Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 10, 2025 ...

Liquid Spring Suspension

June 15, 2018, 10:53:31 am

In the FMCA magazine of June 2018 there is a presentation of what I would see as liquid filled air bags/shocks/struts  to conventional suspension on the rear of a Class C coach.  That way overly simplifies the concept.  It is sold as a suspension upgrade, meaning to change out the original suspension, as LiquidSpring's Class system.

Maybe you can check their web site.  In any case they use a compressible liquid and system of valving and electronic management to manage ride height and control vehicle sway as drive.  I did not catch if they use it for leveling.

The article, page 36, is that the $12,000 system retrofitted to a Class C gave a ride equal to a DP.

Just a technical curiosity me but also wondering what the future holds for this concept.

CLASS Suspension System from LiquidSpring

Quote Selected

Re: Liquid Spring Suspension

Reply #1 – June 15, 2018, 10:59:26 am

Mike,

At the Chandler FMCA Convention I and another member of the FMCA Technical Advisory Committee did a test drive in a new Ford F53 chassis coach with this suspension.  Note, this is for leaf spring replacement, not applicable to air suspension coaches. Did the test drive right before I presented the Suspension/coach ride and handling seminar. 

The test drive was VERY impressive. Both ride and especially handling were materially improved.  Ain't cheap, but a material upgrade.

This upgrade has been used for years on ambulances.  At least on the FMCA website, Liquid Spring is scheduled to be at the FMCA Convention in WY.

Quote Selected

Re: Liquid Spring Suspension

Reply #2 – June 15, 2018, 11:47:36 am

Hasn't Citroen been using different iterations of this suspension concept since back in the 1950's?

http://www.citroenet.org.uk/miscellaneous/hydraulics/hydraulics-1.html

In the link posted by Mike (above) they keep talking about a "compressible liquid" or "compressible fluid".  I always thought "liquid" was, for all practical purposes, incompressible.  This is why hydraulic actuators can transmit force - you move a piston at one end of the hydraulic hose and the (incompressible) hydraulic fluid (oil) transmits equivalent force to the piston at the other end.

Guess this must be a different deal...

Quote Selected

Re: Liquid Spring Suspension

Reply #3 – June 16, 2018, 01:37:49 pm

I thought the same thing Chuck but we all know that marketing speak has nothing to do with real life physics.

see ya
ken

Quote Selected

Re: Liquid Spring Suspension

Reply #4 – June 16, 2018, 01:52:51 pm

The liquid spring is controlled by a sophisticated computer with a number of inputs.

That is completely different than the old Citroen hydraulic suspension.

Anyone remember the Citroen SM-- powered by the Maserati V6?  Beautiful car and FAST. Same type of Citroen hydraulic suspension..

Quote Selected

Re: Liquid Spring Suspension

Reply #5 – June 17, 2018, 08:35:04 am

Lots of neat tech around these days.  My motorcycle has, count em, 6 separate computers and active suspension that adapts to road conditions as well.  Several gyroscopes that monitor pitch, yaw, wheel rotation.  I suspect this liquid spring device is a variable damping and compression valve, not so much  compressible liquid as liquid under compression.  Fast, cheap chips make it possible to adjust to each pebble in the road.  I'll bet it rides well.

Quote Selected

Re: Liquid Spring Suspension

Reply #6 – June 19, 2018, 04:34:32 pm

Yes, the Citreon SM was one heck of a car.  The system powered the brakes as well.  The one I drove had a large button instead of a brake pedal to step on.  Weird.  Very quick and had superb handling.  The British Leyland Mini had a Hydrolastic suspension that coupled the front and rear wheels hydraulically.  The earlier ones had a rubber cone suspension using rubber donuts.

Nothing new under the sun they say.

Keith

Quote Selected