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PostPosted: Wed Nov 23, 2011 10:56 am 
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wassertreter wrote:
While I have nothing to add to the topic posed, when it comes to stems and their softness, I'm perpetually puzzled how people are riding their bikes so that stem rigidity makes a difference.


Sorry, slightly OT, but I had very negative experiences with a Rotor stem - everytime I used the brakes I could feel it flex down. Very unpleasant and not confidence inspiring.

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PostPosted: Wed Nov 23, 2011 4:47 pm 
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veloruche wrote:
I'm glad you posted this I was just looking at this stem from FWB, I plan to use the Zipp SL handlebars also. What was Nm used?

The on-line specs for torquing (which I can't find today on the Extralite web site, but downloaded to my computer about a year ago and will send to you by PM if you wish) are that "5Nm maximum torque be applied to the stem-to-steering tube bolts" (not 2.5Nm as the print version states) and "the stem-to-handlebar torque" is listed at "3Nm" as compared to 2.5Nm in the printed specs. I used 4.5Nm on the stem-to-steering bolts and 3Nm stem-handlebar and I've had no problems.

According to Sergio (Extralite) the issue with higher torque on the bolts is "stress corrosion". Here is what he wrote (excerpted from an e-mail to me from Extralite):
Please note the following:
1) Fork steer tube should be round at the diameter of 28.55mm (+/- 0.05mm).
2) 5Nm is the maximum allowed torque, it's safer to release it during winter or when you are not using the bike for a long time.
Notes about "stress-corrosion"
This phenomena happens to high-strength alloy when the part is constantly subjected to an excessive tension and this lasts for a long time (the excessive high tension is normally produced by an excessive and/or uneven bolt strain).
Additionally storing the bike with the tensioned part in a humid place will significantly speed up the stress-corrosion process.
After the "stress-corrosion" starts to show its signs the part is not repairable and its not usable anymore.
The usage of the bike and the part is not a cause of the stress-corrosion, the reasons are excessive tension and storage in a permanently humid environment.

Best regards

Sergio Riva
Extralite


And here are some comments about the issue of "stress corrosion" of these bolts (as mentioned by Sergio of Extralite in the above comments) from a mechanical engineer/cyclist:

"I think he is referring to micro cracking at the molecular level which can allow the "skin" of anodization to crack enough to expose the underlying raw material to the elements. When this happens it can corrode (oxidize) which as the material is thin, can be a problem causer over time. I wouldn't worry about it, simply keep your bike clean and make sure you inspect your bike regularly (which you should do anyway).

Remember that any clamping part like this is effectively working as a spring, it's under tension to hold parts in place. What he suggests is to let the spring back to it's untensioned state during periods of disuse, to avoid it getting a memory (which means you could tighten it more and more over time potentially until it cracked over the years). The margin of safety is outside of this happening, he's just being cautious."

KAC


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Posted: Wed Nov 23, 2011 4:47 pm 


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PostPosted: Wed Nov 23, 2011 5:30 pm 
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Posts: 18
KAC,

Thanks so much for the data, I hope to pull the trigger on this stem shortly.

Thanks,

Veloruche


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PostPosted: Wed Nov 23, 2011 10:53 pm 
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Madcow sold me my stem 110 and I was put off by the max 3nm. But on my zipp sl bar with the right set up it holds the line, has not moved, and at 170lbs and bombing down 15% grades and less then smooth roads I would not have picked another stem. I like it and love the weight.

madcow wrote:
We've sold a lot of them over the last few years and have never seen a broken one. A few people stripped the bolts, mostly in earlier versions which were allen instead of torx but none broken. It's certainly not the stiffest stem, but that's to be expected at that weight.

Overall I think they are a very nice stem. My only complaint is lack of grip on the bar on the road version. On the mtb version since your hands are parallel with the front of the stem you don't have much leverage, but on a road bar since your hands and therefore a lot of your weight are several inches in front of the stem there is a lot more leverage which can cause the bar to slip in some circumstances.

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PostPosted: Thu Nov 24, 2011 4:56 am 
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i love this stem i have it on my dogma... you can see my build. I bought it from fairwheel and it's great. light and reliable. i haven't felt too much or any flex issues. i am surprise most people don't use it as it is less expensive then carbon stems, and lighter!


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PostPosted: Wed Jun 20, 2012 1:36 am 
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just got a roadstem, it'll take a while still to ship

so people are using carbon pste and 4-4,5nm at fork and 2,5-3nm at handle bars, is that it? Ive been using do all 4nm and have zero problems with my bars. I'll be using what appears to be a classic combo (extralite with either zipp sl or ergonova/sum ltd)..


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PostPosted: Wed Jun 20, 2012 1:45 am 
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leosantos wrote:
just got a roadstem, it'll take a while still to ship

so people are using carbon pste and 4-4,5nm at fork and 2,5-3nm at handle bars, is that it? Ive been using do all 4nm and have zero problems with my bars. I'll be using what appears to be a classic combo (extralite with either zipp sl or ergonova/sum ltd)..



Yup paste and go a fraction under the recommended max torque.. You should have no issues

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PostPosted: Wed Jun 20, 2012 2:06 pm 
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wassertreter wrote:
While I have nothing to add to the topic posed, when it comes to stems and their softness, I'm perpetually puzzled how people are riding their bikes so that stem rigidity makes a difference.



Seriously? I guess handle bar flex, crank flex, wheel flex and the sorts are also irrelevant?


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PostPosted: Wed Jun 20, 2012 2:17 pm 
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Zig, well, drivetrain is a different story. Maybe I'm just too passive a rider putting all the power through my legs. That should not mean that some people would not need top-end stiffness, but again, I'm surprised how many people complain about cockpit components that one regularly sees in the World Tour (Ritchey parts for example).

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