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Crusty's 75th Annv PW #1590 build/mods adventure

OK, so I've been having a issue in that my mirror mounted auxiliary reverse lights would go out every time I started backing up the truck.
Asked the question on here and others say theirs works fine, and we couldn't understand why mine didn't.
Then one member said something about Cailf not allowing cargo lights on when the truck is moving.
So I went digging into the owners manual. Sure enough, right there in black and white in a note, it states California AND Mississippi do not allow the auxiliary reverse lights to work while the truck is moving. WTF?

So me being me, I started looking around in my ALPHA OBD and found this.

If I go into the BCM, scroll to the bottom I find
Car configuration change.

So I click on it and then go to select option and scroll down about half way and find
2014 CBC Config I/O & Feat.-Baggage (Cargo) Lamp Output Disabled with vehicle moving

I then hit set value and select no. then start.
And it changed my setting.

Backed everything out and tried the mirror lights.

THEY WORK! So I now have the mirror axillary reverse lights on my Calif truck. Yea me.
 
So today I also finished off wiring up power to my race radio and speaker. I tied it directly to the battery with a 30 amp fuse. Simple and easy and I dressed up the wiring.
All that's left is to figure out a antenna mount without drilling a hole in the cab roof. Bullet Proof Diesel makes one, but not for the 19 plus. They are still working on the design. And it's not cheap, $350 for a chunk of alunimum. May have to talk my buddy with a 3d printer into helping me make one.
Anyways, my radio knows me.
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Crusty old shellback said:
Well I guess my mind was not working right. Or I was wishing for something that wasn't. :rolleyes:

I reprogramed the truck for a tire size of 34.75". Now my speedo is off by almost 3 MPH. :oops:

I wasn't thinking right. I need to go smaller, not bigger. So tonight I'll reprogram the tire size to 34.25" and see how that does. Should be close.

And as an FYI tires are BFG KO2's 35X12.50R17 on the factory rims running 40PSI front, 35 PSI rear.
Click to expand...
fwiw

I measured my 285/75-18 which mfgr specs at 35.1” and they were actually 34.4” at my desired psi.

I used AEV procal to calibrate my truck to 34.4” and My speedo is 1mph low at 35 (2mph low at 70) if I trust the radar signs. They’re consistently showing me 1-2mph low. I haven’t bothered to change it.
 
ramblinChet said:
Most manufacturers provide a Revolutions Per Mile number for each specific tire. Don't forget that when your tire is loaded with the weight of the vehicle the effective diameter decreases. When manufacturers provide diameter they are measured unloaded.
Click to expand...
Does the diameter decrease or does it just flatten out/deform? I feel like the diameter doesn’t change. Im no engineer unless you consider a pool dude to be a recreational aquatics engineer.

Ok ok it changes with pressure which also increases as the tire gets warm. But, at a given psi and temp.. I don’t think the diameter decreases. The height decreases because the footprint grows as the tire squishes down. But you’re just changing the shape by elongating “one side” not the diameter. You’re making the circle into somewhat of an oval, but material isn’t added or subtracted.
 
But we are not talking about diamater.
We need to look at circumfrence. That will tell you how far you move for each revolution. And the computer has you put that number in in mm.
Hence 2710 mm is right at 34" Diameter with the tire at 35 PSI mounted on the rear of a unloaded truck.
 
Oh, and the goodyears that came on the truck are not 33" like the numbers say, I measured 32 with it mounted on the rim at 55 PSI but not on the truck.
The higher the PSI, the larger the diamater may be as the tire will stretch some.
 
Crusty old shellback said:
But we are not talking about diamater.
We need to look at circumfrence. That will tell you how far you move for each revolution. And the computer has you put that number in in mm.
Hence 2710 mm is right at 34" Diameter with the tire at 35 PSI mounted on the rear of a unloaded truck.
Click to expand...
Yes you’re right. I was talking about circumference the whole time but I kept saying diameter. Circumference gives you revs/mile. The diameter does change with load, the circumference I was questioning.
 
2673mm equates to 34.5 " dia
Take 63360 inches in a mile, divide by 602 revolutions and you get 105.25 inches. Convert to mm and you come up with the same number 2673mm.
So who's math is correct?

Ok, just converted the 105.25 cir to dia and get 33.5".
So BFG is wrong?
Or I need to up my pressure to stretch the tire to 34.5 that they say. Maybe thats measured at max PSI which is 65.
 
Crusty old shellback said:
2673mm equates to 34.5 " dia
Take 63360 inches in a mile, divide by 602 revolutions and you get 105.25 inches. Convert to mm and you come up with the same number 2673mm.
So who's math is correct?

Ok, just converted the 105.25 cir to dia and get 33.5".
So BFG is wrong?
Or I need to up my pressure to stretch the tire to 34.5 that they say. Maybe thats measured at max PSI which is 65.
Click to expand...
Probably max psi.
 
Yea, when I went back and calculated the diamater, it comes up with 33.5, same as you.
So BFG calls it a 35, but says it's only 34.5, until you do the math and it comes up 33.5. :rolleyes:
 
Brewbud said:
Have you done the rear seat tilt mod? I did it on my 07 and I mounted the Kenwood amp on a board I made to fit the back wall. It worked very well. I also had a stereo amp and power distribution junction on the back wall. I was also able to store some thin items back there. Just another option.

I have yet to do the mod on my 2020.
Click to expand...
Got the seat back mod done. The radio sticks out too much for how I wanted to mount it. So just kept to my original idea.
But I did move my recovery straps back there and freed up the storage box under the seat. Easier to get things quickly from the storage box.
 
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