JayKosta wrote:I did try measuring the chainring on my bike, but results were inconclusive. The 3/8inch bit wouldn't fit in any of the valleys, and the 23/64 fit in all - but it seems like some were 'looser' than others. This was done on the large chainring, I changed the inner ring several years ago and do not recall if I changed the orientation of the outer ring at that time ???
I also inspected the old inner ring and it is also difficult to measure. But there seems to be a noticeable visual difference in the 'shark tooth' wear pattern around the ring - And I don't know what the orientation of that ring was on the crank.
Perhaps with an 'inspection magnifier' and a measuring grid, a more exact determination of the wear could be established. I am confident that the teeth around the ring do NOT wear evenly, so the amount of wear could be a meaningful indicator of what sections of the ring contribute most to the crank torque.
Jay Kosta
Endwell NY USA
You should first measure a new ring, to see if they're even. If a new ring isn't even, measuring a used ring isn't meaningful.
You should also skip the teeth that are ramped for changing gears. They'll wear differently because the chain will be askew on those teeth when changing gears, and the links might not line up in length 100%.
The ramps can be slotted or pinned in the ring, and can be assisted by teeth of varied height and thickness. Inspect your ring closely to mark the teeth that are expected to wear differently.
When changing gears, half the chain is on the inner ring (say 39 tooth), and half on the outer (say 53 tooth), so the inner ring will experience 53:39 more torque per tooth than the outer
when changing.
Also note that on a 10 tooth ring, 5 teeth are always engaged. On a 50 tooth ring, 25. You cannot wear just one tooth.