Tiagra /Deore?

[astrocan]

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]

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]

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]

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

 

[roubaixtuesday]

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]

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.

 

[astrocan]

I'm going to give Spa a try, thanks for the steer. Projected difficulties with the chainline is a timely warning, thanks for that too.