Bicycle Mechanics - stem fell out

Bikeforums.net is a forum about nothing but bikes. Our community can help you find information about hard-to-find and localized information like bicycle tours, specialties like where in your area to have your recumbent bike serviced, or what are the best bicycle tires and seats for the activities you use your bike for.



PDA

View Full Version : stem fell out

doug3610
07-12-04, 11:23 AM
I bought my girlfriend a new Schwinn Frontier FS MTB from EBay. After assembling the bike and putting it through a tough break-in session myself, I presented it to her. About a mile into our first ride, the handlebar (w/ entire stem) comes right out of the headset. Luckily, she was barely moving at the time and did not fall. I re-tightened the thing as hard as I could with an Allen wrench. It has an old-school quill-type (wedge) stem. My question is: Do I have to worry about it coming out again? Should I use Loctite or something else to keep it from coming loose? Obviously this is a huge safety issue, because it would not be pretty if it came out while she was riding 20mph in traffic.

Retro Grouch
07-12-04, 11:26 AM
That's an unusual problem. Are you sure you had the stem inserted into the steerer tube past the minimum insertion mark?
doug3610
07-12-04, 11:34 AM
That's an unusual problem. Are you sure you had the stem inserted into the steerer tube past the minimum insertion mark?

It was as far down as it would go. I am wondering if the wedge is out of position wrt to the stem shaft. Also, the Barnett manually recommends greasing the stem-bolt, the stem shaft, and the top of the wedge - which I never did - would this help? It seems to me that adding grease is just going to increase the probability that grease will get on the outside of the wedge and allow it to slip out even more easily.

demoncyclist
07-12-04, 11:40 AM
The pressure exerted by a properly torqued wedge will far exceed the ability of the grease to let it all pull apart, but will keep the parts from fusing together due to corrosion. It does sound like the stem wasn't inserted properly. The wedge may not have been loose enough to easily slide into the steerer.
doug3610
07-12-04, 11:49 AM
Well, I think I will re-install it per the Barnett manual, which warns against having the wedge be too loose and sliding in too easily:

"Symptom: Stem will not Secure
Cause: Stem was installed with stem binder bolt too loose, and slope-style wedge has rotated 180deg out of position.
Solution: Remove stem and install with stem-binder bolt no looser than necessary to get stem into fork."

Thanks for the feedback.

doug3610
2001 Cannondale M400 fully-rigid MTB with Azonic Double Wall risers, LX drivetrain, Mavic X517's, and Michelin Wildgripper Rocks 26 x 1.75