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The EZS steering damper
(Possibly useful information for both EZS & EML sidecar owners)

http://bmwmotorcycletech.info/ezs-steering-damper.htm
sidecar section, article #SC11
Copyright, 2014, R. Fleischer

NOTE: See both articles 54-8A and SC2 for steering dampeners and shock absorber units that cover sidecar usages in depth!


The purpose of a steering damper on a sidecar rig is to eliminate, or nearly so, any steering oscillations, usually initiated/caused by road irregularities.  This oscillation effect, very common to sidecar rigs, particularly withOUT dampers, is due to the reduced trail and/or effects of the sidecar loading, & occurs at rather low speeds, no greater than 40 mph, & usually considerably lower, from, perhaps, 8 to 20 mph.  The problem often suddenly appears if the TRAIL of the front end of the tug was shortened; sometimes it appears even if not shortened.  The effect has been likened to a supermarket shopping cart where the wheels might suddenly oscillate, fast and even furiously.

If EXCESSIVE damping is used, the steering will be heavy, requiring more force, which is tiring to the driver.  The steering will also have less of a good tendency to return to straight ahead, more or less.  There is always a desirability for the steering to TEND-TO return to straight ahead. The amount of this is a variable depending on how the rig was designed & aligned.  As noted, excessive damping can reduce the return-to-center effect, increasing the needed drivers physical effort.  NEVER use more steering damper than is required to JUST eliminate most of any oscillation effect.   In SOME instances, the stock steering damper than came with the motorcycle (many have NONE) may work.  Some old bikes came with FRICTION dampers, instead of the more modern hydraulic cylinder types.  The friction dampers have slightly better characteristics for sidecaring use, and last nearly forever. 

If you decide to install a steering damper, do not get one that requires excessive force to move the rod/piston. If that is excessive, you will likely NOT find a stroke adjustment that will work well. See next paragraph.

In many instances, you can mount the damper in such a way that you can adjust the stroke distance per unit of steering movement. Use the minimum damper rod movement that does the required job. I have photographs of the VW type of steering damper that I used on my BMW Airhead (R100RT) Ural chair rig, on this site;....I made the stroke length adjustable, by using several mounting holes at various distances from the fork, so I could select the stroke I wanted.....as the amount of stroke needed varies with the type of tire!  Flatter tread tires require LESS stroke, that is, less shock rod/piston movement, per steering input amount.

For photos of my adjustable mounts & more discussion on dampers for use with sidecars, see the following article, and scan down half way to the section on steering dampers:  http://bmwmotorcycletech.info/
sidecartech.htm
 

The PRIMARY problem I personally had with my K1100LT-EZS-EML rig (EML sidecar attached to motorcycle with EZS sidecar conversion to the TUG...front end and wheels, brakes, etc.) was that the EZS damper was leaking at the rubber sleeve area. Secondary problem was excessive damping.  This rig has automobile tires, which, in themselves, require less steering dampening than motorcycle tires, due to the auto tires having more rubber contacting the road. See two paragraphs above; regarding dampening needed that varies with tires.

The EZS steering damper is a bit unusual in that it has a bellows that fits over the shock absorber, and the bellows fills and empties oil from and into the shock absorber.

EZS steering damper 'rubber bellows'...a rubber sleeve, ...tends to crack from age & sun exposure.  It will then leak oil.    You will need Oetiker clamp pliers & the two Oetiker clamps to install it, although sturdy nylon zips will work OK (but can bunch up causing leaks).

After contacting Pete Larsen (Liberty Motors, EZS sidecars USA) about this item, he referred me to EZS in Holland.  The factory, at first, wanted me to return the entire shock damper unit to them in Holland, for overhaul or exchange!  The cost was 152 Euros & 35 Euros for shipping.   Keep in mind this was some years ago, when the Euro had a lot more value compared to the U.S. Dollar, so the cost was high.  A new damper, no exchange, was 195 Euros, and the same 35 Euros for shipping!   After several communications, not altogether satisfactory due to the language & interpretation problems with the EZS factory, I determined that the rubber sleeve was priced, in October 2008, at 16.75 Euros, plus 9.00 Euros for shipping.  They could not accept any form of payment but Wire Transfers.  The cheapest Wire Transfer I found at any commercial bank at the time was $30.00.  This brings the total price to a ridiculous amount, not to mention the cost of the part which was high, in MY estimation. 

There was NO WAY I was going for any of this.  I could easily modify an inexpensive damper, such as the VW style, but decided to try to fix this damper.  BUT, I decided to search for a substitute part, and not use a VW damper.

The rubber sleeve covers two small ports (holes) & the rubber expands & contracts only modestly during operation of the dampener, even over large strokes.   The rubber is used as a mild bellows, although there are no folds, curves, etc.  Very little fluid/air is ever in the stock bellows.

A garden hose section won't likely work....and you'd need one with the proper inside diameter (possibly could stretch a 1" I.D. type to fit, but they would not have much bellows action, so that idea was rejected).

The shock absorber body tube outside diameter is 28 mm (1.10").

Note:  The two shock holes that allow that bleed of air/fluid into the bellows can not be plugged...I did experiment....and performance was not good enough.

Below are photos of the stock shock with the stock rubber bellows:
 

Stock shock unit, stock rubber bellows

Stock rubber bellows, up-close

Note that just inside the end is a ridge of rubber, that fits into a groove on the shock absorber body, providing a decent oil seal.  The substitute (bellows) I found and used does not have that ridge, yet there were NO leaks, after thousands of miles in using the substitute bellows.  Should there be leaks in the future, it is likely going to be from the zip ties I used, & if that happens I may look for a narrow metal adjustable band-clamp.

During my search for an acceptable rubber part, suggestions that have been made to me included the possibility that some existing motorcycle damper may have a similar rubber part.  I visited several motorcycle stores, & the parts men did not recognize the part.    

A messy looking substitute that I did not try was a hub coupling as used with piping.  There is also a plumbing shop item called a Dressler fitting, but the size was wrong, & the look horrible.

In my older McMaster-Carr (www.mcmaster.com) catalog, I found a rubber bellows used for 'small U-joints', as item 94205K67 on page 3673.   That catalog page number is probably obsolete now, but the item number may be good.  That item looked very promising.  The size was 1.79" long & 2.03" O.D.; the inside diameter is 1.12"....very close to the shock diameter. There is no internal ridge as noted a few paragraphs above, but I thought it was worth a try.

This rubber bellows is actually a product of the Lovejoy company, 2655 Wisconsin Avenue, Downers Grove, IL  60515.   It is sold to McMaster Carr as "D8 upper boot w/ties".

I ordered one of these.  In October, 2008, the cost was $13.66 plus shipping. Photo of the new bellows as installed:


 

 

 

 

To install it I first removed the original Oetiker clamps & old sleeve.  I held the stock shock with the ports downward, & manipulated the shock rod in and out until the shock was totally emptied of fluid.

I then carefully clamped the shock in soft vice jaws (LIGHTLY!), with the ports end upwards.

I did some research on the needed oil.  A VERY light oil is needed. 
I am comfortable in recommending the following oils.  I doubt that any installation, even with motorcycle tires and not car tires (mine are car tires, requiring less dampener action) would require heavier oil.  I test rode my rig withOUT the damper;  the damper is barely needed on MY rig, so I wanted a very light oil, even thinner than stock as shipped with the damper.   I could not find any oils lighter than the ones below, and the ones below ARE OK, & similar to the stock oil, maybe a small amount lighter.  NOTE that the viscosity index of the Belray is lower than the others, this is OK for this application, as the damper does not get hot.

Spectro SX400 (order number O.SXSF) Shock & Fork oil, 2.5W.   16 ounce size (1 pint) was lots more than needed.  Specification:  10.9 Cst @ 40C,  1.9 Cst @100C. 
I preferred this oil.


Golden Spectro ULTRAlight shock fluid (order number L.SFUL).  Specification is 10.4 Cst @ 40C, 4.4 Cst @ 100C.   Compared to the above SX400, this oil would have a higher viscosity, compared to the O.SXSF, as temperature rose (in the shock from lots of bumpy roads, and atmospheric temperature increase).

BelRay Fork oil 2.5W.  specification:  9.2 Cst @40C, 1.9 Cst @ 100C.    This oil is almost the same as the SX400, and if you prefer the BelRay brand, use this one.
 

You will need ~ 100 cc of fluid, to fill the dampener.  You will need an additional small amount to add to the bladder (rubber bellows).  A total of ~ 132 cc will be needed. You do NOT have to fully fill the bellows, not at all.  To fill the shock I used a hypodermic of 20 cc, with a long non-sharp needle.  
 

How to fill the shock:

Start SLOWLY injecting fluid while you lower the rod a little bit at a time.  You can tape over one of the holes if this is helpful for you to avoid spillage...I used my finger.

When the rod is fully down wait a minute, then VERY SLOWLY raise the rod again. When oil just barely starts to come out the hole(s), then repeat the process.  Repeat until you cannot add any more.  NOTE that the process of installing fluid will cause aeration & microscopic bubbles. You may have to set the rod in some position & let it sit overnight.  I did the filling over several days & nights.  I preferred to do it this way rather than the 'bucket of fluid & suck the stuff in' method, which aerates the fluid badly.

Once the shock is filled, you can hold your fingers over the two ports using some  pressure & see if the shock works well over the ENTIRE range of rod travel, WITHOUT any dead spots.  Finish this portion of the filling with the shock only filled, & the rod fully
out.  Try to put more fluid in if you can.  
 

NEXT:
Keep the shock vertical, ports upwards.  I suggest mounting the other end in soft jaws of your bench vice. Clean the shock body VERY carefully.  Get every bit of oily fluid off of it.  Use a good solvent that evaporates to very dry.  Wipe the inside of the new bellows with solvent. This is particularly so where the new bellows will fit to the shock body.   Let that solvent also evaporate.   Install the bellows over the shock eye, & position the bellows.  The bellows comes with two kind of narrow zip nylon ties; which are OK.  I used stronger slightly wider ones from my shop.  Fasten the LOWER ONLY zip tie as tight as you can without busting it.  Be sure the top of the bellows is even with the top of the shock body.  Clean up sharp edges after you cut the excessive length.

Using the hypo again, add about 10 or 15 cc more oil, sliding it down between the bellows top & the shock body.  Try not to get the top of the bellows oily, nor the body, where the final zip tie will be put.

Note, in case you have not read the above carefully, the bellows is only zip-tied at one end to the shock body at this point...so don't try to overfill or oil-pressurize the bellows...a totally unnecessary thing to do.

NOW add the zip tie at the other end.   Tighten quite securely, snip excess, clean up sharp edges.    Wipe the area with a rag that has some evaporating solvent on it.

Operate the shock, with the bellows both UPWARDS & DOWNWARDS this time.  The shock should not leak oil & should provide good action over any portion of rod travel. The bellows may expand and contract as you test the shock.

Re-clean the bellows at both ends...I used a strong spray solvent.  I used then black RTV to seal the bellows ends to the body.  This was strictly an idea to add some additional oil sealing.  Probably was not needed.

I installed the shock the evening of 10-13-2008 & adjusted the mounts slightly so the steering could be moved through its entire range without binding the shock ends (no Heim joint is needed on this installation).

Time will tell....but no leaks, not even any weeping, after maybe 8000 miles...and, still no leaks, at the end of 2015.

Note:  this bellows can hold lots more oil than the stock sleeve.

 



Revisions:
10-13-2008:  final revision and released fully.

10-24-2008:  minor update
10-03-2010: MINOR clarifications (and, it still does NOT LEAK!!
05/30/2011:  Clean up article a bit more.  Still no leaks!
09/27/2012:  Add QR code, add language button, update Google ad-sense code
05/15/2013:  update notes, minor other editing for clarity.
late 2013, and then 02/18/2014:  Remove language button due to javascript problems.  Revise and edit article a bit.  A final editing was not done until October 24, 2015.
02/20/2016:  Increase font sizes; update metacodes; narrow article; put two photos in a table format; minor clarifications.
06/16/2016:  Again updata metas; H.L., minor clarity improvements....etc.

Copyright, 2014, R. Fleischer

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Last check/edit: Thursday, July 07, 2016