Shorter crank arms?

dracothered

dracothered

New Member
Ok, I have a springer front end with a 26" wheel and a 24" rear wheel. So I have noticed if I am leaning in a turn and my crank arm is in the down position on the side I'm leaning to my foot (toes) will rub the ground. I haven't had the pedal hit the ground yet, but sure don't want to have it do that when I get the motor on there.

What I am thinking of doing is change the One piece crank to a shorter armed one. It now has a 7" arm crank and it looks as if I can replace it with a 6 1/2" or 6" arm. What I want to know is how this will effect pedaling of the bike?
 
smaller cranks is like lowering your gear. you'll have to pedal more to get the same speed as you would with longer cranks.

you won't feel much if you go an inch shorter.

my race bike has 20" wheels, and i've got 5" cranks so they don't hit the ground. i'm running a 48 tooth on the front and a 16 in the back. it's harder to get it rolling, but it works great to keep my speed up.
 
as long as the bearings aren't flatspotted or deformed, the raced aren't cracked, and the cups aren't pitted, you're good.

as far as grease goes, i use "red and tacky" grease, but you can use wheel bearing grease, white lithium, or pretty much anything.

since i don't pedal as much with a motor, i don't worry much about my crank bearings. as long as they're adjusted right. i hate when things are loose.
 
bairdco said:
as long as the bearings aren't flatspotted or deformed, the raced aren't cracked, and the cups aren't pitted, you're good.

as far as grease goes, i use "red and tacky" grease, but you can use wheel bearing grease, white lithium, or pretty much anything.

since i don't pedal as much with a motor, i don't worry much about my crank bearings. as long as they're adjusted right. i hate when things are loose.
Click to expand...

Loose bottom brackets and/or loose headsets drive me nutz.......mine are always tight and adjusted.
 
If you want to stay with the 1 piece crank design, here are many to choose from at really good prices:
Bike Parts
They have tons of good stuff there.
 
keep in mind shorter cranks also require more force for braking (less leverage) ;)
I am using little 5" ones for clearance since upping to the 99cc
good thing my pedals are basically rotating footrests !!! laff
 
What you have now is an American style one piece crank. The advantage to that is, you can run smaller front sprockets with that kind of crank, and it's a less expensive crank to replace.

The disadvantage is there's not much you can do about the width between the crank arms, unless you can find someone who makes a special wide one. They either clear the motor or they don't. Another problem is the bottom bracket requires periodic maintenance, and it's steel, so it's heavier.

Another option would be to change to a european style 3 piece crank. With this kind of crank you get a maintenance free, sealed bottom bracket. You can buy these kind of BBs in many different widths. The crank arms, and chain rings are lighter alloy.

This is what a sealed BB looks like.

picture.php


When I went lowrider, I went from just under 7" crank arms, to 4 1/2" crank arms, with 121mm width BB. They have even wider than that available. I changed the front chain ring from a 44T to a 34T, and the rear from a 18T to a 22T. Even with that low of gearing, it's still pretty hard to peddle from a stop, but with a 5 web crank 34T is the smallest chain ring that fits.

Knowing what I know now, I could have lived with 5" crank, but not more than that.

The main disadvantage to a 3 piece crank is cost. Bottom brackets are only about $10, but new crank arms are about $60 and up. Then there's possible chain ring size issues.

picture.php
 
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