Torque wrenches – may the torque be with you | WORKSHOP
Our Mad Manx, flat cap wearing Jedi, Nick Prince has been torqueing about his tight nuts all week. Thankfully he has it all in hand so this week, in his ‘Something for the weekend‘ series, he’ll be helping you to check yours…
They’re nuts
I’ve spoken to fellas who have built countless engines that travel the length and breadth of Europe and been amazed that some still don’t use torque wrenches.
The main reason to use one is for the longevity of the engine casing, crank casing, hub and just about anything you bolt onto a scooter. Using a torque wrench confirms that any fastener is at the recommended tightening figure. A torque wrench stops you over-tightening, damaging the thread or under tightening.
However, all the threads need to be in good condition to start with to get the desired torque setting correct. There’s no point fighting against a damaged or distorted thread because these can make your torque wrench ‘click’ before the fastener is even tight.
Use the torque
You should use the correct torque settings rather than just tightening as much as you can, don’t use the force, use the torque. It will assist you in avoiding wear from overtightening or things working loose, or worse case scenario, studs working loose and falling out from under tightening.
An example of where torque is useful is when you mount your wheel rim onto the hub. Studs and hubs cost hard earned cash. Using a torque wrench and the correct torque setting will ensure the rim is tightened correctly and not causing any damage to your hub. Wheels are one of the most common places where people don’t use torque wrenches. For example the stud pictured above has been over tightened and could lead to serious consequences if it fails. A rear wheel stud should be 14.5-16.6 lbs/ft
The last three scooters I have worked on I’ve noticed that all the wheel studs (front and rear) have been nowhere near tight enough, or near the correct torque setting. As scooters get more and more powerful it becomes ever more important that the wheel studs are at the correct torque, as you don’t want to be in a situation where the wheel decides to part from the scooter.
Nut and bolt check!
If you travel long distances in a day, for example on a rally or Euro trip, carry a torque wrench (one between a group is enough) and check your wheel rim nuts with the wrench at the end of each day, it takes two minutes and can save you a lot of trouble in the long run.
Always wind your torque wrench back to zero after you have used it, or it can end up weakening the spring in the wrench, giving you a false setting.
It is imperative when you purchase a torque wrench that you check it can set left hand and right hand torque. As some only go one way and you need left-hand for your flywheel torque which is 50 ft/lbs on a Lambretta. For Vespa riders this is less important as all the important threads are right-handed.
The place to find your torque settings for Lambrettas is easy, just look in Sticky’s (Yoda) Workshop Manual page 205.
Size of your tool
Torque wrenches come in all shapes, sizes and various ranges – for example ones for your back wheel, front wheel, wheel rims etc. A good all purpose one at a good price to carry on your scoot is the Hartford 3/8-drive torque wrench at approx. £50. The big Tengtool torque wrench (red one in the pic) goes from 48 to 150 ft/lbs and costs £87, ideal for your rear wheel. These two will cover everything you need. If you’re on a budget the Hartford one will do everything apart from your rear wheel. By far the best torque wrench you can buy though are digital ones, such as Draper which come in at £190 but they are the most accurate.
Words and photos: Nick Prince
A useful guide to using a torque wrench from Norbar
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I only ever use a torque wrench for engine rebuilds. Tightening big end and mains cap nuts and bolts etc. Experience teaches when and how much force needs to be applied and using a shorter spanner will help you with nuts and studs in alloy.
Trusting a torque wrench when threads are lubed with oil or grease can end in heartache. They need to be used with caution because of their length and resulting leverage. . Sorry but I find the idea of carrying one for wheel nuts laughable, but that’s just my viewpoint after years of working on and bikes and cars.
Everyone has their own way of doing things
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how bout for tightening heads after kit fitting?
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Yes definitely. Head bolts, cylinder base bolts, clutch centre nut etc. anything where the tightening is critical.
People do quite rightly get nervous when it’s steel into alloy. Especially things like disc bolts or casing bolts.
I have to say I’d sooner trust my “feel” for the item rather than blindly put my trust in the click of a torque wrench. eg) After years in the heating and cooling of an exhaust manifold I wouldn’t torque up an exhaust nut/stud with a torque wrench, I’d sooner do it by feel with a shorter spanner or socket. Tightening to the original torque especially after applying coppergrease etc. could be a disaster.
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Thats great for you, but there are many more people that don’t have a clue on how much to tighten nuts, bolts and studs, so for them, if not you, a torque wrench is a very useful tool.