Rear Derailleaur Extender query

[Ajax Bay]

@Graeme_FK

 

[bobdaspider]

Hi all,

Thanks all for your feedback - especially AB. First, the cassette spec is 13 x 26 (not 25 as I'd originally stated), and attach pics re the chainring / cassette setup (small / small and large / large) and re the query about a 'B' screw - this was raised with the LBS but this rear derailleur model doesn't have one (typical). But it sounds promising that the consensus seems to be suggesting that the chain is currently too long and can afford to lose a link or two?

 

[Ajax Bay]

Yes - at least one (inch) link. See the Campagnolo diagram I shared earlier/upthread.
Your 53-39 and 13-26 set up is within the spec for this RD (I think 26t max).
But just shortening the chain may not sort your actual issue which is how high the guide pulley wheel is running.
I don't run Campagnolo but I have a spare part groupset (9sp and post 2001 like yours, bought in case my daughter's bike needed spare items (2014)) but irritatingly can't find the box to check its RD physically).
Searching offers this clue as to what might be an improvement:
"The pulley cage will need to be removed and then the pivot bolt that holds the inner plate to the derailleur will need to be removed. The spring inside (M) will have to be installed correctly and then the inner cage rotated to the proper position."

Obviously there is 'take it apart and can't get it back together again' risk.

Campagnolo recommends using a short cage derailleur with a maximum cassette cog size of 26 teeth even though it will [in practice] shift to a 29 tooth cog. 9 and 10 speed rear derailleurs use the same three cage lengths; 55, 72.5 and 89 mm (pulley wheels c-c) with a chain wrap (CW) capacity of 27, 36 and 39.
For a 39/53 and a 13/26 combo you need a minimum CW of 27. NB You say yours is medium (can verify by measurement).

 

[bobdaspider]

Yes - at least one (inch) link. See the Campagnolo diagram I shared earlier/upthread.
Your 53-39 and 13-26 set up is within the spec for this RD (I think 26t max).
But just shortening the chain may not sort your actual issue which is how high the guide pulley wheel is running.
I don't run Campagnolo but I have a spare part groupset (9sp and post 2001 like yours, bought in case my daughter's bike needed spare items (2014)) but irritatingly can't find the box to check its RD physically).
Searching offers this clue as to what might be an improvement:
"The pulley cage will need to be removed and then the pivot bolt that holds the inner plate to the derailleur will need to be removed. The spring inside (M) will have to be installed correctly and then the inner cage rotated to the proper position."
View attachment 730222
Obviously there is 'take it apart and can't get it back together again' risk.

Campagnolo recommends using a short cage derailleur with a maximum cassette cog size of 26 teeth even though it will [in practice] shift to a 29 tooth cog. 9 and 10 speed rear derailleurs use the same three cage lengths; 55, 72.5 and 89 mm (pulley wheels c-c) with a . chain wrap value of 27, 36 and 39.
For a 39/53 and a 13/26 combo you need a minimum CW of 27.

Thanks AB, will speak with the LBS and gauge their feedback - the easiest option is to remove one chain link if chain wrap value of 27 can be achieved. Re the other option of taking the RD apart - sounds tricky. Maybe I'll start to look for a short cage RD as well - you never know, there might be one out there in good condition. The RD I have was bought new from the US so will contact the vendor and see what they say. But thanks again for your feedback and advice with this query - it's very much appreciated and means that I won't be looking any further at an RD extender!! 🙄

 

[Ajax Bay]

Thanks AB, will speak with the LBS and gauge their feedback - the easiest option is to remove one chain link if chain wrap value of 27 can be achieved. Re the other option of taking the RD apart - sounds tricky. Maybe I'll start to look for a short cage RD as well - you never know, there might be one out there in good condition. The RD I have was bought new from the US so will contact the vendor and see what they say. But thanks again for your feedback and advice with this query - it's very much appreciated and means that I won't be looking any further at an RD extender!! 🙄

Think your RD is Campagnolo Mirage (RD4-MI9S)
https://www.disraeligears.co.uk/site/campagnolo_-_2006_products_range_page_17.html

 

[T4tomo]

its now quite obvious that the chain is too long, as was suggested as an issue well before a decent photo was upload.

take a pair of links out and see if it works before worrying about anything else.

and re the query about a 'B' screw - this was raised with the LBS but this rear derailleur model doesn't have one (typical).

I doubt this but cant be sure, I'm not sure you LBS are advising you well, otherwise they'd have whipped a link out or told you to do such.

I think Campag adjustment for distance from sprockets is as shown below, which is different to Shimano and SRAM "B screws"

might be worth reading this and relate guides, most stuff on a bike is easy to sort out if you take the time to read / watch guides and understand how stuff works.
https://www.parktool.com/en-int/blog/repair-help/rear-derailleur-adjustment

 

[Ajax Bay]

The H screw (if it exists on this RD (some periods (of years) don't, research suggests) adjusts the balance between the upper and lower springs in the rear derailleur. Whereas the Shimano 'b' screw has a more agricultural function of moving the cage pivot axis.

Not Mirage

 

[bobdaspider]

By way of an update, I contacted the vendor in the US who sold me the rear derailleur and based on my questions (that included information from yourselves) he said the following:

"The “B” screw is now on the barrel/pivet arm of the cage where it attaches to the body.

In choosing chain length, it is not the traditional one extra link when the chain is wrapped around the big chainring and the largest cog with the derailleur stretched taut. Campagnolo instructions are to put the chain around the small chainring and small cog. There should be 3-4mm of distance from the jockey wheel and the chain in this position."

So, based on this information, I can go to the LBS and hopefully have a positive outcome so that I can at the very least use my two lowest gears! A big thanks again to all those who have offered advice to me re this issue - especially Ajax Bay.

 

[Ajax Bay]

the vendor in the US said:
In choosing chain length, it is not the traditional one extra link when the chain is wrapped around the big chainring and the largest cog with the derailleur stretched taut. Campagnolo instructions are to put the chain around the small chainring and small cog. There should be 3-4mm of distance from the jockey wheel and the chain in this position."

"the chain rubs against part of the derailleur when using the lowest gears 1 and 2." Which part?
https://support.campagnolo.com/media/files/035_259_Technical manual - Mechanical units rear derailleur - Campagnolo_Rev03_02_23_EN.pdf

"with the derailleur stretched taut" - No; with the chain not fed through the cage at all, for the 'traditional one'.
"distance from the jockey wheel ([which one] to the chain" - will be zero for all set ups.
Well the manual says 8-15mm but 4mm will do (see the diagram I shared ^ ^ and repasted below). I'd point out that the Campagnolo instructions completely depend on the RD's specifications to be respected (size of largest sprocket, wrap capacity) and yours is that: 53-39 and 13-26.
With that caveat, this method will result in the same length chain as large-large plus not less than one link (1").

May you always have a tailwind.

 

[lazybloke]

The H screw (if it exists on this RD (some periods (of years) don't, research suggests) adjusts the balance between the upper and lower springs in the rear derailleur. Whereas the Shimano 'b' screw has a more agricultural function of moving the cage pivot axis.

Not Mirage

My Mirage and a spare Xenon RD have high and low screws.

Edit: Ah, mine are 10 speed.