I think a lot of it depends on the gear you are pushing.  I started to have knee pain a couple of years ago when I decided to get "serious." I thought my seat was set right and I too was doing 70-80 cadance.  I broke a rear deraileur and was pretty much "mashing" the petals with my big chainring. The guy at the shop suggested I spin more at a higher gear.  When I started monitoring my cadance with my new bike computer I concentrated on using a higher gear and spinning a little faster.  Now I try to maintain 85 to 90 and it feels pretty good.  Less load on the joints.

My next problem was my hip hurting when I brought my Mtn bike.  It came with clips and I had been using Crank Bros. petals on my road bike.  I was also riding the mtn bike in tennis shoes or casual shoes and the pain would come and go.  I finally figured out that the intermittent pain was from not having my feet in the same position in the clips (toes pointed slightly inward?). I brought clipless for my mtn bike and now the hip pain is gone.

That's been my experience.

Don

Thanks for your tips!

I just got a much lighter bike, a LeMond Poprad and have been peddaling clipless. I had the bike set up for me by a shop. No more knee pains.

I don't mash the gears anymore. I can go much further too!

By the way, I live in southern Lapeer County and want to get in on some of the slow spokes rides around Freedom Hill area. Do I have to pay a fee to be a slow spokes member? I don't mind if I have to.

Tony