I am using downtube friction shifters, I know my shifter's pull of 28.5 mm multiplied by the Shimano 105 RD's pull ratio of 1.4 gives me 40mm of travel, enough to traverse the entire width of my 35 mm 8 speed freewheel. I am worried that my 8 speed chain will be too fat to roll across the jockey wheels of the 11 speed 105 rear derailleur...should I be ?

I have an 8 speed freewheel.

  • You should probably be using an 11s chain. Any reason why you want to stick with the 8s one?
    – MaplePanda
    Oct 9 '20 at 19:30
  • I have an 8 speed freewheel, wouldn't an 11s chain fall between the gaps between the cogs of my freewheel?
    – mancini0
    Oct 9 '20 at 19:32
  • Jeez, I’m bad at reading nowadays. Completely missed the “8 speed freewheel” part. That then leads me to the question, why the 11s derailleur?
    – MaplePanda
    Oct 9 '20 at 19:36
  • Shimano ties their quality level to the number of speeds - there is no 105 level quality derailleur at the 8 speed level. If the jockey wheel performance is independent of the chain width, the 105 would be a good derailleur at a good price. I also want to keep the option open of doing an 11-speed conversion this winter.
    – mancini0
    Oct 9 '20 at 19:44
  • 1
    @mancini0 105 is not the high quality level, that would be Ultegra. 105 comes with basic jockey wheels and the latest model is also partly made from plastic. You would be many times better off finding a vintage derailleur. There also just is not a major quality difference between 105 and Claris derailleurs - the latter is mostly steel rather than lighter alu but it's still a quality component. Just get a Claris derailleur, or seek out a vintage part.
    – thelawnet
    Oct 10 '20 at 13:51

The internal width of the chain will be fine, as this has not changed in decades, so it will roll over the cogs and jockey wheels. The problem will be the external width of the chain. It will probably not fit though the 11 Speed derailleur cage, and if it does is likely to rub in some gear combinations. According to Park Tools, 11speed is 5.5mm and 8 speed is 7mm.

On balance it is one of those things that might work, might not, where 'work' is something you define. If it works, mixing and matching components like this is as likely to end up with Claris performance at 105 prices as anything.

  • Agree wholeheartedly with the The last sentence. OP will not notice any benefit from the 105 derailleur with a friction shift setup. Oct 10 '20 at 11:20
  • I have to disagree here. Downtube friction shifters, unlike bar end shifters, give very direct feel to what happens at the derailleur so with good derailleur it's easy to shift very accurately.
    – ojs
    Oct 10 '20 at 18:10
  • The OP will notice a vast difference friction shifting with the new 105 derailleur --- the new design has a different cable ratio so there will be more lever movement between shifts allowing for more accuracy. The old style Shimano derailleurs are frustrating to shift especially on eg rough surfaces.
    – JoeK
    Oct 11 '20 at 20:55

I think this is a non-issue. If the 8 speed chain seems slightly too wide for the cage, which is quite likely, you can put a thin washer or spacer on each side of the jockey wheels (as the cage is split in two halves) or use 8sp specific aftermarket jockey wheels with the same number of teeth.

  • This would also require sourcing longer pully bolts.
    – mattnz
    Oct 10 '20 at 23:15
  • You may need to replace the pulley bolts. They have the same thread as the bottle cage bolts (M5).
    – JoeK
    Oct 11 '20 at 20:57

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