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Australian Car GuideYou're on the Australian Car Guide. Buy, sell and discuss cars at eCars. |
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Four Wheel Drive
Four-Wheel-Drive Tyres.
Please don't ask "what sort of four-wheel-drive tyre should I buy?" Get four people around a camp fire and you will get four different opinions on the best 4WD tyre! What is important is that tyres be kept at their recommended
pressures when driving on-road.
It is often necessary to lower pressures for off-road conditions (mud, sand)
but this can cause the tyre to "roll off" the rim
under cornering loads.
The danger is greatest with tube-less tyres
because there is an instant loss of all tyre pressure
which can lead to a
roll-over
even for an experienced driver.
Pressures should be returned to normal as soon as possible,
and definitely before resuming highway speeds.
BFG - BF GoodrichThe BFG All-Terrain and Mud-Terrain (left) tyres
are popular in muddy old
Victoria
(some people think that BFG
stands for Very Frightfully Good).
The Mud-Terrain is rather more aggressive than the All-Terrain
so it clears itself better although given sticky enough clay (left)
its tread can still get filled up.
The All-Terrain is reported to wear well,
particularly in the larger sizes, e.g. 235/80-ish. 
SimexSimex tyres are made in Malaysia,
some of them from ex-Dunlop moulds.
The tyres are gaining a reputation for good value for money.
This type (left) was fitted to the winning vehicle of the
1999 Malaysian Rainforest Challenge, in attendance at the
Victorian
Four Wheel Drive Show - 
SwampersThe escalating tyre war has given rise to diameter creep, from the basic 31" (7.50x16) to 33", 35" and these 38" Super Swampers [7/'00]. The objectives are to climb steps more easily and
to keep your diff' above the crown of the ruts
dug by the other guy. Size Conversion"Old" tyre dimensions are in inches, e.g. 7.50 x 16. The tyre carcass width and height are both 7.5", so there is no need to specifiy an aspect ratio (it is 1.0), and the overall tyre diameter is 2 x 7.5 + 16 = 31", in this case. The most common Jeep / Land Rover / Cruiser tyres were from 6.00 x 16 to 7.50 x 16, although some went up to 9.00 x 16. (A 7.50R16 tyre is just the radial-construction equivalent of a 7.50 x 16.) Newer tyre dimensions are a mixture of metric and imperial quantities,
e.g. 245/80 x 16, indicates a tyre carcass width of 245mm,
an aspect ratio of 0.8 or 80% and a wheel rim diameter of 16"!
A change became necessary when tyre technology enabled aspect ratios
of less than 1.0.
Low aspect ratio tyres give better on-road handling,
all other things being equal,
but there is still a place for the trusty 7.50 x 16
on 4WDs. Tyre measurements, and calculated quantities, are "nominal"
because they depend on manufacturing tolerances, tyre inflation pressure,
wheel-rim width, load, temperature, wear, See the split-rim (repairs) and Tireloc pages
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