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Supported by The British Army

Treading the line

How good’s your grip? Find out what’s at stake and get measuring your tyre tread.

You will need

  • Rulers
  • Access to a car (with the correct manual)

Before you begin

  • This activity’s part of a series of short activities in the Scouts Mechanic Activity Badge.
  • Decide how you’ll run these activities. You could run a mechanics activity day with a few vehicles, so small groups can try different tasks on different vehicles at the same time. You could also run the activities as short bases during a meeting (while other activities take place).
  • Decide who’ll run and supervise this activity. All of the practical activities for the Mechanic Badge should be run and supervised by a qualified mechanic (or someone with enough knowledge gained through experience).

Chat about tyres

The person leading the activity should ask everyone why they think legal standards exist for tyres? If a tyre’s damaged, it could burst at any point and cause an accident. If a tyre doesn’t have enough tread (deep enough grooves and ridges in the rubber), it could make the vehicle skid off the road, or mean it isn’t able to stop in time so it crashes.



These guidelines are generic guidelines for modern vehicles. Always check the handbook for the vehicle you’re using or get advice from a qualified or experienced mechanic: we don’t want any broken cars on our hands. This activity must always be supervised and guided by someone competent.

  1. If you can, remove the wheel to check for tyre damage so you can see all the way around it. Check out Pit stop practice to find out how. If removing the wheel isn’t an option, move the car floor slightly after checking the tyre so you can check the part that was on the floor. Make sure everyone’s completely clear of the vehicle while the driver moves it.
  2. Check all areas of the tyre for obvious signs of damage including cracks, splits, bulges, or punctures. If you find any of these, the tyre needs to be replaced.
  3. Check the tread of the tyre to make sure it meets legal requirements. The law says that vehicle tyres’ thread must be at least 1.6mm deep in a continuous band around the central three quarters of the tyre. An uneven tread could be because of a wider problem so you should get it checked by a qualified mechanic.
  1. Remove any small stones or debris from the tread so they don’t rub and wear the tyre.
  2. Check the tyre valve. Look for wear on the seal, damaged screw threads, and dirt or grit in the valve itself. Any of these could make the tyre fail at speed.
  3. If anyone spots any problems with a tyre, let the owner of the vehicle know so that they can take it to a local garage as soon as possible to get it checked out by a professional (and replaced if necessary).
  1. Wash your hands thoroughly – wheels and tyres can get very dirty.


This activity was all about developing skills. Why’s it useful to be able to get stuck into vehicle maintenance? It helps keep people safe and can save you money too. It’s also better for the environment to look after vehicles so less resources are used to repair avoidable faults (or even replace cars). Was it easy to learn this skill? Is this skill the same for every single vehicle, or would people still need to check the manual?

This activity also gave people the chance to be independent. How did it feel to get stuck into a practical task? What role did the adults have in this activity? They supervised to make sure no one (and no vehicles) got hurt.


All activities must be safely managed. Use the safety checklist to help you plan and risk assess your activity. Do a risk assessment and take appropriate steps to reduce risk. Always get approval for the activity and have suitable supervision and an InTouch process.


This task involves the use of potentially harmful fluids or chemicals. Make sure you follow all relevant safety guidance. Make sure you dispose of them appropriately too, in line with safety guidance.

Manufacturer’s guidelines

All vehicles will be different so always follow the manufacturer’s guidelines.

Outdoor activities

You must have permission to use the location. Always check the weather forecast and inform parents and carers of any change in venue.


Before completing this activity make sure you have suitable personal protective equipment (PPE). This could include eye or ear protection, gloves, and anything else you need to protect yourself. You’ll know what you need as a result of completing the risk assessment for the activity.

Vehicle readiness

Before completing this activity, make sure that the engine’s fully cooled. The vehicle should be parked on flat, stable ground with the parking brake applied.