Slop in Drive Train

When I'm climbing and the power pedal goes just over top dead center,
there's a 3- or 4-degree slip in the drive train of my old Nishiki
Ariel Mountain Bike. What can I do to fix it? I have tightened up
the horizontal bolts in the crankset. What else could it be? Thanks.

On Oct 22, 8:15*pm, jl wrote:
When I'm climbing and the power pedal goes just over top dead center,
there's a 3- or 4-degree slip in the drive train of my old Nishiki
Ariel Mountain Bike. *What can I do to fix it? *I have tightened up
the horizontal bolts in the crankset. *What else could it be? *Thanks..

Check the bottom bracket for slop by dropping the chain and grabbing a
crank arm and giving it a good wiggle. Check the power plant for slop
as well. ;-)

On Oct 22, 6:15*pm, jl wrote:
When I'm climbing and the power pedal goes just over top dead center,
there's a 3- or 4-degree slip in the drive train of my old Nishiki
Ariel Mountain Bike. *What can I do to fix it? *I have tightened up
the horizontal bolts in the crankset. *What else could it be? *Thanks..

If it were a bike with an Octalink BB, I would say that the splines
were misaligned and shot, but it might be that your square drive crank
is wollowed out. You might also have a slipping pawl in your freehub
-- maybe because it is gunked up and not engaging periodically. If
your BB is loose, the crank will rock side to side -- grab the pedals
and see if you can rock the crank. Even if it is loose, that doesn't
cause that slipping feeling. If it is always in the same place coming
over the dead spot, my guess is that your crank is shot. -- Jay
Beattie.

Jim Limp wrote:

When I'm climbing and the power pedal goes just over top dead
center, there's a 3- or 4-degree slip in the drive train of my old
Nishiki Ariel Mountain Bike. What can I do to fix it? I have
tightened up the horizontal bolts in the cranks. What else could
it be?

Let's get the description tied down more closely. From what you say,
it seems a square taper crank was ridden with the retaining bolt(s)
loose. This would cause backlash at the top of the left pedal stroke
because the right crank is directly attached to the chain and cannot
develop spindle slop.

Consider that torque in the BB spindle is from left crank forces.
That means that only the left crank can develop rotational backlash
although that can reside in either or both spindle/crank interfaces.
This cannot be repaired, so a new pair of cranks must be purchased.

Please report back.

Jobst Brandt

On Oct 23, 12:44*am, wrote:
Jim Limp wrote:
When I'm climbing and the power pedal goes just over top dead
center, there's a 3- or 4-degree slip in the drive train of my old
Nishiki Ariel Mountain Bike. *What can I do to fix it? *I have
tightened up the horizontal bolts in the cranks. *What else could
it be?

Let's get the description tied down more closely. *From what you say,
it seems a square taper crank was ridden with the retaining bolt(s)
loose. *This would cause backlash at the top of the left pedal stroke
because the right crank is directly attached to the chain and cannot
develop spindle slop.

Consider that torque in the BB spindle is from left crank forces.
That means that only the left crank can develop rotational backlash
although that can reside in either or both spindle/crank interfaces.
This cannot be repaired, so a new pair of cranks must be purchased.

Please report back.

Jobst Brandt

Thanks to everyone. I'll tear into it and see what's worn out. Then
let you know what it needed to fix it.

On Oct 22, 9:34*pm, landotter wrote:
On Oct 22, 8:15*pm, jl wrote:

When I'm climbing and the power pedal goes just over top dead center,
there's a 3- or 4-degree slip in the drive train of my old Nishiki
Ariel Mountain Bike. *What can I do to fix it? *I have tightened up
the horizontal bolts in the crankset. *What else could it be? *Thanks.

Check the bottom bracket for slop by dropping the chain and grabbing a
crank arm and giving it a good wiggle. Check the power plant for slop
as well. ;-)

LOL. Very funny!

On Oct 23, 12:44*am, wrote:
Jim Limp wrote:
When I'm climbing and the power pedal goes just over top dead
center, there's a 3- or 4-degree slip in the drive train of my old
Nishiki Ariel Mountain Bike. *What can I do to fix it? *I have
tightened up the horizontal bolts in the cranks. *What else could
it be?

Let's get the description tied down more closely. *From what you say,
it seems a square taper crank was ridden with the retaining bolt(s)
loose. *This would cause backlash at the top of the left pedal stroke
because the right crank is directly attached to the chain and cannot
develop spindle slop.

Consider that torque in the BB spindle is from left crank forces.
That means that only the left crank can develop rotational backlash
although that can reside in either or both spindle/crank interfaces.
This cannot be repaired, so a new pair of cranks must be purchased.

Please report back.

Jobst Brandt

I have removed the retaining bolts, and it looks like the aluminum
cranks are pressed onto the square-end crankpin. How do I remove the
cranks-- with a puller?

Thanks. I already tried one but didn't want to break anything.

There is slop in the crankpin's bearings. That may be where the
problem is.

I love this old bike. This is my airport bike, way out in the western
NC sticks, and it keeps me in shape.

jls -- ancient aircraft mechanic

PS: I'm looking for a mountain bike with 29-inch wheels, a 29er. I
tried a Specialized hardtail at the local bike shop and loved it. Any
pros or cons?

On Oct 23, 9:48*am, jl wrote:
On Oct 23, 12:44*am, wrote:



Jim Limp wrote:
When I'm climbing and the power pedal goes just over top dead
center, there's a 3- or 4-degree slip in the drive train of my old
Nishiki Ariel Mountain Bike. *What can I do to fix it? *I have
tightened up the horizontal bolts in the cranks. *What else could
it be?

Let's get the description tied down more closely. *From what you say,
it seems a square taper crank was ridden with the retaining bolt(s)
loose. *This would cause backlash at the top of the left pedal stroke
because the right crank is directly attached to the chain and cannot
develop spindle slop.

Consider that torque in the BB spindle is from left crank forces.
That means that only the left crank can develop rotational backlash
although that can reside in either or both spindle/crank interfaces.
This cannot be repaired, so a new pair of cranks must be purchased.

Please report back.

Jobst Brandt

I have removed the retaining bolts, and it looks like the aluminum
cranks are pressed onto the square-end crankpin. *How do I remove the
cranks-- with a puller?

Thanks. *I already tried one but didn't want to break anything.

A gear puller would work in a pinch but there's a standardized crank
puller tool you can get from any bike shop that stands less chance of
damaging things:

http://www.parktool.com/products/det...6&item=CCP%2D2

-pm

Jim Limp wrote:

When I'm climbing and the power pedal goes just over top dead
center, there's a 3- or 4-degree slip in the drive train of my old
Nishiki Ariel Mountain Bike. Â*What can I do to fix it? Â*I have
tightened up the horizontal bolts in the cranks. Â*What else could
it be?

Let's get the description tied down more closely. Â*From what you say,
it seems a square taper crank was ridden with the retaining bolt(s)
loose. Â*This would cause backlash at the top of the left pedal stroke
because the right crank is directly attached to the chain and cannot
develop spindle slop.

Consider that torque in the BB spindle is from left crank forces.
That means that only the left crank can develop rotational backlash
although that can reside in either or both spindle/crank interfaces.
This cannot be repaired, so a new pair of cranks must be purchased.

Please report back.

I have removed the retaining bolts, and it looks like the aluminum
cranks are pressed onto the square-end crankpin. How do I remove
the cranks-- with a puller?

If these are reasonably good cranks, you can buy a puller designed to
remove them that screws into the threads at the bore from which you
unscrewed the retaining bolts. The most common and damaging error
made extracting cranks occurs from not removing the flat washer that
was under the retaining bolt as well as not screwing the extractor in
fully. Both of these errors lead to stripping the threads and making
extraction impractical thereby destroying the crank.

Thanks. I already tried one but didn't want to break anything.

There is slop in the crankpin's bearings. That may be where the
problem is.

That cannot cause rotational backlash but merely side to side wobble,
something that can be manually tested with the bicycle at rest.

I love this old bike. This is my airport bike, way out in the
western NC sticks, and it keeps me in shape.

jls -- ancient aircraft mechanic

I assume that was before the wright brothers, but then they were
bicycle nerds anyway. From your questions, I am not sure you are as
familiar with machinery as you should be or you wouldn't ask. There
are books on "how to" for bicycles and it seems this could be a long
thread if you want to get this bicycle back in working order, so get
the book.

http://tinyurl.com/5ns8uf

PS: I'm looking for a mountain bike with 29-inch wheels, a 29er. I
tried a Specialized hardtail at the local bike shop and loved it.
Any pros or cons?

Hold it, we haven't resolved the first problem. Start a new thread
on what bicycle to buy, but we've had one of those recently.

Jobst Brandt

On Oct 23, 10:52*am, wrote:
Jim Limp wrote:
When I'm climbing and the power pedal goes just over top dead
center, there's a 3- or 4-degree slip in the drive train of my old
Nishiki Ariel Mountain Bike. *What can I do to fix it? *I have
tightened up the horizontal bolts in the cranks. *What else could
it be?
Let's get the description tied down more closely. *From what you say,
it seems a square taper crank was ridden with the retaining bolt(s)
loose. *This would cause backlash at the top of the left pedal stroke
because the right crank is directly attached to the chain and cannot
develop spindle slop.
Consider that torque in the BB spindle is from left crank forces.
That means that only the left crank can develop rotational backlash
although that can reside in either or both spindle/crank interfaces.
This cannot be repaired, so a new pair of cranks must be purchased.
Please report back.
I have removed the retaining bolts, and it looks like the aluminum
cranks are pressed onto the square-end crankpin. *How do I remove
the cranks-- with a puller?

If these are reasonably good cranks, you can buy a puller designed to
remove them that screws into the threads at the bore from which you
unscrewed the retaining bolts. *The most common and damaging error
made extracting cranks occurs from not removing the flat washer that
was under the retaining bolt as well as not screwing the extractor in
fully. *Both of these errors lead to stripping the threads and making
extraction impractical thereby destroying the crank.

Thanks. *I already tried one but didn't want to break anything.
There is slop in the crankpin's bearings. *That may be where the
problem is.

That cannot cause rotational backlash but merely side to side wobble,
something that can be manually tested with the bicycle at rest.

It would feel pretty similar while riding, except that in my
experience a loose crank arm is more likely to produce a noticeable
clunk once per revolution, and not twice which was the initial
symptom.

-pm
-pm