mikeeg02
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If your empty, drop the rears to 40 . That's where I run my 16" dually rears empty ~55 in the front
F450 suspension ?
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Tree Trimmer
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he's just gotta find that happy medium and decide if he wants to air them up every time he loads to have the best ride unloaded, or if he's gonna run them somewhere in the middle and give up some potential ride but not have to air them up every time cuz he let the air out to get the most ride he can.
mikeeg02
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I agree. I was surprised the other day when I put a pallet of sakrete in the the bed. Even with that at 40 psi the tires had plenty of room. Though I have the stock 235/85 size. A pallet of sakrete is ~3,300 and it ended up sitting rearward, because they couldnt push it in because of the tailgate.
The problem comes from the sidewalls getting hot from being under inflated for the weight.
Have you figured out how much weight the tires can hold at 40psi?
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mikeeg02
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I have personally never seen a tire data sheet that gives tire ratings at anything other then a max rating (not to say there arent tires rated that way, I just havent seen it myself) at 40 psi in a DRW configuration, even with that pallet of sakrete on the bed (though only a 25 mile trip home from lowes) the sidewalls were not any warmer then usual. Towing regularly heavy, or when I get loaded for coal which puts ~1.5-2 ton in the bed, plus another ~4.5-5 ton in the trailer I will air up my rear tires. I wouldnt advise to tow heavy at 40 psi but.............
Like I have quoted above, he typically drives it empty and even when he tows he is towing a jetski or a small single axle trailer. If he gets 2k on the tongue of that truck, I would be surprised. I keep my rear tires low to help with tire wear, because anyone running 235/85-16's knows they always wear out the center before the outer lugs, its just the dually way.
In a SRW configuration, I have never had any trouble running 65psi flat. Though in a short bed configuration, so less can be put on the rear axle, and the trailer tongue weight properly setup. Just my experience, your mileage may vary.
tbsimmons
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Do not haul anything with 19.5's and 40 psi in them or you will be asking to break a bead. If you don't know the beads are very different in half size tires. Don't compare what someone does with 17's or 16's wth someone with 19.5's.
Its harder to do with 19.5's because of the sidewall but to figure pressure out for tires and load do the following:
Get the truck straight in the road.
Mark across the tread from the inside to outside.
Drive straight for a few 100 feet or so.
Look at the mark across the tread.
If it is evenly worn, you have the right pressure.
Worn in the middle, too much pressure.
Worn on the side, not enough.
Its harder to do with 19.5's because of the sidewall but to figure pressure out for tires and load do the following:
Get the truck straight in the road.
Mark across the tread from the inside to outside.
Drive straight for a few 100 feet or so.
Look at the mark across the tread.
If it is evenly worn, you have the right pressure.
Worn in the middle, too much pressure.
Worn on the side, not enough.
mikeeg02
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My mistake if he said he's running 19.5s disregard what I've said . That's a commercial Tire. Our '11 450 at the shop is a pickup 450. It either has 17 or 18s. Can't remember . D80 rear, dissapoitinigly enough
Zmann
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the anemic 450 d80 years SMH
OP has is a real 450 with a D110
OP has is a real 450 with a D110
footlong70
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Something else I should add when your playing with spring rates to soften ride, the best rides have rates similar front to back. You can put the softest, most plush riding springs in the front that you want, but if the stock aggressive spring rate is used in the rear, not much gets accomplished as the opposing diagonal corners of the truck are absorbing shock unevenly. If the soft rate passenger front tire/springs rolls over a raised bump, it absorbs most of the bump, the truck is lifted slightly transferring minimal additional force to the stiff rate driver rear tire/springs. The front spring will not be able to force the rear opposing spring to compress much so it'll absorb the majority of the shock which is fine. However when we drive in straight lines the rear must go over the same bump now doing the opposite. The rear passenger spring will not absorb the shock much, lifting the truck up and forcing the front driver tire/spring to compress. Rocking the truck side to side. If that makes sense. Think of it like a farm tractor/wheel loader. One axle articulates (front soft spring rate) and the other is solid mounted(rear stock very stiff spring rate), The stiff axle dictates how the vehicle shifts/rocks side to side going over bumps in the road.
So the idea is to adjust the front and rear rates half-as equally to significantly improve the ride. Personally if I was trying to keep things cheap and simple, I'd go to the lowest spring rate coil up front. See how she sits height wise/bottoms out, use a cheap simple leveling kit spacer to bring the front back up if desired. The spacer won't change the ride, just add height. Then in the rear, start pulling leaves from the bottom of the pack to soften the rate. You'll loose the height of each leaf pulled, plus from the softer spring pack. If you need to bring the rear back up then add a small lift block. If you add a lift block, it would be the perfect time to add traction bar/block.
So the idea is to adjust the front and rear rates half-as equally to significantly improve the ride. Personally if I was trying to keep things cheap and simple, I'd go to the lowest spring rate coil up front. See how she sits height wise/bottoms out, use a cheap simple leveling kit spacer to bring the front back up if desired. The spacer won't change the ride, just add height. Then in the rear, start pulling leaves from the bottom of the pack to soften the rate. You'll loose the height of each leaf pulled, plus from the softer spring pack. If you need to bring the rear back up then add a small lift block. If you add a lift block, it would be the perfect time to add traction bar/block.
mikeeg02
New member
I may be mistaken but I believe the pickup 450s come with 350 running gear, and the c&c 450s came like a real 450. Not sure if that's changed. I'm still pissed they bought that truck, paid 10k too much for a lighter version of what they wanted I told them not too, but they had to learn the hard way.....
AllGo'N'Show
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11-14 apparently, for 15+ they changed back to 'real F450' driveline.
08Powerstroke6.4L
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Wow thanks for all the useful info guys. Will be playing with tire pressure only when unloaded to see what kinda ride I can get. If I do plan on hauling anything heavy I'll be sure to air the tires up to the correct range. 
https://static1.1.sqspcdn.com/static/f/589830/23447320/1378330097907/Discount+Tire+inflation.pdf
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mikeeg02
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Well thats certainly a handy link. And in a dually configuration with my tires, at 40 psi they are rated for 1,865 each X 4 tires back there = 7,460 on that axle
At max they are 3,042 each, so with the four of them 12,168. But even at 40 psi it still looks pretty safe to have what I had in the bed.
Thanks for the link!
At max they are 3,042 each, so with the four of them 12,168. But even at 40 psi it still looks pretty safe to have what I had in the bed.
Thanks for the link!
Tree Trimmer
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7460 includes the weight of the truck, not just the load in the bed.
mikeeg02
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I understand that, hence why I said on that axle. Last I weighed my truck it was 7900 with me in it, and the old diesel trucks are a bit from 50/50 but if you said 50/50, 3950 + 3300 for the concrete, would put you at 7250. Still under what the tires rated for. Again, I am not suggesting to run loaded at 40 psi. Just that I did once on a trip back from lowes, when I didnt intend on even buying concrete, and came home with a pallet of it. I checked my tires and they were fine, now that I have that tire load data, I know for a fact it was safe, not just because my sidewalls werent hot, or touching.
psduser1
Active member
That is a valuable chart! Thanks for posting.:toast:
