Advice re wheels please



Originally 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

1. Campagnolo 10T guide pulley wheel is compatible (remember this is not essential)

2. Yes, without the chain on.

3. Yes, you need to adjust the distance via the B screw.

Another question ... are you certain that you have made the chain the correct length?
 
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 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.
 
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:

  1. 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.
  2. I then set the RD to 1st gear (ie the 36T sprocket)
  3. 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)
  4. 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)
  5. I then shifted the 7800 STI lever to 9th position and tensioned the shifter cable until the chain shifted to 9th gear.
  6. I further checked the shifting by shifting to 1st and back to 10th gear ... all good, even very good.
  7. For this setup, it was now shifting as good as (well, very close to) my DA 7800 RD setup
  8. 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 :)
 
Hi, Many thanks for all who've responded and all the excellent and helpful suggestions (also via PM). Finally I've got it working! Turns out that there was probably nothing wrong with the numerous derailleurs or cassettes that I tried... How I fixed it - To solve the problem I took the chain off and viewed the movement of the derailleur from above. It was then clear that the jockey wheels weren't moving by an even amount with each index. This eliminated the cassette and chain from being the problem. So I blasted tons of spray lube (GT 85) into the shifters and worked it in. More importantly I also replaced the gear cable inner and outer (again!) as I think it was snagging on a piece of outer housing before. My findings - For the record, it looks like a shadow mech like the XT M772 (tested) and XTR M972 (tested) is the best type of derailleur to use with these large cassettes. It seems to be the only one I tried where the B screw actually has any effect (this may be due to me running too short a chain, but I think it's correct). On my bike there's an issue fitting long screws to the other derailleurs as the angle tends to mean they don't sit well on the little tab on the hanger, and so aren't very effective. The Shadow has a different design and a much longer B screw - seems to work better for this application. With the chain off and with a 36T cassette fitted, the Shadow is the only derailleur I've found where the top jockey wheel actually clears the largest sprocket. I haven't tried fitting smaller (10T) jockey wheels. With the chain on, then on the non-shadow derailleurs (XT M771 and XTR M970) the top jockey wheel does clear the 36T sprocket but only by virtue of the chain bringing the derailleur forward and downwards... I don't know though if this is the way it's meant the be set up - maybe my chain is too short? I have used the guide from Sheldon brown (http://www.sheldonbrown.com/derailer-adjustment.html#chain) to determine correct chain length. Using his instructions you thread the chain in the large/large combination without the derailleur, and then look to obtain an overlap of one complete link. Anyway hope this helps someone. I need to do some fine tuning but so far (one test ride) it's working pretty well with the XTR M972 shadow derailleur, SRAM 1070 12-36 cassette and a Shimano 105 chain. Dave
 
Hi treefrog911, that's excellent, well done :)

If you do what I have described in my previous post it will work flawlessly. I also believe that this setup will work flawlessly with a much larger range of chains, although the Shimano Ultegra and Dura Ace chains are the best for this setup, IMO. :)

I will try and post a picture ... they say a picture is worth a thousand words (so, they say) :)
 
You are on the right track. An MTB cassette, 11-34, with a Deore Shadow medium cage der will work very well with a compact crank, 50/34. Triple cranks are heavy and cross the chain up more, causing adjustment issues and wear that your compact won't. Even MTB's are going to compact or even single chainring setups now.

Shimano is actually making a longer-cage rear der for road bike use, it's basically the same size as the med. cage Deore Shadow but is being used on touring bicycles.

I have a bike I set up that has the SRAM 11-34 cassette and the Deore Shadow der and it works beautifully with a compact crank. Gives a 1:1 low gear.
 
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:

  1. 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.
  2. I then set the RD to 1st gear (ie the 36T sprocket)
  3. 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)
  4. 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)
  5. I then shifted the 7800 STI lever to 9th position and tensioned the shifter cable until the chain shifted to 9th gear.
  6. I further checked the shifting by shifting to 1st and back to 10th gear ... all good, even very good.
  7. For this setup, it was now shifting as good as (well, very close to) my DA 7800 RD setup
  8. 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 :)
Hi All, here are the pics I promised of the RD setup I have quoted above.
As I have indicated this RD setup changes nearly as good (very close) as my previous DA7800 RD 12-27T setup :)

36T sprocket, 39T chain wheel


12T sprocket, 39T chain wheel


28T sprocket, 53T chain wheel


12T sprocket, 53T chain wheel


36T sprocket, 53T chain wheel ... Even though this will not harm any of the drive train, this is something I will not be doing unless it happens by acident, which is unlikely :)
 
Hi All, I have changed my SRAM 1070 11-36T cassette to an Shimano XT 11-36 CS-M771-10 cassette and the M772 XT RD to an M972 XTR RD, while still using my 7800 STI lever and KMC X10SL chain.

The process I used is as follows. Note that my RD and chain are already fitted and the following adjustment is from that point of view:
  1. I screwed the B screw in as far as it would go.
  2. I then set the RD to 1st gear (ie the 36T sprocket)
  3. I then loosened the RD securing bolt and set/moved/rotated the RD as far forward as it can go to achieve the 4-5mm 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)
  4. 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)
  5. I then shifted the 7800 STI lever to 9th position and tensioned the shifter cable until the chain shifted to 9th gear.
  6. I further checked the shifting by shifting to 1st and back to 10th gear ... very good to excellent shifting.
  7. This setup shifts at least as good as my DA 7800 RD setup

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 will tend to be in a horizontal position, not a downward inclining position.
  • that the chain is always sitting on half the sprocket

Alfeng, you are right the XTR RD is an excellent RD :)

The interesting point with this setup is that Shimano state that it should/will not work, and is not compatible, but that is incorrect. It works/shifts perfectly :)

The KMC X10SL chain definitely shifts better with the Shimano XT 11-36 CS-M771-10 cassette and the shifting is quieter. The XT cassette is also lighter than the SRAM 1070 11-36T cassette :)

I believe that this setup will work/shift even better with an Ultegra 6700 or DA 7800/7900 chain ... nice :)