of the truck, and I HAD BOTH HANDS ON THE STEERINGWHEEL!!!! talk about PUCKER

And all for a few extra pounds of weight that we COULD carry that most times we didn't. And then to find a out of town tire service that carries that size tire was almost impossible. They ended up running them on Semis but left the Truck & Trailers alone with the old school duels. Going to the mountains when chains were required was foul, it was like throwing 3 rail chains WAPITA!!!

 

[AH64ID]

yes it will- the good part is I have the 4.10 gears so it should bring my rpms down to a good sweet spot

I think you will find you have overshot that sweet spot by a LOT!!!

I also have to assume the 245/50R22.5 is a typo, as 245 is not a SS width. 445/50R22.5?? A 445/50R22.5 has a rev/mile of 517, which matches the 39" you referenced. They are just over 40" tall static.

You said you have 4.10's which means an auto, so the .69 OD of the 48RE and 4.10's with a 39" tire means you have to be doing 82-90 in OD to be in the "sweet spot" which is above their 75mph tow rating. Cruising at 75 would be 1830rpms, which is generally too low for towing at that speed.

In 3rd you will gain some ground 57-71 will be good towing at 2000-2500, but 1st will flat out suck with any load. 1st will now carry you all the way to 30mph before a shift at 2500 rpms, maybe a little slower since the torque converter won't lock. Getting a HEAVY load moving will be fun and generate a lot of heat.

The tires alone weigh ±180lbs, plus the wheel. The Alcoa 14" wide wheels weigh 54lbs, for a total of ~230lbs counting for tread wear, which is around 50lbs heavier per rear corner than stock.. .really not too bad. I am about 50lbs heavier per corner with my SRW 19.5's.

EDIT: I see you have referenced 245's and 445's in the thread, so 445's are probably the correct size with 245 being a typox2.

Actually duals are centered, one is offset in and one is offset out, for a total of zero.

Nick

They have an effective offset of zero, but I am not sure that the WMS is centered on the bearings. IIRC the WMS is outboard of the bearing centerline. I do know that inner wheel bearing on a DRW is larger than a SRW axle, not for load but for the wider footprint and loads of 2 tires vs 1. Both DRW and SRW have the same rating.

 

[Shadrach]

Looking on this site http://earthroamer.com/xv-lt/driving/on-road/ where they build an F550 into an RV they use 37" 22 ply Michelin tires 295/60R22.5 Singles with Alcoa rims instead of the stock 225/70R19.5 that Furd put on the truck.

Now if they would Just build it on a Dodge 5500.... Doesn't matter I couldn't afford it anyway. David

 

[MadMax06]

I think you will find you have overshot that sweet spot by a LOT!!!

I also have to assume the 245/50R22.5 is a typo, as 245 is not a SS width. 445/50R22.5?? A 445/50R22.5 has a rev/mile of 517, which matches the 39" you referenced. They are just over 40" tall static.

You said you have 4.10's which means an auto, so the .69 OD of the 48RE and 4.10's with a 39" tire means you have to be doing 82-90 in OD to be in the "sweet spot" which is above their 75mph tow rating. Cruising at 75 would be 1830rpms, which is generally too low for towing at that speed.

In 3rd you will gain some ground 57-71 will be good towing at 2000-2500, but 1st will flat out suck with any load. 1st will now carry you all the way to 30mph before a shift at 2500 rpms, maybe a little slower since the torque converter won't lock. Getting a HEAVY load moving will be fun and generate a lot of heat.

The tires alone weigh ±180lbs, plus the wheel. The Alcoa 14" wide wheels weigh 54lbs, for a total of ~230lbs counting for tread wear, which is around 50lbs heavier per rear corner than stock.. .really not too bad. I am about 50lbs heavier per corner with my SRW 19.5's.

EDIT: I see you have referenced 245's and 445's in the thread, so 445's are probably the correct size with 245 being a typox2.



They have an effective offset of zero, but I am not sure that the WMS is centered on the bearings. IIRC the WMS is outboard of the bearing centerline. I do know that inner wheel bearing on a DRW is larger than a SRW axle, not for load but for the wider footprint and loads of 2 tires vs 1. Both DRW and SRW have the same rating.

I appreciate your input. With that said would you recommend I stick with my Alcoa 19.5" duals and run a H rated 16 ply tire to make up for the wear
Also since you have 19'5"S where are your rpms at 70MPH. do you have the 4.10's? Ratio with 19.5 tires?

 

[SnoKing]

Hey Big, do you remember back in the day, the Camper Special 12:00x16.5's the RV guys used with their 4x2 trucks? They were a small super single

I dang sure don't like them on a big truck, they just don't look right Give me the standard duals.

Nick

I had wide 16.5's on my 1993 Dodge/Cummins. Ruff ride does not go far enough in talking about how 16.5 ride!!!! It did however look good!!! SNOKING

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[AH64ID]

I appreciate your input. With that said would you recommend I stick with my Alcoa 19.5" duals and run a H rated 16 ply tire to make up for the wear
Also since you have 19'5"S where are your rpms at 70MPH. do you have the 4.10's? Ratio with 19.5 tires?

It's hard to say, if your just going for wear then the SS is the way to go. It will effect towing quite a bit to go with such a tall tire thou, so I am not sure they are the best compromise if you tow heavy.

LRF or LRH will probably wear the same, I am not sure the tread is much tougher as I think it's mainly sidewall. Have you looked into 19.5's in a solid rib tread?

With my 245/70R19.5's and a NV5600 w/ 3.73's I am 1980 at 70.

I too eat up tires, but that's just life towing on back/dirt roads with decent weight and torque.

Something like the M143 from Toyo would work well, and it happens to be a LRH tire. It also has a higher speed rating than many 19.5 or 22.5 tires at 81mph.

 

[MadMax06]

It's hard to say, if your just going for wear then the SS is the way to go. It will effect towing quite a bit to go with such a tall tire thou, so I am not sure they are the best compromise if you tow heavy.

LRF or LRH will probably wear the same, I am not sure the tread is much tougher as I think it's mainly sidewall. Have you looked into 19.5's in a solid rib tread?

With my 245/70R19.5's and a NV5600 w/ 3.73's I am 1980 at 70.

I too eat up tires, but that's just life towing on back/dirt roads with decent weight and torque.

Something like the M143 from Toyo would work well, and it happens to be a LRH tire. It also has a higher speed rating than many 19.5 or 22.5 tires at 81mph.

I just looked and Atlas makes an all position LRM tire (22) ply for $156 each. not sure on speed rating yet

 

[MadMax06]

Ok- still looking into this- Found a good resource online and shows that if I had 39" tires going 65mph would put me at 2290 RPM having the 4.10 gears. Is that not a good spot to be, especially with fuel mileage or is the problem getting up to the 65mph to hit the 2290 rpm mark? Thanks

 

[SnoKing]

Ok- still looking into this- Found a good resource online and shows that if I had 39" tires going 65mph would put me at 2290 RPM having the 4.10 gears. Is that not a good spot to be, especially with fuel mileage or is the problem getting up to the 65mph to hit the 2290 rpm mark? Thanks

That does not seem right. Even with a manual transmission the RPM should be lower that that in final OD gear. Did you account for OD ratio in top gear? Snoking

 

[MadMax06]

no. used these two calculators.
http://www.tacomaworld.com/forum/tirecalc.php?tires=235-80r17-265-80r22.5

http://www.wallaceracing.com/calc-gear-tire-rpm-mph.php

 

[SnoKing]

no. used these two calculators.
http://www.tacomaworld.com/forum/tirecalc.php?tires=235-80r17-265-80r22.5

http://www.wallaceracing.com/calc-gear-tire-rpm-mph.php

Where do you input OD ratio? Snoking

 

[SnoKing]

Try this one. My 47RE has a .69 OD

At 2290 RPM with 4.10 and 39" tires third gear 1.0 is 64.8 MPH and OD .69 is 93.92 MPH. Snoking

http://www.tremec.com/calculadora.php

 

[MadMax06]

http://www.powerspec.cummins.com/site/home/index.html

 

[MadMax06]

Best axle gear ratio is a somewhat loaded question and does consider tire diameter. I wrote magazine Q&A columns for fifteen years in the 4WD Jeep, 4x4 truck and muscle car fields. Gearing was a constant question with tangible solutions. In the late '80s, I got a nifty calculator program from Wolverine, intended for camshaft selection, tire sizing and the right gearing choice. Though DOS based and no longer accessible (thanks to Microsoft 7 and up), that program provided a great calculator utility.



Fortunately, there are similar calculators for axle gearing and tire diameter now online. Here is one downloadable software calculator that you can trust. It's directly from Cummins and includes your '06 Cummins 5.9L ISB Dodge Ram 4x4 Mega Cab—directly from the source: http://www.powerspec...home/index.html. You'll find a great calculator for Cummins' commercial diesel engines. Note: I use the earlier version 4.2.4 software for the 5.9L ISB engine; the latest version only covers the 6.7L ISB, although this engine is similar in most ways for this calculation.



I use this program, and it's very cool, addressing tire diameter, axle gearing (include the 0.69 ratio for overdrive on the 48RE) and engine rpm. Cummins has a recommendation for optimal commercial performance, which is actually close to the weight and load factors you and I anticipate: occasional towing, hefty accessorizing, the lift (which makes our trucks like pushing a billboard down the road) and both town and, primarily in my case, highway use.



There's one caveat when using the PowerSpec program: The program aims at commercial haulers. Cummins wants to see a higher rpm (2100-2400) than I prefer. My approach for maximum fuel efficiency with a modified truck weight similar to ours (9000-9300 pounds curb weight) and the 5.9L H.O. ISB engine is in the neighborhood of 1900-2000 rpm at highway cruise. I see a prompt and notable drop in fuel mileage for engine speeds over 2000 rpm—although power remains great between fuel stops!



For gasoline powered trucks or a trail Jeep, here's a quick reference chart that you'll find useful: http://www.jeep4x4ce...om/calculators/. The chart's baseline is 65 mph with a 1:1 high gear ratio. You need to factor the overdrive ratio into the final engine speeds at cruise. Multiply the rpm times 0.069 for your 48RE transmission. We have a significant 31% overdrive.



There are other calculators online that allow for plugging in the overdrive ratio variable (0.69, 0.75, 0.85, etc.). Here is one that offers space for the overdrive ratio in the equation: http://www.4lo.com/4LoCalc.htm.



As for picking between 4.10, 4.56 and 4.88 gears (the only ring-and-pinion options for the AAM axles) in your specific truck, the answer is subjective. I'll tackle the question, though, and will share what I believe each of these ratios will deliver with your 37" tires:



1) 4.10:1 would nearly restore your gearing to the OEM level with stock diameter tires; still some overdriving effect, more like OEM tires with 3.55 gears instead of 3.73:1. I would definitely not use this gearing for trailer pulling. Town traffic would be sluggish, too.



2) 4.56:1 would be quite livable, all around. Acceleration would be slightly better than OEM tires and gearing at the OEM curb weight and normal cab height. This is my gearing now for 35" tires, and I know that a change to 37" would be feasible. I'm spinning the engine close to 2,000 rpm at 65 mph...To drive at 75, like you want, the Cummins calculator actually thinks the engine should spin faster—I think it would be right on for performance and reasonable fuel efficiency at this load. (I'm figuring 37" tires at 560 revs per mile. Is this correct for your tires? Confirm for calculations.) 560 revs per mile and 4.56 gears in overdrive cruise mode would put your engine at 2202 rpm for 75 mph and 1909 rpm at 65 mph. This would deliver peak fuel efficiency at 65 mph and decent performance at 75 mph, a satisfying all around choice for your truck with the 5.9L ISB engine.



3) 4.88:1 would be okay if you trailer all the time and would like to hold speed at 65-70 mph while towing. (You could push to 70 mph if fuel costs do not sway your thinking.) Acceleration in stop-and-go would be impressive, the load on the engine and 48RE transmission would be less. Extra piston travel per mile could reduce lifespan of the 5.9L engine; however, the reduced load would likely offset this...If I had a 9-horse trailer, this would be my gearing, holding the truck to 65 mph and keeping the engine and horses happy!



As for target mph on the highway, that's a subjective question, too. You have a plan for 70-75 mph at cruise, and with a trailer, that would keep the engine at Cummins' recommended 2100-2400 rpm range in overdrive. While I repeatedly emphasize the 1600-1900 rpm "sweet spot" for fuel efficiency, there is the realistic lugging factor that places the engine under stress below 1900 rpm when toting severe loads.



So, I think you'll be happiest with 4.56:1 gearing at 37" diameter tires. I can feel with our truck that it's doing just what I wanted: Delivering trailer pulling torque, adequate horsepower and peak fuel efficiency at 65 mph. 4.10:1 would have restored the tire/gearing to stock, but as I've noted, this truck is way too heavy and tall at curb (unloaded with fuel in auxiliary tank) to survive on stock equivalent gearing. I've equated my modified truck to pulling a tent trailer—all of the time!



As for highway versus town driving, you need to consider both. Town driving is getting the mass rolling. Highway is keeping that mass rolling. Both impact fuel efficiency and loads on the engine. Again, the 4.56:1 will enable town driving without taxing the powertrain much. 4.88:1 would make town driving easier, especially when moving a big trailer from a dead stop; however, the highway cruise engine speeds you plan would make 4.88:1 wasteful on fuel. (2,357 rpm at 75 mph in overdrive is near peak rpm for Cummins commercial use recommendations.)



You're right about dyne tests to confirm power curves on a dramatically altered engine with camshaft modifications, fuel timing changes, added turbo boost and other alterations. Let me start by saying "chips" will not dramatically alter the torque rise on a diesel engine. Tuning measures will unleash suppressed power, but the curve shape will be similar.



Camshaft, compression or turbo mods are another story, as changes here can move the power curve around. Although everyone seems horsepower fixated, diesel power is all about the quick torque rise and peak at a lower rpm. I believe the Cummins ISB engine has the edge here, a lower rpm, traditional diesel design suited for medium duty truck use and patterned after commercial truck and off-highway equipment performance.



That said, drive your Cummins diesel accordingly. I have "redlined" our truck's engine to its advertised 3,400 rpm peak on less than a half-dozen occasions in 121K miles. Redline is pointless when the engine's torque peak is at 1,600 rpm. 2,400 rpm should be a sensible peak, maybe 2,800 rpm on a lengthy grade with our trailer in tow—and certainly not for a sustained period.



Note: Gale Banks and I met after the Off-Road Expo in 2011. I visited Banks Power at Azusa, and we talked. Gale is a Duramax diesel dealer and strong advocate, and his descriptive for the Cummins ISB engine was, "We blow the cylinder head off the block on those engines!" They do when drag racing with engines built for extreme output and competition—or even when running these engines "to destruction", presumably at redline for sustained periods. I have known Gale for thirty years, and he is expert at high performance and race engineering. By contrast, I served an apprenticeship with the Operating Engineers Union in the mid-'seventies, and we worked large highway construction jobs. If we ran a 1693 Cat inline six off-highway equipment engine much over 1,500 rpm, we were in jeopardy of losing our job. These engines peaked horsepower below 2000 rpm and peaked their torque just off-idle!



Trust this helps. It's really not that complicated once you establish a firm goal. Even with the four-speed automatic, I've gotten as good or better fuel efficiency with the 48RE as others with the NV5600 6-speed manual overdrive transmission. We get the added advantage of a torque multiplying converter, too!



I can assure owners with the manual transmission, Cummins engine and the right gearing that 22-25 mpg fuel efficiency is very attainable on the highway under light loads and at normal cruising speeds...It all comes down to driving technique. Running empty, my upshift points would be between 1,400 and 1,600 rpm per gear.

 

[SnoKing]

So you rambled all over, however did not address the fact that 4.10's and 39" tires is not 65 MPH in OD. Direct yes, OD is 93.92 MPH. Snoking

 

[AH64ID]

Ok- still looking into this- Found a good resource online and shows that if I had 39" tires going 65mph would put me at 2290 RPM having the 4.10 gears. Is that not a good spot to be, especially with fuel mileage or is the problem getting up to the 65mph to hit the 2290 rpm mark? Thanks

As mentioned that is in drive, not overdrive. Overdrive at 65 will be 1584....so plan on keeping the stock turbo around, or a very small secondary if you go twins. Overdrive would be all but useless with a bigger single and those tires, especially with the 75 mph rating.

A auo Trans does get torque multiplication, but that is maximized with zero output shaft speed... i.e. Starting from a dead stop, and that's where it needs it with a 1st ratio that is 44% of a manual trans.

The redline on your engine is 3200, not 3400, and has a rated rpm of 2900. Fuel cuts very quickly from 2900-3200+ and it is nearly pointless to rev above 2900 on stock tuning.

It takes more than just torque to tow up a grade, you need torque and horsepower. Torque tells you how much work you can do, and horsepower is how fast you can do it. Torque has no time associated with it. 2200 is the stock motor sweet spot for towing (5.9 HPCR), and it runs up to about 2400-2500 before the restrictive turbine starts to take an effect on long pulls.

1600 rpms makes 610 ft/lbs but only 185 hp. 2200 rpms makes at least 555 ft/lbs and 232hp, it's probably closer to 250/600 and will pull hills a lot better than 1600 rpms.

Most trailers towed by pickups have tires that are only 65 mph rated.

39" tires with a auto and 4.10's will be less than enjoyable while towing below 20mph, really annoying below 10 mph. OD will also be useless with any decent trailer, or small incline. You effectively have a 3 speed auto with that setup, and I'm not sure even 4.88's would do enough good.

 

[SnoKing]

Bigger is not always better. Because 22.5" rims and tires can be fitted under a pickup does not mean it is a good idea. Note the balance issue posted by another user. The suspension of a pickup may be to light to account for balance issues with tires this size. Snoking