Originally Posted by
1Lieutenant
...3. HIlls were significantly different. The last two miles of my ride has two hilly sections. The first is a 1/2 mile 9-11* grade. I am usually in my lowest gear 42 x 42 and sucking wind at the top. Today was in the second lowest gear 36 x 42. I did not do this intentionally, I just shift when I feel the need. I was surprised when I reached the top that I felt much better and it was only then when I looked down did I realize I was not in the lowest gear. The last hill is a killer that is almost a mile long with a center section that reaches 13*. Again, I felt much better at the top although on this hill I did shift into 42 x 42.
Same impressions I've had with the old Biopace rings. I mostly notice the difference on climbs at slower cadence. And into stiff headwinds. I had both Sunday, a 5 mile roller coaster climb into a 20 mph headwind, and a 2 mile gradual climb into a slightly less stiff headwind, maybe 15 mph by then.
My steel frame '89 Ironman came with the original 52/42 conventional round chainrings and 7-speed 13-24 freewheel. After a few rides in 2017 I realized I'd need to swap the gearing around to suit myself. I finally settled on a 50/39 round chainring and 13-25 freewheel combo, that I rode happily for a couple of years.
Then last year a '93 Trek 5900 (carbon fiber) bike I bought from a friend was fitted with 52/42 Biopace, taken off another Centurion Ironman (the Shimano group Ironman models had Biopace, while the Suntour equipped Ironman models came with conventional round rings). I'd been wanting to try Biopace. I did swap around wheels between 13-25 freewheel, and 13-28 freewheel and cassette wheels. The 13-28 suited me.
After stripping the Trek frame for an overhaul recently I moved the Biopace rings and crank over to the Ironman. I figured I wouldn't be able to handle the 52/42 chainrings on the heavier steel bike. Nope. Rides just fine. There's something about the eccentric Biopace rings that seem to offer a bit of leverage, but for me it works best at slower cadence and harder gears (smaller cog).
After I finish overhauling the Trek the Biopace rings and crank will go back on it. It'll be interesting to see if I can handle the old 52/42 round chainrings on the Ironman again. If not, that'll be a reasonable indicator that the eccentric smaller ring does offer a little mechanical advantage -- at least with my choppy, stompy pedaling style.