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Shifting problems



 
 
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  #1  
Old May 15th 07, 06:05 PM posted to rec.bicycles.tech
Chris Nelson
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Posts: 163
Default Shifting problems

So I picked up a used tandem (Trek T900) and its a hoot but it has
some rear shifting problems. More specifically, when shifting the
chain momentarily sits on top of the cogs before settling in, creating
a temporary cadence increase. Once shifted, it runs fine. It happens
on up and downshifts, and I believe to have it adjusted correctly as
far as indexing, because it shifts flawlessly in the workstand. It
only has problems under load.

It has very few miles on it as the previous owner only used it a
couple of times, so I believe it has nothing to do with wear. It has a
mixed set of drivetrain components, which may have something to do
with it.

SRAM 850 11-32 8 Speed Cog
SRAM MRX 8-Speed Twist Shift
Shimano 8 Speed Chain - IG
Shimano Deore 9-speed derailleur

I've lube and cleaned it a bazillion times and I ready to start
replacing stuff in order to get it to shift better, but I'm unsure of
the order that I should replace stuff and what to replace it to.

Chris

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  #2  
Old May 15th 07, 06:19 PM posted to rec.bicycles.tech
Bill Sornson
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Posts: 4,098
Default Shifting problems

Chris Nelson wrote:
So I picked up a used tandem (Trek T900) and its a hoot but it has
some rear shifting problems. More specifically, when shifting the
chain momentarily sits on top of the cogs before settling in, creating
a temporary cadence increase. Once shifted, it runs fine. It happens
on up and downshifts, and I believe to have it adjusted correctly as
far as indexing, because it shifts flawlessly in the workstand. It
only has problems under load.

It has very few miles on it as the previous owner only used it a
couple of times, so I believe it has nothing to do with wear. It has a
mixed set of drivetrain components, which may have something to do
with it.

SRAM 850 11-32 8 Speed Cog
SRAM MRX 8-Speed Twist Shift
Shimano 8 Speed Chain - IG
Shimano Deore 9-speed derailleur

I've lube and cleaned it a bazillion times and I ready to start
replacing stuff in order to get it to shift better, but I'm unsure of
the order that I should replace stuff and what to replace it to.


Sounds like simple cable tension. Turn the barrel adjuster counter
clockwise a bit?


  #3  
Old May 15th 07, 07:28 PM posted to rec.bicycles.tech
Chris Nelson
external usenet poster
 
Posts: 163
Default Shifting problems

On May 15, 1:19 pm, "Bill Sornson" wrote:
Chris Nelson wrote:
So I picked up a used tandem (Trek T900) and its a hoot but it has
some rear shifting problems. More specifically, when shifting the
chain momentarily sits on top of the cogs before settling in, creating
a temporary cadence increase. Once shifted, it runs fine. It happens
on up and downshifts, and I believe to have it adjusted correctly as
far as indexing, because it shifts flawlessly in the workstand. It
only has problems under load.


It has very few miles on it as the previous owner only used it a
couple of times, so I believe it has nothing to do with wear. It has a
mixed set of drivetrain components, which may have something to do
with it.


SRAM 850 11-32 8 Speed Cog
SRAM MRX 8-Speed Twist Shift
Shimano 8 Speed Chain - IG
Shimano Deore 9-speed derailleur


I've lube and cleaned it a bazillion times and I ready to start
replacing stuff in order to get it to shift better, but I'm unsure of
the order that I should replace stuff and what to replace it to.


Sounds like simple cable tension. Turn the barrel adjuster counter
clockwise a bit?- Hide quoted text -

- Show quoted text -


I've adusted that lots, there is no g-spot.

Chris

  #4  
Old May 15th 07, 09:51 PM posted to rec.bicycles.tech
Jay - BFri Commuter
external usenet poster
 
Posts: 39
Default Shifting problems


"Chris Nelson" wrote in message
oups.com...
So I picked up a used tandem (Trek T900) and its a hoot but it has
some rear shifting problems. More specifically, when shifting the
chain momentarily sits on top of the cogs before settling in, creating
a temporary cadence increase. Once shifted, it runs fine. It happens
on up and downshifts, and I believe to have it adjusted correctly as
far as indexing, because it shifts flawlessly in the workstand. It
only has problems under load.

It has very few miles on it as the previous owner only used it a
couple of times, so I believe it has nothing to do with wear. It has a
mixed set of drivetrain components, which may have something to do
with it.

SRAM 850 11-32 8 Speed Cog
SRAM MRX 8-Speed Twist Shift
Shimano 8 Speed Chain - IG
Shimano Deore 9-speed derailleur

I've lube and cleaned it a bazillion times and I ready to start
replacing stuff in order to get it to shift better, but I'm unsure of
the order that I should replace stuff and what to replace it to.

Chris

Chris,

Everyone in RBT knows more than I do about bikes, so keep that in mind;

Your drive train is very similar to my current bike. I am using a Shimano
11-28 8-speed cassette, which is working great with that shifter.

Since you don't know for sure about the bike history, I would measure the
chain for stretch. (Do previous owners ever tell the truth, the whole truth,
and nothing but the truth?)

Perhaps the derailleur hanger is bent.

Could also be inner wire friction inside the cable housing.

J.


  #5  
Old May 16th 07, 12:21 AM posted to rec.bicycles.tech
Michael Warner[_2_]
external usenet poster
 
Posts: 483
Default Shifting problems

On 15 May 2007 10:05:24 -0700, Chris Nelson wrote:

So I picked up a used tandem (Trek T900) and its a hoot but it has
some rear shifting problems. More specifically, when shifting the
chain momentarily sits on top of the cogs before settling in, creating
a temporary cadence increase. Once shifted, it runs fine. It happens
on up and downshifts, and I believe to have it adjusted correctly as
far as indexing, because it shifts flawlessly in the workstand. It
only has problems under load.


IME a bike which shifts perfectly on the stand but badly under load
has an over-worn chain and/or cluster. Try replacing the chain, but
you'll probably also have to replace the cluster.

--
Home page: http://members.westnet.com.au/mvw
  #6  
Old May 16th 07, 02:11 AM posted to rec.bicycles.tech
A Muzi
external usenet poster
 
Posts: 4,551
Default Shifting problems

Chris Nelson wrote:
So I picked up a used tandem (Trek T900) and its a hoot but it has
some rear shifting problems. More specifically, when shifting the
chain momentarily sits on top of the cogs before settling in, creating
a temporary cadence increase. Once shifted, it runs fine. It happens
on up and downshifts, and I believe to have it adjusted correctly as
far as indexing, because it shifts flawlessly in the workstand. It
only has problems under load.

It has very few miles on it as the previous owner only used it a
couple of times, so I believe it has nothing to do with wear. It has a
mixed set of drivetrain components, which may have something to do
with it.

SRAM 850 11-32 8 Speed Cog
SRAM MRX 8-Speed Twist Shift
Shimano 8 Speed Chain - IG
Shimano Deore 9-speed derailleur

I've lube and cleaned it a bazillion times and I ready to start
replacing stuff in order to get it to shift better, but I'm unsure of
the order that I should replace stuff and what to replace it to.


Review basic derailleur/ gear train setup. Here's the FAQ:
http://draco.acs.uci.edu/rbfaq/FAQ/index.html

Get you head behind the rear changer. Is it vertical and parallel to the
chainrings? Is the derailleur itself bent or damaged? Pulley screws
tight? Is the chain sufficiently long to shift big-big? Any obvious
damage such as loose wheel bearings or excessive play in the cassette?
Loose lockring? If you think it is all properly set up and undamaged:

Slack or detach gear wire. Set outer limit (H) and inner limit (L)
screws by shifting smartly with your thumb. If you do not have any other
provision as an assistant to stand on the off side, hold the front brake
tight and lift at the saddle.

Once the derailleur limits are set, ensure the gear wire moves freely
and that there are no kinks, frays or other damage (plastic ferrules?)
to the wire or casing. Attach the gear wire such that it is just taut in
high gear. Turn the adjuster(s) so it runs quietly in a middle gear.

Take care to avoid an 'error of one' where the first click does nothing,
second click is first shift, etc.

Those things cover a few common issues; there may be others.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
  #7  
Old May 16th 07, 08:25 AM posted to rec.bicycles.tech
Michael Press
external usenet poster
 
Posts: 9,202
Default Shifting problems

In article
.com,
Chris Nelson wrote:

So I picked up a used tandem (Trek T900) and its a hoot but it has
some rear shifting problems. More specifically, when shifting the
chain momentarily sits on top of the cogs before settling in, creating
a temporary cadence increase. Once shifted, it runs fine. It happens
on up and downshifts, and I believe to have it adjusted correctly as
far as indexing, because it shifts flawlessly in the workstand. It
only has problems under load.

It has very few miles on it as the previous owner only used it a
couple of times, so I believe it has nothing to do with wear. It has a
mixed set of drivetrain components, which may have something to do
with it.

SRAM 850 11-32 8 Speed Cog
SRAM MRX 8-Speed Twist Shift
Shimano 8 Speed Chain - IG
Shimano Deore 9-speed derailleur

I've lube and cleaned it a bazillion times and I ready to start
replacing stuff in order to get it to shift better, but I'm unsure of
the order that I should replace stuff and what to replace it to.


If it were friction shifting, then you would simply shift and
ride. Since it is indexed shifting, the indexing is out of
registration. QED

You say it is not this and not that, but maybe it really is one of
the things you dismiss. Desperate times, desperate measures. Clean
all the cable points; pull the cable if necessary. Do the shifters
work properly? Is there any shift between a pair of cogwheels that
works properly, or are all of them equally balky?

--
Michael Press
  #8  
Old May 16th 07, 07:57 PM posted to rec.bicycles.tech
Chris Nelson
external usenet poster
 
Posts: 163
Default Shifting problems

On May 15, 7:21 pm, Michael Warner wrote:
On 15 May 2007 10:05:24 -0700, Chris Nelson wrote:

So I picked up a used tandem (Trek T900) and its a hoot but it has
some rear shifting problems. More specifically, when shifting the
chain momentarily sits on top of the cogs before settling in, creating
a temporary cadence increase. Once shifted, it runs fine. It happens
on up and downshifts, and I believe to have it adjusted correctly as
far as indexing, because it shifts flawlessly in the workstand. It
only has problems under load.


IME a bike which shifts perfectly on the stand but badly under load
has an over-worn chain and/or cluster. Try replacing the chain, but
you'll probably also have to replace the cluster.

--
Home page:http://members.westnet.com.au/mvw


I ordered a new chain, its an 8-speed SRAM chain so it may fit the cog
better. Derailleur looks straight, cable is nice a smooth. I guess its
OK that the derailleur is a 9-speed?

If the chain doesn't work out, I'm ready to just get all new 9-speed
MTB stuff, this way I can get higher quality XT level. The hub is a
noname. If the hub fits an 8-speed cog, will it also fit a 9-speed
cog, or will I have a problem there?

Chris

  #9  
Old May 16th 07, 10:42 PM posted to rec.bicycles.tech
Chris Nelson
external usenet poster
 
Posts: 163
Default Shifting problems

On May 15, 7:21 pm, Michael Warner wrote:
On 15 May 2007 10:05:24 -0700, Chris Nelson wrote:

So I picked up a used tandem (Trek T900) and its a hoot but it has
some rear shifting problems. More specifically, when shifting the
chain momentarily sits on top of the cogs before settling in, creating
a temporary cadence increase. Once shifted, it runs fine. It happens
on up and downshifts, and I believe to have it adjusted correctly as
far as indexing, because it shifts flawlessly in the workstand. It
only has problems under load.


IME a bike which shifts perfectly on the stand but badly under load
has an over-worn chain and/or cluster. Try replacing the chain, but
you'll probably also have to replace the cluster.

--
Home page:http://members.westnet.com.au/mvw


I just ordered an SRAM PC-68 8SP CHAIN, maybe that will go better with
the cog that's on there. Everything else seems to be in order(thanks
everyone for the input). If that doesn't do it, I'm thinking of going
to all 9-speed stuff instead of the mix that's on there now. This
would also allow me to upgrade to higher level components such as XT.
The rear hub that is on there is a no name. If it takes an 8-speed
cog, should it be able to take a 9-speed cog? Or might I run into a
problem there?

Chris

  #10  
Old May 17th 07, 05:31 AM posted to rec.bicycles.tech
JeffWills
external usenet poster
 
Posts: 409
Default Shifting problems

On May 16, 1:42 pm, Chris Nelson wrote:

If it takes an 8-speed
cog, should it be able to take a 9-speed cog? Or might I run into a
problem there?

Chris-


No problem. 8-speed and 9-speed cassettes fit on the same hub without
modification. I'm planning the same conversion soon.

Jeff

 




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