chain line problem

I have a Trek 5500 which I built up from a frameset using Dura-Ace 9
speed components including a BB-7700 bottom bracket and 12-25 cassette.
From day one which was years ago I have had the following problems:

1. Can't use 53T front chain ring with second biggest 23T rear cog. The
chain makes a lot of noise and appears to be at a large angle. Sometime
the chain gets pulled off the front 53T ring onto the small ring.

2. When I use the 39T front chain ring with the biggest rear 25T cog
the chain makes more noise than normal.

Initially I took to my LBS who had installed the BB. They checked the
chain line and told me it was ok and that on some bikes you just can't
use that gear. They also tightened the drive side crankarm as much as
they could to get it as close to the frame as possible. So I just lived
with the problem for years.

Today I took apart my crankset to fix a clicking noise. While doing so,
I measured the distance from the end of each crankarm to the chain
stays. The drive side measured 3mm further from the chain stay than the
non-drive side. I am not sure if this means anything. Do I have a chain
line problem? If so, how can I fix it? I see no way to make any
adjustments.

Thanks - Joel

Joel wrote:
Today I took apart my crankset to fix a clicking noise. While doing so,
I measured the distance from the end of each crankarm to the chain
stays. The drive side measured 3mm further from the chain stay than the
non-drive side. I am not sure if this means anything. Do I have a chain
line problem? If so, how can I fix it? I see no way to make any
adjustments.
Since you removed the crankarm, you may want measure the length of the
bottom bracket spindle and verify with the data on this page,
http://www.sheldonbrown.com/bbsize.html
Look for DA7700. Sounds like the spindle may be too long.

Check the BB length. Should be 109.5mm. Alternatively, check the chainline
with the RH crank installed. Should be 43.5mm from the centreline of the
bike frame to the midpoint between the chainrings.

Nick

"Joel" wrote in message
oups.com...
I have a Trek 5500 which I built up from a frameset using Dura-Ace 9
speed components including a BB-7700 bottom bracket and 12-25 cassette.
From day one which was years ago I have had the following problems:

1. Can't use 53T front chain ring with second biggest 23T rear cog. The
chain makes a lot of noise and appears to be at a large angle. Sometime
the chain gets pulled off the front 53T ring onto the small ring.

2. When I use the 39T front chain ring with the biggest rear 25T cog
the chain makes more noise than normal.

I measured the distance from the center of the chainrings to the center
of the frame and it does seem to be close to 43.5 mm. Of course I had
to do a lot of sighting and eye-balling escpecially with the carbon
frame. I guess it must be normal for the 53 front / 23 rear to be an
unusable gear with a 12-25 cassette.

Thanks - Joel

Same problem with one of my DA bikes. Used the proper 109.5 BB, but had
to use a spacer behind a 12-23 cassette in order to be able to use the
53X21. On the other hand, I can ride in the 39X12 without any noise.
Some frames just have screwed up chainlines.
My other two bikes don't have any problem riding in the "Big-big" ( One
DA and the other Campy) They also have the typical noise when slipping
into the 39X12& 13

Bill,

Yes, I think a spacer would help. Do you know what thickness spacer you
used?

Thanks - Joel

Bill K. wrote:
Same problem with one of my DA bikes. Used the proper 109.5 BB, but
had
to use a spacer behind a 12-23 cassette in order to be able to use
the
53X21. On the other hand, I can ride in the 39X12 without any noise.
Some frames just have screwed up chainlines.
My other two bikes don't have any problem riding in the "Big-big" (
One
DA and the other Campy) They also have the typical noise when
slipping
into the 39X12& 13

Bill K. wrote:
Same problem with one of my DA bikes. Used the proper 109.5 BB, but had
to use a spacer behind a 12-23 cassette in order to be able to use the
53X21. On the other hand, I can ride in the 39X12 without any noise.
Some frames just have screwed up chainlines.

Only damaged bikes with bent frames.

My other two bikes don't have any problem riding in the "Big-big" ( One
DA and the other Campy) They also have the typical noise when slipping
into the 39X12& 13

Assuming none of your frames is bent, it's probably that one of the
bikes has shorter chainstays than the others.

Short chainstays exacerbate chainline issues, because for a given amount
of chainline error, the resulting chain _angle_ will be greater on a
frame with short chainstays.

Unfortunately, there's a widely held superstition to the effect that
short chainstays somehow make a bike faster, so a great many
"performance" type frames suffer from this sort of problem.

Sheldon "http://sheldonbrown.com/chainline" Brown
+-------------------------------------------+
| I millihelen = the amount of |
| beauty required to launch one ship. |
| --Peter Shickele |
+-------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

On Mon, 07 Mar 2005 11:16:44 -0500, Sheldon Brown
may have said:

Unfortunately, there's a widely held superstition to the effect that
short chainstays somehow make a bike faster, so a great many
"performance" type frames suffer from this sort of problem.

Shorter stays = less weight, perhaps? Dumber things have been done in
the quest for the ultimate reduction in bike mass.

Personally, I prefer a frame which provides a longer wheelbase.

(wondering how long it will take for somebody to point out that 'bents
have the edge in that test...)





--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.

"Virtus est medium vitiorum." - Horatius
On 6 Mar 2005 17:07:37 -0800, "Joel" wrote:

I have a Trek 5500 which I built up from a frameset using Dura-Ace 9
speed components including a BB-7700 bottom bracket and 12-25 cassette.
From day one which was years ago I have had the following problems:

1. Can't use 53T front chain ring with second biggest 23T rear cog. The
chain makes a lot of noise and appears to be at a large angle. Sometime
the chain gets pulled off the front 53T ring onto the small ring.

2. When I use the 39T front chain ring with the biggest rear 25T cog
the chain makes more noise than normal.

Initially I took to my LBS who had installed the BB. They checked the
chain line and told me it was ok and that on some bikes you just can't
use that gear. They also tightened the drive side crankarm as much as
they could to get it as close to the frame as possible. So I just lived
with the problem for years.

Today I took apart my crankset to fix a clicking noise. While doing so,
I measured the distance from the end of each crankarm to the chain
stays. The drive side measured 3mm further from the chain stay than the
non-drive side. I am not sure if this means anything. Do I have a chain
line problem? If so, how can I fix it? I see no way to make any
adjustments.

All the Trek 5XXX models with which I'm familiar have come from their
maker with a spacer fitted between the right bottom bracket cup and
the bottom bracket shell. The spacer is ~1.5 mm thick and moves the
crank outboard by that amount. As I understand it, the spacer is
supposed to lessen the liklihood of damage to the bottom bracket shell
in the event of a chain thrown to the inside of the inner 'ring.

As already noted by Sheldon B, chainline issues are made increasingly
fussy with bikes with short chainstays. It may be that you'd benefit
from adding a spacer (equal in thickness to the one at the bottom
bracket) between the freehub body and innermost cassette sprocket to
compensatorily shim the cassette outboard. If not already done, also
make sure the rear derailleur hanger alignment isn't compromised.

-------------------------------
John Dacey
Business Cycles, Miami, Florida
Since 1983
Comprehensive catalogue of track equipment: online since 1996.
http://www.businesscycles.com

I used an extra 9 speed spacer to move the cassette out. The hub was a
Shimano "clone", so it's possible that my trick won't work on a Shimano
hub. If it doesn't, try a thinner spacer that allows you to get two to
three threads of the lockring to engage. It also works with Mavic hubs
because their cassette body is longer than Shimano bodies.
My frame was like this right out of the box. It was a Giant TCR "Team"
frame that isn't really sold in the USA. Very short stays.