Originally Posted by
HillRider
The first and most important thing to allow upgrading is money. Given enough of that you can upgrade anything.
Why really should be the first question, absolutely nothing wrong with Acera or Alivio, but generally they are fitting on lower end bikes (lower end but still good bikes, far from BSO level) and there is often little point in upgrading the groupset, as all the other parts will be lower end as well, as mentioned above, look to at a better bike with the higher spec parts fitted already, as all the other parts, like the frame, shocks, wheels etc will normally be better as well.
Even if your looking at replacing worn parts at this level, you need to look at the overall cost of replacements vs just replacing the whole bike.