Sachs/Sram chain Freewheel compatibilty problem



B

Bob

Guest
I have some later model (LY-9?) 7spd freewheels that I am trying
to run. I mounted them up on a bike with some Sachs SC-40 chains.
The derailleurs are friction.

This has resulted in a very serious - as in totally unrideable -
chain skip/slip problem. It actually seems to be skipping several
teeth at once every couple revolutions. It all works fine in the
stand but on the road there's a serious issue.I tried two chains and
freewheels, both new, same problem.

I switched
the freewheel over to a Suntour 7spd and it ran fine on a long run
with lots of pumping action. So, it really appears to be a
freewheel/chain issue.

Is this a known incompatibility? I thought the Sachs SC-40 chain and
the Sachs freewheel were about the same vintage and both for 7spd
setups (?)

THanks,
 
Anyone?

On Tue, 20 Sep 2005 14:57:02 GMT, Bob <[email protected]> wrote:

>I have some later model (LY-9?) 7spd freewheels that I am trying
>to run. I mounted them up on a bike with some Sachs SC-40 chains.
>The derailleurs are friction.
>
>This has resulted in a very serious - as in totally unrideable -
>chain skip/slip problem. It actually seems to be skipping several
>teeth at once every couple revolutions. It all works fine in the
>stand but on the road there's a serious issue.I tried two chains and
>freewheels, both new, same problem.
>
>I switched
>the freewheel over to a Suntour 7spd and it ran fine on a long run
>with lots of pumping action. So, it really appears to be a
>freewheel/chain issue.
>
>Is this a known incompatibility? I thought the Sachs SC-40 chain and
>the Sachs freewheel were about the same vintage and both for 7spd
>setups (?)
>
>THanks,
>
>
>
>
 
Modern freewheels are "profiled" to help shifting. This means that at
the manufacturer they grind down the teeth so that the chain doesn't
have to rise as much to shift. This means that with some modern
freewheels they are "pre-worn" and your chain is probably objecting to
a design feature of the LY-9 freewheel.

So in reality it would make sense that getting rid of the LY-9
freewheel and using a full-height freewheel (suntour) would fix the
problem.

The only time i've ever experienced chain skip is when one or both
parts were old. And it usually only happened in one gear - not in all
of the gears.

- Don

Bob <[email protected]> writes:

>Anyone?


>On Tue, 20 Sep 2005 14:57:02 GMT, Bob <[email protected]> wrote:


>>I have some later model (LY-9?) 7spd freewheels that I am trying
>>to run. I mounted them up on a bike with some Sachs SC-40 chains.
>>The derailleurs are friction.
>>
>>This has resulted in a very serious - as in totally unrideable -
>>chain skip/slip problem. It actually seems to be skipping several
>>teeth at once every couple revolutions. It all works fine in the
>>stand but on the road there's a serious issue.I tried two chains and
>>freewheels, both new, same problem.
>>
>>I switched
>>the freewheel over to a Suntour 7spd and it ran fine on a long run
>>with lots of pumping action. So, it really appears to be a
>>freewheel/chain issue.
>>
>>Is this a known incompatibility? I thought the Sachs SC-40 chain and
>>the Sachs freewheel were about the same vintage and both for 7spd
>>setups (?)
>>
>>THanks,
>>
>>
>>
>>
 
Bob wrote:
> Anyone?
>
> On Tue, 20 Sep 2005 14:57:02 GMT, Bob <[email protected]> wrote:
>
> >I have some later model (LY-9?) 7spd freewheels that I am trying
> >to run. I mounted them up on a bike with some Sachs SC-40 chains.
> >The derailleurs are friction.
> >
> >This has resulted in a very serious - as in totally unrideable -
> >chain skip/slip problem. It actually seems to be skipping several
> >teeth at once every couple revolutions. It all works fine in the
> >stand but on the road there's a serious issue.I tried two chains and
> >freewheels, both new, same problem.
> >
> >I switched
> >the freewheel over to a Suntour 7spd and it ran fine on a long run
> >with lots of pumping action. So, it really appears to be a
> >freewheel/cha in issue.
> >
> >Is this a known incompatibility? I thought the Sachs SC-40 chain and
> >the Sachs freewheel were about the same vintage and both for 7spd
> >setups (?)


There was a thread here not too long ago (months?) about a similar
problem with an essentially new chainwheel. The problem was excessive
profiling of the teeth, in a defective way, resulting in essentially a
pre-worn chainwheel out of pitch with a new chain. Unfortunately I
don't remember the subject but I believe it was John Dacey who
described the solution, try googling his posts over the past few
months.¿
 
On 25 Sep 2005 13:37:28 -0700, "41" <[email protected]> wrote:


>There was a thread here not too long ago (months?) about a similar
>problem with an essentially new chainwheel. The problem was excessive
>profiling of the teeth, in a defective way, resulting in essentially a
>pre-worn chainwheel out of pitch with a new chain. Unfortunately I
>don't remember the subject but I believe it was John Dacey who
>described the solution, try googling his posts over the past few
>months.¿


Thanks boys... I will do a little more research. I am 99% sure that I
switched Sachs freewheels (both new) along the way and that it did
not cure the problem. Also, this is a new Sachs chain and newer design
labeled "designed for index systems")

But, I will swap a little more and see what other facts I can pull
out.

Bob