Crankarm Bolts

[ryandood]

During a ride today with my roommate the crank arm on his loaner bike (my backup daily rider) started to come off from the bolt coming loose. Well we tried to finish the ride while tightening the bolt every so often but it's kinda stripped and he doesn't have the metric tool to rethread it so I need a new one. Do I need to buy a crank arm specific bolt or can I just get a bolt with a washer?

Thanks for any input you may have.

[northshore]

Originally Posted by ryandood

During a ride today with my roommate the crank arm on his loaner bike (my backup daily rider) started to come off from the bolt coming loose. Well we tried to finish the ride while tightening the bolt every so often but it's kinda stripped and he doesn't have the metric tool to rethread it so I need a new one. Do I need to buy a crank arm specific bolt or can I just get a bolt with a washer?

Thanks for any input you may have.

To clarify....is it the crank arm bolt on the chain ring side and not the chain ring bolts itself? I know the crank arm bolt on my FSA Moto cranks tends to unscrew itself every 10-15 miles and its pretty annoying. You begin to hear the squeaks and changing rings with the front derailuer goes to hell. I plan to use some white pipe tape or thread lock. I'm unsure if you can buy this single piece. Check with a local LBS or contact the company that produces them.

[ryandood]

it is the bolt on the non-drive side.

[DBD]

Originally Posted by ryandood

During a ride today with my roommate the crank arm on his loaner bike (my backup daily rider) started to come off from the bolt coming loose. Well we tried to finish the ride while tightening the bolt every so often but it's kinda stripped and he doesn't have the metric tool to rethread it so I need a new one. Do I need to buy a crank arm specific bolt or can I just get a bolt with a washer?

Thanks for any input you may have.

What kind of cranks? Splined or square tapper?

[ryandood]

Originally Posted by DBD

What kind of cranks? Splined or square tapper?

Some super cheapo brand, not sure. I also don't know what either of those are but If I had to guess it'd be square tapper because when the crank arm is off it is square.

[jeffj]

Assuming the crank arm isn't wallowed out (ruined):

If it's the bolt that stripped:

http://www.jensonusa.com/store/produ...g+Bolt++C.aspx

If it's the bottom bracket, you'll need to get the right size, but it'll be something like this:

http://www.jensonusa.com/store/produ...m+Bracket.aspx

What exactly is stripped? The bolt or bottom bracket?

Are the crank arms ruined?

[ryandood]

Originally Posted by jeffj

Assuming the crank arm isn't wallowed out (ruined):

If it's the bolt that stripped:

http://www.jensonusa.com/store/product/BB408F02-Sugino+Hex+Crank+Arm+Fixing+Bolt++C.aspx

If it's the bottom bracket, you'll need to get the right size, but it'll be something like this:

http://www.jensonusa.com/store/product/BB309F06-Shimano+Un54+Bottom+Bracket.aspx

What exactly is stripped? The bolt or bottom bracket?

Are the crank arms ruined?

Based on those links my bottom bracket/cranks are square taper. The cranks and the BB are fine, just the bolt (same looking as in link above) is slightly stripped at the bottom of it's threads (as far as I know). I may need to do some further inspection to see that the BB is not stripped. The bolt is only slightly stripped though so I think the BB will be OK.

[DBD]

Originally Posted by ryandood

Some super cheapo brand, not sure. I also don't know what either of those are but If I had to guess it'd be square tapper because when the crank arm is off it is square.

Square tapper it is.

I would think the bolt is not stripped and if anything stripped it would be the spindle unless it was a low grade bolt but I have put some serious torque on cheep square tappers and never stripped one.

I am gonna go out on a limb and say, get a new crank set. If ya have a pic it would help but what tends to happen with square tappers, once they start to loosen up they tend to do so all the time after that as you witnessed.

What happens if you ride with them loose is it rounds off the spindle on the bb and it rounds the hole in the cranks so it will never stay tight after that again, even with red loctite and even if it is slightly worn on the edges.

[ryandood]

Originally Posted by DBD

Square tapper it is.

I would think the bolt is not stripped and if anything stripped it would be the spindle unless it was a low grade bolt but I have put some serious torque on cheep square tappers and never stripped one.

I am gonna go out on a limb and say, get a new crank set. If ya have a pic it would help but what tends to happen with square tappers, once they start to loosen up they tend to do so all the time after that as you witnessed.

What happens if you ride with them loose is it rounds off the spindle on the bb and it rounds the hole in the cranks so it will never stay tight after that again, even with red loctite and even if it is slightly worn on the edges.

Well I hope that I didn't ruin anything here. this bike was purchased for so cheap it really wouldn't be worth getting a new crankset unless I could get a used one for super cheap.

I picked up a replacement bolt and it fit and threaded right into the BB. I put the crank arm back on and bolted it back up. I don't know where our red loctite is so I just left it dry for now but when my roommate gets home I'll take it apart again and use the loctite.

Thanks for all the help guys, hopefully my setup will last. If not then I guess I'll be on the lookout for a super cheapo crankset/BB. Thanks again.