Upgrading a heavy duty bike I have been using my bike for about 10 years for daily commuting and occasional traveling. It is a "trekking cycle" with a flat handle bars. I use it mostly for road riding, i.e. on streets and paved ways.

At the moment, it has original Shimano Deore LX shifters which are totally worn out. I am emotionally highly attached to frame/handlebar, etc. so I think upgrading is the way to go for me. This time it will be a major overhaul, i.e. I would like to exchange everything related to shifting / gears, and also rim/spokes, bottom bracket, hub. 

I am now wondering which components to choose. I want to assemble things myself, so I am 100% familiar with the setup. I have been told that maybe an SRAM x7 group might be good, as it should be easier to work with with its 1:1 ratio. 


Are there limits to the brakes/brake levers that I can choose? Must they "fit" the shift levers?
Are there problems I do not see? I.e. when switching from a shimano to a SRAM shift group?


PS: Hope this is all understandable, English bicycle tech vocab is not one of my strengths (yet).
Well, going SRAM means new shifters and new derailleurs (and while you're at it, you may as well install all new cable housings and cables). Depending on your hub, you may need to get a new hub (or more likely, a new rear wheel) to fit a 9/10 speed cassette that the current x7 group uses -- however if you have an 8/9/10 speed freehub already, you should be good to go. Note that the # of gears in the front &amp; back have to match what your shifter expects.

As for brakes/brake levers, depending on what levers you have, you may need new ones (if they're in the same unit as the old shifters, for example, you need new ones). You're free to mix and match the brands of brake levers with the shifters, but you may find that the proprietary clamp systems (e.g. Matchmaker/i-spec) will give you better positioning of the shift and brake levers than mixing and matching. 

I don't think SRAM or Shimano will be "easier to work with" -- go with whichever one you prefer (usually dependent on brand loyalty/how you prefer to shift).