The first for their chains shows placing the chain over the big ring and largest cog, and then adding 1 link + power lock (http://cdn.sram.com/cdn/farfuture/lE2r6 ... __2_07.pdf) for sram derailleurs. I.e two additional links in total.
The second specifically for their derailleurs shows the same method as above, but add 2 links + power link. http://cdn.sram.com/cdn/farfuture/c90h_ ... eurs_6.pdf. I.e 3 additional links in total.
I've always done the first option (+ 2 links in total, incl power link).
Anyone else come across this? And what do you generally do?
I recently went through the same thing with my red group. the first method gave me 106 links and the second gave me 108. For me the 108 was correct.
I have also found that you can double check your length by running the chain through the rear derailluer and small small in this position the rear derailluer jockey wheels should almost be horizontal. (hope this makes sense)
This might explain it better as well as pics!
I prefer to use the the little/little method to set my chain length as long as possible. Then you'll never have to worry about having enough chain length, if you change to a cassette with a larger big cog. That's basically what Campy suggests. That same chain length can be used for an 11-23 cassette or 12-29.
First, set the 'B' screw to fit your cassette. Selecting the smallest sproket and the small chainring. You want to choose the chain length that gives you enough tension to allow the chain to clear the jockey pulley. It is a bit of a fine line between choosing a 'shorter' or a 'longer' chain, as the spread of links sometimes forces a choice between the two. Generally, my recommendation is based on the use to which the bike is to be put.
For an all-purpose bike (or an inexperienced rider), I usually recommend erring on the 'long' side. This is how I set-up my wife's bikes and my girlfriend's bikes. A little bit of chain slap and play may be ok in that application. Also, it may allow the rider to choose a larger cassette for use in the mountains.
For a race bike, the better choice is to err on the 'short' side. The additional tension on the chain may save a dropped chain or a chain-suck problem one of those desperation cross-chain counter-attack 'incidents' that seem to always happen on a bumpy, off-camber change in terrain (hmmmmm. Why does that always seem to happen? ) The 'risk' to the derraileur is probably acceptable in a pure racing application where you have no-one to blame but yourself for cross-chaining and throwing 1,200 watts through it (whereas the wife/GF might kill you).
pushstart wrote:I am going to buck the trend and suggest not erring on the side of too long. It depends on your derailleur but my last 105 derailleur didn't wrap enough chain (using 2+link method) on my compact (34/50) to keep chain from slapping against chainstay when in small ring and smaller cogs. I now use the 1+link method and seems to work great.
If by a link you mean one inch of chain, there is no method that suggests adding 2 inches of chain to the minimum length. If you want the longest possible chain, without it hanging loose in the little/little, you shift into that combo and adjust the length to create some tension on the lower section of chain.
The minimum increment of change to the length is 1 inch and that is actually 2-links, if you use the same terminology used when chains are sold. A 114 link chain will be 57 inches long.
One issue with today's road bikes is the range of largest cogs is likely to be from 23 to 29. That's 1-1/2 inches of chain, but of course, it requires 2 inches of additional length in order to join the chain.
Due to the many possible combinations of large chainring, largest cog and chainstay length, it's rare for a chain not to have some amount of excess length.
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