park tool is worthless...
marimba_artist said:
I recently installed the DX-10 on a customer's bike and measured it's stretch with the Park chain checker. Over ten links, it was stretched about 0.25mm right out of the box. For comparison, Campy 10v Chorus chain I installed the other days was stretched about 0.00mm right out of the box. For my money, I recommend genuine Campy chains.
What you were measuring is the difference in roller displacement, not the pitch of the chain. While the pitch should always be .500 inch when new, the roller OD, ID and clearance between the bushing is not always the same between brands, so a Park tool may produce a different reading with a different brand. It does not tell you anything about the tolerance the chain is built to. If a chain were very far off tolerance when new, it would skip, even when mated with new cogs.
After the chain has been used a few thousands miles, it's possible for the roller wear over the very short 5.7 inch length measured by the Park chain tool to be larger than the change in the chain pitch. This would make the tool read twice the actual amount of elongation. The only accurate way to measure the chain pitch is either with a scale, 12" or longer, or by comparison over the whole length with a new chain.
I prefer campy chain myself, but it is possible to have the chain elongation be only 1/4 of the allowable 1/16 inch per foot and have totally shot rollers. Both areas of wear need to be measured to evaluate the condition of the chain. New rollers wil check about .210 inch in between them. I consider them shot at .235-.240. This amount of wear is 20-30 times the wear that's tolerable in the pins and their bushings.