Stripping thread on threadless handlebar stem

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20130814
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Stripping thread on threadless handlebar stem

Postby 20130814 » 16 Oct 2016, 8:25pm

Hi,

Last year I bought a Specialized Hardrock bike 2nd hand.

After a while I noticed that some play was developing on the h/bars - e.g. I could put the front brake on and when I rocked the bike to and fro, instead of it being nice and solid, there was a bit of play.

I tightened the top bolt on the bars - e.g. this one:
Image

But instead of tightening, it kept on spinning, so the thread appeared to have stripped.

I took it to a LBS, and they said the thread had gone, and something to do with the forks was bust as well, I can't remember what it was, but they had to replace the forks and the headset - you can see the new forks and h/set here:
Image
Image

The trouble is that now the same thing has happened (play in bars, thread stripped when I tightened it) - unfortunately as you can see in the 2nd photo on this post, the allen bolt hole has also stripped.

I wondered what I should do - could there be some kind of design flaw with this model of bike -it seems funny that the same thing has happened twice.

I am 100% sure I did not apply a ridiculous amount of force when tightening the top bolt, I have done a fair bit with bikes over the years and know not to over-tighten bolts. The thread went on the 2 different occasions without me over-tightening.

I am unsure whether to take this to the bike shop again, and risk sending good money after bad.

The alternative is to write it off as bad luck (it only cost £95 second hand), strip it for parts and leave it at that.

Any advice much appreciated.

Thanks
Last edited by Graham on 16 Oct 2016, 8:44pm, edited 1 time in total.
Reason: Massive image removed - not necessary

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gaz
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Re: Stripping thread on threadless handlebar stem

Postby gaz » 16 Oct 2016, 8:31pm

You cannot adjust out any play by simply tightening the top bolt. You have to first loosen the bolts securing the stem, then adjust the pre-load with the top bolt. If you have stripped a thread then either it is on the bolt or on the star-fangled nut in the steerer tube.

Unfortunately I do not know what damage may now have been done, nor how best to remedy it.

There will be others on the forum with far more experience of threadless headsets along shortly. They may be able to advise on how best to diagnose further and effect repairs.
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RickH
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Re: Stripping thread on threadless handlebar stem

Postby RickH » 16 Oct 2016, 8:39pm

Had you loosened the bolts on the back of the stem before you tried to tighten the top bolt?

The top bolt adjusts the preload (the pressure that stops the play) but the stem is what holds everything in place (the top cap pushes down on the stem, which pushes on the spacers which in turn press on the headset).

If you try to adjust the top bolt without loosening the stem bolts then you are quite likely to break something.

Video guide to adjusting here

20130814
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Re: Stripping thread on threadless handlebar stem

Postby 20130814 » 16 Oct 2016, 8:43pm

Thanks for your replies. No, I didn't loosen the other 2 bolts. I should have read up about what to do first, as this is the only bike I've had with a threadless stem.

So could I have written off a 2nd pair of forks and headset?

I realise that won't probably be possible to answer, and that I'll have to go back to the bike shop.

Thanks again

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gaz
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Re: Stripping thread on threadless handlebar stem

Postby gaz » 16 Oct 2016, 8:49pm

20130814 wrote:So could I have written off a 2nd pair of forks and headset?

AIUI it is possible to replace a star-fangled nut with the correct tools and there are also alternatives to using a star-fangled nut.

It's outside my experience, await more replies.
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fastpedaller
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Re: Stripping thread on threadless handlebar stem

Postby fastpedaller » 16 Oct 2016, 9:01pm

I'ts important to loosen the 2 screws (with allen key) that hold the stem to the steerer tube, otherwise tightening the one on the top cap is ineffective and (as you have found) likely to strip the thread in the star -fangled nut. The screw in the top cap is only there to give a LITTLE pre-load before the 2 on the stem are tightened. The 2 on the stem hold it all in place, and the one in the top cap is pretty much superfluous.

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531colin
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Re: Stripping thread on threadless handlebar stem

Postby 531colin » 16 Oct 2016, 9:12pm

Assuming the steerer is steel, it is possible to remove the damaged star nut and replace it.
Its a fairly brutal affair, but i would be happy riding the thing after I had done it.....apparently the shop you used were more circumspect.

gerrymcm
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Re: Stripping thread on threadless handlebar stem

Postby gerrymcm » 16 Oct 2016, 9:23pm

Does the old star nut need to be removed? Can the new one simply not be installed on top without the old one being removed?

I've also seen double star nuts
http://www.ebay.co.uk/itm/Bike-Headset- ... Swr41XIGtq

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531colin
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Re: Stripping thread on threadless handlebar stem

Postby 531colin » 16 Oct 2016, 9:29pm

Well, I have never ever seen a star nut with a single flange. :wink:
But yes, you can bang down the original star nut and insert another one on top of it, and people do just that, however I worry that you are then scoring up the (inside of) the steerer below the stem, where it is stressed, rather than in the bit where the stem clamps.

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NATURAL ANKLING
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Re: Stripping thread on threadless handlebar stem

Postby NATURAL ANKLING » 16 Oct 2016, 10:40pm

Hi,
Pushing the star nut down the tube an inch is less traumatic than anyway of removing it, so in a steel steerer you will be safe and the marks are down along the tube not round it.
Assuming that the centre bolt will come out easy if now damaged?
Ah I see its the socket you've %^$%£*& it, Brucey will no doubt say that the star fangled nut will have dug into the inside of tube, but this is within the area of clamping (that will need checking?) so a fix is to hacksaw a slot / angle grind a slot in top of allen bolt Centre top one and use a large screwdriver.
New top cap needed, though its damage is cosmetec only as you don't yank the thing down normally.

Clamp bolts have a 5 or 6 mm hexagon socket, you did not use 3/16" I hope.
USE a new allen key / grind off the rounded worn splines on key near end (shorten).
Use both hands to keep the allen key located square in bolt and ease the bolt undone (two on side) sixth of a turn then reposition the key back to where you started (take out and put back a flat anticlockwise), this stops you bending the key out of line, both hands, lay bike down on grass or get someone to hold bars firm.

When clamping the stem back on steerer it does not need to be that tight, check you can not move the bars with wheel between knees and tighten only another 1/2 turn max.
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MikeF
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Re: Stripping thread on threadless handlebar stem

Postby MikeF » 16 Oct 2016, 10:53pm

The top cap needs only gentle tightening. Just enough to remove any play - that's after undoing the the two stem bolts as others has said. Also the steerer tube must be below the top spacer or stem as is your case otherwise all you will do is clamp the top cap to the steerer and not load the bearing however hard you tighten it. The star fangled nut is another abomination in my view - just a nut crudely jammed in the steer tube. I've used expanding clamps meant for carbon tubes instead.
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Abradable Chin
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Re: Stripping thread on threadless handlebar stem

Postby Abradable Chin » 17 Oct 2016, 6:02pm

If the thread in the SFN is stripped, then shouldn't the top cap bolt pull out easily? This could be done by loosening the stem bolts, and pulling the stem up off the steerer, or knocking it if needs be with a mallet. Doing this will save an embarrassing trip to the bike shop.
Add another SFN, or drill it out and use an expander type top cap, or a headlock.
Isn''t there a method of preloading the headset bearings without using anything? I thought Sheldon did something with his Raleigh Twenty that involved walking the clamp down the steerer?

20130814
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Re: Stripping thread on threadless handlebar stem

Postby 20130814 » 17 Oct 2016, 6:06pm

I took it to the LBS today, got a new bolt and SFN, and another spacer was added to aid it all tightening up properly. It cost £18.

Thanks for all of your helpful replies.

nigelnightmare
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Re: Stripping thread on threadless handlebar stem

Postby nigelnightmare » 24 Oct 2016, 1:39pm

20130814 wrote:I took it to the LBS today, got a new bolt and SFN, and another spacer was added to aid it all tightening up properly. It cost £18.

Thanks for all of your helpful replies.


Sounds like the LBS didn't put the right spacers on in the first place. :shock:
Glad you got it sorted though.