How to Choose and Buy an RV

Solar that Really Works! covers the design, installation and use of solar in cabins, camper trailers, travel trailers, fifth wheelers, campervans and motor homes.

eBook versions

Paperback version

Prices for the paperback version including delivery can vary dramatically.  RVBooks recommends you shop around.  We've included a number of reputable booksellers you may wish to consider. Any bookshop, whether online or bricks and mortar, can order copies of How to Choose and Buy an RV. Just ask.
ISBN: 978-0-6487945-5-4.

The Camper Trailer Book

Fourth Edition

by Collyn Rivers

The Camper Trailer Book was first published in 2006. Camper trailers and usage, however, changed so fast it has been updated several times.

This book has not yet been converted to an eBook format and is not yet available as a paperback. While printed copies of previous editions may still be available, we have decided to publish this new edition of The Camper Trailer Book on this website.

Each week we will add a new section.  Over time the complete book will be available on this site. As each section is added it will also be completely searchable.

If you own or are interested in travelling with a camper trailer you will find this book invaluable.  It covers every issue you are likely to encounter and then some.  We trust you will find this helpful and useful.

The Camper Trailer Book – Chapter  5: Chassis and suspension

Updated 2021

Outback roads and tracks are littered with trailers with broken springs, axles and chassis. Many have wheel studs snapped. This is not helped by overloading. It is mostly due, however, to inadequate suspension. Road shocks are transmitted directly to the trailer superstructure and contents. The associated forces are surprisingly high. Chapter 5: Chassis and suspension explains all.

Most trailer chassis are similar but differ considerably in how they are sprung. The MC2 shown (below) is used on TVans. It was designed initially for mobile radar units. Few are this good. Many cheaper trailers are like horse-drawn carts – yet towed at many times the speed.

The Tvan’s military-based (MC2) suspension provides long travel and soft well-damped springing. Pic: Track Trailer.

Chapter 5: Chassis and suspension springing basics

A trailer’s springs sandwich between a trailer’s wheels and axle (unsprung mass) and its body and contents (sprung mass). If unsprung mass is light relative to sprung mass, the springs absorb much of the blows. Springing thus works best with soft springs; plus light axle, wheels and tyres.

There is one other vital issue. A spring is compressed by a wheel encountering a bump. Once over it, released spring energy jack-hammers wheels and axle down. The wheels strike the road surface very hard. This imposes shock loads on their bearings and studs. Driving fast over corrugation is thus like smashing a tyre up and down with a sledgehammer. The forces at 80 km/h are 16 times higher than at 20 km/h, and applied about 1300 times/kilometre.

Ride harshness depends on the ratio of sprung weight (shown here in grey) to its unsprung weight (springs, axle and wheel assembly). The greater this ratio, the more effective the suspension. Pic: RV Books.

To dampen spring energy as it is suddenly releases, shock absorbers convert some of it into heat. They do so on both upward and downward strokes. Shock absorbers are an essential part of a sprung suspension system. They also assist braking: none can exist unless the tyres are firmly on the ground. Further, by lessening shock loads, shock absorbers enables trailers to be lighter built.

Sadly, a few trailer makers fit springs so stiff they barely deflect. They may insist that interleaf friction alone provides damping. It does, but only on the upward stroke. There is almost none on the downward stroke. This, they seemingly overlook.

Despite the outback littered by trailers with broken springs and axles, even that fails to change their views. Nor did a poll showing almost 50% had experienced failures. A trailer lacking shock absorbers has suspension so hard its springs do not deflect enough to break. Everything else breaks instead, yet makers seemingly cares little about it.

Basic hydraulic shock absorber. RVBooks.

Not all are like that. The rough looking trailer (pictured below) is an old Russian-made unit seen in Uzbeckistan in 2007. It had been carting heavy rocks over a 50 km dirt track every day for a then 35 years, and probably still is now. It has a tubular central backbone, swing axle coil sprung suspension supplemented by progressive rubber bump stops, and big shock absorbers.

The owner said, ‘its brakes stopped working in the 1980s but as we only need to stop when we get here, we’ve never bothered to fix them’.

Despite its looks, this 1960s Russian trailer is way ahead technically of many today. Copyright: RVBooks.

Chapter 5: chassis and suspension explains all – beam axles

For reasons that are explained below, there is little if any point in using independent suspension on a camper trailer. The main reason why so many makers do is substantially marketing based.

This Finnish-made trailer has longleaf, supple and well-damped springs, plus disk brakes. Pic: RVBooks.

A well-engineered beam axle and damped supple springs are simple and very effective off-road – and axle/ground clearance remains constant. For self-building, consider a hollow beam axle and Toyota Hi-Lux rear springs with leaves removed so that it deflects 50 mm when fully laden. Use also the Hi-Lux’s shock absorbers.

Chassis and suspension explains all – independent suspension for trailers

Independently sprung wheels are essential only for softly sprung steered wheels. Whilst marketed as ‘superior’ (for trailers), a well designed and engineered beam axle and leaf spring system is adequate. Sadly very few of the latter are. It is mainly that which may independent suspension a better choice.

Trailing arm independent suspension on a well crafted DIY trailer.

AL-KO rubber suspension

AL-KO rubber (independent suspension) is used on many travel trailers and camper trailers. It can be used without shock absorbers because rubber has is partially self-damping. Shock absorbers are optionally available.

This suspension is also worth considering by DIYers. It simplifies design and construction as the whole assembly bolts onto and strengthen the chassis.

Such suspension can be used off-road but if planning to do so contact AL-KO engineering directly as specialised advice is essential.

Trailer chassis and suspension: summary

Whether suspension is beam axle or independent matters less than how well it is designed and made. Sadly, apart from many well-made DIY camper trailers, only a few beam axles systems are.

The AL-KO axle assembly unit can be obtained in various forms – including those that bolt directly onto the chassis rails.

 

The AL-KO rubber suspension mechanism. The axle causes the inner section (shown in orange) in the ‘normal’ state to rotate (shown in red) and compress the rubber pads. Pics: AL-KO.

Except for carting rubbish to the local tip do not consider any camper trailer that lacks shock absorbers even for on-road use – let alone off-road. There are too many abandoned trailers with broken springs and stub axles, lacking even provision for shock absorbers, littering outback Australia to do otherwise. Moreover, think carefully before towing anything over 1300 kg (2870 lb) on sand for other than short distances. Many owners do, but such trailers are hard to retrieve if deeply bogged down.

Buying an off-road trailer then using it only on-road is not in itself a problem – but you may need a heavier and larger tow vehicle than otherwise required.

This trailer lost a wheel at speed when a stub axle and wheel broke off (it lacked shock absorbers). The 4WD truck in the background is our previously owned OKA. Pic. RVbooks.com.

Collyn Rivers is a semi-retired automobile research engineer.  He is the author of seven books, five of which are about making RVs and solar work optimally.

How to Choose and Buy an RV

Solar that Really Works! covers the design, installation and use of solar in cabins, camper trailers, travel trailers, fifth wheelers, campervans and motor homes.

eBook versions

Paperback version

Prices for the paperback version including delivery can vary dramatically.  RVBooks recommends you shop around.  We've included a number of reputable booksellers you may wish to consider. Any bookshop, whether online or bricks and mortar, can order copies of How to Choose and Buy an RV. Just ask.
ISBN: 978-0-6487945-5-4.

Caravan & Motorhome Electrics

The essential handbook for anyone with an RV of any kind.  Everything you need to know to make the electrics in your rig work for you.

eBook versions

Paperback version

The book retailers set their own prices which can vary substantially. We'll aim to keep a selection of the better prices above.

Any bookshop, whether online or bricks and mortar, can order copies of Caravan & Motorhome Electrics.  Just ask.
ISBN: 978-0-6483190-8-5

The Caravan & Motorhome Book

The Caravan & Motorhome Book covers every conceivable aspect of campervan and motorhome usage. If you own a camper van or motor home, you'll want this book.

eBook versions

Paperback version

The book retailers set their own prices which can vary substantially. We'll aim to keep a selection of the better prices above.

Any bookshop, whether online or bricks and mortar, can order copies of The Caravan & Motorhome Book. Just ask.
ISBN: 978-0-6483190-5-4.

Why Caravans Roll Over
and how to prevent it

Explains in detail every aspect of tow vehicle and travel trailer stability. This is what you need to know to be safe on or off the road.

eBook versions

Paperback version

The book retailers set their own prices which can vary substantially. We'll aim to keep a selection of the better prices above.

Any bookshop, whether online or bricks and mortar, can order copies of Why Caravans Roll Over.  Just ask.
ISBN: 978-0-6483190-6-1

Solar That Really Works!

Solar that Really Works! covers the design, installation and use of solar in cabins, camper trailers, travel trailers, fifth wheelers, campervans and motor homes.

eBook versions

Paperback version

The book retailers set their own prices which can vary substantially. We'll aim to keep a selection of the better prices above.

Any bookshop, whether online or bricks and mortar, can order copies of Solar That Really Works!  Just ask.
ISBN: 978-0-6483190-3-0