REPAIRS PAGE 11
ALLOY WHEELS - A CASE OF WINTERS REVENGE
Nice though alloy wheels undoubtedly
are, there have been a couple of cases recently where members have reported some
difficulty when removing their wheels. In these cases when all the wheel nuts
were removed the wheel still remained stubbornly attached to the car!
Fortunately the cars were on their owners’ drives at the time and a little
‘persuasion’ soon solved the problem. If however they had happened to puncture
in the middle of nowhere with few tools then they could have been well and truly stuck!
This problem is by no means unique to MR2’s - it
can happen to any car with alloy wheels. The culprit is electro-chemical
corrosion which can occur in certain conditions when two dissimilar metals are
in contact with each other. In a nutshell the
hub flange is steel and the wheel is aluminium alloy and if salt water
happens to get between them, they act literally as a battery cell. This starts
corrosion and then they try to weld themselves together.
This can then make the wheel difficult to remove - the
inner wheel rim needs tapping with a hammer (obviously with a soft dolly in
between to avoid rim damage). Repeated tapping with the wheel rotated a bit in
between taps eventually releases the wheel from the hub (hint - leave 2 wheel
nuts on just loose to stop the wheel from finally hurling itself off the car!)
This can only be done safely with the car firmly chocked up - to
rely on the jack alone is not safe hence the above comments on it being a problem in the middle of nowhere!
So that's the problem, and its pretty obvious that
British winter driving conditions with salt spray and long damp periods are
ideal for encouraging this sort of corrosion. There is however a relatively
simple way to minimise this problem, lightly
coat the hub flange with grease before refitting each wheel. It’s not perfect,
but it does make things a good bit better. The grease acts as a barrier to water
ingress and slows the corrosion down. I use a standard wheel bearing grease
(lithium based) if you want protection for really extended periods then use a
more waterproof grease (ie calcium or PTFE based.) Clearly don’t swamp the whole area,
you really don’t want it on your discs or pads! Really
it is the sort of job that can be done whenever a wheel is removed during servicing or maintenance,and
as such it is effectively a zero cost option which could prove invaluable should a puncture occur.
Don’t forget, while the wheel is off clean out the wheel
arch especially those rear arch lip mudtraps!
ALAN JONES