Shock Absorber Retrofit - Fiberglass RV


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Old 07-26-2006, 05:51 PM   #1
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Trailer: Boler (B1700RGH) 1979
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I wanted to improve the handling of my Boler B1700RGH, and decided that the suspension needed more damping, so I added shocks. Here's a step-by-step review:

1 -Before
The stock B1700RGH suspension.

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2 - Retrofit Kit
Monroe (Heavy Duty division) RV Retrofit Kit. Mounting hardware for one axle (two shocks) is included - one set (for one shock) is shown. The left hardware is for the top mount - the 2" space for the thickness of the frame rail is visible. The right hardware is a replacement spring plate with a bolt through it. Both mounting bolts are equipped with sleeves to match the 5/8" diameter bushing in the shock.

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3 - Shock and Mounts
Monroe Gas-Magnum RV shock, Monroe part 555002, shown with mounting hardware loosely assembled (without the plate).

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4 - Plate Removed
I have removed the U-bolts and nuts which hold the original plates in place, and the plates themselves. I had soaked all threads with WD-40 a couple of days earlier.

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5 - Lower Mount
New spring plate incorporating the shock mount has been installed. I used new U-bolts and nuts.


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6 - Shock Installed
I drilled a hole through the frame, inserted the top bolt, added the kit's spacers and the shock and installed the nut loosely, then compressed the shock to line it up with the lower mount and installed that bolt, then tightened both.

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The other side was the same process.

I can supply substantially more information if people have specific questions about details or aspects of the selection or installation.
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Old 07-26-2006, 07:38 PM   #2
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Thank you for posting that.
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Old 07-28-2006, 10:38 AM   #3
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Very neat job, Brian! Two questions:

Is the shock trailing the axle or leading the axle?

Where did you find the kit and shocks? $$?

THanks;

Vic
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Old 07-28-2006, 11:23 AM   #4
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Thanks, Vic.

The shocks on both sides are mounted leading (ahead of the axle tube). Monroe says either can be done, but I had a little more room around the frame on the leading side. Cars and pickups have used what Ford used to call "stagger mounted" shocks (one leading, other side trailing), but I believe that is for windup control or just mounting convenience.

I bought the kit from an RV dealer (Woody's RV), who go it from Coast. Coast has discontinued this item (selling existing stock only), and had to bring it in from their eastern Canadian warehouse; however, it still appears to be a current Monroe Heavy Duty division product. I found out about the kit from various websites, and had expected to buy it from a spring shop, but stumbled across it in the Coast catalog.

Due to the RV supply route, the kit was probably excessively expensive, at about $90 (Cdn). Having decided to go ahead with the project and already standing in the parts department, I just went for it.

I bought the shocks from a retail automotive supplier (Bumper To Bumper), from the store at their regional warehouse (170 St, Edmonton) where they were supposed be available. They were actually not in stock locally (a part number confusion problem), and were brought in from a warehouse in a different region. The RV shocks are part of the Monroe Heavy-Duty line, and most automotive suppliers of Monroe products did not have them in their catalog.

The price seemed excessive for an ordinary pair of shocks, even though they are heavy-duty gas-charged units, but I could not find another brand which would fit. They were about $45 (Cdn) each.

The new U-bolts with nuts are not required by the kit, and not included. I bought them as one boxed set for both sides (complete with spring plates which I didn't need or use) for about $16 at Princess Auto.

The same RV dealer had a Dexter kit in stock and complete with shocks for about what I paid for the Monroe retrofit mounting kit alone.
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Old 07-28-2006, 11:35 AM   #5
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So the big question is, how much has the handling improved since adding the shocks?
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Old 07-28-2006, 01:13 PM   #6
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Quote:
So the big question is, how much has the handling improved since adding the shocks?
Significantly, in my brief test driving so far.

I tried some relatively quick (short of panic swings of the steering wheel) lane changes at normal and high speeds on a highway, and found that the trailer seemed to [b]stay in synch with the van better, and did not roll back and forth an extra time after completing the lane change as I have experienced before, and feeding less lateral force into the hitch coupling. This is roughly what I was wanting and expecting.

The highest test speed was with the fastest traffic on a freeway, which was above the 110 km/h (68 mph) speed limit; this is, of course, not legal, too fast for economical towing, and much higher than my preferred cruising speed. The higher speed just exaggerates the handling response issue, making the difference more apparent. At lower speeds, there was less of an issue to start with, but an improvement is still apparent.

I would like to minimize lean, since leaning takes time and hurts response. The trailer still leans more than the van; shocks just damp oscillations, they don't change the state the vehicle will eventually settle into in a steady condition. I realize that it doesn't need to (and should not) corner like a race car, and it is probably reasonably compatible with a 1970's sedan, but I think it still needs more roll stiffness to be a good match to a 21st century family van. The shocks definitely help this behaviour, by limiting how far the trailer leans during the time of a maneouver, but I would like an antisway bar.

I was not very concerned about [b]rough-road handling, but would expect better damping to both make the trailer more stable in rough conditions, and to reduce the pulsating forces transmitted to the van. In this respect the shocks [b]worked very well on my test drive, handling potholed and broken pavement with gravel patches (on a minor rural highway) at 85 km/h (53 mph) very stably and noticeably more smoothly (as felt at the van steering wheel and in the driver's seat) than before. I don't know yet if the ride inside the trailer is significantly smoother, and I don't have a good way to judge this. As with the highway test, that speed is faster than I would normally tow on such a surface, of course.

In a straight line on a smooth road, there's no noticeable difference, since there is no suspension motion. What most people call trailer "sway" - yaw oscillations - seem to be associated with roll motions as well, so I would expect the shocks to reduce that, but that wasn't generally a problem for me before, so it will take some trips to have any idea if it has really been reduced.
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Old 07-29-2006, 05:27 PM   #7
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Good post on the shock install and follow up Brian. When we picked up our 1980 17 with the same layout as yours, but has the flat R.V. door with built in screen, in P.E.I.and towed back to Montreal I did not have the brake controller nor the anti sway bar 1 inch ball installed on the van(full size GMC diesel).driving down a very long down hill section in N.B.started to get trailer push and then hit wide open spaces with cross winds and a slight curve at the bottom of the hill,trailer wiggle to say the least.Now with trailer brakes and anti-sway bar installed its like driving on rails, lane changes too.
Get a anti-sway bar installed.............you will love it.
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Old 07-29-2006, 06:19 PM   #8
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Quote:
...I would like to minimize lean, since leaning takes time and hurts response. The trailer still leans more than the van...
I think it still needs more roll stiffness to be a good match to a 21st century family van.
...I would like an antisway bar...
Quote:
... towed back to Montreal I did not have the brake controller nor the anti sway bar 1 inch ball installed on the van(full size GMC diesel...
Now with trailer brakes and anti-sway bar installed its like driving on rails, lane changes too.
Get a anti-sway bar installed...
Lloyd, thanks for sharing your experience with this type of trailer, and for the suggestion, but it seems we are talking about two quite different devices when using the term "anti sway bar". Brakes, on the other hand, we're in agreement on - I would not be without them.

When I was discussing trailer lean and mentioned an "antisway bar", I meant a torsion spring in the suspension which adds roll stiffness to reduce lean - this is what an anti-sway bar (or "swaybar" or sometimes "stabilizer bar") means in the automotive world. They're used both front and rear suspension of virtually every current production car and light to medium duty truck, but I've never seen one in a trailer.

In trailering, a friction-type sway control device (which is usually in the shape of a rectangular bar) is sometimes called an anti-sway bar. I think this is the type of device to which Lloyd is referring, based on the 1" ball reference. I do not like friction damping, and do not expect to install such a device.

Sorry about the confusion.
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Old 07-29-2006, 08:08 PM   #9
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I believe there may be some confusion of terms here.

I think Brian is talking about an anti-roll bar, mounted to the frame of the trailer, which reduces the amount of "lean" the trailer experiences when cornering. It's typically a U-shaped round bar mounted in bushings to the frame, with the points of the U connected via links to the axle. When the spring on one side of the axle compresses, the bar transfers some of that force to the other spring, thus minimizing body roll. Very common in automotive applications.

I think Lloyd is referring to an anti-sway device which mounts between the tongue of the trailer and the hitch on the tow vehicle. It provides a resistance to extending and retracting as you would get when turning either left or right. A device like this helps to prevent trailer "sway", or more accurately, yaw.

"Sway bar" is used in both automotive and trailering contexts, but they generally mean different things.

Brian, I wonder if you could do some junkyard shopping and salvage an anti-roll bar off of a junked car or truck? If you're reasonably handy and have some fabrication skills and resources, I don't think it would be too hard to come up with a decent system for not too much $$$.
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Old 07-30-2006, 12:32 PM   #10
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Well said, Lee - I think you've nailed the confusion , with a nice clear explanation. Yes, I agree that both "antiroll bar" and "rollbar" should have been in my list; "rollbar" gets confused with the protective strucutral cage used in race cars and some convertibles, so I avoid the term. Apparently, I was still drafting my response while you replied.

I have considered salvage parts for an anti-sway bar installation, but haven't done a serious search yet. The problem (aside from the time, effort, and expense), is that the Boler frame is 55" wide (on centre). While I wish it were even wider, that's still much wider than the frame spacing on even a full size pickup, and probably wider than a medium-duty truck, so I doubt I'll find a bar shaped to have mounts that far apart. Structurally, I don't want the bar bearing on a crossmember too far in from the frame rails, or applying force to the axle too far in.

I'm not ready yet to resort to custom fabrication, which I suspect would include the service of a spring shop.
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Old 07-31-2006, 09:31 AM   #11
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Well said, Lee - I think you've nailed the confusion , with a nice clear explanation. Yes, I agree that both "antiroll bar" and "rollbar" should have been in my list; "rollbar" gets confused with the protective strucutral cage used in race cars and some convertibles, so I avoid the term. Apparently, I was still drafting my response while you replied.

I have considered salvage parts for an anti-sway bar installation, but haven't done a serious search yet. The problem (aside from the time, effort, and expense), is that the Boler frame is 55" wide (on centre). While I wish it were even wider, that's still much wider than the frame spacing on even a full size pickup, and probably wider than a medium-duty truck, so I doubt I'll find a bar shaped to have mounts that far apart. Structurally, I don't want the bar bearing on a crossmember too far in from the frame rails, or applying force to the axle too far in.

I'm not ready yet to resort to custom fabrication, which I suspect would include the service of a spring shop.
All this talk of rollbars(anti sway bars) takes me back to my Rally days with BMC cars and inside wheel lift. I do not get lean on the corners with my unit, maybe because the tug is a lot heaver than your Honda and I do not feel it behind me or the spring rate could be stiffer.Mite be your springs are on the softer side.A trip to Princess Auto ?????
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Old 07-31-2006, 10:20 AM   #12
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I don't notice lean in steady cornering either, partially because I'm not cornering at the speeds that I would without the trailer; it's really only in sharp manouvers (like lane changes or dodging stuff on the road) that I notice it. The general effect is that the trailer behaves like an upside-down pendulum (or a musician's metronome), swinging (leaning, not yawing) to one side and back the other way. I think that compared to the typical smaller trailer, this 17' unit does it more because of additional height.

I don't think that the tug should affect how much the trailer leans, unless there is a coupling system connecting them which resists roll, such as most weight-distributing hitches. I don't use a WDH.

The roll stiffness - without an antisway/anti-roll/stabilizer bar - does entirely come from the springs, so I agree that's a possible area for improvement. Their effectiveness is limited by the fact that they are only 55" apart (on centre), while the track (tire spacing) is 72". Trailers with independent suspensions (such as the rubber torsion axle systems) do not have this problem. In addition, that 72" track is too narrow (by automotive standards) for a vehicle which is this wide (I think about 90", from memory).

I checked with Standen's (who made the axle) and the 5-leaf springs are the highest-capacity made for this axle - the 4-leaf would have had sufficient capacity for the trailer ratings - so I don't see going any further there.

I could add "overload" coil springs to the shocks, which have significantly wider spacing (that's why I mounted them outboard), although it seems for ride smoothness that stiffer may not be the way to go. It is something to consider, though. Thanks for the suggestion, Lloyd.
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Old 07-31-2006, 02:22 PM   #13
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While I wish it were even wider, that's still much wider than the frame spacing on even a full size pickup, and probably wider than a medium-duty truck, so I doubt I'll find a bar shaped to have mounts that far apart.
A dumb question, but you never know....... How about using two anti-roll bars from narrow vehicles? They will be half as stiff as they were in their original vehicle but, as we say, 'owts better than nowt' (=something is better than nothing).

If you could find some bars with 90-degree bends, where the ends run perfectly fore and aft, you could simply join them with a couple of well-spaced U-bolts - then bearings in the centre of the frame would not be required.

Andrew
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Old 07-31-2006, 02:47 PM   #14
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Andrew, that's a truly innovative idea! I think it would take more than a couple of U-bolts, but might still be practical: time for another mental design exercise, and maybe a CAD drawing...
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