STI Chainring Compatibility

[citizenthom]

I'm currently looking to buy an 8 speed shimano Sora STI lever.

Are these levers general and can be adjusted for either double and triple chainrings, or are there specific models for the different chanrings?

I have found conflicting information on the web.

 

[andy_wrx]

Shimano list them separately - ST-3300 as a double and ST-3303 as triple.

http://www.shimano.com.au/media/tec...V-ST-3300_3303-1886_v1_m56577569830609256.pdf

http://www.shimano.com/publish/cont...hnical_service/faq_s/road_faq_s.html#FAQ_0006

I used to have triple and they said 'Triple' or similar on them.

They simply had three positions, no trim capability.
Perhaps the double version just has two positions.