Singlespeed & Fixed Gear - cranks, bent spindle; what the...?

So I'm looking over at my fixed bike today and I noticed that the crank arms are not exactly 180 degrees opposite of eachother. The left arm is rotated foward by degree or so. I suppose I've bent (twisted) the spindle. Funny I didn't notice it while riding, but now its going to drive me nuts until I replace it. Thats never happened to me before, even in years of BMX jumping, acid drops, wall rides, etc. I skip-stop frequently, but I've never crashed or acid dropped my fixie or anything. I can't imagine that skipping causes enough torque to bend the crank spindle. In fact I mostly skip with my left foot back, which would torque the spindle in the opposite direction. I'm just wondering how the hell I torqued my spindle so hard that it bent, or is it possible that its just a poorly made spindle and that the crank arms have never been properly lined up?

The crank not the spindle most likely. Do not ride until it is replaced.

yeah, you may have rounded out your taper a little bit...

yeah, you may have rounded out your taper a little bit...

When I get home tonight, I'll pull off the crank and have a looksee.

if I hadda guess I would blame a good hard pedal strike. Check your undies for other signs of something like that having occurred recently.

OK, so I pulled the crank arms off and I've concluded that its definately the spindle thats bent-twisted.

The crank arms and taper part of the spindle are in good shape. I put a spare set of crank arms on the spindle, and the same thing...the left one is rotated forward, so it must be the spindle, not the crank arms. Next, I put my crank arms on another bottom bracket spindle that I'm not using and they are perfectly straight. So I must conclude that the spindle currently on my fixie is twisted-bent.

Hard pedal strike, crash, or random acts of violence are out of the question...haven't had anything like this happen, and I don;t park my bike outside, so vandalism is ruled out as well. Several weeks ago, I took apart the BB and lubed the bearings (its a cup and cone) and everything looks fine. I bought this bike used (old Bianchi road conversion), so I suspect it was bent all along and I just now noticed it. Nothing else looks damaged however; possibly the current spindle is not the stock spindle.

i find it hard to believe that you twisted a solid half inch bar of steel using only your legs

i find it hard to believe that you twisted a solid half inch bar of steel using only your legs

http://www.thesop.org/attachments/124-i.jpg

^^^^ yeah, me too!

is it possible that the cartridge slipped out of/broke the fixing cup on the other side, and now is diagonal?

i find it hard to believe that you twisted a solid half inch bar of steel using only your legs

Well, so do I. I'm a strong cyclist but not that strong; thats why I'm perplexed.

is it possible that the cartridge slipped out of/broke the fixing cup on the other side, and now is diagonal?

Nice suggestion...but, no, the spindle is not diagonal. I inspected the BB and BB shell for damage and theres nothing wrong with it. It spins straight and smooth; the bottom bracket is undamaged, installed correctly, etc. The crank arms are simply not perfectly 180 degrees opposite from eachother. As noted above the crank arms and square tapir part of the spindle are in good shape, not rounded...all I can figure is that the spindle is twisted.

I've seen people collapse crank spiders sprinting out of a trackstand, but bending a BB spindle would be waaaaay past that.

....and people tell me having a beer and gazing at my bike serves no purpose.

I snapped one off once. Noone at the bike shop would believe me till I brought it in to show them.

http://www.thesop.org/attachments/124-i.jpg

we train together

http://static.flickr.com/28/50392096_0375885b94.jpg

I've seen people collapse crank spiders sprinting out of a trackstand, but bending a BB spindle would be waaaaay past that.


The right crank doesn't really torque the spindle when pedaling..the force goes directly to the spider into the chainring. The left on the other hand, torques the spindle. So its really only possible to twist the spindle with the left arm..but I agree, the cranks or frame are probably more likely to break before the spindle twist/bends.

granted, it was one of those flimsy Kooka CNC jobbies...

http://static.flickr.com/6/10052289_6f3f47357d.jpg

bent frame maybe?

granted, it was one of those flimsy Kooka CNC jobbies...

http://static.flickr.com/6/10052289_6f3f47357d.jpg

bent frame maybe?


dude, you should change that..you might throw your chain. I hope you are using brakes!

granted, it was one of those flimsy Kooka CNC jobbies...

http://static.flickr.com/6/10052289_6f3f47357d.jpg

bent frame maybe?


Is that one of those biopace chainrings? :D

we train together

http://static.flickr.com/28/50392096_0375885b94.jpg

gnarly! what kind of crank was that

we train together

http://static.flickr.com/28/50392096_0375885b94.jpg

(A little OT)

Is it safe to mount your chainring on the back of the spider like that, or will my crank arms explode too? It might be an easy way to fix my wonky chainline.

(A little OT)

Is it safe to mount your chainring on the back of the spider like that, or will my crank arms explode too? It might be an easy way to fix my wonky chainline.

They'll explode. It happens to roadies all the time riding on the little ring.

spindles can and do twist after a long time of fatigue. its very common in heavily used old cottered cranks. ive seen it plenty of times before on cottered, but never on a square taper. unless its super old id guess it to be a manufacturing defect.