hair07

Hi,
i'm having a problem w/ the bike i built up the other day. the 5 bolts which attach the crank to the chainring keep loosening themselves up while i'm riding. i did really lay into them w/ the allen rench, so i know they were tight before i started riding. but about halfway through my ride i noticed they were loose. this results in the chainring moving around a little when stopping and starting. and i just worry that they might work themselves off while i'm standing and pedaling and then that would end badly. anyone have any tips on how to get these guys to stay tight? they're bmx bolts i believe, b /c they are not very long(only long enough for 1 ring). thanks for any and all help.

dan

Phatman

loctite?

RegularGuy

Use a chainring nut wrench to hold the back of the bolt still while cranking them down with the Allen wrench. Don't have a chainring nut wrench? Use a big old screwdriver.

I've found that a drop or two of blue loctite helps, too, but this is controversial. Some say you should use grease on chainring bolts, others say oil, and still others say crank 'em in dry.

Click here to see a chainring nut wrench.

Rev.Chuck

A dime will also work in place of the ring bolt wrench.

riderx

Use blue loc-tite.

I'd also check to make sure the bolts aren't bottoming out. This would make them feel tight but the subsequent pedalling would loosen then.

djbowen1

is the chainline setup good?

hair07

you know, i think it's good, but (and this is something i've been meaing to ask) how does one know for sure? is it an eyeballing measurement. like, does it just look good(it does) or is there a more precise way? i've tried laying a straight edge(unfortunately all i've got is a metal measuring tape) from chainring to cog, and while the measuring tape is pretty flexible it does look good. is there a better way to do this?

i'm going to try using a dime to hold onto the back of the bolts instead of a screwdriver and i'll really give em a good crank. hopefully that'll work.

alexs

sheldon brown has some advice on measuring chain line here:
https://www.sheldonbrown.com/gloss_ca-m.html#chainline

captsven

If it is a conversion, did you replace the bolts with shorter bmx bolts?? It is very obvious question but I have to ask.

I used to have this problem with chain ring bolts. I then got one of those chainring bolt tools and no more problems. They only cost a couple of bucks and will last a life time.

hair07

ok, so far for the last 2 days the crank has stayed tight.

and i think my chainline is off by a few mm, like 3-4. is this very bad? i will try to get some spacer's tonight for between the crank and chainwheel, but is 3-4 mm very bad for a chianline to be off by?

yes, i am using bmx bolts. so they are short, but as someone pointed out, maybe they are too short and are bottoming out. must check.

thanks all for your help. very kind

dan