One key issue for me was that my Klein Pinnacle was a poor climber, which surprised me on something so stiff and so responsive on the flat. At the time I attributed it to a very slack seat angle but I have been trying to check that recently with a Klein geometry chart, but haven’t found one. I wonder if the seat was too far back because the frame was too small, thus giving a very slack virtual (literal) angle....
From a 2004 MTBR post:
‘...Older Klein's were notoriously under-sized. I can't tell you how many people bought Kleins that were one size too small. You try to convince them to go up a size, but in the end, they would insist on the smaller size - only to come back 6 months later with a crack in the seat tube radiatiing out from the seat tube slot. If you are 6', you would probably be better fit on what they called the 22" (if I recall correctly, their sizing was center to top of seat tube - and they had a lot of seat tube showing - so that 20" is almost like an 18" center to top of top tube).
But - most important - don't size the bike by the seat tube. Size it by the top tube. That's the crucial factor. And if you end up with the 20", do yourself a favor and make sure the seat post is burried in the seat tube to well below the bottom level of the top tube...’