fthomas

Swapped out cassette to a 11-34 with a 105GS and Durace Bar Ends. Worked with no adjustments. Indexing is fine.

The only issue I ran into is the B Screw does not engage the tab on the frame. I picked up a 4x25mm B Screw thinking I would need it. Discovered the existing B Screw did not engage the tab and using the 25mm offered no improvement. Took the original and flipped it and it barely engaged the tab. The cage / upper pully has 2-3mm clearance from the 34t cog.

Is there a way to bend the tab the B Screw is threaded to so it will engage?

Edit:

After some research I guess I can get a 4mm self locking nut and put on B Screw to increase size to contact the tab on the hanger. This is on a Jamis Aurora Elite - Jamis missed the spec's here for sure.

dsbrantjr

try putting a 4mm fender washer (or two, for strength) between the screw head and the nut for an even larger surface: Shop The Hillman Group 4-Count 4mm x 12mm Zinc Plated Metric Fender Washer at Lowes.com

Andrew R Stewart 

And check for chain clearance with the inside edge of the B screw's head. Some bikes have so little gap between the chain and the drop out that even a little bit larger a B screw diamerer can touch the chain when in the small cog. Andy.

gsa103

34t cog is too large for a 105 RD. Your frame is fine, you're using the rear derailleur well outside its limits. It can be made to work, but the fault lies with user not with the manufacturer.

fthomas

Actually, the B Screw did not make contact with the frame with the original 11-30 cassette installed, but that is what the bike came with from Jamis. Yes, even the one used by Jamis is outside the 28t limits for the 105 RD. I know it is outside Shimano's recommendations, but you do not offer a suggestion for a work around. Thanks for your time.

gsa103

If you have 9/10-speed components, the best solution is to use a 9-speed mountain rear derailleur, the cable pull is the same, and the geometry is more accommodating of the B-screw. The most important thing is that its a 9-speed derailluer, Shimano 10-speed (Dyna-Sys) components are in-compatible with their road brethren.

fthomas

Thanks for the info. That is something that I certainly took into consideration. The bike comes with Shimano Bar Ends, which I believe are not compatible with a 9-speed Mountain RD or I would have gone with that and an 11-36 cassette. Unfortunately, the right bar end cannot be switched to friction. That would make the swap much simpler and far less costly.

Tim_Iowa

If you have 11 speed shimano bar-end shifters, then NO they are not compatible with any mountain RD.

If you have 10 speed shimano bar-end shifters, then YES they are compatible with a 9-speed mountain RD.
I currently have Shimano BS-7900 bar-end shifters paired with a 9-speed Deore XT RD-M772 on my Rivendell. It indexes perfectly across an 11-34 cassette.

Shimano 10, 9, 8, 7, and 6 speed road (except 6s/7s/8s Dura Ace) and 9, 8, 7, and 6 speed MTB -- they all use SIS indexing and are cross-compatible. Meaning, the indexing is controlled by the shifter and can work with any RD.

Davet

Using a 9-speed Shimano MTB rear derailleur is a very common thing to do when needing larger rear cogs than a road rear der can handle. 9 and 10 speed Shimano 'brifters' along with bar-ends work perfectly.

The only thing to watch out for is that some rear ders are rated for max 34t, others 36t.

shelbyfv

It would help if you gave more complete info early on. Guessing that you have 10 speed 7900 bar ends, as those are the first that don't have the friction option. If so, they will work fine with a 9 speed mtb rear derailleur and 10 speed cassette. However, if your 105 (5600? 5700?) whatever has clearance between the largest cog and the jockey pulley, you are good to go. Sorry, just went back and read first post again where OP says it works. Not sure what the issue is. BTW, I'm not aware of any function of the B screw beyond keeping the cog and jockey pulley apart. Will be happy to learn if there is more to it.

fthomas

I could have stated clearly the entire system - Bar Ends through Rear Derailleur and Cassette more clearly for sure. Thank you all for some really good information provided. At minimum I now know that I can go with a Mtn RD using the 7900 (why in the world Shimano eliminated the friction capability from the 7900's is beyond me. Limitations instead of expanding compatibility particularly since they are used on some touring bikes.). I also replaced the chain to make sure the fit was right with the new front 48t front crank and 34t rear cog.

Thank you all again! Merry Christmas! I have about 3mm of clearance from the 34t cog and the top pulley. As long as it continues to function under normal operating conditions I'm good to go.