Join Date: Aug 2008
Location: Ann Arbor, MI
Bikes: '15 Kinesis Racelight 4S, '76 Motebecane Gran Jubilée
Mentioned: 9 Post(s)
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I think this is a pretty advanced fit issue, which specifically has to do with the position of the saddle relative to the cranks. This is most commonly expressed by the seat tube angle (ST).
Your Raleigh Sports probably has a fairly relaxed 72º ST, which is common on MTBs, so I don't think, unless you're riding a rather small frame (they tend to build those with steeper STs), that geometry is the issue, and without knowing which frame you've ridden that caused pain, it's impossible to say with certainty one way or the other.
My guess is that moving the saddle further rearward of the cranks on the troublesome MTB you've ridden might yield some clues. By doing so, you'll be reducing the degrees of flexion in the knee when you're applying power, which may be the source of the problem. If you can get that bike again, try pushing the seat all the way back on the rails, or if it isn't fitted with a layback seatpost head, get a seatpost with layback so that you can get more backward adjustment out of the saddle.
Of course, other factors may be your forward reach on the bike and how your weight is centered over your knees. Handlebar height and reach are important here, and if I were to guess at another fix for the offending MTB, I'd suggest a shorter reach stem with more rise, to move your weight back onto the saddle.
Like I said, it gets complicated, but I don't think that ruling out MTBs in general makes much sense. It's about getting the right sized frame and setting it up right.
I hope that helps!