Bobbed deuce speed

[TristanTyler454]

I’m getting a bobbed deuce that has 53” tires on it, I was just wondering what rpm would be the best for the motor for long distance driving and how much more speed it will have with the bigger tires?

 

[Slate]

Too fast for a truck like that. 70 or so. Be a fun way to kill yourself . Might want to put a headache rack on it and a four point harness, if you're going that fast. 2100 would cruise just fine.

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[porkysplace]

Brakes are your weak point , they were state of the art in 1949.

 

[Elijah95]

Member @4XDesign built that truck iirc


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[Floridianson]

Truck looks good. I do not remember where the torque and HP crossed so do not quoit me but see what 1850 / 1900 rpm get you up to.

 

[cattlerepairman]

Here is a way to figure this out:
Max engine rpm 2500
Axle gear ratio: 6.79

Transfer case: in high it's 1, so can omit.

Tire diameter: 53"

Transmission gear ratios:
1st gear 6
2nd gear 3.31
3rd gear 1.89
4th gear 1
5th gear 0.85

Go to a suitable web site calculator, such as https://www.blocklayer.com/rpm-gear.aspx and plug in these values.

I am getting 68 mph at 2500 rpm with the above. The exact values will depend on the true tire size (1 in diameter difference is a good 2mph in speed difference).

 

[V8srfun]

Nice looking truck. What wheels are those.

 

[Menaces Nemesis]

Your tires appear to be Goodyear AT-2A's. Per Goodyear factory specs, "Maximum Speed Service" is 55 mph for both the 14R20 and 16R20 sizes...
https://www.otrusa.com/wp-content/uploads/2017/07/Goodyear-OTR-Databook-3.pdf
Porkysplace comment about "Brakes were state of the art in 1949" is just friggin awesome! My sentiments exactly, coupled with the fact that your suspension was also state-of-the art in 1949, and your tires likely being older than 10 years, I'd say 55 mph is more than plenty fast (and you may be pushing your luck with that).

 

[TristanTyler454]

Nice looking truck. What wheels are those.

I’m not sure

 

[TristanTyler454]

I just didn’t want to run it at too high rpms and blow the motor

 

[Menaces Nemesis]

Maybe a bit off-topic, but I believe the real advantage with 53" tires is that they would couple nicely with the Spicer 3052 transmission. The 3052 had 5 nicely-spaced gear ratios. If your truck has the typical 3053A transmission, you probably notice one heck of a dip in RPM when you shift from 3rd to 4th gear, even more noticeable with the taller tires. The reason for this is that Spicer modified the 3052, into the 3053, mostly by taking out what was 4th gear position in the 3052, and changing it to an overdrive gear in the 3053. So, basically, the 3053 is missing a gear in between what has always been 3rd, and what is now 4th (4th now being 1-to-1 and used to be the 5th and final gear). They kept the old 5th gear ratio and shift pattern placement, that's why we have that screwy inverted U shift from 3rd to 4th (what used to be 5th) and then straight up to 5th overdrive (which is really like a 6th gear sitting in the old 4th gear slot). With the taller tires, and a 3052 transmission, you could still achieve 55 mph without winding the motor out too much, and you'd have a much nicer, well-spaced shift from 3rd to 4th.

 

[Menaces Nemesis]

A lot of this depends on an accurate measurement of speed too... I know speedo adapters were available to make the gauge read correctly with 395/85R20 tires (46"), but I don't know if there's a similarly easy method to correct the speedo for 53" tires. IMO, using your phone/GPS to track speed, as long as you kept it 55 mph or under, and didn't go over 2550 rpm getting there, should be no problem for the motor. Others will say you should be able to bounce the governor constantly and it'd be fine, I just prefer not to run it that hard. Others may also say you could run it to 75 mph, but remember how much the truck weighs, no airbags, no rollover protection, if it rolls, it's going to wipe off all the "high-spots" really easily, i.e., the cab, mirrors, stack, human occupants, etc.

 

[Karl kostman]

Those tires look huge on a Deuce! RPMs I have found to be a very controversial subject for the Deuce, like the post above 2550 is fine for this individual, myself on the other hand have never had my Deuce over 2200 RPM If I am driving down the highway its at 2200 RPM and with stock tires that puts me around 53 MPH. I also have stock brakes and granted they work exactly as they should and were designed to work but its nothing like modern brakes please keep this FACT in mind whenever your over 50 mph. You lost a bit of weight with the bob job but those tires are going to stop a lot harder than stock tires also. The truck was never designed for tires like this and your going to be pushing a few things running them!

 

[TristanTyler454]

Those tires look huge on a Deuce! RPMs I have found to be a very controversial subject for the Deuce, like the post above 2550 is fine for this individual, myself on the other hand have never had my Deuce over 2200 RPM If I am driving down the highway its at 2200 RPM and with stock tires that puts me around 53 MPH. I also have stock brakes and granted they work exactly as they should and were designed to work but its nothing like modern brakes please keep this FACT in mind whenever your over 50 mph. You lost a bit of weight with the bob job but those tires are going to stop a lot harder than stock tires also. The truck was never designed for tires like this and your going to be pushing a few things running them!

I was wanting to switch to a semi-truck brake system where if I lose one brake I won’t lose all, but Im still new to this truck

 

[USAFSS-ColdWarrior]

Too fast for a truck like that. 70 or so. Be a fun way to kill yourself . Might want to put a headache rack on it and a four point harness, if you're going that fast. 2100 would cruise just fine.

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You raise an important point.

As a follow-up, and from my perspective as a DEATHCARE PROFESSIONAL, I would highly recommend this list of extra documents for the operator:

LIVING WILL
DNR ("Do Not Resuscitate" Order)
POWER OF ATTORNEY for Next of Kin
LAST WILL AND TESTAMENT
FUNERAL PREARRANGEMENTS - Specified and Fully Funded

But I'm just one of those who believes in the Boy Scout Motto: BE PREPARED.

Carry on.

 

[frank8003]

" I’m getting a bobbed deuce that has 53” tires on it, ~"

Your truck was a tactical military vehicle built to do a job. Whatever it is now
it can not do the jobs it was originally designed and built for. Also it is missing two brake drums and the weight/balance is drastically changed to the front. The gauges in the truck are +-10% or worse so don't rely on that tachometer too much.
If you do get it going really fast then don't post it here where all the lawyers can find it.
If it was not way expensive to put dual brakes in a Deuce than hundreds of us would already have done it.

As for long drives in it, report back after a few long drives.

 

[V8srfun]

engine rpm is widely debated and what I have decided to follow as my rule may never be acceptable to others. Governed engines like the multifuel, almost any diesel, tractors, small engines, generators, and any type of industrial engine have a pre set (governed) rpm limit. This limit is not the rpm with which the engine will damage itself but rather the maximum rpm the manufacturer wants the engine to be able to achieve under full load for extended periods of service. The white 2-155 has the same engine as our trucks with different accessories And in order to run pto accessories I think they ran them at 2200 rpm but could safely run all day at 2400 as per manufacturer. These engines have been used in pulling competition and have seen well in excess of 4000 with out issue but this is only for short bursts. For example my Honda beater I think can rev to somewhere in the 6000 range and I have no problem taking it there but I won’t dare hold it there all day.

I have and see no problem with running a deuce at 2400 for extended periods of use and honestly wouldn’t have problem with short bursts above that as long is it was not being held there. But this is based off of my understanding and research on the subject. Others will have different opinions and that is ok. I suggest that you do lots of reading on the subject and form your own opinion as well. You will find that there are lots of opinions on the internet and most of them have merit but not all of them are valid.

I enjoy learning and finding answers to questions that I have. For example if I ask someonehow to do something and they say it can not be done I may say ok and change my approach but I am now curious. Now I have to learn why it can’t be done or in other words figure out how to do what was said can not be done. In my work I was told that there are certain things that I could not do and not to waist my time even trying. At first I let it go but as I became experienced I started to revisit those jobs that (can’t be done) and believe it or not I learned how to do some of them and they are actually really easy. Now I have taught a bunch of people how to do these jobs and we are all making more money and have happier customers. The moral of my long winded response is stay curious and always be willing to learn something even if you think that you fully understand a particular subject you will be amazed what you can learn.

 

[M37M35]

...myself on the other hand have never had my Deuce over 2200 RPM If I am driving down the highway its at 2200 RPM and with stock tires that puts me around 53 MPH.

This.
Cruising down the highway, I don't run above 2,200 RPM. That puts me at exactly 53 MPH with 11x20 tires. I'll occasionally go up 2,300-2,400 while shifting.

 

[cattlerepairman]

The topic of rpm has been hotly debated over the years. There are plenty of LDT engines that were wound out for every shift, run at the governor at 2500 rpm endlessly and they live to see another day. There are other LDTs that grenaded and ended up with a hole in the block. Who is to say that it was the 2500 rpm that killed them, as opposed to decades of abuse by uniformed operators that could not care less about whether the truck lived or died? You don't know the true shape of the engine, unless you rebuilt it, that's what I am trying to say. Treat it with respect and hope it will live, or like a rented mule...really up to you. The trucks are out of warranty!

My LDS is good for 2600 rpm as per the TM. The motor pool saw it fit to turn the governor down to 2400 (the engine came out of a 5ton). I had the tools in my hand and, after some contemplation, decided to leave the governor set as-is.

Flat out, at 2400rpm, with 11.00R20 tires, she does 60mph on the nose (with the 0.71 OD modification). I never go that fast, other than to briefly test that she still gets full fuel flow and the filters are not clogging.

My highest, sustained "comfortable" travelling speed is 90 km/h or 56 mph at around 2150 rpm. She seems to like it there.

 

[Menaces Nemesis]

I should clarify, 2500 rpm is about as fast as I ever wind mine up, *and only momentarily to get the revs up to prepare for the 3rd to 4th gear shift when going up a hill. Otherwise, 2200 rpm is about my max, and that gets me 55 mph in 5th with 46" tires and 3053A trans (GPS confirmed). Shifts from 1st to 2nd are done around 1500 rpm, 2nd to 3rd around 1800, 3rd to 4th 2200-2500*, 4th to 5th 2000-2200.