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Tread depth on tyres


val douest
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On two occasions now I have had tyres which I thought were within the legal limit, ie not quite worn down to the little raised tell-tale in the tyre tread, declared as illegal. The first was when I took my car in to have it repaired after a rear-end shunt, and the "Expert" who inspected it condemned the rear tyres. Fortunately that had no effect on the insurance claim! The second was a friend's car, following a CT.

I obviously haven't kept up with this, but I guess the law on minimum tread depth has changed.  I can appreciate the difference between 1.6 mm and 3mm tread depth, particularly if you need to stop quickly in the wet. However, the tyres concerned were only about three years old, so the tyre manufacturers don't seem to have kept up.

Anyone else encountered this issue?

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Well, the age is immaterial for a kick off.  How many Ks had they done?

Often it's more about uneven wear - ie you can have enough tread by the markers and - due to poor balance - not enough elsewhere.  IMHO, you need to do regular checks (every three months or so) around various parts of each tyre with a tread guage (cheap as chips).  If they seem to be wearing unevenly then get the wheel balancing done at a local garage or tyre shop.[:)]

http://www.firsttyreplusmobile.co.uk/tyrebalancing.html

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I am sure Coops knows, but just so nobody goes to the garage and mentions the incorrect term...the correct phraseology for correcting uneven tyre wear is "wheel alignment...toe in (or out)...or tracking". Wheel balancing is placing balance weights on the rim of the wheel to correct shake at the steering wheel or vibration felt through the car.

Nowadays, all tyre shops balance wheels upon fitting new tyres as a matter of course. IMHO this is very often a means of generating a little more profit because the margins on tyres are small. Tyres these days (unlike years ago) are manufactured to a much better degree so are less likely to be "out of balance".

Before anybody says so. I agree that a badly out of balance tyre can cause wear on the tread, but if it were so out of balance to do so it would most probably be a fault that could not be rectified by balancing.

Phew! I feel better now.

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Well, thanks to you all for your help.

I don't think balancing or uneven wear comes into it in my case. The "Expert" who came to examine the car and verify the cost of repair condemned the rear tyres with just a cursory glance, so he would not have known if they were out of balance or unevenly worn. I do have a tread gauge, and confirm that the tread depth was above 1.6mm (just!).

I mentioned the age simply because I thought that three years ago tyre manufacturers might still have been putting their "tell tales" at 1.6 mm, whereas tyres of more recent manufacture might have the tell tale further out. These tyres had done about 25,000 Ks, and were originally on the front. I put them on the back and had the fronts replaced.

I take Weedon's point, since the local garage did not bother to balance the tyres when they replaced them, even though they have the facilities to do so. I have experienced no out of balance problems, either on the new or old tyres.

I guess I'll ask the CT man what the rules are nowadays. If I find out anything useful, I'll post again.

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Weedon. Whilst I'm sure tyre fitters are keen to maximise profits, I wouldn't enjoy driving a car without balanced tyres/wheels. The vibration through the steering can be awful, as I found out last year when the fitter overlooked balancing the new tyres (I had only gone about half a mile before I had to turn around to go back to get it sorted).
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The law on tread depth has not changed for many many years and stands at 1.6mm over 75% of the tyre width so maybe this is what caught you out. If the tyres have been run underinflated the it's quite likely that the outer edges will be worn more than the center and anybody accustomed to assessing tyres will be able to judge instantly whether they are legal or not. Also running on the front of a front wheel drive car will naturally tend to scrub the outer edges even when properly inflated.

I can't agree with Weedon on balancing I'm afraid. Even well known quality branded tyres can be significantly out of balance and I have not noticed any improvement nor deterioration it that over many many years. Also wheels themselves are not always perfect, in difficult cases removing a tyre completely and remounting it in a different position can make the difference between a successful balance and not. Some try to save a few pennies by only having the fronts balanced but that is a false economy as whilst you might not feel any imbalance it's still there working your rear suspension and shock absorbers to death. Not often but I've seen cars on the road where a badly out of balance rear wheel was bouncing that much that it was almost leaving the road yet the driver seemed totally unaware of what was going on !

I agree with SD that 1.6mm should be regarded as a legal limit not a safe one, I never run mine much below 3mm.

Finally, although it's understandable that most would fit a new pair of tyres to the front wheels, it is almost universally accepted that they should be fitted to the rear, particularly so on a front wheel drive car where the weight transfer under braking makes the back go very light with the resultant risk of skidding and loss of control. The best plan is to rotate your tyres so that they all wear at a similar rate then replace all 4 at the same time.

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[quote user="Weedon"]

I am sure Coops knows, but just so nobody goes to the garage and mentions the incorrect term...the correct phraseology for correcting uneven tyre wear is "wheel alignment...toe in (or out)...or tracking". Wheel balancing is placing balance weights on the rim of the wheel to correct shake at the steering wheel or vibration felt through the car.[/quote]

You would get some odd looks if you said that in my garage! For those of us who live in France I believe it's Alignement, Pincement (Ouverture) and Equilibrage.

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[quote user="AnOther"]

 Not often but I've seen cars on the road where a badly out of balance rear wheel was bouncing that much that it was almost leaving the road yet the driver seemed totally unaware of what was going on !

Finally, although it's understandable that most would fit a new pair of tyres to the front wheels, it is almost universally accepted that they should be fitted to the rear, particularly so on a front wheel drive car where the weight transfer under braking makes the back go very light with the resultant risk of skidding and loss of control. The best plan is to rotate your tyres so that they all wear at a similar rate then replace all 4 at the same time.

[/quote]

A bit of an exaggeration in your first sentence there ANO. I have never ever seen that, and I cannot believe that anybody would be driving a car where that is happening and not be aware of it.

As for the back end breaking away and skidding. You have to be driving pretty fast to make that happen I reckon.

I would never advise rotating the tyres so as to have them be replaced all at once, much better to do 2 at a time IMHO. As far as it being universally accepted that new tyres go on the rear, I don't think that is true at all.

I am shortly to need 2 tyres because the fronts have worn slightly badly on the inside edge. Ordinarily I would elect to have them fitted to the front but in this case I will have them fitted to the rear with the rears coming to the front, as I want to make sure that any out of alignment has been fixed properly. That is not because of any safety road holding issues, as I reckon I never drive so fast as to lose the back end (neither do I normally drive like a doddery old fool), but I am more conscious of how much things cost.

Having said all that I am quite happy to accept that because my experience is originally based on selling and fitting Dunlop D75s, Michelin Xs and Mohawk's, like everything else in life the way things are done now seem to supercede all that went before. Those were also the days when it was sometimes impossible to balance remoulds successfully and Chinese tyres sold very well because they were black and made of rubber.

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[quote user="Jay"][quote user="Weedon"]

I am sure Coops knows, but just so nobody goes to the garage and mentions the incorrect term...the correct phraseology for correcting uneven tyre wear is "wheel alignment...toe in (or out)...or tracking". Wheel balancing is placing balance weights on the rim of the wheel to correct shake at the steering wheel or vibration felt through the car.[/quote]

You would get some odd looks if you said that in my garage! For those of us who live in France I believe it's Alignement, Pincement (Ouverture) and Equilibrage.

[/quote]

I was assuming that most intelligent people would look up the appropriate wording in a dictionary before asking at a garage. It's what I do when I don't know, which is most of the time.

Incidentally, much better to ask for Parallelisme des roues, for those of us who live in France. 

I believe that a lot of French people would most probably understand what you were getting at if you said pedantic rather than pédant, as well.

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[quote user="Weedon"]

Incidentally, much better to ask for Parallelisme des roues, for those of us who live in France. 

I believe that a lot of French people would most probably understand what you were getting at if you said pedantic rather than pédant, as well.

[/quote]

Ohhhhhh, bitchy!

There seems little point in quoting English terms for complex phrases which a garage mechanic in France will not understand. Much better to give the English plus a translation. If you click on my translation it will take you to the site I used to find the specific terms.

I doubt "pedantic" would be understood by a French person.

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[quote user="Weedon"][quote user="AnOther"]

 Not often but I've seen cars on the road where a badly out of balance rear wheel was bouncing that much that it was almost leaving the road yet the driver seemed totally unaware of what was going on !

Finally, although it's understandable that most would fit a new pair of tyres to the front wheels, it is almost universally accepted that they should be fitted to the rear, particularly so on a front wheel drive car where the weight transfer under braking makes the back go very light with the resultant risk of skidding and loss of control. The best plan is to rotate your tyres so that they all wear at a similar rate then replace all 4 at the same time.

[/quote]

A bit of an exaggeration in your first sentence there ANO. I have never ever seen that, and I cannot believe that anybody would be driving a car where that is happening and not be aware of it.

As for the back end breaking away and skidding. You have to be driving pretty fast to make that happen I reckon.

I would never advise rotating the tyres so as to have them be replaced all at once, much better to do 2 at a time IMHO. As far as it being universally accepted that new tyres go on the rear, I don't think that is true at all.

I am shortly to need 2 tyres because the fronts have worn slightly badly on the inside edge. Ordinarily I would elect to have them fitted to the front but in this case I will have them fitted to the rear with the rears coming to the front, as I want to make sure that any out of alignment has been fixed properly. That is not because of any safety road holding issues, as I reckon I never drive so fast as to lose the back end (neither do I normally drive like a doddery old fool), but I am more conscious of how much things cost.

Having said all that I am quite happy to accept that because my experience is originally based on selling and fitting Dunlop D75s, Michelin Xs and Mohawk's, like everything else in life the way things are done now seem to supercede all that went before. Those were also the days when it was sometimes impossible to balance remoulds successfully and Chinese tyres sold very well because they were black and made of rubber.

[/quote]

If you’re replacing only two tires, be sure to have the new tires installed on your vehicle’s rear axle. Here’s why:

  • New tires will provide better wet grip than your half-worn tires.
  • When new tires are installed on the rear, it helps reduce

    the potential for your vehicle to fishtail or hydroplane in wet

    conditions.
Source = MICHELIN

Regular rotation helps extend the life of your tires, saving time and money in the long run. (same source)

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You can choose to believe me or not but I know what I've seen.

I don't understand how you can advise not rotating which will ensure that all 4 tyres always have roughly the same amount of tread, surely the ideal situation, and on what possible grounds can it be better to do only 2 at a time actively creating an imbalance between front and rear regardless of which axle you fit them to ?

As regards fitting to the front or rear (and I said almost universally accepted BTW as clearly there are detractors [;-)] ) I suggest you do some research for yourself but here are a couple of starters for you

http://www.michelinman.com/tire-care/tire-saving-tips/replacement-questions (watch the video at the bottom of the page and also note the relatively low 45mph speed)

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=52

http://en.allexperts.com/q/Tires-2359/2-New-tires.htm (note the authors credentials)

 

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I have seen the phenomenon that ANO describes several times, always on the rear wheels of FWD vehicles, donc lightly loaded, the wheel does not need to be out of balance by any significant amount but if the shock absorber is knackered once the vehicle speed reaches the natural frequency of the spring/mass system (wheel and suspension) then a forced vibration results like that which destroyed the Tacoma Narrows suspension bridge.

I have been amazed that the drivers seem unaware, only someone brain dead would fail to realise something grave was amiss, however it always seems to be the same vehicles that only the brain dead would buy or drive [6]

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