Originally Posted by
jim p
The auto shifting is happening in the 48 tooth front gear and the 4th largest cog on the rear. I think that the 4th cog is a 20 tooth.
3/32" wear over 12" is 0.7% wear. I thought that you could go as high as 1% wear. What percentage wear do you guys shoot for as the max wear on a chain?
As far a chain lube, I drip some motor oil on the chain about every 100 miles. Then I just let the chain sling the oil all over the rear wheel and wipe things down about every 2 weeks. Since I only do hill repeats it takes me about 6 months to put 500 miles on the chain. I did make an exception this weekend and rode 63 miles on a course with only about 3000 feet of climbing.
Motor oil is not a good lube for chains as it was designed for pressurized system that floats the rotating parts away from each other. Better oil to use has more extreme-pressure & temperature additives such as lubes used for hypoid gears. Check out the Chain-L oil, it's amongst the best. I get 8-10k miles out of a chain before 1/16" wear. Every 250-miles, I'll spray WD-40 through the chain and wipe off all the old crud. Then lube with oil that has the better additives package.
Your auto-shifting could be due to the extreme wear. This causes the next tooth to engage the chain-rollers too soon and the chain may then ride higher on the tooth rather than slip into the valley in between.
Another idea is the oscillating pressure-changes from the pedaling-stroke. This causes waves of lateral-motion to move up and down the length of the chain. A left-moving wave coupled with the bike rocking to the right can throw the chain off. Try unbolting the BioPace and rotating 144-degrees forward (2 bolt-holes). I've found through lots of testing that this evens out the power-delivery. This rotation places the larger lever/radius of the chainring in use when there's the highest leg-force. And puts the smaller radius when there's little force. The result is you have more even torque-transmission to the rear-wheel. It's the opposite of the original BioPace idea that exaggerates the up-down lobsided pedal-stroke.