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1、自行车链条线设计参数TripleChain lineCha in li neDoubleChain lineThis refers to how straight the chain runs between the front and rear sprockets. Ideally, both sprockets should be in the same pla ne, so that there is no sideward motion or stress to the chain. This con stitutes perfect cha in li ne.In the case
2、of derailer geared bicycles, the chainline is notperfect in most gears. The worse the chainline, the worse the mechanical efficie nty of the drive train.Correct chainline for a derailer system is a matter of opinion,and depe nds on the inten ded use of the bicycle. There are two simple an swers to t
3、he questio n of what con stitutes proper cha in li ne:1. One view is that the middle of the cluster should line up withthemiddle cha inring (or half-way betwee n the two, in the case of adouble.2. From the parts manufacturers point of view, the chainline dependson the diameter of the seat tube where
4、 the front derailer mounts.For fatter seat tubes where the front derailer is farther to the right, derailer manufacturers want the chainline to be farther to the right also, because their main priority is shifting performance, and their front derailers have an optimal chainline with respect to the e
5、dge of the seat tube. This is particularly a concern in the case of bicycles with indexed front shifting.From the riders point of view, chainline is partly dependent on how you are going to use your gears. For instance, consider a road triple vs a mountainbike triple:, With a road triple, you mostly
6、 use the two bigger rings, the grannyis only occasionally used, and only with the larger rear sprockets. For a road triple, having the cranks close-in is good, because it increases the usability of the big ring., With a mountain bike, the small ring is used much more often, and must often be used wi
7、th fairly small sprockets to avoid having to shift the front under load. For mountain bikes, a more outboard chainwheel position is often preferable.Chainline Standards:Application Dimension NotesShimano spec, measured to the midpoint between the rings.with typical 5 mm chainring spacing, this puts
8、the inner at 41 Road Double 43.5mm, the outer at 46 mm.Shimano spec, measured to the middle ring. Road Triple 45Shimano spec, measured to the middle ring.47.5 preferred, but for frames with oversized seat tubes, the 47.550 MTB Triple longer dimension may be needed, because the fat tube places mmthe
9、derailer mechanism farther to the right.Track/CoasterBrake Older bikes with 110 spacing would be on the smaller end of Traditional 40.5-42 this range One-Speed mm Newer bikes with 120 mm spacing normally use 42 mm Most internalgear hubsSinglespeed Wider chainline need for chainstay clearance on MTBs
10、. 52 mm MTBRohloff 54 mm This is close to the chainline of the outer ringSpeedhub (58 mm of a typical MTB triplew/13tooth)White Industries ENO hubs use this chainline, which lines up Singlespeed with the middle position of a typical MTB triple. MTB 47.5 mm Its also fairly close to the outer position
11、 of a typical road Alternate double.Chain li ne Measureme nt-Fr ontChain li ne is measured from the cen terli ne of the frame to the cen ter of the cha in.You can measure the front chainline directly with a simple ruler.Simply hold the ruler aga inst the seat tube or dow n tube and measure the dista
12、 nee to the middle of the cha inring teeth. I n the case of triple cha in wheel sets, measure to the middle cha inring. In the case of doubles, measure to the halfway point betwee n the two rin gs.Cha in li ne Adjustme nt-Fro ntIf you need to adjust the front chainline, there are severaldiffere ntop
13、ti ons to accomplish it:,Change the Bottom BracketMost bottom brackets made since the mid-90s are symmetrical, they stick out the sameamount on each side. If you replace your prese nt bottom bracket withone that is, say, 4mm shorter, it will move the chainline 2 mm to the left, because itwill be 2 m
14、m shorteron each side.If you go this route to a n arrower cha in li ne, make sure that there wont be a cleara nee problem betwee n the frame and the crank or cha inring.,Bottom Bracket SpacerIf you n eed to in crease the cha in li ne (move the cha inring to theright) you can usuallyadd a spacer wash
15、er betwee n the right-side bottom bracket mountingring (or cup) andSturmey-Archer the bottom bracket shell of the frame. The usual spacer for this is asprocket spacer. These fit all threaded bottom brackets exceptItalia n size. Sorry, I dontknow of any source for a spacer that will fit an Italia n (
16、36 mm)bottom bracket.,Chainring SpacersFor a single chainring, you can add spacers between the chainring and the crank spider.If your chainring is mounted on the outside of the spider, you can move it to the rigtht this way. If its mounteed on the inside of the spider, you can move it to the left as shown.This uses the same 10 mm
