"Yuri Budilov" wrote:

Lately, when I change from large chain ring to small one the chain simply
drops off (every 3rd-4th change).

My LBS checked it and in
test could not fault it. The only advice they could offer me was to change
a
few rear cogs up/down so that the chain is more or less "straight" when I
am
about to change from small to large chain ring or vice versa.

It's generally a good idea to shift to the small front ring before you get
to the largest rear cogs (and vice versa).

Is this as good as it gets with Sora? Is there anything else that can be
done/adjusted? The LBS did adjust the chain and pronounced it good.

Will a 105 or Ultegra group set suffer from the same gear-change problem?

I don't think there's any inherent difference betweeen Sora, 105, and
Ultegra in this regard.

I think you should be able to eliminate the drop offs by:

1) Adjusting the limit screws on the front derailleur.

2) Having some slack in the cable tension when on the small ring.

3) Getting the derailleur cage as close as possible to the teeth on the big
ring (~1mm).

4) Adjusting the angle of the derailleur cage slightly (as viewed from
above).

See:
http://www.sheldonbrown.com/derailer...ent.html#front

and

http://www.parktool.com/repair_help/...railleur.shtml

Art Harris