Derailleur Matching

[Venod]

On the turbo bike I have a Shimano 105 10 speed ss well used rear derailleur matched with 105 5700 10 speed shifters, I have to use a goat link on this frame to use a 32t largest sprocket, it doesn't give the smoothest of shifting, I have a Tiagra 10 speed 4700 gs rear derailleur that would clear the 32t sprocket without the need for a goat link, but the activation ratio is 1.4 the 105 is 1.7, has anybody successfully run the combination of 10 speed 105 5700 shifters with a 10 speed Tiagra 4700 rear derailleur ? if so how?

A Jtec shift mate looks an option, although that combination is not listed but looking at the numbers Jtec 3 or 4 might work.

The cable pull of the 10 speed 105 shifters is 2.32mm the sprocket spacing of the 10 speed cassette is 2,95mm and the activation ratio is 1.7

so 2.32 x 1.7 = 3.944

The Tiagra has a 1.4 ratio

so 2.32 x 1.4 = 3.248

The Tiagra needs 0.7mm more pull per click to work correctly.

Any thoughts ?

 

[si_c]

I don't think it will work unfortunately. The Tiagra 4700 parts work at the same cable pull ratio as Shimano 11 speed road and that's not a combatible option on the JTek either so it doesn't look as though it supports that 10speed setup with an 11speed type derailleur.

Not sure what the alternatives are.

 

[vickster]

Why do you need a 32t on a turbo bike, genuine question. Can’t you just fit a cassette that works with the mech?

 

[fossyant]

Change to a smaller cassette.

 

[Venod]

Why do you need a 32t on a turbo bike, genuine question. Can’t you just fit a cassette that works with the mech?

Yes I could change to a smaller cassette but then I would have to reduce the turbo resistance to get up some of it the mountains in the Tacx/Garmin collection, I prefer to keep the resistance at 100% this simulates the difficulty in real life.
Another reason is I like a challenge bodging wise

 

[Venod]

The Tiagra 4700 parts work at the same cable pull ratio as Shimano 11 speed road

That's not quite correct, the Tiagra 4700 rear derailleur has the same actuation ratio of 1.4 as the 11 speed derailleur but the 4700 10 speed shifters have to pull more cable per click than the 11 speed shifters.

11 speed road cassette spacing is 3.74

so 3.74 divided by 1.4 (derailleur activation ratio) = 2.67 pull per click.

10 speed road spacing is 3.95

so 3.95 divided by 1.4 = 2.82 pull per click

 

[vickster]

Yes I could change to a smaller cassette but then I would have to reduce the turbo resistance to get up some of it the mountains in the Tacx/Garmin collection, I prefer to keep the resistance at 100% this simulates the difficulty in real life.
Another reason is I like a challenge bodging wise

Or keep the resistance high with the smaller big cog if you like a challenge

 

[Venod]

I spotted a Shiftmate 8 on ebay, looking at the numbers for its intended purpose I thought it might suite my requirements so I bought it, I now have a Tiagra 4700 10speed derailleur working with 105 5700 10 speed shifters, it's not perfect but all the gears are available and the jockey wheel is in a much closer position to the cassette than with the 105 ss with a goat link.

Anybody looking to use a Shiftmate to get a Tiagra 4700 10speed derailleur working with 105 5700 10 speed shifters, I would suggest the model 3 is the best match.