A straight line, drawn between the center of the casette and the center of your ring gears or ring gear, should appear parallel to your cogs and ring/rings. If not, the bottom bracket needs to be adjusted in or out. If it can't be done, you need a new bottom bracket with a different spindle lenght.lescor said:
I’ve given my opinion in response to the question. I’m fairly confident that lescor knows what somewhere near the middle means and if he/she doesn’t then they will ask.lks said:
Sounds like you have a triple, they generally run a 50mm chainline. If you want to run a single ring or a double then set it up at 47.5mm, yes a slightly shorter bottom bracket.lescor said:
I would suggest, that the vast majority of viewers are not equiped to go beyond my above post #2, or will ever need to. To use your chain line specs., or even the mfg's, requires instruments to make at least 8 precise measurements and then the calculations to come up with their chain line, which is when CLf=CLr. Depending on the bike, there is no guarantee that they can achieve this with any bottom bracket, because of chainstay clearance and/or chain rub on large chainrings when in the cross gears. Follow my post and then adjust your front and rear derailleurs correctly and everything should run smoothly. If it doe's, but the chain drops off the smallest ring gear, to the inside, buy one of the after market devices that clamp to the seat tube and will prevent that. Some of the Tour mechanics, install them when they set a new bike up. If everything is done right, don't worry if you can't cross chain all the way on both rings, without the chain rubbing on the front derailleur. It shouldn't happen with a 39-53 but it will on a compact, at least those with shorter and tighter radius derailleur cages. I am a KISS mechanic. Keep It Simple, Stupid!gclark8 said:
Can I suggest you stick your head between your knees and do just that!lks said:
: http://sheldonbrown.com/derailer-adjustment.html#chainline
My post said, "I am" It didn't say "you were". But if the shoe fits and you are not man enough to admit it, you can always try to impress the viewers with a vulgar response instead of a civil technical response, unless you don't know how to.gclark8 said:Can I suggest you stick your head between your knees and do just that!
If in doubt, ask The Captain
Fantastic. How many millimeters off center doe's "roughly the middle", become "roughly not the middle"?Insaneclimber said:He only wants a single, why you guys gotta confuse the issue. if you have a tripple and you want a single just remove the big ring and the smallest ring and put a bash ring. if you have a double remove the big ring and put a bash ring. your chain line is presumably already correct and to start buying different size bb an crank offsets is way to complicated for even these turkeys. there must be at least a half dozen different bb systems so even if you can understand the shimano book it may not relate. If you convert the bike to single and the chain jumps or falls off, get back to us and then well tell you about chainline.
ps: i know what roughly the middle means
Hey man why dont you stop reading about how to do it and start doin it, real world experience will help you alot. i imagine you probably check axel width with a micrometer.lks said:
