Thread depth legality

SpannerMonkey · 12-05-2014 8:31pm #1

Hi guys just wondering whats the legal thread depth of tyres . I know its around 1.6-1.8mm but does that need to be across the entire face of the weel . I ask because i have a second set of rims and tyres but the cars tracking was a mile out and it heavily wore the tyre on the inside quarter . The most of the tyre has about 3-3.5mm thread left but the inside is about 1mm. It is literally just the inside 1/4 . But just wondering if they are still legal or not .

challengemaster · 12-05-2014 8:35pm

I'd say they're not safe anyway.

NCT failure is for

Depth of less than 1 .6mm in the central three-quarters of the tread pattern.

Greenmachine · 12-05-2014 8:38pm

Depends on the vehicle. Motorcycle and class car only require 1mm.
Cars otherwise require 1.6mm.

The minimum thread depth must be across 2/3 of the tire if I remember correctly.

In reality they should be replaced sooner than this. Especially with cracked sidewalls or thread showing in any part of the tyre.

CiniO · 12-05-2014 8:39pm

So you can have tread of less than 1.6mm on 1/8 of tyre width on each sides.

F.e. on 205/55 tyre that would be about 25mm on each side, where tread is less than 1.6mm.

CiniO · 12-05-2014 8:41pm

Greenmachine wrote: »

Depends on the vehicle. Motorcycle and class car only require 1mm.

It only applies to classic cars first registered before 1931.

The minimum thread depth must be across 2/3 of the tire if I remember correctly.

Centre 3/4

longhalloween · 12-05-2014 8:44pm

Greenmachine wrote: »

In reality they should be replaced sooner than this. Especially with cracked sidewalls or thread showing in any part of the tyre.

They should be replaced around the 2.5 mark. The 1.75 is the point where the tyres become illegal.
They should also be replaced when they're damaged. Tyres are your only point of contact with the road, so really they should be in good form.

CiniO · 12-05-2014 8:47pm

longhalloween wrote: »

The 1.75 is the point where the tyres become illegal.

timmy4u2 · 12-05-2014 9:02pm

SpannerMonkey wrote: »

Hi guys just wondering whats the legal thread depth of tyres . I know its around 1.6-1.8mm but does that need to be across the entire face of the weel . I ask because i have a second set of rims and tyres but the cars tracking was a mile out and it heavily wore the tyre on the inside quarter . The most of the tyre has about 3-3.5mm thread left but the inside is about 1mm. It is literally just the inside 1/4 . But just wondering if they are still legal or not .

The official and legal requirement under the CE&U of Vehicles Act 1963 as amended by the Act of 1990 state

vi) in the case of vehicles other than mechanical propelled cycles, or vehicles first registered before the 31st day of December, 1930 the main grooves of the tread pattern of the tyre do not have a depth of at least 1.6 millimetres throughout a continuous band around the entire outer circumference of the tyre, or
(vii) in the case of mechanically propelled cycles and vehicles first registered before the 31st day of December, 1930, the grooves of the tread pattern do not have a depth of at least 1 millimetre throughout the entire breadth and around the entire circumference of the tyre

This is qualified by the Act as the centre three quarters of the tyre but if read with the Principle Act what it is accepted to be is 1.6mm across three quarters of the road contact surface area.
You can have the treads worn down on both the inside and outside of the tyre provided the carcass is not showing.
Of course if you are sensible are you aresafety conscious you will not run below 3mm

sandydan · 12-05-2014 9:26pm

thought there is guide thread between grips if its level with thread they should be replaced

coylemj · 12-05-2014 9:40pm

As already stated, it's 1.6mm across the middle 3/4 of the tread. That means that you can disregard 1/8 of the tread on each side and all of the remaining tread in the centre has to have minimum 1.6mm tread depth.

Of course the more tread the better but that's the legal minimum.

punisher5112 · 12-05-2014 9:49pm

Hi just a question is there anywhere in Wicklow that will fit tyres already have and how much?

Thread depth legality

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