Fiori

ok so on my way to a job interview today the bolt on the clamp of my stem fell out. When I picked up the bolt it's threads were filled with a spiral of alu. when i picked up the bike I was told the clamp was 26.4, and there were 26.4 giro d'italia bars in it. I took the bars off found a longer fixing bolt from another cinelli stem and tied to screw it in. I couldn't get the clamp shut with the new bolt, so I tried putting the clamp in a c-clamp and clossing it. When I had the stem clamp closed I tried the bolt again, and it screwed in and closed. It appears the stem is 26, I have a 26 pair of giro d'talia bars in there now.
am I waiting for disaster? should I try to put some loc tight on it? have the clamp re taped at a bigger diameter? just suck it up and get a new stem?

I don't want to have to get a new stem, this one has "Fiori" machined into the side of it...

cyclotoine

a picture is worth a 1000 words.

Fiori

no digital camera...
and you can't see the threads inside the stem

Otis

did you whistle in the elevator?

John E

1) This is not a good application for Loctite.
2) I would be concerned about cold-working the jaws open and closed. This is obviously a very safety-critical component, second only to your fork assembly and front wheel.

coelcanth

i don't really understand..

your bolt fell out while you were riding ?

you squashed your 26.4 stem smaller to fit 26.0 bars ?

overtightening the bolt to fit smaller diameter bars maybe is what damaged the threads in the first place..

you could retap to a larger diameter thread but then where will you be able to find a bolt to fit ???

McDave

It sounds like you only have a few threads holding the clamp together now. It may or may not hold, time will tell.

Drilling and tapping for a larger bolt would probably get too close to and interfere with the bar.

I would start shopping for a new stem now and try not to put much weight on the bars, up or down, in the meantime.

Fiori

the last owner or 2 owners ago apparently fit a 26.4 pair of bars into a 26 stem

unworthy1

I'll throw in a few related thoughts, FWIW:
Alloy stem clamps can take a lot more opening and closing than most of us would think possible, or safe, without cracking...but once you see any sign of fracture (hairline) don't ride it.
I'd look into a Heli-coil (brandname) to replace the stripped threads and still retain the original bolt, IF there's enough material to allow the Heli-coil to be installed without seriously weakening the structure...also easy for me since I already have the tool and a supply of inserts, but might be more cost than the part is worth if you have to invest. (Heli-coils ARE a worthwhile investment if you work on bikes/cars/motos with aluminum alloy anythings)
Another great tool/investment is an adjustible reamer, with one of these you can easily make a 26.0 (or 25.8) clamp fit an older Cinelli 26.4...I've done it. Also helps to have that digital caliper to really measure fractional MMs. Hey, I'm a tool freak, can't help myself.
Edit: I just looked at a stem and realized that installing a heli-coil in the clamp of a typical would be a real BEAR, so ignore my suggestion for THIS application...but everything else about heli-coils still stands, they are a great product and have saved my chestnuts many-a-time. You MIGHT me able to salvage this by boring out an retapping to the next-up metric size bolt, but use caution and sense before you go that route...McMasterCarr has LOTS of metric fasteners. If it's originally a 6mm bolt you might have enough "meat" to go to a 7mm bolt but McMCarr don't have those, you can shop for one or look at a 5/16".