Lock-nut question

hi,

i bought a new genesis flyer a few weeks back, my first fixed gear bike in about 8 years (had a beautiful old carlton flyer fixed back when i was pedicabbing). I got it set up fixed 48/16 with SPDs and plan to use it as a platform to tweak. like i said it had been a while since i had ridden fixed so I was easing myself in. Having got some confidence up i've been skidding and messing about the last week or so until at the week end i went to pull a skid on friday and i had this big jarring jump like the chain had skipped or something the pedals spun back about a quarter turn and I popped out of my cleats and nearly came off.

a few minutes later while getting stuck in going up waterloo bridge the opposite thing happened - it was like the sensation of the drive chain suddeenly slipping in the other direction a quarter turn. like doing a sudden and unexpected wheelspin. again, i very nearly came a cropper.

the bike was new so i took it back to cycle surgery where i bought it for the free first service (what the hey, it's free) and they assured me they'd sorted out the stretched chain, missaligned wheel and dodgy lock-nut.

then the same thing happened this morning. and thee times tonight. every time i brake hard or skid i think the rear cog is coming suddenly unscrewed... then whenever i get back on the power it slips the other way. it's nearly un-biked me a good half a dozen times now and is really sapping my confidence. any idea what's up or what to do? new lock-nut? superglue? just unweight more and stop putting so much force through the thing?

sorry i keep writing such long posts for a noob btw. i'm feeling verbose today for some reason. brevity will be my byword in response to any gratefully appreciated replies.

thanks,

dooks.

Hi dooks, welcome to the forum.

It sounds like a classic issue - sprocket is not done up tight enough. I am, of course, assuming that you are running on a fixed hub (threaded twice on one side, once in each direction) and that you have a lock ring installed?

You need to do the sprocket up very tight on to the hub (search on here or Google for the 'rotafix' method and then that your lock ring is done up nice and snug.

One recognized (and suitably 'manly') technique is to screw the sprocket on as tight as possible, tighten the lockring, sprint up Highgate West Hill (Swain's lane would be overdoing things unless you are scarlett or lpg) and then do your lock ring up a bit more.

Hope this helps.

This would happen to me with my old KHS. Turned out the threads were fucked (the chain ring had made its own threads when put back on at some point) and the rear chain ring would slip loose when I'd skid, and then move back in when I'd pedal hard.

@horaio : That kinda sucks, if it's the case here. I suppose that it's a new bike so if the threads are fucked then it ain't your fault - throw up a stink until they replace the rear wheel or build you a new one.

The only other approach is loctite...

you are all wrong, well maybe wrong

this happened to me, the problem is most likely that the sprocket is too thin and the lockring cannot grip on it. so by tightening the lockting you will strip the threads as it will get to the end of the thread but still turn.

buy a thicker cog, dura ace lockring and see what can be done

i hope this helps

ps - welcome to the forum

try mashtons way 1st, flicks second. if neither of them sort you out then get out the hammer and bag of rocks, its bike fixin time

Here's a link to the rotafix method: http://204.73.203.34/fisso/eng/schpignone.htm

I've got no idea why it doesn't have a domain name :S

yup, had it on 2 bikes.

1. Roatafix the f**k out of the sprocket http://204.73.203.34/fisso/eng/schpignone.htm
   
2. check you have the correct lockring (i had on with a small lip, wasn't gripping to the sprocket)
   
3. tighten that with a chainwhip
   
   

I wouldn't glue it unless the threads are ruined.

good luck!

sweet. thanks for all them helpful replies. and the welcome. will have a look at it tonight and see if i can figure out what's required. cheers.

dooks.

just thought i'd let you know that i did the rotofix thing on saturday (thanks for the links) and got a goodly amount of budge. didn't want to overdo it and strip the thread but i think it's about a tight as is feasibly possible. the lock-nut itelf was barely fingertight so i went at that with a hammer and screwdriver too. don't think it's going to to be slipping again.

lost the back brake, replaced the aero levers with a single crosstop and retaped the bars this weekend too. next up i'm thinking nice chrome stem and some nitto drops, remove decals and maybe brooks leather saddle and bartape.

it's nowtro

I was told you can use a BB lockring on a standard threaded hub, any experience of this?

A BB lockring will use the same thread as the sprocket and so there's more chance it it undoing (sp?) itself. Don't risk it, use a proper lockring.