Old SRAM PC-870 chain (top); new SRAM PC-870 chain (bottom).
Measuring from the center of one rivet to the rivet 23 away on a new chain is 12 inches (~30.48 cm). My chain was over 1/4 inch longer. Park Tool recommends replacing the chain when it is 1/16 inch too long.
Replacing the 8 speed cassette is a problem because of the dearth of parts, considering I need a ≥28 tooth lowest cog. I’ve found Miche 13-28 Campagnolo compatible cassettes on eBay in the UK and Italy, but then I start to wonder whether I should keep trying to support shifting components that were last produced in 1997.
I’ve also found on Branford Bike that a Campagnolo 9 speed hub could be used by dropping one sprocket and using a Wheels Manufacturing 8 speed spacer kit, but that spacer kit is also no longer available.
The last time I crashed the Merckx, I was going to have the shop straighten the derailleur hanger, but since this wasn’t the first time I’ve bent one, I thought I might as well invest in a Park Tool DAG-2.2 Derailleur Hanger Alignment Gauge
Using the tool is straight forward. One end of the tool threads into the the derailleur mounting hole. Using the tool as a lever allows the hanger to be bent back into alignment. There is an adjustable indicator that measures the run-out from the braking surface of the rim. When that distance is equal at four points (measured at 90 and 270 degrees for horizontal alignment and 0 and 180 degrees for vertical alignment), the derailleur hanger is in alignment.
Park Tool’s video on How to Align a Derailleur Hanger Using the DAG-2.2: