Fixed cup coming loose on old Italian style bottom bracket.

I can do most things on a bike but this was the first time I attempted to do
a bottom bracket. I read the stuff on the net but I was replacing the bottom
bracket so I had to pull off the fixed cup. Upon instaling the new one, I
thought I had it tight enough but clearly I didn't because after riding about
5 miles I noticed that the pedalling felt funny and I looked down to see the
right (fixed) cup had come out almost all the way. After a miserable trip
home, I pulled the crank and re-tightened the fixed cup this time, hitting the
fixed cup wrench (Park HCW-4) with a hammer several times to make sure
it was really tight. I rode it about 3-4 miles after that and it seems to be holding.
If it loosens again, I think I'm going to have to resort to locktite.

What is confusing me is that when I pedal, the spindle is moving in the same
direction as the cup would move to tighten so why would pedalling cause it
to loosen? Clearly, I'm not understanding the physics of this. I would think
the left side would loosen from pedaling, not the right.

--Bill Davidson
--
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What is confusing me is that when I pedal, the spindle is moving in the same
direction as the cup would move to tighten so why would pedalling cause it
to loosen? Clearly, I'm not understanding the physics of this. I would
think
the left side would loosen from pedaling, not the right.

--Bill Davidson


Look up "precession". Sheldon Brown has an explanation on his web pages
somewhere.

--
Ted Bennett
Portland OR

The spindle moves in the tightening direction, but the ball bearings
movement on the cup is in the loosing direction.


"Ted Bennett" wrote in message
...

What is confusing me is that when I pedal, the spindle is moving in the
same
direction as the cup would move to tighten so why would pedalling cause
it
to loosen? Clearly, I'm not understanding the physics of this. I would
think
the left side would loosen from pedaling, not the right.

--Bill Davidson


Look up "precession". Sheldon Brown has an explanation on his web pages
somewhere.

--
Ted Bennett
Portland OR

"Bill Davidson" wrote ...
I can do most things on a bike but this was the first time I attempted to
do
a bottom bracket. I read the stuff on the net but I was replacing the
bottom
bracket so I had to pull off the fixed cup. Upon instaling the new one, I
thought I had it tight enough but clearly I didn't because after riding
about
5 miles I noticed that the pedalling felt funny and I looked down to see
the
right (fixed) cup had come out almost all the way. After a miserable trip
home, I pulled the crank and re-tightened the fixed cup this time, hitting
the
fixed cup wrench (Park HCW-4) with a hammer several times to make sure
it was really tight. I rode it about 3-4 miles after that and it seems to
be holding.
If it loosens again, I think I'm going to have to resort to locktite.

I always used loctite on my old Marinoni's BB. It's a lot less trouble than
hitting the wrench with a hammer, more effective, and you don't get hammer
marks on the wrench...
--
mark

"Bill Davidson" wrote ...
-snip-
bracket so I had to pull off the fixed cup. Upon instaling the new one, I
thought I had it tight enough but clearly I didn't because after riding
-snip-
right (fixed) cup had come out almost all the way. After a miserable trip
home, I pulled the crank and re-tightened the fixed cup this time, hitting
the fixed cup wrench (Park HCW-4) with a hammer several times to make sure
it was really tight. I rode it about 3-4 miles after that and it seems to
be holding. If it loosens again, I think I'm going to have to resort to locktite.

mark wrote:
I always used loctite on my old Marinoni's BB. It's a lot less trouble than
hitting the wrench with a hammer, more effective, and you don't get hammer
marks on the wrench...

Professional mechanics use a length of pipe ( or in our case
a Reynolds tube - because we have one!) instead of a hammer.
Oh, and blue loktite.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

On 2003-12-03, Bill Davidson wrote:

What is confusing me is that when I pedal, the spindle is moving in the same
direction as the cup would move to tighten so why would pedalling cause it
to loosen? Clearly, I'm not understanding the physics of this. I would think
the left side would loosen from pedaling, not the right.

Friction acts in the opposite direction from the rotation; therefore
the cup tends to loosen. That's why English thread BBs have a left-hand
thread on the fixed cup side.

Use locktite on the cup and you should be OK.

--

-John )

wrote:
The spindle moves in the tightening direction, but the ball bearings
movement on the cup is in the loosing direction.

I spent some time thinking about this and it sort of makes sense but
the ball bearings are moving along the cups in the tightening direction.
However, as they roll, they are also spinning on their own axis as you
say in the loosening direction so I think I get it now. Pushing against
the bearings pushes the cup in the loosening direction. It also occurs
to me that if I have the left side too tight, it might make this effect worse
though I'm not sure about that.

This would also explain why the left cup has a tendency to tighten rather
than loosen and why the lock ring functions as a lock ring in spite of not
really catching on anything. I may have to go back to the left side and
loosen it a bit to compensate for this.

There has to be a first time for everything eh? I've been working on my
own bike for 17 years. It's about time I learned to do the BB.

--Bill Davidson
--
Please remove ".nospam" from my address for email replies.

Support the Electronic Frontier Foundation
http://www.eff.org
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bill- Upon instaling the new one, I
thought I had it tight enough but clearly I didn't because after riding about
5 miles I noticed that the pedalling felt funny and I looked down to see the
right (fixed) cup had come out almost all the way. After a miserable trip
home, I pulled the crank and re-tightened the fixed cup this time, hitting the
fixed cup wrench (Park HCW-4) with a hammer several times to make sure
it was really tight. I rode it about 3-4 miles after that and it seems to be
holding.
If it loosens again, I think I'm going to have to resort to locktite.

The bearings are rotaing backward loosening the cup..
DO NOT use loctite. Have the BB shell faced, install with proper tools(like a
Campagnolo or similar fixed cup tool). Use grease and teflon tape...

Peter Chisholm
Vecchio's Bicicletteria
1833 Pearl St.
Boulder, CO, 80302
(303)440-3535
http://www.vecchios.com
"Ruote convenzionali costruite eccezionalmente bene"

bill- Upon instaling the new one, I
thought I had it tight enough but clearly I didn't because after riding about
5 miles I noticed that the pedalling felt funny and I looked down to see the
right (fixed) cup had come out almost all the way. After a miserable trip
home, I pulled the crank and re-tightened the fixed cup this time, hitting the
fixed cup wrench (Park HCW-4) with a hammer several times to make sure
it was really tight. I rode it about 3-4 miles after that and it seems to be
holding.

Qui si parla Campagnolo wrote:
If it loosens again, I think I'm going to have to resort to locktite.
The bearings are rotaing backward loosening the cup..
DO NOT use loctite. Have the BB shell faced, install with proper tools(like a
Campagnolo or similar fixed cup tool). Use grease and teflon tape...

Why not locktite? That is precisely why it was developed -
rocking movements or vibration on threaded fasteners. We
use a drop of blue locktite.

If you suspect a stubborn cup has a locktite film in its
threads, the stuff breaks down with a heat gun at about 250F
so it should never be an impediment to disassembly. ( That
is safely below paint damage temperatures)

(I will agree that in theory teflon tape should be OK but I
don't have as much experience with that or many other new
technologies. I still do water/gas pipe joints with pipe
joint paste. I suppose when the can is empty I will switch
to the teflon tape -if I live that long)
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

Andy- Why not locktite? BRBR

Had to take a 'few' hours to muscle a right cup outta two framesets lately.
Both were dry and it sure looked like they had been loctited by somebody...no
grease. Unless you really oooze loctite on, it is essentially being assembled
dry...

rocking movements or vibration on threaded fasteners. We
use a drop of blue locktite. BRBR

We use blue loctite in some places, like on friction shifter bolts, etc.




Peter Chisholm
Vecchio's Bicicletteria
1833 Pearl St.
Boulder, CO, 80302
(303)440-3535
http://www.vecchios.com
"Ruote convenzionali costruite eccezionalmente bene"