new tyres front or rear?

[jamei]

I'm very lucky in that my current FWD car wears its front and rear tyres at the same rate.

I wonder what properties of the car affect the differential in wear rate between front and rear.

[Astraist]

It's a matter of weight distribution, suspension geometry and wheel alignment, as well as engine torque and how much of it the driver uses. If your car has a relatively even weight distribution, and you foot on the throttle is light, the wear should be relativelly even. Smooth steering is just as important.

Nevertheless it's important to perform periodic rotations, and to replace the tyres at about the time spawn I mentioned. The weather in the UK is not as hard on the tyre rubber, but nevertheless, it's amazing how far rubber degrades and grip drops within three to four years of age, or 30 to 42 thousand miles. Beyond that upper limit, I would replace the tyre regardless of it's tread depth or appearance.

[fungus]

IIRC, the critical speed at which a vehicle fitted with good tyres, (ie. 7-8mm tread depth) will aquaplane is 54mph. Tyres that are less than 3mm will aquaplane at speeds considerably lower than that. A tyre that is at the UK legal limit of 1.6mm is probably running at 10 per cent effiency in the wet.

I personally change my tyres when the tread is 3mm, and always make sure that the least worn are on the rear.

[Gareth]

A tyre that is at the UK legal limit of 1.6mm is probably running at 10 per cent effiency in the wet.

I would like to know what you mean by this as, to my ears, the statement has no practical meaning that I can apply to how things feel when I am driving.

[fungus]

A tyre that is at the UK legal limit of 1.6mm is probably running at 10 per cent effiency in the wet.

I would like to know what you mean by this as, to my ears, the statement has no practical meaning that I can apply to how things feel when I am driving.

I remember about three or four years ago on one of the motoring programmes, I can't remember which one now, but they were testing the efficiency of tyres with differing tread depths, and it was mentioned that tyres on the legal limit had only 10 per cent of the efficiency of tyres that were virtually new in wet conditions.

[dth]

Information I have obtained from current forensic crash investigators is this:

Tyres have lost 30-40% of their efficiency when down to 1.6mm (measured by the ability to disperse water).

Tyres should be changed at 3mm which is the point at which efficiency starts to drop off rapidly as above.

New tyres should be put on the rear axle regardless of the driving wheels for reasons of stability during skids (unless vehicle manufacturer guidance says otherwise)

I'm happy to go with the advice given to me by those who deal with the aftermath of those who got it wrong and who have exceptionally high levels of knowledge and qualification in order to do what they do.

[fungus]

Information I have obtained from current forensic crash investigators is this:

Tyres have lost 30-40% of their efficiency when down to 1.6mm (measured by the ability to disperse water).

Tyres should be changed at 3mm which is the point at which efficiency starts to drop off rapidly as above.

New tyres should be put on the rear axle regardless of the driving wheels for reasons of stability during skids (unless vehicle manufacturer guidance says otherwise)

I'm happy to go with the advice given to me by those who deal with the aftermath of those who got it wrong and who have exceptionally high levels of knowledge and qualification in order to do what they do.

May be they were using shock tactics to encourage drivers to change their tyres more frequently.

I would have thought that a tyre that was at 1.6mm would have lost considerably more than 30-40% efficiency in the wet though.

[dth]

May be they were using shock tactics to encourage drivers to change their tyres more frequently.

Just a private conversation. Nothing to do with shock tactics at all.

I would have thought that a tyre that was at 1.6mm would have lost considerably more than 30-40% efficiency in the wet though.

Maybe you would but as I said, I'm happy to accept their expert and exceptionally well-informed advice.

[TripleS]

A tyre that is at the UK legal limit of 1.6mm is probably running at 10 per cent effiency in the wet.

I would like to know what you mean by this as, to my ears, the statement has no practical meaning that I can apply to how things feel when I am driving.

No, I don't buy some of this stuff either. It's all very well reproducing what the tyre companies say, but they are hardly unbiased are they? Of course it would suit them better if we were to discard tyres at a tread depth of 3 mm or so, rather than 1.6 mm!!

....and I still maintain that roads are not just wet or dry. There are all sorts of variations of "wet", so I shall continue to go by what feels appropriate to me, based on experience, indeed quite a lot of experience in a very wide range of conditions. So there, Astraist & Co.

Best wishes all,
Dave.

[Mr Cholmondeley-Warner]

Modern steel-belted radials wear little at the tread. Rather, they become unworthy of use in terms of grip and handling, merely due to the chemical changes that the rubber experiences over time, usually after merely three years of age or 35,000 miles.

I don't know what kind of tyres you're buying, but I can assure you modern steel-belted tyres do wear at the tread and that's the main reason they need replacing on modern cars used in daily driving in the UK. 15,000 miles would be a pretty good life for most tyres other than those made of extremely hard compounds, and many owners will be uncomfortably familiar with much more frequent tyre changes in this country. A performance car such as Waremark's probably does very well if it achieves 10,000 miles from its driven tyres - Mark?

[Gareth]

I'm sure it depends as much on the person and their style of driving - the last car for which i have figures was quite consistent in that front tyres would last about 22,000 miles and rears about 24,000 - fwd Alfa 146, 2.0 litres.

This makes me think that someone who doesn't demand so much from their tyres may easily get significantly more out of them.

In the UK a reasonable number of people talk about tyres having a life of about 6 years, but the majority of people who are little interested in cars or driving probably never think to check, and therefore could end up using tyres that are significantly older.

[waremark]

A performance car such as Waremark's probably does very well if it achieves 10,000 miles from its driven tyres - Mark?

Spot on: I replaced the fifth set of rears at 49,000. Each set of fronts has lasted 18,000; not bad for high performance tyres on a high performance car, which has attended a handful of track events. As mentioned front and back are of different sizes. There have been times when the fronts had more tread depth than the rears, but I really don't believe that the car was or would have been significantly unstable.

When I last changed the front tyres on another car which has the same size all round, I put the new ones on the back and the part worn ones on the front. I must say I did not consider their age, which Astra would think meant they should be replaced. They have been doing very well in the snow this week.

The tyres on my glider trailer are 8 or 9 years old - they have travelled very few miles. I look at them carefully for signs of cracking - should there be any visible evidence of a need to replace them as a result of age?

[TripleS]

I'm sure it depends as much on the person and their style of driving - the last car for which i have figures was quite consistent in that front tyres would last about 22,000 miles and rears about 24,000 - fwd Alfa 146, 2.0 litres.

This makes me think that someone who doesn't demand so much from their tyres may easily get significantly more out of them.

You're quite right on all of that, I'd say.

My first car, an Austin-Healey Sprite Mark 1, was fitted with Dunlop 'Gold Seal' tyres as original equipment, and the life of those didn't seem particularly good. At that time Michelin X tyres were being talked about favourably because of their longer life and lower rolling resistance, though the use of radial ply tyres had not yet become popular; this was about 1961.

Anyhow, I had a pair of the Michelin X tyres fitted on the rear of the Sprite, and they lasted 86,000 miles, which was far in excess of my expectations. I attributed this to a combination of a small lightweight car (front engine, rear wheel drive) generally smooth and sympathetic driving, and of course the good wear characteristics of the tyres themselves. In those days I hadn't heard about the merits of 'balancing' the car when cornering, and I still don't really understand that aspect. Even so, it would apopear that what I was doing couldn't have been too bad from a handling point of view.

Incidentally, I don't think my cornering was particularly slow, but it was done with a fair degree of smoothness and mechanical sympathy in mind, so that probably accounts for the surprisingly long tyre life.

Best wishes all,
Dave.

[Kevin]

IIRC, the critical speed at which a vehicle fitted with good tyres, (ie. 7-8mm tread depth) will aquaplane is 54mph. Tyres that are less than 3mm will aquaplane at speeds considerably lower than that. A tyre that is at the UK legal limit of 1.6mm is probably running at 10 per cent effiency in the wet.

I think there are too many variables to say at exactly what speed a tyre will aquaplane. NASA did quite a lot of research on the subject, the results of which can be found on tinternet, for anyone who's interested to the point of obsession.

[jamei]

Modern steel-belted radials wear little at the tread. Rather, they become unworthy of use in terms of grip and handling, merely due to the chemical changes that the rubber experiences over time, usually after merely three years of age or 35,000 miles.

I don't know what kind of tyres you're buying, but I can assure you modern steel-belted tyres do wear at the tread and that's the main reason they need replacing on modern cars used in daily driving in the UK. 15,000 miles would be a pretty good life for most tyres other than those made of extremely hard compounds, and many owners will be uncomfortably familiar with much more frequent tyre changes in this country. A performance car such as Waremark's probably does very well if it achieves 10,000 miles from its driven tyres - Mark?

This is in Europe of course. In the US they prefer lower-grip squealing tires that are guaranteed to run 40K miles or more.