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RV Shocks. Who is using them and how do you like them?
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Originally posted by JeffC View Post
My understanding from the posts in this thread was that there was a single shock part number for all the kits. Is that not correct?
You might be over thinking this whole thing. None of the shocks in these kits are Heavy Duty that would have an adverse affect on the trailer.
We're talking about a total weight range delta among kits of 3000-4000. For a generic shock on a trailer, I feel that's a non-issue.
Compression on these shocks is low. Its rebound dampening that really slows the oscillation and results in a smooth riding trailer.
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Originally posted by JeffC View PostAll of the above makes sense to me.
A shock absorber has a single function, to dampen oscillation. All shocks are designed to work within specific weight and performance (dampening, rebound, travel, etc) parameters. An empty 450 would still not be optimal using the same shock as a loaded 150. (pick any other analogy that you like, it is the difference in load and travel that I'm talking about)
Using the same shock on a 10K TT and a 20K 5th wheel still does not make sense to me. Is it better than running without? Maybe. Over dampened is not a good thing anymore than under dampened.
I would be much happier if there were two or three different shocks available depending on load.Last edited by Guest; 02-11-2020, 04:07 PM.
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Suspension systems are designed to be critically damped with normal inputs. The graph (if it posts correctly) shows three graphs. Underdamped, critically damped and overdamped. In a passenger car it seems a critically damped system would be ideal where on the heavy truck or heavy trailer I suspect there is a compromise between being critically damped when lightly loaded and slightly underdamped when fully loaded. Taking a shot and thinking this may be a best case compromise. Not trying to talk folks into the shocks but rather I believe, or hope there was some engineering on the best choice of damping for a reasonable compromise.
https://www.bing.com/images/search?v...x=4&ajaxhist=0
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Guest -- only thing I can do to add to this thread is post your chart for ya! I don't know a thing about what you guys are writing about, other than I know when it works and when it doesn't.
Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.
2017 Ford F-350 DRW, '19 315RLTSPlus
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I ran across this old video I took of the underside of my 2600RB Imagine. Was looking at several different scenarios back then such as simulated sway and aggressive sharp turns on pavement and the effects on the hangers. But for this discussion an interesting observation can me seen at time 2.0 minutes. The drive moves from pavement to dirt and back to pavement where the drive overall was reasonably smooth.
https://www.youtube.com/watch?v=6RhEKItnjCY
Jim
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There is a lot to agree with in the last few posts.
If you can't obtain theoretical perfect, underdamped on the compression stroke is probably better for a trailer but rebound is what makes the ride smooth. The springs themselves do a fine job of compression dampening but the total lack of rebound control is what makes the trailer bounce.
Properly designed suspension systems balance all the componentry to operate in a specific load and speed range. That range is designed to work within the empty and total weight range of the vehicles they support. You should not have to change shocks based on load although the most sophisticated shock and suspension systems do exactly that through a variety of mechanical and electrical means.
However, a perfectly designed shock absorber that will support a 7K axle and a 12-14K trailer is not the same set of specs required for an 8K axle and a 20K + trailer.
OTOH, it is almost certainly better than nothing. I just wish there was a bit more specificity in application.2017 310GK
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JeffC,
Great feedback. Take a look at the video I posted on #38 and you will see my Imagine is underdamped at 2 minutes into the video. This input was not severe at all but the underdamped oscillation and the undamped compression (jounce) and rebound can be seen.
Jim
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Great graph of under-damped vs critically damped vs over-damped . . . this is what we are discussing! (I think I remember this graph from a first year engineering text book )
This is usually measured in the fore-aft direction (I will get back to this). When I began to consider adding dampers ("shocks" is a really confusing name for these things) I watched the side of the trailer in the mirror. I could not see under-damped motion. The trailer settles after jounce impact very much like critically damped. So, I got Cate to video the trailer in her mirror so that I could study the trailer motion more closely. Essentially "critically damped" with the control element seeming to be the damping in the center spring "equalizer" connection.
In my discussions with Sonny Dismuke (Joyrider designer) he led me to believe that all systems use the same damper regardless of axle diameter. As I have said before . . .this doesn't make sense to me . . . based on several years of automotive damper tuning experience.
Back to fore-aft vs side-to-side . . . Jim Guest brought this into the discussion. I added stronger springs to the left side of my 303RLS to carry the 800 lb heavier weight on that side. (a whole other story). Before this, the trailer would always fall to the left (heavy) side on every road impact. With the springs matched to the load being carried, the trailer now "bobbles" from side to side on road impact. I can see where damping could be an asset in controlling this. (Thanks Jim )
So, I am thinking that the damper sales guys sell their product because the trailer never needed fore-aft damping in the first place. What they damp is side-to-side oscillation which does give the trailer a smoother ride.
I still don't like how the main two brands of dampers require two sets of relatively large diameter mounting holes close together near the centre hanger attachment to the frame. This is a critical load area for the frame rails and most of the frame rail strength is in the lower flange.
In the cost/benefit analysis . . . I'm still not convinced that this would be (a significant amount of) money well spent.
RobCate & Rob
(with Border Collies Molly & Angel + Kitties Hazel & Elsie)
2015 Reflection 303RLS
2022 F350 Diesel CC SB SRW Lariat
Bayham, Ontario, Canada
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Rob,
Thinking each rig may respond differently and also do not prefer how the joyriders mount close to the center hanger. I'm confident in my X factor bracket in removing most if not all lateral motion in the center hanger so if the channel can handle loads in the Z direction, I would be ok. There are no failures that I can find on the internet.
Looking back to my video, it appears shocks may help in my case since the dirt section of my drive was not rough at all on the TV. But the rig does appear to be underdamped at the 2 minute point. In my case, the older Lippert chassis uses 3 inch axles but they are 3500lb with 1750lb springs. So this rig may not fit within the one size fits all category for a 3 inch axle, and may end up being overdamped with shocks.
We have some feedback from EMetz582 on the 2017 2800BH where the results were deemed as excellent. This rig would have had the same chassis as my 2017 Imagine. Not sure how much clearance he had but my Imagine does not have the necessary 4 inch tire/frame clearance for the Lippert shocks. Also not liking my thin wall square tubing on my rig, but believe I have a few solutions in mounting the joyriders should I go this route. I also spoke with Sonny who is confident in the upper mounts on the 0.20" channel where the damping rate from his shocks, the spring rate and other factors would be needed to calculate these loads on the channel while using the self tapping bolts. He tells me he uses a 60/40 damping rate with his shocks for jounce/rebound.
Glad I could spark your interest Rob.
JimLast edited by Guest; 02-12-2020, 10:56 AM.
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Spoke with Sonny who mentioned he was aware a single failure of the upper brackets. In this particular case, the customer did not use the correct size pilot drill bit where the self tapping bolts did not have the necessary grip at the thread and as a result, they pulled out. He also re-confirmed he uses a 60/40 damping ratio for jounce/rebound.
He also confirmed his 3" axle kit would work well for the 3500lb axles where from our discussion he has allowed for damping that covers a wide range of loads where the theory is, some damping while not being optimized is better than nothing. I may still take some other measures on the 0.2" thick upper brackets on my Imagine where Sonny mentioning of no known failures with proper installation buys me some confidence.
Below are a couple articles on the installation of the joyrider system where one is a review where two fellows are riding inside the rig for a subjective evaluation. Funny stuff but in engineering subjective evaluations using ones Buttometer is commonly done as well as with data. However never heard of tests with a cat as part of the evaluation. The first article bases the results on the contents being moved about inside the rig where at a minimum some of us ( I plan to) can gather some video.
http://rvimprovementsystems.com/arti..._Joy_Rider.pdf
https://www.youtube.com/watch?v=u0aizlG4c68&sns=em
JimLast edited by Guest; 02-13-2020, 11:54 AM.
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This is my first year going out west with my 303rls, I thought the worst roads in the country were in southern Michigan and Indiana, they are not. We spent almost a month in Louisiana and that state by far has the worst roads and highways. That is when I started looking into adding shocks to my suspension, Lippert shocks mainly for ease of install at my annual bearing service appointment in their shop. But the quote for them to install which includes the shocks is $650. Is it worth it?
I have read through your posts here (thank you) and because my main objective is protecting the box and contents riding on the frame I wonder if they would be of benefit vs installing something like sumo springs? My 303rls rides great, no sway and other than the usual bucking when going through really bad areas on the highway.
Any thoughts of sumo springs vs shocks? This would save me about $200 because it looks like an easy install for me to do myself. I also wonder if it would help reduce bounce when stationary.
https://www.superspringsinternationa...op/tss-107-47/Last edited by Beachcamper; 07-17-2021, 09:19 AM.Vivian
2018 Reflection 303rls
Ford F-350 diesel long bed 4 x 4 SRW
Demco Recon
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Beachcamper Yoda
Hi Vivian,
A "timely" revisit of this topic. I have also been considering these alternatives. Based on Keith's detailed writeup and reported results on the Sumo springs https://gdrvowners.com/forum/operati...all-tss-107-47 I am going to go this way. I like that this will dampen the side-to-side motion of the trailer when parked and I like that the Sumo springs do not require holes in the lower flange of the frame rails.
RobCate & Rob
(with Border Collies Molly & Angel + Kitties Hazel & Elsie)
2015 Reflection 303RLS
2022 F350 Diesel CC SB SRW Lariat
Bayham, Ontario, Canada
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