HELI BIKES !
Motorcycle Safety Initiative!
www.helibikes.co.uk!
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Who’s not a happy camber then!!
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Why can one bend be different to another? Why can a rider be more vulnerable on a particular bend
depending on which direction they are travelling?!
Well if we consider identical or rather very similar bend types and environmental conditions including
weather and road surface conditions to be the same…and traffic density to be the same, then the one
remaining substantial factor that can affect the stability of a ride is road camber!!
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What is road camber?!
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Camber is a slight curve or angle from the centre of a road surface to the road sides, which makes water
flow to the side and drain away which helps to prevent standing water. !
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Of course there is never perfect water drainage and under heavy rain or persistent rain, roads can still
become flooded. Where roads have been worn away or deformed slightly, then puddles can form.
However essentially the road camber is a design feature to minimise the effect of rain on the road surface.!
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CROWN
BER
CAM
Grass
Verge
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CAM
BER
Curb
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How does it affect a rider and the motorcycle stability? On a straight road it may cause the bike to drift to
the side of the road which will require a rider control input to correct.!
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Gravity!
Pushing!
Down on
uneven or
sloping
surface to the
right!
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Gravity!
Pushing!
Down!
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Gravity!
Pushing!
Down on uneven or
sloping surface to
the left!
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If a motorcycle is travelling in
a straight line and is riding on
the crown of the road, then
the forces on the motorcycle
will be pushing the bike
straight down onto the road.
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If a motorcycle is travelling in a straight
line and is riding on the left camber of
the road, then the forces on the
motorcycle will be pushing the bike
straight down onto the road. The
sloping surface or camber to the left
will induce a force that will pull the bike
to the left. The rider will have to
consciously or subconsciously correct
to maintain the bike in a straight line.!
If a motorcycle is travelling in a straight
line and is riding on the right camber of
the road, then the forces on the
motorcycle will be pushing the bike
straight down onto the road. The
sloping surface or camber to the right
will induce a force that will pull the bike
to the right. The rider will have to
consciously or subconsciously correct
to maintain the bike in a straight line.!
Many times this correction is not even
noticed by the rider!
Many times this correction is not even
noticed by the rider!
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When on a bend and the motorcycle is being leaned over, then as well as the above forces, the motorcycle
and rider is subjected to centrifugal and centripetal forces which will ‘pull’ the rider to the outside or inside
of the bend respectively.!
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Let’s consider a left hand bend!!
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On a left bend, gravity pushes the
bike/tyre down, centrifugal force
pulls the bike/tyre to the outside of
the turn and this is somewhat
resisted by the upward slope or
upward camber of the road.
This effectively allows for greater
tyre and road surface interaction
and greater contact patch
performance.
This may be referred to as a positive
camber and is beneficial for a rider
to gain optimum grip for a given lean
angle.
On a left bend, gravity pushes the
bike/tyre down, centrifugal force
pulls the bike/tyre to the outside of
the turn and this is partially resisted
by the level road surface.
This may be considered as a neutral
position which allows average tyre
and road surface interaction and a
neutral contact patch performance.
This may be referred to as a neutral
camber and although still providing
good grip capability, it is not
optimum.
On a left bend, gravity pushes the
bike/tyre down, centrifugal force
pulls the bike/tyre to the outside of
the turn and this is marginally
resisted by the downward slope or
downward camber of the road.
This may be considered as a
negative camber and allows the
least tyre and road surface
interaction and least contact patch
performance.
The negative camber gives the least
benefit to the rider and the least grip
for a given lean angle.
Anytime, when riding, the rider needs to be aware of the road camber, especially so on bends and
particularly more acutely when riding in wet or damp conditions. Of course not always the case, but more
often than not, when riding on the left (UK) on a level plateaux bend to the left, there will be a positive
camber to assist the rider. When riding on the right (US/EUROPE) on a bend to the left there will be a
negative camber. However please take note that this is not definitive...it really depends on the local
geography. In certain cases where the camber differs from above it is not uncommon for there to be a
warning road sign to highlight this.!
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Let's consider a right hand bend!!
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On a right bend, gravity pushes the
bike/tyre down, centrifugal force
pulls the bike/tyre to the outside of
the turn and this is marginally
resisted by the downward slope or
downward camber of the road.
This may be considered as a
negative camber and allows the
least tyre and road surface
interaction and least contact patch
performance.
The negative camber gives the least
benefit to the rider and the least grip
for a given lean angle.
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On a right bend, gravity pushes the
bike/tyre down, centrifugal force
pulls the bike/tyre to the outside of
the turn and this is partially resisted
by the level road surface.
This may be considered as a neutral
position which allows average tyre
and road surface interaction and a
neutral contact patch performance.
This may be referred to as a neutral
camber and although still providing
good grip capability, it is not
optimum.
On a right bend, gravity pushes the
bike/tyre down, centrifugal force
pulls the bike/tyre to the outside of
the turn and this is somewhat
resisted by the upward slope or
upward camber of the road.
This effectively allows for greater
tyre and road surface interaction
and greater contact patch
performance.
This may be referred to as a positive
camber and is beneficial for a rider
to gain optimum grip for a given lean
angle.
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When riding on the left (UK) on a level plateaux bend to the right, there will be a negative camber which
will be a disadvantage to the rider. When riding on the right (US/EUROPE) on a bend to the right there will
be a positive camber which will have increased benefit to the rider. However please take note that this is
not definitive...it really depends in the local geography. In certain cases where the camber differs from
above it is not uncommon for there to be a warning road sign to highlight this.!
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With this in mind any rider should pay particular to the road layout, the geography and learn to read what
the camber is. This will be of particular benefit when riding on unknown roads and especially in wet
conditions.!
Many of the motorcycle accidents on bends are partly attributed to rider errors, misjudgments of speed and
position for the conditions. Many times an accident occurs when a rider had attacked a bend with a
negative camber in the same manner as a bend with a positive camber. This undetected difference in
either aid or hindrance had been the crucial factor which has led to an accident or a very near miss by a
rider running wide.!
Over many years of accidents, especially where riders were not seriously injured and were coherent, a
common reaction or remark has been:!
"I don't know what happened. I ride these roads all the time. I just went through that other bend with no
problem, but I couldn't make this one which is the same!"!
What the rider wasn't factoring for was camber...especially negative camber! !
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As well as all the other things a rider should consider, one of the most important is the lay of the road and
the quality of the road. Using good forward vision and looking both near and far to judge the condition of
the surface and the camber, whilst estimating how the bike/tyres will perform. This estimation and constant
analysis will allow the rider to better judge approach speeds and entry speed and position…especially on
bends. !
Of course this is also hugely affected by the condition of the tyres, by the amount of tread left, the tyre
pressure and the quality, condition and settings of the suspension. However for this article I am assuming
that the tyre condition and pressures are satisfactory and the suspension setting is also.!
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One note of caution which is purely anecdotal. Although sharp bends require absolute attention by the
rider, they are somewhat easier to determine the necessity for a slower entry and transit speed, therefore
the forces acting on the bike/tyre are less to make negative camber a crucial factor.!
More often has been the lesser sharp bends which have been attacked at higher speeds…especially when
the bend exit is easier to see. When the rider is at speed, the forces acting are greater, therefore any
negative camber has an increasing factor, which has led to many of these type of accidents…with a
combination of higher speed, poor position and lack of camber acknowledgment.!
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Riding whilst looking for cambers is something that I constantly do and constantly practice…regardless of
how many years I’ve been riding or driving. I look for positive cambers to afford continued or greater speed
and greater braking if required…and I look for negative cambers too which I reduce speed for and adjust
my braking to suit. Ultimately it is about modifying control inputs to exploit or compensate for the positive
or negative cambers respectively. !
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Next time you go for a ride, take the time to look ahead and try to determine the camber of the bend in the
road and practice with modifying speeds and positioning, but be extra mindful to make very gradual
adjustments. !
If you are unsure, go slowly and cautiously at first during a quiet low traffic density period, and then build
on from there. You’ll be surprised how quickly you will see cambers appearing before you.!
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RIDE AWARE!/RIDE SAFE!