自行车链条线设计参数

All About BicycleAll About Bicycle ChainlineChainline ChainlineChainline This refers to how straight the chain runs between the front and rear sprockets. Ideally, both sprockets should be in the same plane, so that there is no sideward motion or stress to the chain. This constitutes “perfect chainline“. In the case ofderailer geared bicycles, the chainline is not perfect in most gears. The worse the chainline, the worse the mechanical efficienty of the drive train. “Correct“ chainline for a derailer system is a matter of opinion, and depends on the intended use of the bicycle. There are two “simple“ answers to the question of what constitutes proper chainline: 1.One view is that the middle of the cluster should line up with the middle chainring (or half-way between the two, in the case of a double. 2.From the parts manufacturers point of view, the chainline depends on the diameter of the seat tube where 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 perance, and their front derailers have an optimal chainline with respect to the edge of the seat tube. This is particularly a concern in the case of bicycles with indd front shifting. From the rider s 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 use the two bigger rings, the granny is 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 with 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:Chainline Standards: ApplicationApplicationDimensionDimensionNotesNotes Shimano spec, measured to the midpoint between the rings. with typical 5 mm chainring spacing, this puts the inner at 41 mm, the outer at 46 mm. Shimano spec, measured to the middle ring. Shimano spec, measured to the middle ring. 47.5 preferred, but for frames with oversized seat tubes, the longer dimension may be needed, because the fat tube places the derailer mechanism farther to the right. Road DoubleRoad Double43.543.5 Road TripleRoad Triple4545 MTB TripleMTB Triple 47.5-5047.5-50 mmmm Track/CoasterTrack/Coaster BrakeBrake TraditionalTraditional One-SpeedOne-Speed Most internalMost internal gear hubsgear hubs SinglespeedSinglespeed MTBMTB RohloffRohloff SpeedhubSpeedhub 40.5-4240.5-42 mmmm Older bikes with 110 spacing would be on the smaller end of this range Newer bikes with 120 mm spacing normally use 42 mm 52 mm52 mm Wider chainline need for chainstay clearance on MTBs. 54 mm54 mm (58 mm(58 mm This is close to th