EBay CNC Crank

Discuss light weight issues concerning road bikes & parts.
bm0p700f
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by bm0p700f

Will i die. Lets find out.

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prendrefeu
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by prendrefeu

tmr5555 wrote:Why are they not available in bigger lengths?


They are advertised for 'Brompton' for a reason. :wink:
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spud
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by spud

check these things frequently for cracks if you ride them. I've busted a crank in mid-flight, not fun. My tail bone hurt for months afterwards (and I didn't even land on it)

whydobearsxplod
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by whydobearsxplod

spud wrote:check these things frequently for cracks if you ride them. I've busted a crank in mid-flight, not fun. My tail bone hurt for months afterwards (and I didn't even land on it)


Will do. Glad you are ok!

alcatraz
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by alcatraz

Alloy m8x1 bolts on cranks? This can't be a good thing can it?

Some pics in this thread show something else but square taper. Never seen this hexagon axle profile before.

Also worth mentioning is that not only the bb axle length is of interest but the offset aswell. They are not all symmetric. It will influence your chainline and chainring/frame gap.

/a

tmr5555
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by tmr5555

prendrefeu wrote:
tmr5555 wrote:Why are they not available in bigger lengths?


They are advertised for 'Brompton' for a reason. :wink:

Riggggght, Brompton.
The quest for cheap, light cranks continueth...

whydobearsxplod
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by whydobearsxplod

alcatraz wrote:Alloy m8x1 bolts on cranks?

Never seen this hexagon axle profile...

/a


The seller specifically says to use steel fixing bolts to install cranks and then switch to the included alloy.

The hexagonal profile is for Tunes "sixpack" BB

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prendrefeu
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by prendrefeu

I should also note here something relating to 'cranks for brompton' is not just about their available length, it's also a small allusion to the stiffness of the cranks.
If you've ever ridden a Brompton folding bicycle, you may know why they're jokingly called "bomptown" - basically it's super cushy, wonky, and while efficient it can feel like you're riding a clown's bike.

So on a really cushy feeling, twitchy, small-wheeled bike would anyone notice the stiffness of a crank? Nope.

Stiffness of the crank, then, is not a priority in any way for a 'bomptown' build.
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kdawg
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by kdawg

glepore wrote:At some length they probably get very flexy/break prone. My original toplines had pedal holes that were solid in the back, as many of the early ones fractured there. Precludes the use of pedals without flats.

At my weight (58 kg) they were fine. Bigger guys that aren't spinners might beware. Not sure what spindle length will be needed, I think i used 109's with mine that were originally mtb cranks (done that way to get the 110 bcd, q factor be damned).


That’s a good point - me, at 110kg, and you using the same cranks is just silly - and I would imagine Shimano have built them stronger rather than weaker so you would be fine on these. Don’t think I’d trust them through...

The pedal threads look huge though?
I'm left handed, if that matters.

bm0p700f
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by bm0p700f

i have middleburn rs2 cranks on an MTB. these are not know for there stiffnes so some say but they feel like cranks to me. I have never noticed flex in a crank regardless of the axle used carbon or alloy arm heaviliy machined or not. This whole stiffness thing is overblown. I think I will be fine with them and they are light and will on on the hill climb special.

bm0p700f
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by bm0p700f

only in asymmetric form according to the listing.

whydobearsxplod
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by whydobearsxplod

Confirmed 335g with alloy fixing bolts. I have a few upgrades I'm working on for my bike. After that, I'll experiment with this crankset and give a little feedback on them.

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