Problem with chain skipping when pedaling hard If I pedal hard, i.e. while standing/taking off/going uphill, the chain skips over the cogs making a load screeching noise and my foot just sinks to the bottom position.

I attempted to fix this problem so I replaced the crankset, cassette and chain with brand new Shimano Drore M590, Shimano Alivio HG400 and KMC X9 93 chain but the problem remains. I needed to replace these anyway since they are 2 years old and I had low quality components (i.e. drive side crank arm becomes vertical with pedal in bottom position).

I feel like either the free wheel or tension in the back derailleur is causing the problem. I removed the front derailleur because I only use the middle chainring.

I read all the other questions on this issue and they talk about the chain or the cogs being old but this does not apply since mine are brand new.

What is the likely cause of the problem in my situation? How can I make sure?
Since the rings, cogs and chain are new, and decent components we can safely eliminate the possibility that there is a problem with the chain grabbing the rings or cogs.

Here is what I suspect might be happening: it's your derailleur: due to wear, damage or perhaps weakened springs.

Here is how: as you pedal, the chain temporarily catches in the derailleur cage. The next thing that happens is that, since the chain is not moving through the derailleur, the entire derailleur is pulled by the chain and rotated backwards, which basically peels/unwraps the chain from the cassette until it loses grip.

You only notice this when there is significant load on the chain, like going uphill. Under light load, you just need one or two teeth of grip, if the chain and cassette are new.

There is no substitute for having someone watch what is going on. Or attaching a camera to a chain stay or seat stay to record what is going on.

If the derailleur is the culprit, you probably wasted money on the new crankset. Two-year old rings are probably still okay, and in any case, individual rings can be replaced, not the entire crankset.