Compression plug slipping

[dedroo]

Hello,

My compression plug keeps slipping when it's at the recommanded torq (5-7NM), my top cap bolt with pull it when I try to remove the play. I'm below 2NM at the top cap bolt.
The only way I found to stop making it slip was to either use the 30mm one at about 8-10 NM, or use my 80mm plug at about 10-12NM. I tried carbon paste and cleaning all the surfaces, but it didnt help much. Now my worry is that it is over tighten and that it could break during a ride due to the tightness.
For reference, I am using the aliexpress compression plug offered by 3-4 brand (they all look similar).
https://www.aliexpress.com/item/1005005610090649.html?spm=a2g0o.productlist.main.3.38c2WC0qWC0qEl&algo_pvid=d270c083-a21c-4869-ab9c-f900e900f669&algo_exp_id=d270c083-a21c-4869-ab9c-f900e900f669-0&pdp_ext_f=%7B%22order%22%3A%222484%22%2C%22spu_best_type%22%3A%22price%22%2C%22eval%22%3A%221%22%2C%22fromPage%22%3A%22search%22%7D&pdp_npi=6%40dis%21CAD%213.52%213.52%21%21%212.42%212.42%21%402103110517823197372476645e5bfd%2112000033740997428%21sea%21CA%21909343360%21X%211%210%21n_tag%3A-29919%3Bd%3A18ca7f7f%3Bm03_new_user%3A-29895&curPageLogUid=dUPsBXB7taaT&utparam-url=scene%3Asearch%7Cquery_from%3A%7Cx_object_id%3A1005005610090649%7C_p_origin_prod%3A#nav-review

Thanks for helping me clear that up.

[alfiomotrambo]

I don't think using carbon paste is a solution; in fact, I think it could damage the inside of the tube. Have you tried another brand like Ztto https://it.aliexpress.com/item/1005008055295190.html?
Or what order are you tightening the bolts in?

[dedroo]

Yes. I have 2 different ones, tried again earlier at 8nm and it slips. I really need 10-11nm to make it tight.

[alfiomotrambo]

What frame + handlebar did u have?

[dedroo]

Winow tt119 and their cockpit. The issue is really with the comprrssion plug actually.

[mark335]

Yes. I have 2 different ones, tried again earlier at 8nm and it slips. I really need 10-11nm to make it tight.

I had similar issue. I overtight compression plug and nothing happend as long as you tight it up with tighting stem in the same time. In such a case, the walls of the steerer tube rest against the walls of the stem.

[dedroo]

I had similar issue. I overtight compression plug and nothing happend as long as you tight it up with tighting stem in the same time. In such a case, the walls of the steerer tube rest against the walls of the stem.

But how do you apply pre load if the stem is already a bit tight on the steer tube?

[dedroo]

after a quick ride at 10-11 NM, the plug lifted about 1,5mm from the fork tube. Stem is still super tight. I saw some compression plug that comes with a sleeve that you put inside the fork, maybe someone used this before.

[mingc]

The compression plug serves two purposes. First, the plug and top cap is used to preload the stem on the steerer tube before the stem is tighten. Once the stem is tightened, the pre-load function is done and no longer needed. So, for instance, you should be able to remove the top cap without affecting how the stem/steerer tube/head tube connection. Second, the compression plug supports the inside of the steerer tube against the outside pressure of the stem.

In your case, once you've tightened the stem to spec, I'd loosen both the top cap and plug, tighten the plug to spec, and replace the top cap without tightening it to the point that it pulls the plug out.

[dedroo]

The compression plug serves two purposes. First, the plug and top cap is used to preload the stem on the steerer tube before the stem is tighten. Once the stem is tightened, the pre-load function is done and no longer needed. So, for instance, you should be able to remove the top cap without affecting how the stem/steerer tube/head tube connection. Second, the compression plug supports the inside of the steerer tube against the outside pressure of the stem.

In your case, once you've tightened the stem to spec, I'd loosen both the top cap and plug, tighten the plug to spec, and replace the top cap without tightening it to the point that it pulls the plug out.

Ok, so I would be adding an extra step. I could let the plug slide a little bit then tight my stem, but would it be dangerous if I untight my plug to drop it down a few more mm? otherwise maybe I can just tighten everything and just loosen the top cap so the plug doesnt have tension anymore.

[mingc]

I would not want the plug to slip before tightening the stem as it would lessen the pre-load. It seems you had successfully torque the plugs to that point before and had not cracked the steerer tube, so I'd do it again. As I said, after you tighten the stem, I'd loosen the plug and torque it to spec. After that, I'd recheck the torque on the stem bolts and keep the top cap loose without it falling off. You don't need a pre-load at that point.

Perhaps a more fundamental question is, why are the expansion plugs slipping? 2Nm at the top cap is not a lot for it to pull up a tightened plug. Are you reading your torque wrench correctly? Are you using the right diameter compression plug?

[hubba]

There could be few reasons why it's happening. The design of the expander might be not optimal, the bolt of the expander might be a bit tight to move so you put less torque to it than you think. Also the inside of the steerer tube might very slippery.

If there is a smooth slippery clear coat inside there steerer very lightly sanding it gives the compression plug a bit more grip. I've also used a piece of inner tube on top of the compression plug for more grip.

But you also commented that the plug lifted up while riding which is not normal. That sounds like the stem is not properly staying in place. After the stem is tightened the plug absolutely shouldn't move. Does the headset have play after the compression plug has slided up after riding?

As others said after the stem is tightened the compression plug is not holding the headset in compression anymore and should not move.

[dedroo]

I would not want the plug to slip before tightening the stem as it would lessen the pre-load. It seems you had successfully torque the plugs to that point before and had not cracked the steerer tube, so I'd do it again. As I said, after you tighten the stem, I'd loosen the plug and torque it to spec. After that, I'd recheck the torque on the stem bolts and keep the top cap loose without it falling off. You don't need a pre-load at that point.

Perhaps a more fundamental question is, why are the expansion plugs slipping? 2Nm at the top cap is not a lot for it to pull up a tightened plug. Are you reading your torque wrench correctly? Are you using the right diameter compression plug?

I am using a torq wrench and reading it as I should. From what I understand. The plug is also fine, I double checked the spec and it's the riggt size. I just ordered a plug that comes with a sleeve so the force is spread evenly on the fork tube. Some people mentionned that maybe the plug itself isnr expanding evenly right now so I am just torqing on the bolt inside which is "stuck". So my 10 NM could be 7-8NM on the plug and the 2-3 last NM wouldnt be effective.

Now, I am just worried to crack the tube if I release the plug once the stem is already tight. For now I let it like it was, about 1mm outside of the tube.

[dedroo]

There could be few reasons why it's happening. The design of the expander might be not optimal, the bolt of the expander might be a bit tight to move so you put less torque to it than you think. Also the inside of the steerer tube might very slippery.

If there is a smooth slippery clear coat inside there steerer very lightly sanding it gives the compression plug a bit more grip. I've also used a piece of inner tube on top of the compression plug for more grip.

But you also commented that the plug lifted up while riding which is not normal. That sounds like the stem is not properly staying in place. After the stem is tightened the plug absolutely shouldn't move. Does the headset have play after the compression plug has slided up after riding?

As others said after the stem is tightened the compression plug is not holding the headset in compression anymore and should not move.

The plug probably lifted when I did tight the headset. I did not check right before leaving, but only after my ride to see if anything happened. So I doubt it did move 1 mm during my ride... that's my mistake. Because right now, when I press my handle bar from right to left and test with brake, it is still tight. No play occurs. There is a bit of flex in the handlebar, but nothing seems to move at the stem! I even removed the torq from the pre load and the stem is still tight in place. Also. It doesnt move my plug now when I give it 1-2 NM. Maybe its because the stem is tight against it.

[dedroo]

Could it be slipping because I didnt apply grease in the bolt thread and my 10-11NM is actually 6-7NM ?