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My 2nd Thomsom Stem Failure

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My 2nd Thomsom Stem Failure

Old 03-04-15, 11:31 PM
  #26  
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Originally Posted by lopek77 View Post
Many young mechanics often complain that there is no such a thing like standard when it comes to bikes. I guess it's the common pain of every fast growing industry, full of new , never ending designs and ideas.
It would be so much easier and cheaper if we all were riding Flying Pigeons
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Old 03-05-15, 10:21 AM
  #27  
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As I remember, Thompson has a very specific process for torqueing those bolts. I think you're supposed to ease them up in small even increments. They also take a torque spec that was surprisingly little.
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Old 03-05-15, 10:32 AM
  #28  
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You're pretty much guaranteed to crack the faceplate on an X2 Thomson stem, but it seems like it's slightly less common with the X4. Not a chance I'd ride an X2 and I don't think I'd buy an X4.
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Old 03-05-15, 10:47 AM
  #29  
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I recall doing work on engines.. the cylinder head re torquing sequence was designated. and none was cranked down to torque spec in 1 go.

So I'd tend to be bringing up the pressure in a 4 bolt face plate also a bit at a time

and going top right> bottom left; bottom right> top left , a little bit at a time, sort of practice..

and minding the gap so there is the same distance beween the stem and face plate as I proceed.
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Old 03-05-15, 10:56 AM
  #30  
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Originally Posted by fietsbob View Post

and going top right> bottom left; bottom right> top left , a little bit at a time, sort of practice..
.
I suspect that this is part of the reason bolts crack. Criss-cross tightening increases the likelihood of twisting the top plate and putting uneven stress on the bolt tabs.
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Old 03-05-15, 11:01 AM
  #31  
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but the 1/4 turn per each type of working and bringing them all up together a bit at a time part of my statement was omitted..
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Old 03-05-15, 12:08 PM
  #32  
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Originally Posted by fietsbob View Post
but the 1/4 turn per each type of working and bringing them all up together a bit at a time part of my statement was omitted..
Because it wasn't my point. I wasn't speaking about your post in general so I parsed it to the one part I wanted to address. Many people use the cross diagonal sequence, and it can be problematic. It doesn't have to be, but it can be and often is.
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Old 03-05-15, 12:38 PM
  #33  
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Ah, a timely thread for me, I was trying to figure out which stem to buy and had Thomson on my list (as it'll match my seatpost). Struck off the list now, thanks!
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Old 03-05-15, 12:59 PM
  #34  
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Thomson, *not* Thompson. Thank you .
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Old 03-05-15, 01:01 PM
  #35  
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Originally Posted by JohnDThompson View Post
Thomson, *not* Thompson. Thank you .
Yes, you have a 100% clean record of never producing stems that crack.
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Old 03-05-15, 01:06 PM
  #36  
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Originally Posted by FBinNY View Post
Yes, you have a 100% clean record of never producing stems that crack.
I actually did make some stems for some "funny bikes" used in the 1984 Nationals. AFAIK, none broke...
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Old 03-05-15, 01:25 PM
  #37  
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Thomson website not working... Thomson Bike Products
Regarding torquing sequence, it's a pretty basic rule. It's more important with bigger or longer items, but even small items like stem plate need proper torquing. Not only for a safe and strong fit, but also to prevent handlebars from being damaged by plate itself.
Fits that are too tight and fits that are too loose are equally bad idea.
When I bought my torque wrench, I learned that I was over torquing almost every bolt, including stem bolts at around 20-25nm, which was around 4-5 times more than max recommended value. Both stem and handlebar are aluminum...no damage done though.
I like heavy duty things....much harder for me to break it
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Old 03-05-15, 01:36 PM
  #38  
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Originally Posted by lopek77 View Post
Thomson website not working... Thomson Bike Products
The site seems to be working fine, at least for me. I've accessed it both directly and via the link above. YMMV
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Old 03-05-15, 01:48 PM
  #39  
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I was able to order the face plate form Thomson and should be receiving it in a few day.


The method as described by FBinNY, https://www.bikeforums.net/bicycle-me...l#post17604397 in post Number 4 of this thread. Will be the method I use to attach the face plate.
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Old 03-05-15, 02:02 PM
  #40  
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Originally Posted by Geosammy View Post
I was able to order the face plate form Thomson and should be receiving it in a few day.


The method as described by FBinNY, https://www.bikeforums.net/bicycle-me...l#post17604397 in post Number 4 of this thread. Will be the method I use to attach the face plate.
Curious, did they make you pay, or you didn't want to wait out the warranty process?

To expand on my tightening technique. In lieu of tightening to touch and backing off 2 turns you can use a feeler gauge of some kind, like a cone wrench, to set the upper bolts to equal gaps, then tighten the lower to an intermediate torque. After that you can tighten both top and bottom bolts but have to stay sensitive to the length change (no. of turns) and torque applied both. It's a touch and judgement process, with the goal of preventing a twist in the plate.

I'm sure there are other methods that work, but the key is to be mindful of maintaining distance and preventing twist instead of blindly going by torque.
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Old 03-05-15, 02:12 PM
  #41  
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Originally Posted by FBinNY View Post
Curious, did they make you pay, or you didn't want to wait out the warranty process?

To expand on my tightening technique. In lieu of tightening to touch and backing off 2 turns you can use a feeler gauge of some kind, like a cone wrench, to set the upper bolts to equal gaps, then tighten the lower to an intermediate torque. After that you can tighten both top and bottom bolts but have to stay sensitive to the length change (no. of turns) and torque applied both. It's a touch and judgement process, with the goal of preventing a twist in the plate.
Going through the warranty process would have been a wast of time.
I do have all the required information and documentation, but the stem was purchased back in 09 which would clearly make it void of any warranty that Thomson provides for this stem. Needless to say... I did purchase a new face plate.

Thanks FBinNY for the expanded note to your tightening technique and the face plate offer.

Last edited by Geosammy; 03-05-15 at 02:52 PM.
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