Take the 2-minute tour ×
Bicycles Stack Exchange is a question and answer site for people who build and repair bicycles, people who train cycling, or commute on bicycles. It's 100% free, no registration required.

Often guidance will be given to tighten a nut to "20 lbs of pressure" or something along those lines.

What's the best way to ensure you tighten things up, but not to over-tighten?

Is there any way to do it other than measuring the force? If measuring, how do you measure?

share|improve this question
add comment

2 Answers

up vote 10 down vote accepted

You use a Torque Wrench. You set how much pressure, and when you tighten to that pressure, the wrench will "click" and not tighten the nut/bolt any more.

share|improve this answer
1  
Keep in mind that on bicycles you deal with itty-bitty forces in a lot of places. So you really want a torque wrench with inch-pounds on it. There are many different wrenches with different ratings. –  Jack M. Aug 26 '10 at 0:06
add comment

Saint Sheldon had an opinion on using a torque wrench ...

Experienced mechanics will strip threads as part of the learning process. After you've stripped a few, you get the "feel" for what a given thread diameter and depth of engagement can take. This is a very worthwhile skill to learn.

Bicycles are meant to be user serviceable without needing a lot of exotic tools. Nobody carries a torque wrench for on-the-road repairs, and I never heard of anybody using a torque wrench on a bike before, say, 20 years ago. (note: original post from 2001)

A torque wrench is like training wheels for a mechanic. If you want to become a competent mechanic, you shouldn't be afraid to strip a few bolts in the learning process.

Sheldon "Doesn't Do It By Rote" Brown
Newtonville, Massachusetts

Source:
http://search.bikelist.org/getmsg.asp?Filename=tandem.10108.0031.eml

One area where I’ve found a torque wrench helpful is the left crank arm, it helped me get a feel for how much leverage was needed. This is an area where learning about too little torque can be destructive. A loose crank arm will ruin the press fit of the crank arm on a square taper bottom bracket.

I think more important than a torque wrench is proper lubrication of threads and underside of bolt head. All threaded fasteners must be lubricated for them to be tightened properly. He lays out the lubrication checklist here ...
http://search.bikelist.org/getmsg.asp?Filename=internet-bob.10705.2486.eml

share|improve this answer
1  
Perhaps stripping a few bolts isn't a big deal, but what happens when you strip the threads on a fork eyelet, or the rear triangle of an expensive carbon frame? Sheldon's advice is sound for mechanics but not most riders. –  Neil Fein Aug 23 '11 at 16:29
    
@NeilFein Though I have never stripped a bolt, I will admit to many mechanical mistakes which all served to teach lessons. Portraying a bicycle as a delicate machine whose threads can't withstand some over tightening seems less than accurate. I will agree that an expensive carbon frame is probably not the best bike for learning. A rider in that position would be well served to pick up a used bike and a wrench. –  user2201 Aug 23 '11 at 17:40
    
A torque wrench as training wheels also assumes your torque wrench is the same length as your regular wrenches and ratchets. If your regular wrenches are shorter than your torque wrench (very often true in my experience) then you will need to apply more pressure to the shorter wrench to match the torque. –  STW Aug 23 '11 at 18:29
1  
...the advice I would give is to have the right tools in the shop, and to err on the side of caution when performing field-repairs--under-torque and ride with caution until you can properly repair the bike. –  STW Aug 23 '11 at 18:30
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.