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The highway code states that 'Cars, light vans and light trailers must have a tread depth of at least 1.6 mm across the central three-quarters of the breadth of the tread and around the entire circumference.'
(See this if necessary.)

I do not fully understand this statement.
In particular, what does 'the central three-quarters of the breadth of the tread' mean, please?

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Look at the tire straight on so you are looking at the tread (cannot see the rim). Look at the central 3/4 of the tire (~1/8th of the tire's edges on either side). This is the central 3/4 of the breadth of the tire. The tread in this area must be at least 1.6mm deep across this entire width, going all the way around the tire. This would include where the wear ribs are (small raised portion of rubber at the base of the tread). If the ribs are flush with the tire tread across any part of the tire, the tire needs to be replaced. Here's a graphic to help you. This is an approximation, but between the red lines:

enter image description here

EDIT: Look for these on the tire for the wear ribs (bars):

enter image description here

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  • What does 'If the ribs are flush with the tire tread' mean, please? Jun 27 '15 at 15:48
  • @CalebOwusu-Yianoma - See edit. Jun 27 '15 at 15:54
  • Alright. I will do so. Jun 27 '15 at 15:56
  • I recently argued and lost during my annual inspection over the wear bar issues. In some locales it is interpreted to mean all areas must have 3/32" (1.6mm?) of tread including over the wearbars.
    – mikes
    Jun 27 '15 at 18:25
  • @mikes - 3/32" is actually 2.3813mm ... wondering where the 1.6mm comes from, lol! Anyway you look at it, it's not a lot of tread. Jun 27 '15 at 18:36

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