Converting Triple to Compact

[Kestevan]

I want to convert a Shimano Tiagra triple to a compact double. Is it a simple matter of changing the crankset and BB, and resetting the limit screws on the front mech to stop overshifting or am I missing something obvious/important?

 

[accountantpete]

Yes but

1) A quick google shows some people have trouble with the triple front mech - for others it works great.

2) Shimano recommend that you use the first two lever positions to work the reduced chainset. ie granny ring is 34 and middle ring is 50.

You then limit the movement leaving the levers third position unused.

This prevents undue strain on the shifter.

 

[HLaB]

Sorry if you've posted elsewhere as to the reasons Kest, but my first question would be why?

 

[Kestevan]

Thanks Pete, that's what I suspected. I'll try it with the existing mech, before putting my hand in my pocket

HLaB, It's for Mrs Kes, she's not the most mechanically "understanding" and often struggles with shifts/cross chaining etc..
A slightly larger rear cassette on a compact chainring offers virtually the same range, simplifies changes and reduces the likelyhood of mechanical snafus.