MOT advisories: Tyre worn close to legal limit

qsk

I recently got an MOT advisory: "Tyre worn close to legal limit". When I asked what's my thread depth, they said 3 to 4mm. As a new tyre is only about 7 and legal limit is 1.6, I thought my tyres still have quite some life in it. Am I wrong or are they trying to sell me some new tyres? 

Carrot007

3 sounds reasonable for a warning to me. 4 not so much. But if they mean differes beetween 3 and 4 then again sounds reasonable.

Though personally at around 3 I would have already changed the tyres anyway! Especially at this time of the year.

Where did you go? Trusted garage or some palce no sane person would go? Answering that will give you the answer to ar they wanting to sell tyres!

dipsomaniac

They always want up sell.  Just keep an eye on the tyre(s) and change when you are uncomfortable with the tread depth

neilmcl

As above, nothing untoward with the MOT garage, 3mm is usually the point at when an advisory is issued. Although 1.6mm is the legal limit it is advised to change them between 2-3mm.

daveyjp

OP will be the one when it snows screaming the nuts of their car trying to get anywhere.

If it were the start of spring 3mm is OK.  As we are the start of winter its an ideal time to get them changed.  Chances are they are 3mm in the centre, but lower on the shoulders.

4-5mm of extra tread makes huge difference in slippy conditions.

Herzlos

It's also worth noting that tyres wear faster the lower the tread gets, so you'll chew through 3mm to 1.6mm much faster than 7mm to 5.6mm.
As the advisory says, keep an eye on them with a view to replacing in the next year.

lesalanos

Tyres are made to perform at a safe standard down to the minimum legal tread depth.

Due to the reduced movement of the tread blocks tyres run more efficiently when lower in tread.   Replacing tyres early is a financial and environmental cost.  

DiddyDavies

lesalanos said:

Tyres are made to perform at a safe standard down to the minimum legal tread depth.

Due to the reduced movement of the tread blocks tyres run more efficiently when lower in tread.   Replacing tyres early is a financial and environmental cost.  

Define "safe standard"? 
Once tyre tread gets to about 4mm, there is a marked decline in their ability to grip the road which is why stopping distances increase dramatically from this point:
Tyre Tread Depth and Stopping Distances (rospa.com)

That graph was produced by MIRA, (an independent company with no affiliation to any tyre manufacturers).
I know that the speed of the test vehicle isn't shown but whatever speed it was, the stopping distance is increased a fair bit long before the 1.6mm minimum tread limit is reached.

As to the environmental cost of replacing tyres.
Once a tyre has been manufactured, there is a set amount of rubber that will need to be disposed of at some point and whether it's when the tread has reached 1.6mm or 4mm, that figure will be the same.
The only difference between a tyre at 1.6mm and one at 4mm is that on the 1st one,  2.4mm of rubber has already been removed through driving but that worn away rubber is still in the environment somewhere. It hasn't simply disappeared.

Mickey666

Seems a sensible advisory to me because the tyre is unlikely to last another year and many (most?) people don’t regularly check tyre wear.  What the OP does with the advice is up to them.

Tiexen

Michelin says: “ Modern tyre technology makes it possible to provide high levels of performance and grip from new, and through all of the tyre’s life down to the legal tread wear limit.

“With this in mind, changing tyres early (i.e. before they are fully worn) does not guarantee greater safety, and no current studies have established a direct link between accident levels and tyre tread depth. Suggesting that tyres need to be changed early (before the legal limit / tread wear indicator is reached) is akin to enforcing a form of planned obsolescence.

“Changing tyres too early would result in 128 million additional tyres being used a year in Europe - which would cause nine million tons of additional CO2 emissions every year. In addition to the environmental impact, replacing tyres before they are fully worn also represents a significant and unjustified increase in costs for consumers

As tyre tread depth reduces, the fuel economy of the vehicle will improve, and with one tank of fuel in five being used to simply overcome the rolling resistance of the vehicles tyres, this is a welcome benefit. The rolling resistance of a tyre at the point of removal at the legal tread limit is 80 per cent of that tyre in a new state. Therefore, keeping a tyre on the vehicle until the legal tread wear limit increases the time when it is in its most fuel efficient state, and reduces the motorist’s fuel bill.

on wet roads, some worn tyres can perform as well as some new tyres, and that although the remaining tread depth is a factor in wet braking, the performance of the tyre, at all stages of its life, is more important.

It adds: “Whilst all tyres legally sold in Europe meet this minimum standard when new, Michelin tests have shown that the wet braking capabilities of some tyres reduce quickly when worn, and may fall below this ‘minimum standard’ requirement. However, some premium products not only meet the criteria when new, they do so when worn to the legal tread wear limit.

jimbo6977

Please also buy 2 tyres - left and right. Much safer.