Hi treefrog911Originally Posted by treefrog911 .
A couple of questions if I may...
1. What 10T pulley wheel have you found to be compatible with these Shimano cassettes. I went into a bike shop today but couldn't find anything compatible (wheels I looked at were too narrow to 'fill' the width of the cage).
2. When measuring the distance between the guide pulley wheel and the large sprocket, do you mean with the chain on the bike or without? With the chain on, the tension moves the derailleur forward / backward (depending on which front ring is engaged) and this varies the distance. Without the chain, the pulley wheel actually fouls on the large sprocket when it's over as far as it will go towards the wheel (i.e. lowest gear).
3. Is there any way to adjust the position of these wheels. You seem to imply that there is, but basically the position seems fixed by the design of the derailleur... is it just adjustment of the B screw and size of the pulley wheel?
Hi treefrog911, when you describe the above it actually sounds like the chain is a little short. It would seem that the RD is not hitting the B screw stop with the chain on, but perhaps I have read what you have written incorrectly.Originally Posted by treefrog911 .
2. When measuring the distance between the guide pulley wheel and the large sprocket, do you mean with the chain on the bike or without? With the chain on, the tension moves the derailleur forward / backward (depending on which front ring is engaged) and this varies the distance. Without the chain, the pulley wheel actually fouls on the large sprocket when it's over as far as it will go towards the wheel (i.e. lowest gear).
Hi All, here are the pics I promised of the RD setup I have quoted above.Originally Posted by KLabs .
Hi All, I have finally got my SRAM 11-36T cassette, M772 XT RD and 7800 STI lever working like my 7800 RD. There certainly seems to be a knack to positioning the RD and B screw adjustment.
This is what I have done. Note that my RD and chain are already fitted and the following adjustment is from that point of view:
- I screwed the B screw in as far as it would go. Note that the following is not necessary ... but, I went one step further and changed the B screw to one that is 2-3mm longer and screwed it in as far as it would go.
- I then set the RD to 1st gear (ie the 36T sprocket)
- I then loosened the RD securing bolt and set/moved/rotated the RD as far forward as it can go to achieve the 4-5 distance/gap between the 36T Sprocket and the Guide pulley wheel and retightened the RD securing bolt. (Note that the RD stop pin will nolonger be sitting against the derailleur hanger(DH) stop/platform, but will actually be forward of DH stop/platform)
- I then set the RD to 10th gear and untensioned the shifter cable. (Note that you may need to reset the Hi screw and even the Low screw)
- I then shifted the 7800 STI lever to 9th position and tensioned the shifter cable until the chain shifted to 9th gear.
- I further checked the shifting by shifting to 1st and back to 10th gear ... all good, even very good.
- For this setup, it was now shifting as good as (well, very close to) my DA 7800 RD setup
- In fact this setup is so good that I may now try an M972 XTR RD. I believe that the XTR should provide even more accurate and crisper changes ... so, not finished yet
What you will notice when you do this is that
- the Guide pulley wheel is forward of the Sprocket
- the chain between the Sprocket and the Guide pulley wheel is in a horizontal position, not a downward inclining position.
- that the chain is always sitting on half the sprocket
Note that this cannot be done so easily with a road RD (perhaps not at all), because the road RD relies on the DH stop/platform for B screw adjustment, whereas for an MTB RD the B screw adjustment is built into the RD.
Hi treefrog911, I hope that this is helpful
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