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Old 04-01-09, 07:07 PM   #1
Plainsman
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Over torqued

So I was installing a set of Oval Concept Slam aero bars and did not have the instructions. I looked up the torques in Leonard Zinns book. I wound up stripping the threads out of the clamp brackets and had to order new ones, as I over torqued the bolts. Later found out Oval said 6nm, Zinn said 8nm, I read the wrong line and went closer to 10. Lesson learned...

Anyway, I also overtorqued the armrest bolts, by almost double it appears, but the bolts didn't strip or shear off. I've since backed them off to the right torque (4nm). Question is, is there any danger using something that has been that overtorqued?
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Old 04-01-09, 07:17 PM   #2
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check for cracks or crush ripples.
if you don't see any, it's probably fine since the thing might have been over constructed compared to the manual.
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Old 04-01-09, 07:55 PM   #3
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I'm sure you would feel something give if you seriously damaged something so I wouldn't worry, though I would check.
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Old 04-01-09, 09:51 PM   #4
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I would imagine that the weakest part of your bars would be the threads on the bolts and the threads of where they go. So I'd carefully examine those first. If you are absolutely certain they are fine, you are most likely good to go. But check everything closely first. Got a magnifying-glass?
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Old 04-01-09, 10:02 PM   #5
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You've probably over stretched the bolts.
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Old 04-01-09, 10:49 PM   #6
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Quote:
Originally Posted by Plainsman View Post
So I was installing a set of Oval Concept Slam aero bars and did not have the instructions. I looked up the torques in Leonard Zinns book. I wound up stripping the threads out of the clamp brackets and had to order new ones, as I over torqued the bolts. Later found out Oval said 6nm, Zinn said 8nm, I read the wrong line and went closer to 10. Lesson learned...

Anyway, I also overtorqued the armrest bolts, by almost double it appears, but the bolts didn't strip or shear off. I've since backed them off to the right torque (4nm). Question is, is there any danger using something that has been that overtorqued?
I've always stressed using a torque wrench. With the new metals and carbon fiber to me it is important to use a torque wrench.
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Old 04-01-09, 11:41 PM   #7
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Too often I find my beam torque-wrench will require Yoga to read on a great many bolts. They demand I flip the tool over so the meniscus is upside-down. If someone would develop a cheap T-W with a rotating meniscus, I'd use one all the time (almost).
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Old 04-02-09, 05:10 AM   #8
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Hmmm... something doesn't add up... Torque of 6-Nm would NOT stretch or strip a 5mm bolt, no way! And I bet those aero-bar bolts are probably 6mm. My guess is the threads were already messed up from numerous previous uses and this last overtightening stripped them.

Now that you've got new part, get a torque-wrench and you'd be set. Also be aware that torque-specs are given assuming machine-oil on the threads. Otherwise, friction on the threads would give added resistance and appear to be tight, but the bolt hasn't been stretched enough to give adequate clamping force.
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Old 04-02-09, 07:00 AM   #9
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I always stress the need for would-be bike mechanics to learn what these low torque values feel like, when applied with a short handled hex wrench or 4-5-6mm Y-style wrench. I've been wrenching on bike for over 25 years and never once found the need for a torque wrench on M5 or M6 bolts. All of my bikes have carbon frames, carbon bars and carbon seatposts.

There is always the need to make on the road adjustments. How are you going to do it if you've got no clue about how much to tighten a stem or seatpost clamp bolt?
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Old 04-02-09, 08:38 AM   #10
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6 Nm is approx. 53 inch pounds. So I don't see that damaging a bolt either.
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Old 04-02-09, 07:05 PM   #11
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The issue was I blew past 6 to 10, a double miss, Oval concepts says the torque is 6 but I didn't have their instructions so I went by the chart in Zinn's book that said 8. Unfortunately, I read the wrong line in the Zinn book and went to 10, yikes! Turns out I did strip them. Replacement parts on the way. Lessons learned... Thanks all!
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Old 04-02-09, 07:31 PM   #12
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It does seem like a pretty small torque, though.
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Old 04-03-09, 07:59 AM   #13
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More and more components are coming that have explicit torque settings in the instructions. Due to the OP's experience - and many, many others - with stripping bolts, I have come to highly recommend that even the experienced bike-mechanics out there invest in torque-wrenches. The Park Tools TW-1 & TW-2 are relatively inexpensive, and quite accurate. Cheaper than the aggravation of stripping the threads out of a brand-new derailleur or a Thomson stem.
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Old 04-03-09, 08:10 AM   #14
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I wouldn't be as concerned about the clamp bolts as I would about the handlebars. If the clamps were greatly overtorqued and the base bar is Carbon, that's where the damage is more likely and more dangerous.
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