@Steady I think we all develop our own way, with my left I sort of twist out and up a little works for me even when almost stationary.
@Stonechat are you still on the 9sp Bob or did you upgrade, I ran an 7/8sp up to 8,000+ miles but both did need changing, but I had planned the short lived 9sp upgrade anyway, as there is not much difference in price between a chain and cassette every 8,000 or a chain every 3,000 miles or so, though if you did get a third chain on the cassette then it would be cheaper. Much beyond this there is chance the teeth will wear to much and the chain starts to slip.
10sp it becomes a little more important especially on the higher group sets Ultegra & Dura-Ace and Uletgra cassette is £30+ and Dura-Ace over £100, as
@SatNavSaysStraightOn says it also effects the chainring, back in 2012 I got a 28/38/48 chainset from spa thats was cheap but allowed my to play about with gears ratios blah blah .........., anyway I put this back on last Sept to try briefly, as I was getting the new one and wanted to see how the 38th worked, however the middle just kept slipping, and this I think took the brunt of those 8,000+ miles (my records are not that complete), my current middle looks like it has no wear at all (except being a bit mucky, which it got a cleaned yesterday)
As for a tool you don't need one (and some say they actually give a slightly over wear indication, as they push the rollers and pins further out), if you take an imperial ruler and measure twelve links under tension i.e. the bottom run of the chain as it is under tension from the RD and measure 12" if you measure pin to pin this should be 12" when new, if its less then 12 1/16th (50%) its ok 12 1/16th to 12 1/8 you need a new chain beyond 12 1/8th both chain and cassette are likely to be needed.
My middle ring the other week.
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