RV FEATURE
A common beam-axle leaf-spring setup
found on many bitumen-bound caravans.
make sure it is okay. A repair doesn’t always have
to indicate a failure. It could also have been from
accident damage and the other side may be fine.
“Fatigue in stub axles is very hard to detect but
when checking for a bent stub axle, initially check
the gap between the backing plate and the back
edge of the brake drum. This should be parallel.”
AXLE RATINGS
A trailer’s group axle rating should be equal to –
but preferably greater than – the trailer’s Gross
Trailer Mass. If it isn’t, there’s a big problem.
Fortunately, this scenario is uncommon. And
according to Neville’s experience, the reverse
is usually true. For its part, Simplicity stamps
its products with the weight rating along with a
serial number.
“To determine if the van is legal with the
suspension/axles, we always advise owners to
fill their water tanks and load their vans as they
would travel and put it over a weighbridge,” he
said. “With the van still connected to the tow
vehicle, put the caravan’s wheels only on the
weighbridge. This weight is the GTM and should
not exceed the capacity stamped on the axle or
the GTM stamped on the van’s compliance plate.”
At Simplicity, heavier single axles
rated over 2000kg, and tandem
axles over 4000kgs, as well as other
components used in high-stress
applications, are made from a higher
grade chrome moly steel, grade 4140.
WHEELS AND TYRES
When factoring in stub axle loads, the axle
manufacturer should also also consider the
unsprung weight of the wheel and tyre. Most 15in
and 16in wheel and tyre combinations weigh in
excess of 32kg. The dynamic forces created by
this weight when bouncing over corrugations
and pot holes is quite high. Most reputable local
axle and suspension manufacturers allow for all
of these loadings when rating their product.
“Be aware: what may work in North
America and Europe does not
cut it in Australia,”
Neville said. “Our
conditions are quite
unique and need to
be respected.”
Very good advice.
AXLE STEEL
Most stub axles in the Australian caravan industry,
including some of Simplicity’s products, are made
from a medium carbon steel, grade S1045.
14 \
Among other products, Simplicity
builds a unique load-sharing coil
suspension system.