MOT Q&A – Assessing tyre cuts and brake light legality

Q. Is there a way that I can accurately assess cuts in tyres?

A. The criteria for assessing cuts in tyres at MOT test time can be confusing, however the following process should enable you to always assess a cut tyre correctly.

The first thing to remember is that you should always begin with a visual examination of the tyre to check for cuts. Where a cut is evident and a cord is visible this will constitute a Fail (cords exposed).

If no cord is visible, then assessing the cut requires a more physical inspection. Start by assessing, or measuring, if necessary, whether the cut is more than 25mm long or 10% of the section width – whichever is greater (this will be 25mm for most vehicles as very few light vehicles have tyres wider than 250mm).

If the cut is shorter than this then you should Pass and advise. If the cut is longer than this, open the cut with a blunt instrument, taking care not to cause further damage. If cords are then visible this will result in a Fail (cut deep enough to reach the ply or cords).

Please note that it must be visible cord, not cord felt with the blunt instrument or the ripple of cords under a thin layer of rubber. If no cord can be seen then it is recommended that you should Pass and advise.

Q. High level flashing brake lights are apparently now being fitted to some vehicles – such as the Bugati Veyron – as standard fitment. Kits are also available on eBay to modify current vehicles. These are claimed to be legal, but is this true and what are the implications for the MOT?

A. Stop lamp emergency braking operation should not cause problems, either at annual test or road-side. This is because the stop lamps will not flash when the vehicle is stationary as such systems must not operate at a rate of deceleration below 4 m/s2 and must de-activate when the deceleration has fallen below 2.5 m/s2.

From the description of the aftermarket products, they do not comply with this requirement and would therefore be illegal.