Why ?

Discuss light weight issues concerning mountain bikes & parts.

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Joined: Mon Jul 29, 2002 9:04 am
Location: Koksijde, Belgium

by zandbijterke

Could someone explain to what is exactely the difference between 4 bolt crankarms and 5 bolt crankarms :?: I mean, is it just for saving weight or also for more stifness?
In the 5 bolt crankarms you can choose between standard (110-74) and compact (94-58)? These numbers are the measurements of the distance between the bolts I believe but do they have anything to do with yhe size off your bottom bracket spindle ?

All answers are welcome :!:

by Weenie


by Ryan

5-arm cranks represent that their are 5 'arms' that extend outward from the crank arm, and have a chainring bolt on the end. As opposed to a 4-arm crank which has only 4 'arms'.

Manufacturers choose to design cranks like this because if your a heavier rider, you'll want a 5-arm crank for stiffness. It'll be significantly stiffer then a 4-arm crank, and much stronger while pedaling on impacts from roots, drops, etc.

Also, this principal comes from the ROAD BIKE. Road bikes use 5-arm cranks because their gearing is so high, that when your in a big ring and hammering, the chain wants to twist the ring right off the crank. The 5-arm stiffens it up, and reduces flex (which can cause your chain to rub the front derailleur or other chain rings).


^Dr Evil^

by ^Dr Evil^

Wow !!!!!!!!! i never knew a five arm crank had five arms and a four arm crank has four arms, that is pure brain power there, i am very impressed.

But are you sure they dont extend inward from the chain rings, and what about arms that bolt on would they be innies and fixed arms be outies

four arm are plenty stong so its a better choice on cranks , standard (110-74) or compact (94-5) have nothing to do with the bottom bracket.

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