105 derailleur with Tiagra shifters - limited to 9 speed?

[slowsteady]

Hi everyone,

Looking to leverage the collective wisdom of some smart bike fold on here.

I have an old bike (Avanti Vivace circa 1997) that I am using for my wahoo kickr and it will stay on there, so not my normal outdoor bike.

On the Avanti, I have a 105 rear derailleur with Tiagra shifters and it currently has a 9 speed rear cassette. I have an 11 speed cassette that I would like to put on the trainer but when I do it skips around quite a bit. Obviously there are chain issues between the 9 speed and 11 speed which I need to resolve but:

- If I were to change the shifters to be 105 or above (Ultegra etc) would do you think that I will be able to shift through 11 speeds? In other words, is my range of gears on the back currently limited to the shifters that I have as opposed to the 105 derailleur?

I would love to be able to get some 105 shifters, change the chain and get 11 speed out of the back.

Thanks in advance for your input.

[jules21]

Yes, the derailleur does not affect compatibility. It's only between the shifters and cassette. As long as you are staying with Shimano or SRAM, and not using Tiagra 4600 which is 10 speed anyway and an exception.

So 11 speed shifters and 11 speed cassette will work fine if Shimano or SRAM. An 11 and 10, or 9 speed mix of those will never work.

[Duck!]

You are limited to 10-sp. max with that derailleur, and with any Shimano 10-sp. shifters EXCEPT 4700 (current generation) Tiagra. To run 11-sp. you must also fit a compatible derailleur.

[slowsteady]

Thanks for the opinions all. My follow up question will be, how do I get a cheap used 11 speed derailleur and shifters? Do you think bike shops will sell the old sets cheap if they are swapping out new ones for patrons?

[Duck!]

Yes, the derailleur does not affect compatibility. It's only between the shifters and cassette. As long as you are staying with Shimano or SRAM, and not using Tiagra 4600 which is 10 speed anyway and an exception.

So 11 speed shifters and 11 speed cassette will work fine if Shimano or SRAM. An 11 and 10, or 9 speed mix of those will never work.

I can see what you're trying to say, but it's not entirely correct. The key factor is cable pull/leverage/actuation ratio, which in short is the distance the derailleur moves in relation to cable pull. All Shimano stuff up to 9-sp. MTB and 10-sp. road with the exception, as noted above, of 4700 Tiagra (and by extension RS405 hydro brake levers) work on a common pull ratio, so as long as the right (rear) shifter & cassette are matched for number of gears, any combination will work, barring particular cassette size/derailleur combination limitations. 8, 9 and 10-sp. cassettes are all virtually the same overall width, so to get the extra gears in they're packed closer together, with a correspondingly shorter cable pull between each index point, but the relationship of cable pull to derailleur movement is constant.

11-sp. and 4700 use a different cable pull ratio to the previous grouping so can only be mixed within that family. This group works on a shorter pull ratio, meaning that to achieve a given derailleur movement, more cable needs to be pulled. It won't work with the other family of shifters & derailleurs. Short version is if you want to use an 11-sp. cassette, you also need a compatible shifter AND derailleur.

It's the same reason why Shimano and SRAM shifters & derailleurs don't play together. There are also different families of SRAM stuff, but that's beyond the scope of the query here. For more details, read the "Compatibility Notes" threads in the relevant bits of the Bike Brands subforum.

[slowsteady]

@duck, thanks that makes things clearer for me. I'll keep a lookout for a fully compatible shifter and derailleur. With the time I'm spending looking, I might be better off trying to find an old bike with all the bits already on it.