Hi guys, I have a Cube Agree Gtc 2011 model and I have a very strange problem (well to me anyway). Having failed to find a long cage ultegra derailleur to replace my old short cage, I went down the path of replacing it with a Shimano Deore 10 speed. I bought a 10 speed chain and a new cassette. After watching the vids for some reason when I pull away on my bike I get a horrendous noise from the chainring. The chain appears to jump teeth at the front. I thought it was a freehub problem at first because I couldn't work out how how the chain could slip without jumping off!
After changing the freehub, I getting the same problem. I recently noticed that if I put the chain on the big cog it won't slip but when I put it on the small cog it does . So to me the freehub must be ok. Could it be the inner chainring worn, or maybe a tension problem?

I have messed with the derailleur tensioner but I still get the same problem. Cheers guys. Rhurbarb