What happens when a rim wears out
If you're lucky, you'll be pumping up your tyres nice and hard,
you'll hear a crack, then nano-seconds later you'll hear a loud
bang. When the dust settles and you've recovered from the shock,
you'll notice that a razor sharp aluminium hoop has parted company
from your wheel. You'll also notice that your tyre sidewall is
probably ripped and your tube is history.
If you're unlucky, the same thing will happen to you when you're
out riding. You can fill in the rest...
The image below shows a rim from a customer who didn't know
there rim was worn and replaced a tube & this is what
happened when he tried inflating the new tube.
What to look for
Visually inspect your braking surfaces for excess wear. Usually
this manifests itself as a concave profile on the rim. The easiest
way to see this is by placing a straight edge (e.g. a metal ruler)
across the rim surface. You'll see a significant area of daylight
between the rim and the ruler if wear is excessive.
Also look for grooving running around the rim, often caused by
grit lodged in the brake blocks. These grooves can be the first
places that the rim can fail.
However, don't confuse these grooves with wear indicator grooves
found on some rims. These handy features show you when it's time to
replace the rims - when the groove disappears, it's time to go
shopping. Some manufacturers have other systems to show when rims
need replacing, such as indentations or holes that appear at a
certain point when the rim needs replacing.
Not all rims are created equal
Some rims, especially lightweight ones, have a very thin braking
surface, meaning that they have a much reduced service life. Heavy
duty touring rims like Sun Rhynos, Alesa Endeavours and others have
a thicker, heavier braking surface which results in much higher
mileage between rim replacement. Some high spec rims have a ceramic
coating which drastically reduces rim wear and improves braking and
are well worth the investment for high mileage riders with deep
Tags: Bike Maintenance posted