Tiagra /Deore?

astrocan

Über Member
Location
Abingdon, Oxon
Daughter dear has a Genesis Tour de Fer and has just about ragged out the standard transmission which is Tiagra 3 x 10.
While considering replacing it she says that she rarely uses the highest ratios and has occasionally found that she would like to drop a gear or two when she has already hit the bottom.
Obvs way to go is replace the chain rings (30 - 39 - 50) with smaller. I could do this by getting 3 replacement rings, but I have found this to be complicated and mostly out of stock. The other option I have considered is getting a mountain bike crankset (Deore?) which I could hopefully get as a complete unit but raises compatibility issues.
Can anyone tell me if a Deore crankset (or similar) would work with Tiagra shifters and / or front mech?
If I find smaller rings from a different range (e.g. Deore), assuming the BCD is compatible, would there be anything else that needs to be considered before going ahead and bolting them to the Tiagra crank?
I have thought about a cassette with a wider spread but that may have similar compatibility issues plus the requirement for either a new mech or one of those hanger extender thingys, which I am not keen on if I can avoid it.
If the worst comes to the worst, I might just build a smaller wheel.........it's a thought.
 

Cycleops

Legendary Member
Location
Accra, Ghana
You don't say what the cassette is. Few extra teeth on that might be the simplest solution as you can usually exceed the RD manufacturer's max by a small margin.
 

MichaelW2

Veteran
I run an LX chainset with some Shimano midrange triple front mech on the tourer. The curves dont really match and shifting is not optimal. It would probably work better with a 28/38/48 chainset that I used to use on my commuter bike
 

T4tomo

Veteran
astrocan have you tried spa cycles for chainrings, they have oodles of options...

the complication of switching to a MTB crankset is getting the right BB to get a decent chainline, given differing chainstay layout etc
 
I have a Stronglight chainset on the tandem running Sora 3x9 brifters with 46/36/24 rings and 11-36 cassette.

Slightly outside the nominal range for both derailleurs, but all works perfectly.

I expect a similar setup would be ok for Tiagra 10 speed, though less risky to keep within nominal derailleur capacities if you can meet her gearing needs within them.
 

si_c

Veteran
Location
Wirral
Not sure which chainset you have, but if you have the Tiagra FC-4603 then Spa in Harrogate have compatible rings in stock - their own brand Zicral chainrings - I think you want the 110BCD Outer/Middle and the 74BCD inner but if you give them a call they should be able to tell you. They've currently got 44/34/24 chainrings in stock for example.

Tiagra 4700 moved to a 4-bolt spider instead of a 5 bolt, but there rings which might be compatible, but I'm not sure what the precise options are.
 
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