Bar slipping

Just fitted an admittedly cheap bull horn to my beater, and a quill stem with a single bolt. It is all wrapped now but has slipped twice during riding. I've tightened it as much as I dare but not confident it won't do it again. Now I think about it the cheap bar had no markings or marks in the centre and this lack of friction is probably the problem. Now the bar is wrapped I'm loathe to unwrap it as it wasn't cheap bar tape, but I'm wondering if anyone would consel roughing up the contact area of the bar, and how this may be acheived. As I said it is wrapped but I can expose the area required. Drill? Hammer and screwdriver?

Tell me to GTFO if this is stupid but maybe put some sand on the inside of the clamp. I know from getting that stuff between the two halves of a windsurf mast that it makes moving it again almost, if not impossible. Are the bars chromed?

That's a really silly idea.
Coke can shim.

^ even slippier surely

These things slip if their pinched a bit (as something isn't round). So a Coke can shim FTW.

You can save your bar tape it's Fizik or something with not-so-strong glue.

coke can coke can

Coke can shim, or get a small packet of carbon assembly paste (not dissimilar to the sand idea), and apply a little. Also, take out the clamp bolt, make sure it's greased: threads, under head; and if there's a washer, on that too, as well as between the washer and bolt.

25.4mm bar in 26.0 stem possibly?

no, bars and stem are both 26, and the same brand. I think it is just down to a lack of friction.I also greased the lot with Rock'n'Roll contact grease, which normally would be fine but may exacerbate the problem. Going to give the shim a go. Bar tape is Lizardskins, and I'd be very loathe to take it off and try to rep-wrap, but I have enough wriggle room to sort it I think. Just worried about over-tightening the bolt

ta for the advice chaps, btw!

is the bolt bottoming out?

MIght be worth taking bolt out and filing a lil bit of the end, then greasing the crap out of that bolt just to allow to get more torque on it

You're all wrong, beer can shim.

You greased the point of contact between bars and stem?

There's yer problem.

you greased it!?

sighs

Contact grease though, to prevent creaking

researching it while it seems counter-intuitive, you generally should grease every point of metal to metal contact. While initially it may act as a lubricant it actually fills any voids and increases friction long term. After developing creak in my road bike bars I popped this grease in them and hey presto and the creak was gone, but the bars has marking at the contact point so there is much greater friction there. And no slipping.

Carbon clamping compound ('grease with grit') may be the answer, but I'll try a shim first

You can shim all kinds of parts with a coke can. I've done bars, seatpost and crownrace/forks. Probably and indication of how many jobs I've bodged? Problem is getting hold of a coke can, they're banned in our house!

First I heard about greasing the bar/stem!

http://www.chainreactioncycles.com/Models.aspx?ModelID=75810&utm_source=Google&utm_medium=Shopping&utm_name=UnitedKingdom

people will buy anything

To be fair it is necessary with carbon part.

I was looking for a solution to a creaking bar, and came accross this page: http://www.bicycling.com/maintenance/repair-maintenance/maintain-handlebars-and-stem
I applied the grease in tiny amounts and it worked, and I have had no slippage there. When I got this bar I thought I would do the same. Now I feel pretty stupid as this appears to be the culprit (although I maintain the cheapness of the parts does play a role too) so I'll give the contat area a de-grease and see how that works, but if not tacx is a good option

I still always apply a nanosmear™ of grease to the bar/stem interface. I'm not being convinced to change that practice here.

@Jimmy_Fingers - you can get little sachets of carbon paste that still go a long way. Only a few quid, and you can use the non-p&p places if you end up getting it online.

Like this.

Cheers BMMF, feeling more vindicated now, despite the sadly shaking heads. Going to pop into the LBS and see if I can source some