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Bulletproof BMX Crankarm Set 170mm 110 BCD Forged Black
Single speed crankset. Forged alloy crankset. Does not include chainring. Does not include BB. Weights do not include BB.
Single speed crankset
Forged alloy crankset
Does not include chainring
Does not include BB
Weights do not include BB
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Average Customer Review:
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Most Helpful Customer Reviews
Low cost cranks, decentJul 25, 2013
By Josh Daniel S. Davis
These are sold as Origin8 aka Bulletproof as BMX cranks.
They are alloy with the spiders forged as a single piece to the right arm.
They come in black and silver, in 5mm sizes ranging from 140mm to 175mm.
These cranks go on standard 107mm long, 9/16" JIS square taper spindles.
You can use these as as a single or double chainring setup.
Mount one your large ring outside, and middle/small ring inside.
Alternatively, one ring inside, and bash guard outside.
To go triple, there are special inner-rings with spiders to hang the third, smaller, inner gear.
Bolt Circle Diameter is 110mm, which is common for compact cranks, mountain bikes, etc.
If you get any ring over 50T, expect more flex unless you find a heavy-duty ring.
For really large rings, you may want 130mm BDC.
For single-space, go with the Rocket (now owned by Origin8 too),
because it's stiffer and has longer teeth to hold the chain better.
Chainline w/107mm bottom bracket spindle length is:
39.7 mm inner ring
43.4 mm as double (middle of spider)
47.1 mm outer ring
158 mm tread (Q-Factor)
Note, that the Origin8 130BCD arms want a 103mm BB.