Dan’s mods

[DanielBoondock]

Speaking of agree/disagree, I initially disagreed with Alcan but came over 100% eventually. On tire pressures it was opposite, I started as receptive but have concluded the opposite. Here's why with I think a reasonably accurate technical assessment of road vibration absorption in the suspension

You can think of the vibration in frequency bands, low/mid/high. In the clip above you can see mainly low. Little hard but there's a few places with a gentle change in the road and there's a corresponding response in the leaf springs of something under a 1/2hertz say. It bounces basically. This is all in the 1-20 Hz range according to research I've read. The leaf springs job is to absorb this, and from watching I can see they're doing the job. 

Up from there it's mostly short impulse bumps like a pothole. I'll try to upload a video of that. This comes from transit time over a pothole, say 1' wide hole (big 'un) @ 50 mph. The two edges of the hole are approximately at an 80 Hz low band frequency from the tire transit time over the hole. This is probably the highest frequency you'll see on the road. So we're talking 0-100 Hz (rounding up) frequency band that the suspension needs to manage. Note this 1' pothole is an extreme example to find the boundary, going 50mph over one would not be fun.

Consulting research on tire under inflation performance and getting an AI summary of the research. The point of this is that 

Quote

A trailer tire inflated to 40 psi—typically a standard Special Trailer (ST) tire found on light-to-medium utility trailers, teardrop campers, or boat trailers—occupies a middle ground, primarily absorbing frequencies in the 30 Hz to 120 Hz range.

A tire inflated to 60 psi (typically a heavy-duty Light Truck [LT] tire, commercial van tire, or trailer tire) becomes highly rigid, shifting its primary absorption and resonance profile up into the 50 Hz to 250 Hz range.

So the point is but going with lower inflation's you're simply shifting the frequency response around, at the cost of higher wear, lower mileage and greater tire stress. A higher inflation damps 50+ Hz (e.g. potholes), lower inflation's shifts it 50- which is exactly what the leaf springs and Ez-Flex are for.  From watching on my trip I saw the Ez-Flex only engage on serious potholes, so that system is designed for the higher band. But what about the highest frequencies? Clearly the suspension isn't going to help with 50Hz up, what does it? A higher inflation tire. In summary ...

Consulting sources then here's our lineup

• 0-10 Hz Leaf springs
• 10-50 Hz Dexter Ez-Flex (per their spec)
• 30-100 Hz 40 PSI trailer tire (various internet sources and AI summary)
• 50-250 Hz 65 PSI trailer tire (note a healthy high frequency band not covered elsewhere)

So that's all I'll say on it. My position is that going with a lower inflation level of say 40 Hz is simply giving your Ez-Flex a break. I run at the factory 60-65 psi you can see above, and that inflation level shifts the frequency absorption to a region not covered by the rest of the suspension. In addition to the wear/mileage/stress, a lower pressure is counterproductive and leaving the higher frequencies free to transmit to the trailer, exactly what you don't want. I went down this trail to find out what I was seeing, which was at my 65 psi I saw little to no vibration in the trailer and the suspension system handling it all. Again I'll try to provide some clips to illustrate this. 

No need to go over what's been said before as I've studied those threads, but I'd love to hear a counterargument

Edited 8 hours ago by DanielBoondock
Clarify and cleanup

[2008RN]

I can neither agree or disagree with your theory or info.  There are a lot of engineering factors that go into making the best ride possible and I am not an Engineer let alone a mechanical engineer with Dynamics and materials theory.

If the theory is correct, then their are  more questions :

1.  According the the tire manufacture info I believe that the pressures should be  45 PSI due to the weight of the trailer.  I try to run between 45-50.  I use to run around 55psi more of a safety factor in my mind since I do't use TPS system. I would think the stiffer tire would create less heat, but could also cause even wear.  I just changed the tire this year, due to age and not wear, 25K miles. I old set didn't show any abnormal wear and still looked almost like new My tires also only see the sun 60-80 days of sun sine a year.  When in storage my tires are on concrete, I am planing on putting the Oli on Jack stands and getting most of the pressure off of the tire. I was reading that with large vehicles sitting in one spot for long periods in hard on the tire, causing flat spots in the belts.

2. The Ez-flex probably needs to move as it was designed to move freely.  I don't know what is the latest from Alcan for the torque specs for the wet bolts. But the way the Dexter should bolts are made to allow Fairly free movement of the Ez-flex coupling.  

3. The leafs.  We know that the Dexter 4 leaf was under sprung in their design. The next question  would be is Alcan 5 l-leaf the proper leaf spring, or would it be the Alcan 4-leaf or the Dexter 2200 lbs. I personally have the Alcan 5-leaf and like the ride.  there is still movement but it minimal. 

 

Last Item: I know this is your mod thread, but should this be posted in the mammoth thread on leaf spring that might get more attention?   This could end up causing several more pages of posts.

Edited 5 hours ago by 2008RN

[jd1923]

4 hours ago, 2008RN said:

When in storage my tires are on concrete, I am planing on putting the Oli on Jack stands and getting most of the pressure off of the tire. I was reading that with large vehicles sitting in one spot for long periods in hard on the tire, causing flat spots in the belts.

IMHO, when in storage pumping tire pressure up to the max limit will help to eliminate flat spots but your PSI numbers are correct for towing.

On classic cars I had, I’d put them up on jack stands. For the Oliver, just use your leveler jacks to take most the weight off the tires.

If you visit your storage monthly, get your tires off the ground with the leveler jacks and give the tires 1/4 turn.