Loose Direct Connect Stem

[Schafer_in_wis]

I have a mountain bike with a bontranger stem it is a direct connect type.

The issue is the steerer clamp bolts are already tighten up, But I can still easily make the handle bars slip to the right or left holding the front wheel still between my knees.

I don't want to tighten the bolts any further, as I fear too tight and it will break.

Something else must be needed any help would be appreciated.

thanks

[cyclerUK]

Take the stem off and measure the outside diameter of the steerer tube.
This should be the same size that your stem is designed for.
Steerer tubes generally are 1", 1.1/8" or 1.1/4".
Normally the stem should be a snug fit on the steerer tube before you even tighten the clamp bolts.
If not then perhaps you require an adapter shim?

[Schafer_in_wis]

Thank you for the quick reply, But I believe that the stem and the fork tube are compatible, and most likely original. I don't have a torque wench but I've got the bolts tightened up to where if I go much more I think I could cause damage.

I have another bike, with the same type direct connect stem and those bolts don't have to be as tight to stop the slipping.

Just wondering is there something else that I need to do?

[cyclerUK]

Is it a snug fit without the bolts tightened or does it feel slack or wobble?

[DaveM]

I would check the bolts' and stem's threads to make sure they are clean and undamaged. Make sure you have some grease on the threads. Make sure the top of the steerer and inside of the stem are also very clean. Make sure there are no rough spot on the shoulder where the bolt heads sit on the stem. Is there washers on them? Did there used to be? Are the bolts the originals? I've seen cases where someone replaced them with slightly longer ones and the bolts were bottoming out so you couldn't tighten them any further.

[nd456]

you could slip a piece of rubber in between

[trevgbb]

The top bolt is the one which adjusts the bearings.
Loosen the side clamp bolts until you can just turn the stem on the steerer tube, now tighten down the top bolt until you have eliminated all play but the bars turn smoothly and retighten the side clamps, hold the brake on and rock back and forwards and there should not be any play, repeat if necessary.
If this doesn't work after a couple of go's, you may have to look at the spacer washers to ensure the top of the steerer tube is below the top face of them.