With the mainstreaming of carbon frames and components – and at so many price points – you probably already know that the best way to safely tighten modern carbon parts is by owning and using a torque wrench. Torque wrenches allow you to tighten metal parts properly, too.
But did you know that even some experienced mechanics use torque wrenches wrong? And that incorrect use can damage or break parts the same as not using a torque wrench?
I had no idea until Park Tool Product Manager John Krawczyk was kind enough to clue me in. I was a little embarrassed to admit that my Park Tool torque wrenches were the old beam-and-needle type versus the easier-to-use click-type torque tools Park and other companies sell and recommend today.
Beam versus Click
To explain, a beam type tool flexes as you tighten and, as it flexes, an indicator on the tool points out the torque on a calibrated scale printed on the tool. These tools work fine but you can only tighten a certain number of times before the beam weakens, changing how tight you’re actually getting things. You then need to adjust the tool to zero the indicator again. It's not hard but is a bit of a pain.
Click-type tools are either factory-set to one or several common bicycle torques, or can be adjusted with a dial to the right torque before use. Then, during use, the tool will make a click sound and at the same time stop tightening. You feel the handle of the tool suddenly stop resisting, move forward a bit and stop. The click and the handle suddenly letting go tells you the part is at the correct tightness.
Torque wrench trouble
With a way to hear and feel that you’ve tightened correctly, these click-type tools seems foolproof. But let me hand it over to John to explain the torque troubles they’re seeing at Park Tool. They want to get the word out so that mechanics everywhere understand. He points out that even the best tool is only as good as the mechanic who’s using it.
John says: “Jim, you have no idea how many calls and emails we get insisting that someone cracked their handlebar or frame because their new Park torque wrench was 'defective.' Yet, in all the years people have sent these purportedly defective torque wrenches back, never has one been out of spec or defective. Instead, it was simply used incorrectly.
"Please notice in the photo that there are two torque wrenches with worn away or worn out labels. While we found them still working perfectly and within our spec, they were ones returned as faulty. We put our new torque wrenches in the photo so you can see what the tools used to look like.
"The label damage is from choking up on the tools. It’s amazing how many experienced and professional mechanics (team mechanics, shop mechanics, etc.) do this on their torque wrenches in the mistaken belief that they are then safely under-torquing the bolt. But what they don’t realize is that they are, in fact, doing the exact opposite and actually over-torquing the fastener!
"It’s unfortunate that people will spend hundreds of dollars on carbon bars or stems, or even thousands on carbon bikes – plus even more on a good torque wrench – only to use the wrench incorrectly and do exactly what they want to avoid (i.e. over-tighten and possibly even break their carbon components or frame)!
"The correct way to use a torque wrench – and the only way to get the torque right – is by holding the handle. At Park, we think this is a critical topic and appreciate you sharing it with readers.
"Please watch Park Tool’s Calvin Jones demonstrating the wrong and right ways to use torque wrenches in this short video.”
Tune in next week, when I’ll look at an assortment of Park’s latest torque wrenches and tools.
Jim Langley is RBR's Technical Editor. He has been a pro mechanic and cycling writer for more than 40 years. He's the author of Your Home Bicycle Workshop in the RBR eBookstore. Check out his "cycling aficionado" website at http://www.jimlangley.net, his Q&A blog and updates at Twitter. Jim's streak of consecutive cycling days has reached more than 8,000. Click to read Jim's full bio.