Sun, 19 Apr 1998 00:13:00 +0200
- Message No. 2639
>From: ms@mausd.gun.de (Marcel Sieling)
Subject: reasons for bearing failure
Hi @ buddies,
there's news about the wheel bearings.
After the regular 36000 km service of my @ I noticed, that I could move the
rear wheel a few millimeters to the right and left, when the bike was on
it's main stand. So I dismounted it and examined it closely, the result was
a damaged right bearing on the back wheel. OK so far.
But we examined further, and here is the interesting result:
WW WW
WWWWW WWWWW
XXWWWWWWWWWWWWWWWWWWWWXX
AAYY!ZZZZZZZZZZZZZZZZZZ!YYNN
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAYY!ZZZZZZZZZZZZZZZZZZ!YYNN
XXWWWWWWWWWWWWWWWWWWWWXX
WWWWW WWWWW
WW WW
|<---- DIST ------>|
The above graphic shows the construction of the rear axis. In the middle
you see the axis marked with the letter "A". Note the Nut, which is on the
right end of the axis, marked with "N".
The center part of the wheel (Nabe) is marked with the letter "W". In the
left and right ends of the "Nabe" there are the bearings, which consist
each of two parts: One is rotating and fixed to the "Nabe" (marked with "X"
here) and the other one is standing still in relation to the axis and
marked with the letter "Y". Between "X" and "Y" there are balls of the
bearing.
So finally between both "Y"-parts of the bearings (left and right) there is
a thick steel tube marked with the letter "Z". This tube must be e little
longer than the distance between the inner bottoms of the holes, in which
the bearings are pressed into, so that that the axis can be tightend in the
frame without applying tension to the bearings.
If the tube "Z" was too short, there would be a little space between the
tube and the bearings marked with "!". The Axis "A" and the nut "N" would
press both inner parts of the bearings "Y" too tight together, so that the
outer parts "X" could not follow, because they are stuck in the "Nabe".
This could cause one or both bearings to crash. If one crashes, it will
mostly be the right one, because it's smaller and therefore a bit weaker.
Now we measured the distance between the inner bottoms of the bearing holes
in the "Nabe" and the lenght of the Tube "Z". Remember: The Tube must be at
least as long as the distance in "Nabe". In no case it may be shorter,
because the bearings than can not be built in without tension.
Measurements on my @ (RD07 dated April '94)
Distance in "Nabe": 124,5 mm
Length of Tube "Z": 123,7 mm.
As you see, the inner tube is too short and therefore also a new bearing
will break after a short time.
We will exchange that inner tube to a one which fits exactly and then
exchange all bearings and sealings and hope, that this will work out.
It would be interesting to hear from others, who have a rear wheel
dismounted and who take the above measurements exactly. Note: You will have
to dismount at least one bearing out of the wheel to get the tube to
daylight, which usually damages the bearing, so don't do that on wheels
which are still ok. ;-))
I wonder, if anyone has similar experiences.
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/ \_/\_/ \
|O __ O|
\ /| |\ / Honda XRV750 Africa Twin
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\ /__\ /
/=||/ ||=\ take care - Marcello (rrr#52, ATIC#9, KotFBL).
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dipper@normans.isd.uni-stuttgart.de