What is the maximum tooth sprocket you could fit on the back using a Deore DX rear derailleur?

How?
I’ve posted earlier on this thread of how I’m running a 40 tooth cog successfully.
I’ve been having the same issues to a degree, and an extension helped me.
 
That mech on the extender needs moving up so it is closer to the cog, it'll then wrap better and change over the range a bit better.


To OP.
Get some picture up, and your front setup to.

It could be chain wrap on small to small cogs and the mech is too slack.
A larger rear cog would normally mean a longer chain, but it is really hard to tell as we don't know what it looks like now.

Put it in big-big and take a picture, put it in small front, big rear and take a picture, the the same but small rear.

A middle front an big rear would help to.

We can get this to work for you.


P.S. 9 speed shifter and 8 speed cog was never going to work, so leave that as a distant memory :)
 
11-40 with an ‘95 LX
On my ride today I played around with her. Going up a short steep section I normally do in 22/27 (equivalent to the original gearing) I used 11/40. Worked great.
Tonight on the stand I heard some noise. I have the B screw all the way in and it’s marginal. I had bought some derailleur extentions so threw one on. They work. I still have to figure out how to orient the extension.
Before and after (pardon the filth it’s a working bike)
Hi, thanks for the pictures.

Yes your before looks just like how mine is now.

Very close. It clears it though and works fine so I don't know if there is a need to buy a derailleur hanger unless it would cause some kind of excessive wear so close to the cassette?
 
@retrobiker273891

I would check your rear shift cable is clean and isn't taking any tight bends on any of the outers
oftentimes poor index shifting is just cos of a crappy cable setup introducing some variability

the other thing this may be a symptom of is a bent derailleur hanger (if its a steel frame it can be bent back fairly easily if so)
even slightly bent out of straight might introduce some variability to the shifting - of your don't have the right gauge to check might be one for the LBS to take a quick look at

this is all given your cassette, shifter are both 9 speed and the RD is 'old shimano' pull ratio (which I believe the RD_m771 is)
While I noticed that the bike when I got it had new brake cables it seems the gear cables are old so perhaps that is the issue. The outer casings look good and not worn but looking at the exposed cable it is dirty and rusty so could be decades old. Could that cause indexing issues?
 
How?
I’ve posted earlier on this thread of how I’m running a 40 tooth cog successfully.
I’ve been having the same issues to a degree, and an extension helped me.
I notice people like to discourage me from tinkering as they think I am not qualified to do it. They think I not able to process information and will end up doing nothing, which is not accurate. I bought a bike and am improving it. Nothing complicated about that but people say I am 'over analytical' for asking questions to improve my bike.

Since you have added 40t to your old bike I see we are similar! Nearly everyone else discourages such experiments!

Yes I am sure extension would stop it but was trying to avoid using one and use as last resort. If that is the best idea then I will use it but I wonder if there is any problem with how it is currently with the cassette just being very close to the jockey wheel.
 
Last edited:
That mech on the extender needs moving up so it is closer to the cog, it'll then wrap better and change over the range a bit better.


To OP.
Get some picture up, and your front setup to.

It could be chain wrap on small to small cogs and the mech is too slack.
A larger rear cog would normally mean a longer chain, but it is really hard to tell as we don't know what it looks like now.

Put it in big-big and take a picture, put it in small front, big rear and take a picture, the the same but small rear.

A middle front an big rear would help to.

We can get this to work for you.


P.S. 9 speed shifter and 8 speed cog was never going to work, so leave that as a distant memory :)
I have switched to 2x now anyway since I never used the big cog on 3x anyway. Never understood why you would want to pedal when going downhill.

70 gear inches is my top on 32/12 and that works fine for me for flat riding.

I would not use small, small cogs anyway because it is bad for the chain anyway isn't it.

I am really wondering now if there is anything to fix, I mean in terms of the bigger cassette, the indexing is another issue, as it all seems to be working.

Indexing yes it has to be fixed!
 
@retrobiker273891

I would check your rear shift cable is clean and isn't taking any tight bends on any of the outers
oftentimes poor index shifting is just cos of a crappy cable setup introducing some variability

the other thing this may be a symptom of is a bent derailleur hanger (if its a steel frame it can be bent back fairly easily if so)
even slightly bent out of straight might introduce some variability to the shifting - of your don't have the right gauge to check might be one for the LBS to take a quick look at

this is all given your cassette, shifter are both 9 speed and the RD is 'old shimano' pull ratio (which I believe the RD_m771 is)
I looked at the hanger yesterday when taking off the derailleur to reverse the b-screw and looked very straight.

I think the gear cable could be the issue.

Also, just by eye, I looked for the alignment of the derailleur in relation to the cassette and looked straight too.

Btw my chain is 9 speed. Confirmed by looking up online the model.
 
If the teeth are touching the pully teeth at any point, it wear quickly. It also causes it to jump, pedalling backwards pushes the mech a bit closer, it may also be ike that when gliding, even if you only pedal backwards or the coat rotates the cassette forward a bit...

Your chain should be as short as needed for the big big setup (which is middle for you).
A better overall chainline would be created pushing the drive side out a bit so it is in a double position.

Still pictures, pictures, pictures...
As we like pictures, show it off :)
 
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