As you’re getting into cycling, you think more and more about maintenance. Buying a nice bike is good, but keeping it well maintained is even better. There are few things that give you as much satisfaction as being able to fix things on your bike. But what about those bolts with numbers written beside them? 6NM, 20NM? What do they mean and do you need a special tool called torque wrench for your bike?
You need a torque wrench for your bicycle if you do most of your bike maintenance by yourself. It is especially important if you have a bike with carbon components. It will allow you to accurately tighten the nuts and bolts to the correct tightness without over or under tightening them.
A torque wrench isn’t the cheapest tool for a bicycle but it’s well worth the investment if you intend to maintain your bike. Here are the three best options:
Pro Bike Tool is the simplest and most affordable option. This is all most people need. It’s convenient as you can set the wrench to a specific desired torque and the internal clutch mechanism will kick in as soon as you reach it.
Summit Tools provides a digital readout and a wider range torques. It gives you audio feedback on the torque reading so you know exactly how tight the bolts are.
What is a torque wrench?
A torque wrench is a tool that allows you to tighten bolts and nuts to a specific torque. It has a mechanism built into the head that enables it to sense the the power applied to it.
Torque wrenches are used when certain bolts and nuts need to be tightened to specific torques. The maximum torque or the recommended torque is indicated with a number followed by a unit Nm, kgf-cm, lbf-ft, lbf-in. The most common unit on bicycles is Nm.
Some torque wrenches are made with a clutch mechanism. When you set the torque on them, there is a mechanical clutch release that gives a very obvious click letting you know that you have reached the desired bolt tightness.
Some torque wrenches don’t have the clutch mechanism, but instead they have a digital or an analogue read-out of the torque. When you use one of them, you have to keep an eye on the meter and only tighten as long as you don’t reach the desired tension. Some digital torque wrenches, like the Summit Tools wrench give you audible feedback.
Each torque wrench is made for a specific range within which it measures accurately. Bicycle bolts typically need to be tightened to between 4 and 25 Nm, which is much less than what cars require. Bicycle specific torque wrenches typically work between 2 and 25Nm, although some only start measuring at 5 Nm.
Why is a torque wrench important?
Torque wrenches are important because they enable you to tighten bolts sufficiently without overtightening them. Under-tightening a bolt leads to the bolt coming loose, and may eventually fall out, while over-tightening it can seize the bolt or strip the head of the screw or the shear its thread. An over-torqued bolt can also cause damage to parts of your bicycle.
It’s impossible to accurately gauge the torque without a torque wrench. I only realized it when my saddle kept coming loose and pointing up in my bum causing a considerable amout of pain in each ride. I kept tightening the bolt to the point where I thought I’d damage the bike. It was supposed to be tightened to 22 Nm. I ended up visiting my local bike shop for advice. When my mechanic came with his torque wrench, I figured that I was way too far from 22 Nm.
Under-tightening a handlebar can be not only uncomfortable, but it could also lead to an accident.
What do you need in a torque wrench for your bike?
When you buy a torque wrench, pay attention to the following attributes:
Your torque wrench should cover at least the 5 – 20 Nm range. Most nuts and bolts on the bike need to be tightened in this range.
Most bike tools work with 1/4 inch drive, so this is an ideal head size for a bicycle torque wrench.
Ideally, you should get a torque wrench that comes with all the bits to tighten all the nuts and bolts on your bicycle.
Look for a counter clockwise accuracy of 5% or less. This ensures that the reading on the tool matches reality. Some torque wrenches measure all over the place and don’t function properly.
How tight should you tighten bolts on your bike?
If a bolt needs to be tightened to a specific torque, you will see it indicated with a number and a measurement printed next to it.
Not every single bolt needs to be tightened to a specific torque, but those that do, are always indicated.
Also, read the manual of your bicycle to see whether the manufacturer intends those numbers to be the maximum values or the recommended values. If they are maximum values, you want to aim to 80-85% of that value. It’ll be tight enough without risking of over-tightening it.
Also check whether a bolt needs to be greased or needs to be dry when tightened. Since grease reduces friction, the torque meter will apply more force, which may lead to an over-tightened bolt. In most cases grease isn’t necessary.
Can you use a car torque wrench for your bike?
Car specific torque wrenches aren’t suitable for bicycles since their typical range starts beyond the maximum range of bicycle specific torque wrenches. This means that they aren’t capable of providing an accurte measurement in the 5 – 25 Nm range. This makes them useless in a bicycle owner’s arsenal of tools.
How to look after your torque wrench?
There are a few tips and tricks in order to ensure that your torque wrench will have a long life of service.
Don’t use your torque wrench to loosen bolts. You should only use a torque wrench to tighten bolts and nuts. This ensures that calibration remains accurate.
If you use a mechanical torque wrench with a clutch mechanism, set it back to lowest value after use. Keeping it under tension leads to loss of accuracy.
Handle your torque wrench with care. Don’t drop it or bang it. Never use it as a hammer.
Store your torque wrench in the box it came in to ensure logevity and to prevent it from getting rust from air moisture.
A torque wrench can be a useful tool if you take bicycle maintenance seriously. It’s not the cheapest investment, but it pays off in the long run.