16.00 on M929A2, pros and cons

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tobyS

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I'm thinking about 16.00's on my M929A2 which would free up the 395's on it for my M35A3 4x4. I've read plenty of threads on using 16.00 but none specific on the M929A2.

First, my 929 is turned way down on fuel and rpm...in fact it's a dog. Governor seems to be set at about 1950 and down hill, I can hit 2000. Transmission shifting is even affected by the low rpm but I've found a combination of manual shifting that works pretty well. Putting on the larger tires will make that much worse on the low end.

Second, with the low fuel going into the engine, I cannot bring the loaded dump out of a hole without going to low range. In fact that is the only way, first high range will not do it. It simply does not have the power. Backing....there is no way that I can back where I need to be in high range. I try, but with a load and soft ground, I run out of power and it (backing in low range) is clearly a NO-NO for the later 5 tons. 16.00 will make this problem much worse. The truck is way too nice to think of changes to the OEM layout like a different TC or tranny. I'd rather sell it and start with an older truck, building a more robust (for backing under load) but highway ready driveline.

Availability of 16.00's seems high...probably not as many on the market as the 395's though. The Michelin 395's on the 929 would go to the deuce with 2 extras (including rims)(making a powered trailer a possibility).

I like the looks of the big tires but am on the fence about this change. While I want to "turn it up", right now this dog gets down the road reliably, be it a bit slower than I would like, but I'm not out on highways that require me to keep up with traffic too much.

What say you? Is it worth the extra stress on the TC since I know that I cannot avoid low TC range and "some" backing with a load.

Either way, I want to put more fuel in and get the gov to around 2200-2250.

Pic with the 395's. I keep a wood block in the front of the bed so rain will not collect.
 

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Jbulach

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I’m guessing you linkage, or pedal stop is not adjusted correctly. I think the inability to start with a load, off road, going forward in an a2 is normal, but I have never been even close to not able to move in reverse, high range. Sometimes you have to hold tho throttle wide open for 3-5 seconds to spool the turbo up. My motor will run almost 2300rpm free reeving, and 2100 on the road. If you haven’t already lost your mind dealing with your power issue, I think you’ll be fine with 16s once you figure this out. Now that I have my pyro installed I plan on tweaking my pump a bit to see if I can get rid of most of my low end stall problems.
 
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tobyS

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I have to agree with 98G and AndyDP, that I need to get the power worked out. Jbulach, when you get yours right, come and do mine. It doesn't seem to be the pedal that is the issue with rpm, but I'll take a look at it. Getting into that pump and governor is more than I want to take on while I have so many other projects going.

As I was writing the above, I was thinking that reducing my low end torque by about 25% is going to make the problems worse.

I need tires on the deuce project and the old KISS comes to mind....don't get into changing 2 vehicles tires on the rims.

Staying with 395 makes so I could swap between vehicles later, if needed. Both vehicles (will have) a virgin spare that could rotate for steer on the 929 or deuce to keep fresh tires up front.

I want to build an 809 series 4x4, so will do 16.00 then.
 

98G

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I have 16.00s on two of my trucks. I like them.

But one of the trucks is an M925 with an unmodified NH250 that serves mostly as a toy and not loaded heavy. Even in this usage the loss of low end acceleration was pronounced.

The other one is an M818 that has had a turbo added to the NH250. The turbo adds enough to more than compensate for the 16.00s.

In the setting of a dump truck that actually gets loaded heavy, with a 8.3 liter engine, 395s would be my choice even if prices were the same. Since 395s are considerably cheaper than 16.00s that makes the choice easy.

Having compatibility with your 4x4 deuce project is just an added plus.

Consider also that to run 16.00s on a 939series truck is going to bring with it the additional cost of HEMTT rims to not have clearance issues on the driver side front.

Everything is a compromise. But in the setting of a dumptruck you'd be giving up too much for the 16.00s.
 

tobyS

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Have you considered 16’s on your M35a3 project?
Not really. But I do have room to go up in the front, I'm 3" lower than the back and the angle is noticeable. I'm sure I would clear the wheel well opening in the back, no problem in the rear at all.

Do the 16.00's fit the A3 "metric" rims? 11" wide would seem to be no problem and I have beadlocks.

What has to be done in the front to accommodate them?

I have the larger 1.5" pistons in my brakes (front), and changing them in the rear and have a 50/50 split system, so brakes would be okay. Like Gimpyrobb says "cool beans".
 

Steelreaper80

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Does anyone know what the speed loss will be on the top end from 14.00R20's to 395's? I am still on the fence on either 16.00's or 395's. I am always towing heavy but I also want to be able to do at least 60 MPH.
 

simp5782

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Around 6 to 8mph


Towing you do not want 1600 with no power. It makes the m322 ride a little more level but itll be slower. Alot slower. With my NHC250 Turned up. With the cat 16spd and 1600 with the t1138 transfer case I could barely even get into overdrive unless I was on flat ground.
 
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Steelreaper80

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Around 6 to 8mph


Towing you do not want 1600 with no power. It makes the m322 ride a little more level but itll be slower. Alot slower. With my NHC250 Turned up. With the cat 16spd and 1600 with the t1138 transfer case I could barely even get into overdrive unless I was on flat ground.
Thanks Wes! 395's it is.
 

tobyS

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Yea....what Wes said... when the spedo says 60, I'm at 52-53 with the 395. I want to get the RPM to about 2200 and I should get a true speed close to 60.
 

Buffalobwana

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Toby, sounds to me like your answer is in your question.

1. Your fuel is not turned up. Do that and add gauges first. See how she runs.

2. If you can’t do the job with 395’s, you can’t do it with 16.00’s.

My 923A2 was the slowest, off the line, I have ever driven. (It was a Depot rebuild) So much that it worried me in traffic. Then I put 16’s on it. So it looked cool dragging itself into traffic :)

I bumped up the fuel, and it helped low end acceleration, but the simple “turn this top screw” increase didn’t gain me any top end at all, only in the zero start to 10 mph range increase in acceleration.

She blows smoke now!

BTW, I routinely hit 70 mph on the hwy. avg 65+/- with gps confirmation. That’s with my homemade cruise control turned on. (No, not throttle lock).
 

Lukes_deuce

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I'll also say I would go 395s. Just put 16s on my 923a2 that has a dump hoist on it. Haven't loaded it up yet with my usual 7 yards of crushed concrete or fill but with about 2000lbs in the bed and a S280 in tow, she's running hot in 5th and down to 3rd up hills. I have the fuel turned up and have to live by the EGT gauge. I had to turn the main fuel rack adjustment down to even drive this combo.20190519_120025.jpg

I don't plan on working my truck that much, so I'll have to live with it. I will be adding an intercooler one day, almost have to if your planning on working the truck with 16s.
 

CNC2013

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Hi guys, this is some good advice. I'm in the process of buying a M923A2 right now that has the stock dual rears and I wanted to go up to the 16's for my use as a lake toy. Only thing I would be hauling heavy is a 5th wheel camper through some thick sand. Sounds like I might have to look into the 395's instead as the truck would occasionally make the trip from the lake back home which is around 160 miles.
 

Jbulach

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Hi guys, this is some good advice. I'm in the process of buying a M923A2 right now that has the stock dual rears...
Theres something wrong with this statement. Either the truck is not an A1 or A2, or someone stole the singles off of it? We need pics!
 

Buffalobwana

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OP was hauling very heavy loads up steep inclines.

I don’t see why 14.00’s or 16.00’s shouldn’t
be just fine.
 

CNC2013

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It's an 1989 with a cummins non turbo and allison 5spd. I really need to go a larger tire, have seen alot of the 9 series truck running the 53" tires but didn't really consider any "Cons" over all the "Pro's" to having them in the deep sugar sand. I've seen these trucks with the duals 11" have a harder time through the sugar sand when pulling a camper and then the same model of truck with the 53's more or less floats easily through.
 
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