simple312

Is it typical for cranks to loosen up when riding fixed?

It seems my stock Sugino 75 (from a khs 03) non drive side crank arm started coming loose. It took me a couple of days to figure out what was happening, at which point i walked it over to the bike shop. In the hour walk, it loosed almost to the point of falling off. they tightened it up and i was on my way.

before you ask, yes i should have had a 8mm wench to tighten it, but i didn't.

so, it started to come loose again. (still putting off getting a 8mm wrench) I went to a different shop to get it tightened and figure out what the problem was. He said the arm was starting to round out / strip and that i would need to replace it. In the mean time he suggested i tighten it as much as i can everyday even if it doesn't feel loose

Its barley a year old just wondering if this is normal?
Is putting off the replacement going to to f up the drive side and my bottom bracket?
i'd like to avoid replacing it, but it seems like i would have to take it off to see for sure if its rounding off.

if its relevant im about 230-240lbs, im guessing its a factor, more stress/torque on the drive train.

Lucky-Charms

I don't see why you should have any more problems with your cranks loosening/stripping on a fix as opposed to a mt. bike or road bike, of course I also don't completely buy into the "OMG fixed gear makes so much more torque than anything else in the world" argument.

It would seem to me that if your crank totally strips, it will just spin around the BB spindle, fall off, get caught in your chain, crimp your chain stay and or seat tube as your bike comes careening to a halt and you are thrown over the bars into the path of a semi truck running a red light at 60mph, while two pretty girls standing on the street corner point and laugh at you and a bike messenger spits on you for stealing his culture.

Of course that's most likely the worst case scenario. I'd replace it as soon as you're able, and in the mean time ride cautiously. I don't like to mess around with a loose bb for fear of damaging the bb shell (frame) beyond repair, but I don't see a lot of possibility for catastrophic frame failure from a stripped crank.

If it's rounding off, you'll need to replace it eventually. How long you want to ride on it is up to you and the crank arm.

r0cket-

Maybe get some 14/15mm bolts instead of those 8mm allen jobbies.

eddiebrannan

i laughed

Ira in Chi

My guess is that whoever installed the cranks didn't do it right. It is not normal for this to ever happen. Either kind of bolt is completely suitible for the application, but once the crank arm is rounded, even a little, it will continue to loosen while riding no matter how much or often you tighten it. Fortunately it is the non-drive side, they are much cheaper to replace. On that note, make sure the drive side is tight so this doesn't happen again. Then go buy a replacement NDS crank arm of the same length and you are set.

simple312

thats what i suspected. i'm picking up bike maintenance as things start breaking down, mostly from what seems to be poor assembly in the first place. sounds like im off to get a new crank arm this weekend.

thanks for the help

FixednotBroken

i think the backwards 'braking' force applied to cranks when slowing on a fixed gear machine make this a more common occurence than on a freewheeling bike.

simple312: crank them bolts down, and check them periodically to make sure they're not too loose, or you'll keep rounding out those cranks.

Lucky-Charms

That makes some sense to me, but I really wouldn't want to see him thinking that just because it's a fix means that the cranks are going to become stripped faster. Properly installed, with proper parts, I don't see there being any more trouble with cranks stripping on a fix than on another type of bike. Now, if there was a defect in the installation or part then I'd agree it might be more prone to failure on a fix.

jk610

I just discovered this as well with my bike. My chain side crank was getting loose so I tightened it back down as much as I could. Ill pay more attention to it now that its been mentioned.

HereNT

Um, that sounds like a pretty good scenario to me. Being caught in a thunderstorm at the same time, losing your job because you didn't make it to work, then losing your insurance because you don't have the job, having to go to a quack doctor that botches the stitches on your face so you get nasty scars, which makes your wife leave you and your dog growl every time you go near him sounds more likely...

legalize_it

definately

Lucky-Charms

Thunderstorms make for wet streets and fun skids, jobs are for corporate shills, insurance is only for the unlucky, doctor's Visits are for those lacking the drive to "Do It Yourself", all the better that your wife left you, cuz chicks dig scars, but having your dog hate you sounds like a pretty bad deal.

ryan_c

You may have been running your chain too tight, which can seriously mess up that crankarm/spindle interface, cause your chainring bolts to come out, etc.
Think its a possibility?

edit: just noticed the NON in "non drive side..."

Rancid

I had the same problem a year or so ago. Clean them off, Lube them off, and repeat.
Seriously.
Then reassemble. William Karsten taught me that trick back in the day and it solved the loosening problem for a few months