I decided to "service" my BB's on my 2 bikes, since my "main ride" was getting "gritty" feeling.
It turned out both spindles were the same size and I thought- Why not try the 170MM arms from my "back up" bike on my good bike and put the 175's on the back up. (I didn't have a crank puller before)
The difference is AMAZING!
I'm running the SAME cogs in back, but using the 38T ring instead of my former 46. That's about 21% higher cadence to do the same speed! I think I'm also cruising about 0.5 MPH faster, but it's hard to tell for sure with the wind/cold etc. (edit: after today-did a 9 mile ride- I'm pretty confident I'm doing at LEAST 0.5 MPH faster- maybe closer to 1 MPH!!!!)
Before, I had to keep focused to try to keep my cadence at 65 or it would drop right down to 60 or less. My feet would come off the pedals at around 68 RPM. Now when "madly spinning", my feet still feel "stuck" to the pedals. My cadence is still relatively slow, but at least it's greatly improved. STAMINA has improved as much!
I went on a 15+ mile ride last Sat. I wouldn't have attempted 10 miles on one trip before! (10-12 miles spread over 4-5 separate "errands" per day, with rest breaks in between, was my limit) And, NO PAIN/stiffness!
My conclusion is-
With the longer cranks, I was exceeding the range of motion in my old arthritic/bad knees and was wasting energy on the "down stroke" by having to help "lift" the other leg "over the top".
I'll be curious if another 5MM shorter helps out much more. I certainly don't expect another 20%, but even 5% more would be great. (I ordered a cheap set of 165MM cranks)
My old 175 MM cranks were the stock Specialized from an 86 rock Hopper (26-36-46)
The "new" ones are the cheapest looking Bio Pace that I've ever seen. One piece arm with integrated, riveted rings (28-38-48) off my 91? TREK 820. However, as they say, it works. I don't know if the Bio Pace part helps???
BTW, I'm kind of a "short legged" 6 footer. Maybe a 31" inseam on dress pants? 30" on my Levi's.