Torque Wrench: How to Choose and Use One

Somewhere in every garage there’s a story about a wheel that came loose on the motorway, or a bolt that snapped because someone leaned on a breaker bar “for good measure”. A torque wrench is the cheap insurance against both: bolts that hold wheels on, brakes together and cylinder heads down all have a specified tightening figure, and guessing gets expensive. A good one costs anywhere from about £40 to over £200, which is less than the cost of one snapped stud or one damaged hub. Here’s what to look for, and how to use one so it stays accurate.

What to look for

• Range. Check that the wrench covers the torques your car needs. Wheel nuts on most family cars are tightened somewhere between 80 and 120Nm, suspension bolts similar, and head bolts often higher; a 40 to 210Nm wrench brackets all of it. Check your handbook for the actual figures.
• Accuracy. A decent wrench is accurate to about plus or minus 4 per cent. Cheaper units drift more, and drifting is what rounds threads and distorts gaskets.
• Type. Click type wrenches are the classic choice: you set the value, and the handle clicks when you reach it. Digital types show the reading on a screen and are easier to read in poor light. Beam wrenches are cheapest but the least pleasant to use.
• Drive size. For wheel and suspension work you want a 1/2 inch square drive, because that matches the sockets and extensions already in your set. Smaller 3/8 and 1/4 drives suit low-torque engine bay jobs.
• Reversible. Make sure the direction switch is easy to operate one-handed, because you will be flipping it constantly between tightening and loosening.
• Calibration. Wrenches drift over time and after knocks. Factory calibration certificates, and recalibration every couple of years if you use the tool heavily, keep the numbers honest.

How to use one without wrecking it

Clean the threads, run the fastener down with a normal ratchet first, then finish with the torque wrench in one smooth pull until it clicks. Never use the wrench to loosen fasteners or to spin things down from scratch, never extend the handle for extra leverage, and always wind the setting back to its lowest value for storage. Store it in its case, because a spring left under tension loses its accuracy.

The home mechanic standard

Sealey STW201 torque wrench, 40-210Nm, 1/2 inch drive: Best budget

The STW201 covers 40 to 210Nm on a 1/2 inch square drive, which brackets wheel nuts, suspension bolts and most engine work on family cars. It is the classic first torque wrench for a home garage, and its price varies online, so click through to check today’s figure. Check current prices on Amazon UK.

Digital flexibility without a new wrench

Maximum confidence for critical bolts

Side by side

Wrench	Range	Type	Typical price
Sealey STW201	40-210Nm	1/2 inch mechanical	varies, click to check
ATsafepro digital adapter	10-200Nm	1/2 inch digital adapter	varies, click to check
Draper Expert 77993	40-200Nm	1/2 inch electronic	around £214.60

What we’d buy

For the average home garage we’d start with the Sealey STW201, because a 40 to 210Nm click wrench covers wheel nuts, suspension and most engine work for sensible money. Step up to the Draper Expert 77993 if accuracy on critical fasteners matters to you, and consider the ATsafepro digital adapter as a cheap way to add a digital readout to sockets you already own. Whatever you buy, torque your wheel nuts, then keep an eye on pressure with our tyre inflator guide, and make sure the sockets underneath it are up to the job with the socket set buying guide.