carbon stem and bars..
 

i installed my new stem and bars yesterday.. today i rode with them... and about 25mi into my ride i was on a slight decent and i hit a bump probably going about 27mph or so.. and the bars moved down a tad.. not much.. but it scared the shiznit out of me..... i promptly pulled over and corrected the position of the bars... as i rode home the rest of the way.. i wondered... should i have put some sort of locktite/glue on the stem and on the bars where they meet? 5nm isn't much and i really don't like thinking about eating **** too much.. any suggestions..

Talk to your shop about carbon prep paste. It's designed expressly for this purpose.

Did you use a torque wrench when installing the bars? May not have been as tight as you think. Not an uncommon thing. Locktite on carbon to carbon? Never do this.

tacx assembly paste is useful for adding just an extra bit of purchase for carbon-to-carbon interfaces, like to present a seatpost from slipping into a seat tube.

from your short description, it sounds like you may not have properly secured the bolts on the faceplate of the stem. did you use a torque wrench and tighten them in an X pattern?

i recommend removing the bars and inspecting them carefully. why, you ask? i recently discovered a stripped thread on 1 of 4 bolts on a stem, which caused the bolt to loosen. the opposite side of the carbon bars actually had a small flat spot in it, with some evidence of a very small crack -- perhaps caused by extra pressure on one side when the opposite side's bolt started to fail (just a guess here). i discovered this prior to a ride and did not feel comfortable riding those bars again. fortunately, it is a warranty situation.

i recommend being extra cautious / extra diligent in checking carbon components -- particularly your bars as a failure there could be catastrophic. i don't think my situation was anything other than an anomaly (or just that sometimes $hit happens), but it has taught me to do that quick once-over and investigate further anything that gives a hint that it might be "off".

i know in my situation i was careful about tightening to the proper torque specs, so my point is that it *could* happen even in the best of circumstances.

i'm going with a 1-piece bar/stem combo, which eliminates that bolt interface.

i am very fortunate that a full failure did not occur during a ride, and also that a great shop really helped me out (and that the manufacturer stood behind their product).

be careful. those carbon bars weigh NOTHING!

i'll be completely honest... i didn't use a torque wrench.. but i did do the x pattern for tightening.. after i installed the bars i put the bike on my trainer and gave it a good little test.. i didn't have any problem there.... maybe i should look into getting a torque wrench... and some of that carbon prep paste/assembly paste... i'll report back as soon as i get a torque wrench... any suggestions as to which is the best quality/price.... and yes everybody.. i do know how to use a torque wrench... i used to work on aircraft.... so no need to teach me how to use one :) thanks for all the suggestions/comments..

be sure to get the torque specs from the manufacturer. assuming you tightened the bolts with a small tool, it takes alot more torque than you think to get them to around 9-10n-m (what is recommended by the manufacturer of my bars).

not sure if you need the tacx assembly paste. i don't think there's a downside to it for this application.

putting pressure on the brake levers during a hard stop from speed is probably quite a bit more dramatic than a test on the trainer.

Two Things...

Torque Wrench

Sand grit paste

that sand grit paste can really scuff up carbon bars, from what i've seen. are manufacturers cool with its use?

update.. got my ritchey torque tool... only $20 :) and i got some of the tacx assembly paste... went for a ride today and zero problems... the overnight shipping cost almost as much as the 2 items i got.. but i got it all on friday... couldn't miss the 3 day weekend..