Spontaneous freewheel disassembly

[Benjamin Weiner]

Yesterday on a long ride my Sachs freewheel disassembled itself. I mean the left-threaded cone
unscrewed. I've never heard of this happening before, is this possible under normal conditions, or
could it only have happened if the cone was loose to begin with? Details below.

It's a typical Sachs 7s FW with maybe 1-2000 miles on it. I was riding up a long climb when
something started clicking. Eventually the chain started clattering, the shifting degraded, and I
threw chain off the rear. I started up again but saw that the cogs were loose, and feared either
stripped hub threads or a broken axle (which doesn't explain loose cogs, but never mind). When I
took the wheel out, t he cogs came off in my hand, leaving the inner part of the freewheel body
happily attached to the hub. This was such a surprise that it took me a moment to figure out what I
was looking at. The outer races and bearings were still attached to the cogs, and thankfully did not
fall all over the road.

I was about halfway up a 7 mile climb and last of a group, so I had to keep going, put the cogs back
and pressed on. At this point I must have gotten the cone threads re-aligned somehow - as I climbed,
it was still clunking, but at the top of the climb the cone had screwed itself back in partway: the
cogs were loose, but I couldn't take them off to impress my companions. The cone on a Sachs 7 FW is
partly hidden under the smallest cog, so it wasn't immediately obvious what was going on, or
accessible to fix.

Obviously I had to bail on the ride, although the bike was basically rideable, and in fact the
freewheel tightened up some more during the 30 miles home, though I still feared pulling a Tyler
Hamilton if I tried to stand up and pedal. On disassembly at home, it looks normal/undamaged.

So what the hell happened? I've assumed that the cone is left-threaded so coasting doesn't unscrew
it. Presumably riding/coasting home tightened it up. But how could it have come unscrewed? Perhaps
it was a bit loose and precession unscrewed it (like a loose pedal). It occurred on a long climb
with no coasting and riding in the largest two cogs, which might make the precession worse.

I'm a little wary of relying on this freewheel in the future, although it seems that if I tighten
down the bearing cone good and hard (Loctite?), it shouldn't happen again. Any opinions?

(and yeah, I'm going to put a cassette wheel on my next bike, etc)

 

[Sergio Servadio]

On 3 Mar 2003, Benjamin Weiner wrote:
> Yesterday on a long ride my Sachs freewheel disassembled itself. I mean the left-threaded cone
> unscrewed. I've never heard of this happening before, is this possible under normal conditions, or
> could it only have happened if the cone was loose to begin with?

It has happened to me a few years back. That was a SHIMANO freewheel. I was climbing when I realized
it was unscrewing. I turned back downhill and that ******* mechanism unscrewd completely quite
quickly, probably just bezcause of the free-wheeling rotation. I surely lost a few balls along the
road. Worse than that, I had a 4 mile long walk back home. I wrote a letter to SHIMANO: never heard
a word from them. How nice!

Sergio Pisa

 

[Grenouil]

"Benjamin Weiner" <[email protected]> wrote in message news:[email protected]...
> Yesterday on a long ride my Sachs freewheel disassembled
itself.
> I mean the left-threaded cone unscrewed. I've never heard
of this
> happening before, is this possible under normal
conditions, or
> could it only have happened if the cone was loose to begin
with?
> Details below.
>
> It's a typical Sachs 7s FW with maybe 1-2000 miles on it.
I was
> riding up a long climb when something started clicking.
Eventually
> the chain started clattering, the shifting degraded, and I
threw chain
> off the rear. I started up again but saw that the cogs
were loose,
> and feared either stripped hub threads or a broken axle
(which doesn't
> explain loose cogs, but never mind). When I took the
wheel out, t
> he cogs came off in my hand, leaving the inner part of the
freewheel
> body happily attached to the hub. This was such a
surprise that it
> took me a moment to figure out what I was looking at. The
outer
> races and bearings were still attached to the cogs, and
thankfully
> did not fall all over the road.
>
> I was about halfway up a 7 mile climb and last of a group,
so I had
> to keep going, put the cogs back and pressed on. At this
point
> I must have gotten the cone threads re-aligned somehow -
as I
> climbed, it was still clunking, but at the top of the
climb the
> cone had screwed itself back in partway: the cogs were
loose,
> but I couldn't take them off to impress my companions.
The cone
> on a Sachs 7 FW is partly hidden under the smallest cog,
so it
> wasn't immediately obvious what was going on, or
accessible to fix.
>
> Obviously I had to bail on the ride, although the bike was
basically
> rideable, and in fact the freewheel tightened up some more
during
> the 30 miles home, though I still feared pulling a Tyler
Hamilton
> if I tried to stand up and pedal. On disassembly at home,
it looks
> normal/undamaged.
>
> So what the hell happened? I've assumed that the cone is
left-threaded
> so coasting doesn't unscrew it. Presumably
riding/coasting home
> tightened it up. But how could it have come unscrewed?
Perhaps
> it was a bit loose and precession unscrewed it (like a
loose pedal).
> It occurred on a long climb with no coasting and riding in
the
> largest two cogs, which might make the precession worse.
>
> I'm a little wary of relying on this freewheel in the
future,
> although it seems that if I tighten down the bearing cone
good
> and hard (Loctite?), it shouldn't happen again. Any
opinions?
>
> (and yeah, I'm going to put a cassette wheel on my next
bike, etc)
>

This is confusing - what's unthreading - the bearing cone (in which case it's nothing to do with
the freewheel), the freewheel lockring/or the small screwed-on sprocket, or the freewheel assembly
off the hub?

 

[G.Daniels]

yes, me too! first rebuild. LBS gave 180 bad advice. balls all over the expletive deleted road. red
loctite, clean threads that is to say bury the balls with grease toward the inside and if younscrew
up the threads with goo do it again. on the other I screwed one up by wadding a ball of loctite into
the bearings? duh, but that's felt before leaving for nebraska.

 

[Benjamin Weiner]

Grenouil <[email protected]> wrote:

> This is confusing - what's unthreading - the bearing cone (in which case it's nothing to do with
> the freewheel), the freewheel lockring/or the small screwed-on sprocket, or the freewheel assembly
> off the hub?

None of the above. The left-threaded outer cone which holds the freewheel itself together came
unscrewed. This is the piece which usually has two little holes for a pin spanner. The one Sheldon
advises you not to mess with at "Servicing Freewheels" under
http://www.sheldonbrown.com/freewheels.html. When this cone comes loose you get access to the
interior bearings and pawls (whether you want it or not). See the first picture at
http://www.sheldonbrown.com/mega7/ Fortunately, when mine came apart on the road, the grease held
the bearings in place.

BTW, this is the second freewheel I've disassembled recently (the first was done deliberately) and
neither time did I have much trouble getting it back together, pawls and all. Still, it's getting
time to switch to cassettes.

 

[John Retchford]

"Benjamin Weiner" <[email protected]> wrote in message news:[email protected]...
> Yesterday on a long ride my Sachs freewheel disassembled itself. I mean the left-threaded cone
> unscrewed. I've never heard of this happening before, is this possible under normal conditions, or
> could it only have happened if the cone was loose to begin with? Details below.
>
Had a very similar experience with a Sachs/Maillard seven speed freewheel while climbing up into the
Vienna Woods on the last full day of a tour from Amsterdam. The small cog started to rub on the seat
stay. Cone had unscrewed and I screwed it back and tightened it down as much as I could using a
spike on a Swiss Army knife in one of the pin holes. That is once I remembered that it had a left
hand thread! It gave no further trouble over the next few days of intermittent cycling and when I
removed the cogs to get a pin spanner on it on our return to Australia it seemed pretty tight. Like
you, I could not guess the cause of the problem.

John Retchford

 

[Gary Kamieneski]

Benjamin Weiner <[email protected]> wrote in message news:<[email protected]>...
> Yesterday on a long ride my Sachs freewheel disassembled itself. I mean the left-threaded cone
> unscrewed. I've never heard of this happening before, is this possible under normal conditions, or
> could it only have happened if the cone was loose to begin with? Details below.
...snip

If it helps, I had the same thing occur with a Sachs 7sp 12-21. I torqued it back and never had
another problem. I still continue to use these when I can find them and have never had a repeat
problem. I chalked it up to not having been tightened down to specs at the factory.

 

[Benjamin Weiner]

Gary Kamieneski <[email protected]> wrote:

> If it helps, I had the same thing occur with a Sachs 7sp 12-21. I torqued it back and never had
> another problem. I still continue to use these when I can find them and have never had a repeat
> problem. I chalked it up to not having been tightened down to specs at the factory.

That's my suspicion also. I'll tighten this one down and try it again, though I'll test it on short
rides before venturing miles from home.

I have a feeling that Sachs quality control may have slipped in the last years of these freewheels.
When I got this one, it had too much heavy grease in it and freewheeled forwards (oops). We sent it
back and I got another one, which was somewhat better (I also flushed it with WD-40 and oil before
installing it).

 

[Gary Kamieneski]

Benjamin Weiner <[email protected]> wrote in message news:<[email protected]>... ...
> I have a feeling that Sachs quality control may have slipped in the last years of these
> freewheels. When I got this one, it had too much heavy grease in it and freewheeled forwards
> (oops). We sent it back and I got another one, which was somewhat better (I also flushed it with
> WD-40 and oil before installing it).

I hope that wasn't a mistake for you. I've used these for many years and my take is that they
changed the seals and lubrication on these. I believe they are supposed to freewheel now with more
friction. I noticed this a couple of years ago.

 

[Benjamin Weiner]

Gary Kamieneski <[email protected]> wrote:
> > I have a feeling that Sachs quality control may have slipped in the last years of these
> > freewheels. When I got this one, it had too much heavy grease in it and freewheeled forwards
> > (oops). We sent it back and I got another one, which was somewhat better (I also flushed it with
> > WD-40 and oil before installing it).

> I hope that wasn't a mistake for you. I've used these for many years and my take is that they
> changed the seals and lubrication on these. I believe they are supposed to freewheel now with more
> friction. I noticed this a couple of years ago.

It wasn't a mistake, I expect unrelated to the freewheel coming apart a year or two later. As a
veteran user, you probably know that the Sachs FW has an oil hole which you can access by removing
the cogs, without disassembling the body. That's what I used.

This was supposed to forestall the problem of sticky pawls causing the freewheel not to engage,
which happened on my first sample and is extremely dangerous. The last year of manufacture I've seen
on a Sachs is 99, so I guess that "new" ones have been sitting on a shelf with the grease drying for
a couple of years. I don't care about friction or seal drag within reason when it is freewheeling
and I'm coasting.

 

[G.Daniels]

i get the idea that some assemble the outer ring without locktite! is this possible? when the lump
formed,i let the unit sit in the hot sun without spinning the unit first to disorient the squeezed
out loctite forming up at the bearing race. the advice from beyond suggests trials on each
component before venturing forth. i guess assuming sachs knows what is doing... rumour has it that
the workers who made that mistake in malasia were flogged,then escaped to europe where their
scrweing thisngs up good.