Rear wheel dusty spinouts when climbing

[Catrin]

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Or do you mean that were going around the corner and the rear wheel slipped sideways to the outside of the turn? This probably means you were leaned over too much. When I was riding a lot on knobby tires, somehow or other I learned to keep the bike somewhat perpendicular to the (road or trail) surface. (I think this is because once the front tire skidded sideways when I was leaned over going around a fast corner.) If the speed of the turn required a lean, I'd move my body over, but keep the bike mostly upright. Sheldon et al. say not to do this - it imparts significant non-normal forces in the bike. However, some tires simply aren't able to grip off of perpendicular. Or they might deform, letting the rim roll towards the outside. In summary, be constantly aware of how your tires are contacting the ground and don't ask more of them than they are able to perform.

It is the second of your scenarios - I seem to ALWAYS be in a curve to the right when this happens, and the rear wheel skids out from under me toward the outside of the turn, exactly as you describe. I don't believe that it has ever happened on a curve to the left. This sideways slide happens FAST - perhaps the presence of the dust just adds to the effect. I also didn't think I was leaning, but that doesn't mean I wasn't. I do know I've learned unconsciously in the past (people told me later) so I wouldn't be surprised. There are never obstacles when this happens, typically just a right-hand uphill curve with lots of dust...

The first situation you describe I can easily stop with brakes - and I don't clip in so I can just brake and put my foot down. I am pretty darn good at stopping fast on the trail...