Another slipping expander plug, what torque on the preload you need to sieze the headset?

Discuss light weight issues concerning road bikes & parts.

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Cleaner
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by Cleaner

Posting pictures of the assembled stack up and some pictures of the expander out of the bike as well as the inside of the steerer tube may get more relevant answers. Pictures of the bearing cup damage in the head tube may also offer some clues.


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musiclover
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by musiclover

My expander looks exactly like the one from this thread https://www.roadbikereview.com/threads/ ... ng.373997/

ToileySiphon
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by ToileySiphon

MikeD wrote:You should do up the expander first, then tighten the stem bolts. An expander helps keep from crushing the steerer tube when the stem bolts are tightened. If you have the expander in there without it being tightened up, it's just like not having one in there and isn't providing any support.
Seems like the only logical way to do it if you want to torque according to manufacturer specifications. Otherwise you risk crushing your steerer with the stem when the plug isn't there.

You could install the stem with only a light torque, then torque the expander according to specifications. But the torque would be affected by how much you actually tightened your steerer and would never be as accurate as if it was done in an empty fork. The fact that Enve does it without the stem on somewhat confirms that.

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musiclover
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by musiclover

How to prevent it from slipping out?..

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dj97223
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by dj97223

Are you sure the expander is designed to fill the inside diameter of your steerer? If not, check the expander specsand measure the inside diameter of your steerer.
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dj97223
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by dj97223

Are you sure the expander is designed to fill the inside diameter of your steerer? If not, check the expander specs and measure the inside diameter of your steerer.
“If you save your breath I feel a man like you can manage it. And if you don't manage it, you'll die. Only slowly, very slowly, old friend.”

bikeboy1tr
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by bikeboy1tr

They supply that same long expander with my V2R and I had the same issue so I tossed it aside and used a shorter style expander. NP since then with little torque required to keep components in place.
viewtopic.php?f=10&t=154188
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musiclover
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by musiclover

Yes, those slick expanders clearly have this issue. No, I do not want another expander, just yet... I like the fact that it is long and supportive of the stem area.

I have torqued it to the recommended 8 Nm with B7000 glue on the sides. In the morning, I have torqued the top cap to 6 Nm, then took it off, had a look at the top of the expander - seems tpo stay in place. Torqued it back to 6 Nm again and fixed the stem bolts.

B7000 seems to provide a temporary bodge solution to the problem.

I guess the issue is - how much torque on the stem torque (preload) bolt is enough? Some guides say 1-2 Nm some up to 7... But most just say "enough to remove the play"... Well play is a subjective factor which is hard to measure. Judging by the damage on the carbon cups I assume I had some play which only showed itself on the big bumps. But how do you diagnose and fix this?.. Such a simple system and such a silly problem.

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musiclover
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by musiclover

Funny though how the vast majority are riding on a non cut steerer and then the expander plug just sits at the top doing nothing, and there is not a lot of concern about it not supporting anything.

Nezz0r
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by Nezz0r

musiclover wrote:
Mon Sep 27, 2021 2:50 am
I guess the issue is - how much torque on the stem torque (preload) bolt is enough? Some guides say 1-2 Nm some up to 7... But most just say "enough to remove the play"... Well play is a subjective factor which is hard to measure.
You cannot put a torque rating on that because it is a mechanism to take out fine tolerance on a unique combination of hw (and tolerances). 7nm sounds like an insane number. The production of parts is not to such a tolerance that it can be so finely calculated (imo).

Adjusting to have smooth running bearings and no play is perfectly doable and judge-able (excuse the poor wording) if the system works as intended. I think a slipping expander is causing issues here, not the amount of preload applied. If the expander is not fixed there is going to be no preload - whether you use your fingerspitzengefühl or a number with a torque wrench. All bikes I've worked on you can clearly feel the headset going front play to bearings binding in little force and something in the range of like 1-3 revolutions.

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musiclover
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by musiclover

It is not slipping yet, not after the glue application.

By the way, theoretically, how much torque do you need to use on the preload bolt to sieze the steering or significantly slow it down? As I have applied 5 Nm without the expander slipping and it has no affect on the smoothness of steering.

Maddie
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by Maddie

5nm sounds an aweful lot. That's the torque I use for the stem bolts. Since I don't use a torque wrench for the preload, I would guess it's somewhere between 1 and 3nm max.

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cyclespeed
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by cyclespeed

Expander plugs are a truly crap solution.

Factor went down this route and lived to regret it with a kind of semi-official recall for the Ostro.

First they tried a differently designed plug, then gave up and moulded the M5 nut set into the steerer with carbon. By far the best solution.

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musiclover
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by musiclover

Maddie wrote:
Mon Sep 27, 2021 8:52 am
5nm sounds an aweful lot. That's the torque I use for the stem bolts. Since I don't use a torque wrench for the preload, I would guess it's somewhere between 1 and 3nm max.
Yeah, I get that. 5 Nm is a lot but we don't know what it should be. How much do you need to sieze the steering? 20 Nm?
cyclespeed wrote:
Mon Sep 27, 2021 9:07 am
Expander plugs are a truly crap solution.

Factor went down this route and lived to regret it with a kind of semi-official recall for the Ostro.

First they tried a differently designed plug, then gave up and moulded the M5 nut set into the steerer with carbon. By far the best solution.
Yes, they are, but how do you cut to size? How do you make sure there is just enough space for the top cap but not too much?

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