Rim Thickness

Have an old (1997) pair of AlexRims DM18 MTB rims without wear
indicator. How do I determine when they're best replaced?

--
BobC

On 09/29/2009 06:55 PM, BobC wrote:
Have an old (1997) pair of AlexRims DM18 MTB rims without wear
indicator. How do I determine when they're best replaced?


measurement?

On 30 Sep, 02:55, BobC wrote:
Have an old (1997) pair of AlexRims DM18 MTB rims without wear
indicator. *How do I determine when they're best replaced?



Depends on how nervous you are. Double the inflation pressure on your
tyres and leave overnight. Something may go bang. Relieve pressure
if it hasn't already and examine the rim wall for splitting or bulging
using first your eyes then your fingers. Another method is to
directly measre the thickness of the sidewall with a dental caliper or
use a transfer caliper and a wire for a gauge. The precise wall
thickness before fracture is dependant on tyre and pressure, I
understand that 0.6mm is about minimum.

On Sep 29, 7:55*pm, BobC wrote:
Have an old (1997) pair of AlexRims DM18 MTB rims without wear
indicator. *How do I determine when they're best replaced?

--
BobC

Run your finger along the sidewall. If it's concave, don't use it.

On Sep 30, 8:34*am, "P. Chisholm" wrote:
On Sep 29, 7:55*pm, BobC wrote:

Have an old (1997) pair of AlexRims DM18 MTB rims without wear
indicator. *How do I determine when they're best replaced?

--
BobC

Run your finger along the sidewall. If it's concave, don't use it.

not sure if that's true for all rims, my CR-18s were slightly concave
out of the box.

nate

BobC wrote:
Have an old (1997) pair of AlexRims DM18 MTB rims without wear
indicator. How do I determine when they're best replaced?


While not a perfect method, I put a straightedge on the rim & eyeball
the amount of daylight and compare to a reference like a spoke diameter.
I think 1 mm or so of wear means it's new rim time.

BobC schreef:
Have an old (1997) pair of AlexRims DM18 MTB rims without wear
indicator. How do I determine when they're best replaced?



My very competent LBS says 'when it is wore 0,6 mm it is time to replace
the rim'. So measure.

Lou

P. Chisholm schreef:
On Sep 29, 7:55 pm, BobC wrote:
Have an old (1997) pair of AlexRims DM18 MTB rims without wear
indicator. How do I determine when they're best replaced?

--
BobC

Run your finger along the sidewall. If it's concave, don't use it.


It is always concave Peter after a little use.

Lou

On 30 Sep, 18:11, Jobst Brandt wrote:
Have an old (1997) pair of AlexRims DM18 MTB rims without wear
indicator. *ow do I determine when they're best replaced??
Depends on how nervous you are. *Double the inflation pressure on
your tyres and leave overnight. *Something may go bang. *Relieve
pressure if it hasn't already and examine the rim wall for splitting
or bulging using first your eyes then your fingers. *Another method
is to directly measre the thickness of the sidewall with a dental
caliper or use a transfer caliper and a wire for a gauge. *The
precise wall thickness before fracture is dependant on tyre and
pressure, I understand that 0.6mm is about minimum.

I don't believe that is a reasonable wear test, considering that it is
static, while riding causes lateral forces at the tire-to-ground
contact zone. *Such changes in force can cause a rim to crack at the
bead while a static pressure test produces less stress concentration.

One way to assess how much use is left in the rim is to measure a
newer one and see how hollow-cheeked the worn one has become. *I have
ridden a front rim to 0.5mm wall while descending in rain, a severely
hollow cheeked condition, and have cross sections of that rim in a
collection of worn parts. *I don't recommend going that far, but I was
lucky. *The Stelvio (2000m) is not a trivial descent so I descended
using only the rear brake, after which the rain stopped and I could
use the front brake again, without significant wear.

Foggy brain again? I said 0.6mm, which accounts for a little
displacement at any rim join, should you have these devious new
fangled French extruded rims rather than good honest English solid
spun aluminium rims as fitted to English racers and English roadsters
so the riders can go for a nice jaunt into the English countryside and
seek refuge, good English ale and fud for his sustainance. Served at
a temperature and quantity set down by the crown in imperial measures
not fuddy duddy willy nilly willhemeetus in the bar or the snobs
room.. Wonder when they were last made, spun aluminium bicycle rims,
that is.

* Still Just Me * schreef:
On Wed, 30 Sep 2009 20:23:51 +0200, Lou Holtman
wrote:

BobC schreef:
Have an old (1997) pair of AlexRims DM18 MTB rims without wear
indicator. How do I determine when they're best replaced?


My very competent LBS says 'when it is wore 0,6 mm it is time to replace
the rim'. So measure.

Lou

Best measure when they are new then, so you can compare.




? all the rims I know have flat brake surfaces when new especially the
machined onces. Measure with the depht probe of your vernier caliper.

Lou