Ride quality opinions requested -- 20" SL vs 18" E rated tires on 2023 3.5 Max Tow FX4

[dspa]

Greetings from New Mexico!

Short time lurker, first time poster!

At the end of March, I purchased a new 2023 3.5EB Max Tow FX4 short-bed and generally love the truck.
What I have been less-than-enamored with, however, is the ride. On perfect pavement, at lower speeds, it is extremely smooth. However, at highway/freeway speeds, the thing is jittery as [insert colorful metaphor here]. The 2001 Dodge Ram 2500 Cummins I replaced (and am sorely missing at the moment) rode way smoother at highway/freeway speeds.

This new truck came with the 20" Hankook Dynapro AT2 tires. I first had those tires rebalanced at the dealership. Then I tried having those tires replaced with Michelin Defender LTX M/S. Then I had those road-forced and re-road forced several times. Not sure I'm welcome at that Discount Tire location anymore. I've tried replacing the rear shocks with the Fox 2.0 and the Bilstein 5100. Both were easier to compress than the stock shocks (which goes against the stories I've read about the pre-14th gen trucks). I've also dropped the PSI in all the tires to levels most of you would probably consider irresponsible. Anyway, I've basically come to the conclusion that, barring some problem with the driveline, this truck just rides like, well, a truck. I have come to realize I basically bought the stiffest F-150 you can get.

That all said, I'm looking at sizing down the tires to 18". I ordered the Tremor wheel kit from Ford which I think will look awesome on my gray blacked-out Platinum truck. However, I'm a little concerned with what I'm finding on load ranges on tires for smaller wheels. It appears, to keep my factory circumference (going from 275/60R20 to 275/70R18) would basically require I change from SL to E rated tires.

So, after all my jabbering, here's the question for you experts out there - will 18" E rated tires give me a softer ride than the 20" SL rated tires I have now? If not, what would you recommend I do? (I realize that's actually 2 questions)

Thanks for sticking with me all this way (I know I tend to get wordy), apologies for my overuse of parenthesis, and thanks in advance for any advice and opinions!

-Dustin

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[Polo08816]

Hrm... this seems odd. The truck was jittery on the highway with Michelin Defender LTX M/S tires in a SL load range?

When you say Max Tow, I wanted to confirm that this is not a XL trim with the HDPP right?

 

[dspa]

Hey Polo. Yep... basically all the time at higher speeds. It's not severe... just enough to be annoying. I realize everyone's perception of jitters and vibrations is different, and I know I'm on the sensitive end of the scale (compared to my father, who can drive a car with unbalanced tires and not care a lick).

At first I thought tires, as that's usually the culprit (hence the tire replacement and all the balancing). But now leaning more toward it just being some sort of harmonic or something, or I'm just super-sensitive to the truck's stiffness. None of the factory shocks are leaking oil or anything. The suspension is bouncier than a passenger car when doing the old "push test" on the shocks, but it does come to a rest after a couple cycles.

 

[Snakebitten]

I'm stunned that you report that the oem shocks are stiffer damped than the Bilsteins.
That's the first factory F150 shock that I have ever heard such a thing. They are notoriously underdamped, which combined with the traditional leaf spring rear suspension, is a recipe for double-bounce in a light load condition.

 

[dspa]

Hey Snakebitten,

The rears, at least, are FAR more difficult to compress than the Fox 2.0s or the Bilsteins (the Bilsteins being the easiest to compress, and the Fox being closer to the OEM, but still easier). I have to put my entire upper body weight on the OEMs to get them to compress. They also rebound more quickly than either of the two aftermarket shocks.
I've read many threads about the OEM rear shocks being underdamped garbage on the F-150. The ones I have may still be garbage, but they are very hard to compress.

-Dustin

 

[Snakebitten]

I believe you!
But that begs that Ford has definitely made a change and there's been crickets regarding.

 

[dspa]

Yup, I agree. I saw a video on YouTube not long ago where someone let their kid compress the OEM rear shock they took off their truck. Definitely wasn't my experience!

I do think a lot of this is just me being used to unibody vehicles (and my old Dodge which ran ridiculously smooth for being the HD truck it was), so I'm really hopeful a smaller-diameter wheel will get me where I want to be. Just worried going to an E-rated tire on a smaller-diameter wheel won't be the difference I expect.

Maybe I should have bought an SUV.

 

[Snakebitten]

Ford pick-ups, other than the Lightning, aren't going to give as nice a ride, especially empty, as the coil spring or air spring competition.

The number one comment from the Ram drive comparison is "the ride".

Ford has stubbornly kept their 1/2 ton truck more tow worthy, in my opinion.

 

[Pedaldude]

the Bilstein shocks that I installed in my last truck were a disappointment and I couldn’t tell any difference between them and the Gabriel shocks that were on the truck when I got it.

That being said; just slowly compressing a shock won’t tell you how stiff it is when in actual service depending on the valving. That’s why sometimes a bad shock will seem good when off of a vehicle but when installed, a little push on the bumper makes seem like there’s no damping at all.

Going to 18” from 20” and the whole extra inch of available sidewall on the portion facing the road won’t help as much as a more pliable tire.

E rated is going to be a rough ride whichever tire you go with. If you can; select a non E-rated tire with a similar load range for light/unloaded use and swap in the heavy duty tires for when there’s an actual load.

I had a similar rough ride with my OEM General Grabber APT LT265/70R18C and it totally sucked. I swapped them with some Michelin Primacy XC 275/65R18 and the ride is completely different; making the truck much more livable with the HDPP springs. Before, it felt like riding on bare rims!

Your old Dodge truck likely softened up over the years and your new truck will as well but with the lighter bed/frame; it will never ride as smooth empty. I put a 100lbs rubber horse stall mat in my bed and it was a much more noticeable improvement in ride in addition to damping the empty aluminum bed booming and rattling.

Good luck!

 

[richardrocks]

I’ve also written many posts about vibrations, grinding, and overall discomfort especially on longer drives.

My SL Falkens were a major disappointment — they developed a really bad vibration / ride quality within 1000 miles. I wasn’t thrilled to go to an E rated KO2 but I’ve heard great things about that tire generally. I’ve experimented with different tire pressure (35, 40, 45, 50) and whole BFG says 50 is appropriate for my truck with those tires, I’ve found that 38 is livable. Any more than that and I just think about the ride quality. May end up swapping to another brand that offers SL A/Ts for my 18” wheels.

I think I have driveline issues but it’s not going to be possible getting the dealer to address that. Folks on these forums have offered many pointers for looking into it myself.

 

[wessermgm]

I believe that there must be a problem with the driveline. I certainly do not believe it is an issue with the tires. I hated the stock Hankooks, but not because of the ride quality. It was the smoothest ride I have ever had with a truck.

I have a 3.5L EcoBoost with Max Tow, FX4 - basically the exact same truck. I switched to 285/65/20 KO2s because I am off road on my land quite a bit and I still don't jitter at highway speeds. My wife commented just last week that my truck rides smoother than her Lexus - this is with the 2" level as well.

My point is that I never really heard of anything like you have experienced and that leaves to believe that there is something mechanical, possibly drivetrain, possibly powertrain. I have heard that low oxygenation can cause vibration at high speeds, which could be a wastegate issue on the turbo (smarter ppl than me can weigh in on that).

 

[HammaMan]

Shocks aren't springs -- there's no insight to be gained from being able to compress them. They're pressurized to mitigate oil foaming due to cavitation, not because they're intended to carry any weight. Heavier duty shocks could run higher pressures to further mitigate foaming as running baja for instance is going to give them a helluva workout whereas highway driving is rather light duty. They're not springs and carry no weight.

 

[dspa]

Hi All,
Thanks for everyone's input on this. I do realize that the shocks are not springs, and I'll be the first to admit I only have the most basic of knowledge regarding shocks/dampers: that their basic purpose is to slow down the movement of the suspension (but not too much) and to prevent oscillations in the suspension. I know that's an incomplete list and they do serve other purposes.
Sounds like nobody really thinks going to 18" wheels will help me, so my next step probably is to have a vibration analysis done by a local expert here who specializes in such things. I don't expect Ford to be able/willing to go after this, but if I can go to them armed with some testing results, maybe I can get them to at least look at it.
Thanks again and wish me luck!
Dustin

 

[richardrocks]

Hi All,
Thanks for everyone's input on this. I do realize that the shocks are not springs, and I'll be the first to admit I only have the most basic of knowledge regarding shocks/dampers: that their basic purpose is to slow down the movement of the suspension (but not too much) and to prevent oscillations in the suspension. I know that's an incomplete list and they do serve other purposes.
Sounds like nobody really thinks going to 18" wheels will help me, so my next step probably is to have a vibration analysis done by a local expert here who specializes in such things. I don't expect Ford to be able/willing to go after this, but if I can go to them armed with some testing results, maybe I can get them to at least look at it.
Thanks again and wish me luck!
Dustin

Likewise, I think I’m going to find a local specialist to assess and then present it to dealer unless it’s an easy fix. A little money out of pocket is better than ultimately taking a $10k+ loss on trading vehicles which is what I’ll want to do soon enough.

 

[dspa]

I agree. If the RAM 1500 had the payload capacity of the Ford, we wouldn't be having this conversation.

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