Chainring wobble

[Till Rosenband]

Hi,
I am currently riding a road bike with '96 Shimano 600
components, and it seems like my bottom bracket axle is
bent. Even when there is no force on the cranks both
chainrings move left and right a few mms in the derailleur
cage when I turn the cranks. When I am pushing moderately
hard while riding this lateral deflection gets stronger and
causes the chain to scrape in some gears, no matter how I
adjust the derailleur. I have had some chainring wobble in
two mountain bikes that I rode previously, but I could
always adjust the derailleur to get by without much
scraping. I remember hearing somewhere that BB axles tend
to bend a certain amount initially and then maintain their
shape for a long time. Does anyone know of BBs that have
stronger axles that will work with a Shimano 600 crankset?

Thanks,
-Till Rosenband

[David Earls]

Sounds more like either loose chainring bolts or deformed axle or cup races.
Tear your BB down, examine the ball bearings and all the races. If the races
are pitted or scratched the axle and/or cups need replacing.

--

_____________
David Earls
Not All There
Till Rosenband wrote in message <3605BBA5...@mit.edu>...

[Joseph Jankovsky]

I have the same wobble (with new chainrings) on my ultegra. Here's the
experiment I will soon perform:

1. Mark on the rings where the wobble goes in and out.
2. Take off the crank, rotate 180 degrees, and put it back on the
spindle.
3. If it's a bend axle, the wobble will be opposite. If the wobble is
the same, then my guess is one of the spider arms is bent.

I'll send you my bill.

Joe Jankovsky

[John Everett]

In article <6u4juf$k...@dfw-ixnews10.ix.netcom.com>, ste...@ix.netcom.com
says...

>
>Sounds more like either loose chainring bolts or deformed axle or cup races.
>Tear your BB down, examine the ball bearings and all the races. If the races
>are pitted or scratched the axle and/or cups need replacing.
>

>Till Rosenband wrote in message <3605BBA5...@mit.edu>...

>>Hi,
>> I am currently riding a road bike with '96 Shimano 600
>>components, and it seems like my bottom bracket axle is
>>bent.

Regarding the above answer, a '96 Shimano 600 is almost certainly a cartridge
bottom bracket, so there will be no balls or cups to examine.

I recently checked out a similar problem for a friend and found that the
drive side lock ring had loosened, allowing the whole cartridge to wobble in
the shell.

--
jeve...@wwa.DEFEAT.UCE.BOTS.com (John Everett) http://www.wwa.com/~jeverett
^^^^^^^^^^^^^^^
Things have gotten so bad I feel the need to disguise my email address.
And I don't like this explanation because I just hate long signatures.