I have a 2006 Klein Q-Pro frame that was used to replace a defective 2005 Klein Reve frame (that is another story, which I will not get into). In any event, the component group I have is Shimano 105 Triple that I used on the Reve last season. The same group was placed on this new Q-Pro frame. I have always had problems with the chain slipping in the top (largest) three or four sprockets on the rear cassette while I am pedaling in the smallest chainring on a fairly steep hill (I would guess 8% or higher grade). When I am pedaling with moderate to high pressure up the grade, the chain will come off of the rear sprocket, the crank will slip forward suddenly, and my shoe will dislodge from the pedal. Several times this almost caused me to fall.
Now the bicycle shop has not been able to identify the problem. Several times last year, they simply adjusted the shifting. I think that they also checked the rear derailleur alignment (at least I think they would have done so). And the bike shop mechanics have never experienced the problem when they take the bike out for a spin. But I really doubt if they ever took it up a steep hill to simulate the environment in which the slipping occurs (just this last week, they simply put the bike on an indoor trainer to test it). I am not sure if the bike shop mechanics believe me.
Despite what the bike shop mechanics believe, the problem is very real and it persists to this day. I cannot continue riding with this potentially dangerous condition. Does anyone out there have any ideas what could be causing this problem or could suggest how to further diagnose the problem? I called a technical services person at Bike Nashbar, and he suggested changing out the rear cassette and chain. Thanks for any help you can provide.