bars keeps moving towards me
 

Any tricks here to make it more fixed in place? I tightened all bolts strong enough I believe.
Bike doesn't have any grooves there to make it easier.

remove the handlebar and lightly sand the inside of the stem where it grabs the bar. any debris in that area can cause a slip.
make sure the handlebar clamp area is also nice and clean.
grease the threads of the bolts.
tighten the bolts EVENLY in front of and behind the handlebar.
most BMX stems have some bolt old M8 bolts. you should have no problem putting 12 Nm of torque on those bolts. it's very possible to over-tighten bolts, which can cause the handlebar to get smooshed. it will never really tighten evenly when it gets to that point.

thanks, after sanding it looks like it helped although from time to time I am able to tighten bolts more, like they were backing up.
Don't get why neither clamps or bars has no grooves preventing slippage.

If bars fit so tight that they never slip, you'd break your wrist on a hard enough landing. It should take a LOT of force to make them slip, but if manufacturers started making stems and bars that never slip, you'd regret owning that setup when you land a stair gap with too much front end attitude.

Check your bars to make sure that they are not pinched/crushed where they are in the stem.

Sandpaper/emery cloth
 

Take it apart.

get some sandpaper or emery cloth or crocus cloth. Fold it over itself twice so some faces handlebar, some faces headset, and some folds back into other sandpaper.

With this piece in between handlebar and gooseneck it won’t slip anymore.

the what?

[lol! no one who calls a stem "gooseneck"]

We used to put a piece of aluminum can in the bars or cranks. Square taper aluminum cranks sucked. I've seen a penny in bars too.

i like the term. Shows the user hasbeen around the block a time or 2. Plus stoppes reading BMX Plus in 1986

I think I stopped reading BMX plus in 1994 :lol: I always thought calling them a gooseneck was a weird Canadian thing from the 80's. I didn't know that a gooseneck was actually a style of a extra large road bike stem. I have no idea where or why we started calling them goosenecks but I blame the lack of internets.

Actually very common term in the 70s to the early 80s. While mostly lower end BMX or knockoffs used them in the 80s. Block type stems became the staple so gooseneck fell to the wayside.

I know that. what year is it now?

You don't know its the year of the OX but make fun of others. 🤪🤣

So - carbon assembly paste is another option - it's meant to increase friction, but sanding and torquing to the right amount should be all you need to do.

BMX bikes are pretty much the only style that has anywhere near that much torque on the bar's clamp. Mountain bike bars are pretty close to straight, road bikes don't have near the difference. Time Trial bars would be the only other that would be close in how much leverage is on that joint.