Shimano Nexus roller clutch failing to engage in 5th gear

I have a SG-8R31 hub that has a problem with the roller clutch failing to catch
when I start to pedal in 5th gear.

It does not always happen, and when it does the hub will engage after a half
turn of the crank. The other gears do not have this problem.

Once the roller clutch is engaged it will not slip as long as it is under load,
but sometimes it will disengage between pedal strokes.

This has been an issue since I got the hub, but it seems to be getting worse.

In search of a simple solution, I have replaced the twist shifter with a trigger
shifter, replaced the CJ-8S40 cassette joint with a CJ-8S20, replaced the stock
cable housing and cable with jagwire ones, tried both types of AR washers that
will work with the dropout, and adjusted the cone tension.

The cable housing is free from kinks and sharp bends and is heavily lubricated
with WD-40. It moves quite freely when pulled back and forth by hand. The return
spring has more than enough force.

One possible symptom is that when I shift up from 1 into 4 I get a different
reading from the cassette joint marks than when I shift down from 8 into 4. This
had been constant with both CJs, shifters, and cable housing set ups.

I have tried dialing the hub in going off of both readings and the problem
remains the same.

Does anyone know if shimano has a standard on which reading you are supposed to
use?


The lubrication history is as follows:

When I first got the hub I soaked it in phil's tenacious oil and used phil's
grease on the inside of the hub shell and the bearings.

Six months later I did the same thing.

One year later I soaked the hub is mobile ATF and greased the hub shell and
bearings with phil's again.

From looking at this Shimano document:

http://tinyurl.com/a7bldon

http://www.shimano.com/publish/conte...08%20Speed.pdf


It appears that 5th gear connects to the hub shell via the 3rd roller clutch,
the small one next to the non-drive axle.

Is this correct?

I suspect that I either have a damaged roller clutch (has anyone ever seen
that?) or that the large amount of grease I use on the brake side bearings has
somehow contaminated the roller clutch and caused it to slip rather than engage.

The problem with this theory is that the hub also uses the 3rd roller clutch in 1st gear and 1st gear does not have this issue.

Anyone have any idea if this is possible?

On 21/11/2012 8:38 AM, Frank White wrote:
I have a SG-8R31 hub that has a problem with the roller clutch
failing to catch when I start to pedal in 5th gear.

It does not always happen, and when it does the hub will engage after
a half turn of the crank. The other gears do not have this problem.

Once the roller clutch is engaged it will not slip as long as it is
under load, but sometimes it will disengage between pedal strokes.

This has been an issue since I got the hub, but it seems to be
getting worse.

In search of a simple solution, I have replaced the twist shifter
with a trigger shifter, replaced the CJ-8S40 cassette joint with a
CJ-8S20, replaced the stock cable housing and cable with jagwire
ones, tried both types of AR washers that will work with the dropout,
and adjusted the cone tension.

The cable housing is free from kinks and sharp bends and is heavily
lubricated with WD-40. It moves quite freely when pulled back and
forth by hand. The return spring has more than enough force.

One possible symptom is that when I shift up from 1 into 4 I get a
different reading from the cassette joint marks than when I shift
down from 8 into 4. This had been constant with both CJs, shifters,
and cable housing set ups.

I have tried dialing the hub in going off of both readings and the
problem remains the same.

Does anyone know if shimano has a standard on which reading you are
supposed to use?


The lubrication history is as follows:

When I first got the hub I soaked it in phil's tenacious oil and used
phil's grease on the inside of the hub shell and the bearings.

Six months later I did the same thing.

One year later I soaked the hub is mobile ATF and greased the hub
shell and bearings with phil's again.

From looking at this Shimano document:

http://tinyurl.com/a7bldon

http://www.shimano.com/publish/conte...08%20Speed.pdf



It appears that 5th gear connects to the hub shell via the 3rd roller
clutch, the small one next to the non-drive axle.

Is this correct?

I suspect that I either have a damaged roller clutch (has anyone ever
seen that?) or that the large amount of grease I use on the brake
side bearings has somehow contaminated the roller clutch and caused
it to slip rather than engage.

The problem with this theory is that the hub also uses the 3rd roller
clutch in 1st gear and 1st gear does not have this issue.

Anyone have any idea if this is possible?


My guess is that 1st gear doesn't slip because there is more torque
applied compared to 5th, to cause the clutch to grab.

In 5th you say it sometimes disengages between pedal strokes. I guess
because you momentarily apply so little torque that the clutch slips a bit.

As the clutch relies on friction, manufacturers tend to recommend not
using lubricants with EP additives. Maybe try a different lube?

--
JS.

On 21/11/2012 9:01 AM, James wrote:
On 21/11/2012 8:38 AM, Frank White wrote:
I have a SG-8R31 hub that has a problem with the roller clutch
failing to catch when I start to pedal in 5th gear.

It does not always happen, and when it does the hub will engage after
a half turn of the crank. The other gears do not have this problem.

Once the roller clutch is engaged it will not slip as long as it is
under load, but sometimes it will disengage between pedal strokes.

This has been an issue since I got the hub, but it seems to be
getting worse.

In search of a simple solution, I have replaced the twist shifter
with a trigger shifter, replaced the CJ-8S40 cassette joint with a
CJ-8S20, replaced the stock cable housing and cable with jagwire
ones, tried both types of AR washers that will work with the dropout,
and adjusted the cone tension.

The cable housing is free from kinks and sharp bends and is heavily
lubricated with WD-40. It moves quite freely when pulled back and
forth by hand. The return spring has more than enough force.

One possible symptom is that when I shift up from 1 into 4 I get a
different reading from the cassette joint marks than when I shift
down from 8 into 4. This had been constant with both CJs, shifters,
and cable housing set ups.

I have tried dialing the hub in going off of both readings and the
problem remains the same.

Does anyone know if shimano has a standard on which reading you are
supposed to use?


The lubrication history is as follows:

When I first got the hub I soaked it in phil's tenacious oil and used
phil's grease on the inside of the hub shell and the bearings.

Six months later I did the same thing.

One year later I soaked the hub is mobile ATF and greased the hub
shell and bearings with phil's again.

From looking at this Shimano document:

http://tinyurl.com/a7bldon

http://www.shimano.com/publish/conte...08%20Speed.pdf




It appears that 5th gear connects to the hub shell via the 3rd roller
clutch, the small one next to the non-drive axle.

Is this correct?

I suspect that I either have a damaged roller clutch (has anyone ever
seen that?) or that the large amount of grease I use on the brake
side bearings has somehow contaminated the roller clutch and caused
it to slip rather than engage.

The problem with this theory is that the hub also uses the 3rd roller
clutch in 1st gear and 1st gear does not have this issue.

Anyone have any idea if this is possible?


My guess is that 1st gear doesn't slip because there is more torque
applied compared to 5th, to cause the clutch to grab.

In 5th you say it sometimes disengages between pedal strokes. I guess
because you momentarily apply so little torque that the clutch slips a bit.

As the clutch relies on friction, manufacturers tend to recommend not
using lubricants with EP additives. Maybe try a different lube?


Also, try to apply more even torque. Try to pull back as the crank goes
through 6 o'clock, and push forward through 12 o'clock. You might be a
bouncy rider, which could make the clutch slippage more of a problem.

--
JS.

1. I don't know the system but I'd try backpedaling to setup the shift to 5th

2. could be a problem with the installation wixh would produce consistant error or anomalic readings.

On Tuesday, November 20, 2012 2:06:49 PM UTC-8, James wrote:

Also, try to apply more even torque. Try to pull back as
the crank goes through 6 o'clock, and push forward through
12 o'clock. You might be a bouncy rider, which could make
the clutch slippage more of a problem.

Me personally, I'd throw the hub away before I
required myself to adapt to its shortcomings.

Slipping is one of the more unpleasant malfunctions
to be subjected to, although at least this hub isn't
doing the slip-under-heavy-load thing.

Tom Ace

Frank White wrote:
:I have a SG-8R31 hub that has a problem with the roller clutch failing to catch
:when I start to pedal in 5th gear.

:It does not always happen, and when it does the hub will engage after a half
:turn of the crank. The other gears do not have this problem.

:Once the roller clutch is engaged it will not slip as long as it is under load,
:but sometimes it will disengage between pedal strokes.

:This has been an issue since I got the hub, but it seems to be getting worse.

Your hub is defective, and you should have had it replaced. You're
probably **** out of luck, since you've used something other than
shimano's snot in it, though.


--
sig 118

On Nov 21, 8:32 am, Tom Ace wrote:
On Tuesday, November 20, 2012 2:06:49 PM UTC-8, James wrote:
Also, try to apply more even torque. Try to pull back as
the crank goes through 6 o'clock, and push forward through
12 o'clock. You might be a bouncy rider, which could make
the clutch slippage more of a problem.

Me personally, I'd throw the hub away before I
required myself to adapt to its shortcomings.

Slipping is one of the more unpleasant malfunctions
to be subjected to, although at least this hub isn't
doing the slip-under-heavy-load thing.


Hallelujah, brother - even small aggravations are not worth accepting
(and more costly in terms of well being than people realize) when you
don't have to.

Hi, I have exactly the same problem with my SG-8r35. I'd like to know if you have finally found the solution.