Stem extender

mike killay

Esteemed Pedelecer
Feb 17, 2011
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1,590
I have tried to fit a stem extender but found that no matter how hard I tried to tighten the two screws on the side, the extender did not close up sufficiently enough to grip the top of the stem.
On examination, it is 28.6mm just as my stem is, but the construction is so rigid that it will not get tight.
In fact, even trying to squash it in a vice failed to close the gap.
Has anybody else experienced this?
 

Andy-Mat

Esteemed Pedelecer
Oct 26, 2018
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I have tried to fit a stem extender but found that no matter how hard I tried to tighten the two screws on the side, the extender did not close up sufficiently enough to grip the top of the stem.
On examination, it is 28.6mm just as my stem is, but the construction is so rigid that it will not get tight.
In fact, even trying to squash it in a vice failed to close the gap.
Has anybody else experienced this?
I have not experienced that, and I add some height to each bike I have bought, as I have had back problems for many years. Never had such a problem myself.
Take it back to where you bought it maybe and get your money back? Not fit for use comes to mind....
If you paid with a Credit card or similar, they might help, or PayPal will also help in such cases I find....
Andy
 

vfr400

Esteemed Pedelecer
Jun 12, 2011
8,439
3,381
Basildon
I have tried to fit a stem extender but found that no matter how hard I tried to tighten the two screws on the side, the extender did not close up sufficiently enough to grip the top of the stem.
On examination, it is 28.6mm just as my stem is, but the construction is so rigid that it will not get tight.
In fact, even trying to squash it in a vice failed to close the gap.
Has anybody else experienced this?
What you're saying doesn't add up. Show some photos.
 

Scorpio

Pedelecer
Apr 13, 2020
220
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Portugal Algarve (temporary)
I installed one last month, it seemed to fit OK but on first ride I found it wasn't 100% secured so I had to retighten (overtightened?) the bolts when I got home.
Surely clamping it in a vice has to close up the new extension til the gap becomes nil? Or have I misunderstood ?
 

mike killay

Esteemed Pedelecer
Feb 17, 2011
2,978
1,590
I installed one last month, it seemed to fit OK but on first ride I found it wasn't 100% secured so I had to retighten (overtightened?) the bolts when I got home.
Surely clamping it in a vice has to close up the new extension til the gap becomes nil? Or have I misunderstood ?
No, you have not misunderstood.
Clamping it in the vice hardly closed it at all it was so stiff.
 

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mike killay

Esteemed Pedelecer
Feb 17, 2011
2,978
1,590
which brand of stem extender is it?
Usual ebay no-name.
I did cut the slot higher but the effect was minimal, certainly not enough to trust.
I googled 'problems with stem extenders' and some people think that they are dangerous.
To my mind, the fundamental design is faulty. Much of the tightening effort is to squeeze in the device rather than grip the stem.
 

D C

Esteemed Pedelecer
Apr 25, 2013
1,140
570
Cairngorm National Park
Usual ebay no-name.
I did cut the slot higher but the effect was minimal, certainly not enough to trust.
I googled 'problems with stem extenders' and some people think that they are dangerous.
To my mind, the fundamental design is faulty. Much of the tightening effort is to squeeze in the device rather than grip the stem.
I have a Satori Headsup fitted to one of my bikes and been using it for 7 years, well made and rock solid.
Still available on Amazon
Dave.
 

mike killay

Esteemed Pedelecer
Feb 17, 2011
2,978
1,590
I have a Satori Headsup fitted to one of my bikes and been using it for 7 years, well made and rock solid.
Still available on Amazon
Dave.
Well, I will send for one of those. My guess is that mine is a cheap copy and the tempering is all wrong. It simply refuses to bend very much, even when I cut the slot far longer.
The test will be when the new one arrives to try tightening it before fitting and ensure that it does actually squeeze together.
Must say though, the design for the upper bolt seems to be wrong, it is trying to tighten a closed circle of metal. How many of these seemingly working well are only gripping at the bottom? No wonder a few people report problems although mainly MTB riders.
 

Old Fart At Play

Pedelecer
Jun 11, 2020
104
45
Yep sounds like a cheap knock off. I used a BBB extender years ago and it was fine.

If you are anxious about an extender, do you already have an adjustable stem? I've used the Ritchey one, comes in 3 lengths, can adjust the angle to suit. Rock solid.
 

vfr400

Esteemed Pedelecer
Jun 12, 2011
8,439
3,381
Basildon
Last edited:
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Gringo

Esteemed Pedelecer
Jun 18, 2013
1,250
788
Northampton
Over the years I’ve used several cheap risers off the bay without issue. It sounds to me like you have a duff one, all of mine have been a reasonable close fit prior to tightening the bolts.
 

mike killay

Esteemed Pedelecer
Feb 17, 2011
2,978
1,590
Over the years I’ve used several cheap risers off the bay without issue. It sounds to me like you have a duff one, all of mine have been a reasonable close fit prior to tightening the bolts.
Mine is definitely over rigid. Even with the slot cut further up and also a side cut, it still will only budge a tiny amount in a large vice, let alone just tightening the screws36712
 

Gringo

Esteemed Pedelecer
Jun 18, 2013
1,250
788
Northampton
This still doesn’t make sense to me, if the stem and extender Are both 1 1/8“ (28.6mm) then the slot in the extender doesn’t actually close, in fact the difference in size between it being loose and fully tightened should be barely noticeable by eye.
I’m still curious to know what went wrong just for the sake of knowing.
Its pretty academic now as what you have done to the extender has made it dangerous to use.
 
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mike killay

Esteemed Pedelecer
Feb 17, 2011
2,978
1,590
This still doesn’t make sense to me, if the stem and extender Are both 1 1/8“ (28.6mm) then the slot in the extender doesn’t actually close, in fact the difference in size between it being loose and fully tightened should be barely noticeable by eye.
I’m still curious to know what went wrong just for the sake of knowing.
Its pretty academic now as what you have done to the extender has made it dangerous to use.
Short of hiring a metallurgist with laboratory at huge cost, just to determine the degree of tempering, we will never know.
The replacement has arrived and is working fine.
However, because of the design of these extenders I would caution anyone fitting one to fully tighten the top screw first and check that it is actually holding the steerer tube.