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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.

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  • You should probably be using an 11s chain. Any reason why you want to stick with the 8s one?
    – MaplePanda
    Oct 9, 2020 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, 2020 at 19:32
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    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, 2020 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, 2020 at 19:44
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    @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, 2020 at 13:51

3 Answers 3

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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.

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  • Agree wholeheartedly with the The last sentence. OP will not notice any benefit from the 105 derailleur with a friction shift setup. Oct 10, 2020 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, 2020 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.
    – Noise
    Oct 11, 2020 at 20:55
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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.

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  • This would also require sourcing longer pulley bolts.
    – mattnz
    Oct 10, 2020 at 23:15
  • You may need to replace the pulley bolts. They have the same thread as the bottle cage bolts (M5).
    – Noise
    Oct 11, 2020 at 20:57
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8 speed chain works just fine with the jockey wheels on the 10 speed edition of the 105 RD.

On my 20" 1x folding bike, I tried 7 speed freewheel (14-28T) and also 7 speed cassette (11-28T). I replaced the 44T crankset w. a 46T. The first 46T crankset i got, did not fit an 8 speed chain at all. I use an HG40 chain w. 102L and a 10 spd 105 ss rear derailleur. I used an adjustable wrench to bend the outer plate at the tension jockey just a little bit, to allow the chain to pass freely in 1st and 2nd gear. The 105 rear derailleur replaced a 6/7 speed tourney rear derailleur and is connected to a 7 speed shimano revoshift.

If 14-28T freewheel lacks speed and low cadence, you can always try a 58T chainring.


@Andrew Henle - I 100% agree, that big gears don't make you faster. But 44/14 gives a gear ratio of 3.14 and 46/11 gear ratio of 4.18. Pedals on the first setup is going to spin insanely fast to beat the new setup at the same speed. I ride 30-40km every day, so time is a factor to consider too. I'm going to try a TT bar on the folding bike in the spring.

On my road bike rear wheel, the tyre may be wider than the one on the front wheel. Many people still don't get, that the width of a triathlon bike tyre is relatively unimportant, because left and right side of the tyre makes no contact to the surface you ride on. However, the height of the tyre has got an influence of the overall wheel diameter, which influences the circumference of the circle. Therefore the highest tyre must be mounted to the power transfering wheel. 700x28c = 622mm rim diameter + 2 radials * Pi = Circumference. Eventually check with the manual of an oldschool bicycle computer.

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    If 14-28T freewheel lacks speed... Big gears don't make you faster. Jan 9, 2022 at 18:48
  • Hi, welcome to bicycles. The question was about running an 8-speed chain through an 11-speed derailleur. Since a 10-speed chain is about .5mm wider than an 11-speed chain, your minor bending might not be possible for an 11-speed derailleur.
    – DavidW
    Jan 10, 2022 at 21:04
  • Also, I suspect you've set up at least two separate SE accounts with the same name - that's likely accidental but please use the original account. You can also browse the tour to learn how the site is organised, as a Q&A not as a chatty web forum. Answers have to at least address the question.
    – Criggie
    Jan 10, 2022 at 21:51

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