crank length why diff for BMX to MTB

[d@ve]

Hi, I was just wondering why BMX bikes seem to use much longer cranks than MTB in comparison to rider height. I had a bmx and it came with 180mm 3 peice cranks, I prefer on my MTB either 175 or 170mm cranks, any idea why this is the case?

[fattyandthepiemakers]

maybe because its harder 2 pedal on a bmx because of the size, therefore needing longer cranks so you can get more pedal power in a single downwards push. I dont really know, dont ride bmx, too tall. :D

[echo]

i agree with u. actually i was gonna make the same post lol. but yer they are longer.

[chie]

Would ground clearance be a reason as well? On bmx its not as necessary to worry about clearance because it be unlikely that your gonna be running into roots and stuff.

[fatnold]

i run 180's on 2 bmx bikes and 2 mtb's, both hardtails. i run 175 on my dually. i fing that if the bike bobs at all under cranking then you have trouble with long cranks. my hardtail with 80mm forks feels great with 180's. my hardtail with 125mm forks make 180's feel too long. my logic would follow to the guys with the big bikes ( big travel ) run 165's and 170's. which is the case.

[No Skid Marks]

20" wheels accelllerate easier and ground clearance?????

[No Skid Marks]

Shorter cranks accellerate easier and offer better ground clearance but longer cranks offer better leverage and smoother delivery meaning less wheel spin, better traction and smoother spinning.