new tyres front or rear?

[Mr Cholmondeley-Warner]

I think it's probably due to our different environments. Astraist lives in a hot country with little rain, and the compound of the tyres sold there is probably much harder than ours. We need the soft compounds for grip in the cold and wet.

My figures may have seemed pessimistic to some, but I know my front tyres at least, on the last two cars I've had, last around 15k. Sometimes more, sometimes less. I have reasonably performant cars, and at times I drive them hard. The Skodas in particular were prone to losing grip at the front if pushed, which can only have had a detrimental effect on the tyres. I buy, on the whole, mid range tyres*, sometimes known for their accelerated wear rates, but I reckon I still achieve similar value for money as buying more expensive ones which might last longer but cost more in proportion.

On the Alfa, which I've had for 2 years and about 28000 miles I've seen off the original Pirellis which came with about 6mm, and used 2 or 3 mm each on a set of Hankook winter tyres and some Falken 912s. Still working out at about 15k... which, if you listen to fellow owners, is somewhat higher than average for the model.

* typically Falken, Toyo, Kumho

[Astraist]

It's not so much of a matter of tread compound or weather as it is a matter of milleage and driving profile, which I admit I should have mentioned. In many countries, Israel included, the 'driving profile' of most people is such where driving is done either in short urban trips, or longer trips down open, straight motorways.

This kind of driving style, along with a lower annual milleage for cars used in urban stints or small countries, leads to little wear in the tyre tread, and even less in modern steel-belted radials, which keep the tread flat better than their precedents, and therefore people fail to replace tyres before they reach the shelf life limit of six years or legal tread limit of 1.6 millimeters (elapsed into two millimeters).

In longer annual milleages and in a landscape involving more rural bendy roads, it is fairly possible that tyres will wear down at the tread before they degrade. So, let me revise my suggestion: Tyres should be replaced between two and a-half to four years of age, 32,000 to 49,000 miles, or three to four millimeters of tread depth - the earliest of the three.

[YorkshireJumbo]

Went to the local Costco for some tyres a while ago (they only do Michelins, but are very good value). They said they would refuse to fit new tyres on the front, and claimed they would rather lose a sale than break their rule. Mind you, I'll probably go there again in the spring when I'll need 4 new summer tyres.

They also made me sign to say that I realised that the wheelnuts might come loose and that I would check them later (can't remember whether it was miles or days) so that they wouldn't be liable if I didn't check them. I've never seen that anywhere else...

[jont]

They also made me sign to say that I realised that the wheelnuts might come loose and that I would check them later (can't remember whether it was miles or days) so that they wouldn't be liable if I didn't check them. I've never seen that anywhere else...

I've never had to sign for it, but most tyre depot reciepts I have I'm pretty sure they have in the background print to check the wheel nut torque after 30 miles or so. Mind you, as most of their monkeys don't seem to know how to do that in the first place, so I always check as soon as I get home (along with pressure once the tyres are cold)

[Mr Cholmondeley-Warner]

Hehe - last time I had some tyres fitted I asked the monkey what pressure he had put in them. I assumed he would have looked up the vehicle in his chart on the wall 6 ft away from him, but his reply was "32 - everything gets 32"

I asked him to put a different pressure in them and he was perfectly amenable, but if I hadn't, I'd have gone home with substantially under-inflated tyres. Good eh!

[jont]

Hehe - last time I had some tyres fitted I asked the monkey what pressure he had put in them. I assumed he would have looked up the vehicle in his chart on the wall 6 ft away from him, but his reply was "32 - everything gets 32"

I asked him to put a different pressure in them and he was perfectly amenable, but if I hadn't, I'd have gone home with substantially under-inflated tyres. Good eh!

I had a couple of interesting experiences in the Elise - where similarly they had inflated to 32, but the car is designed to run at 24(f)/26(r).

[Astraist]

Hehe - last time I had some tyres fitted I asked the monkey what pressure he had put in them. I assumed he would have looked up the vehicle in his chart on the wall 6 ft away from him.

Regardless of whether or not the details on the chart were accurate or not, it is important to rely ONLY on the manufacturer's recommendations as they appear in the car (on the A or B pillar, front door, glove compartment, etc...) or handbook. I have seen many charts in tyre shops and filling stations that were incomplete, inaccurate, not up to date or even with typo's - ranging from small differences to big mistakes like one that specified that a certain model's tyres should be inflated to 73 psig! (instead of 32)

I would also not trust the pump itself (especialy the analog models, but even the new digital ones) and use a small personal gauge to at least validate the accuracy of the pump and it's gauge on at least two of my tyres, each time. The pump is often not maintained as well as it should, gets knocked out of callibration and mainly - achieves lower accuracy due to a very large range of pressures it needs to support.

[tonyh1950]

Refering back to recommended tyre depth to replace, I was recently informed that on the continent, the legal limit his 4mm and that is why there appear to be part worn tyres available here for sale, mostly at 4mm.
Rospa recommend no less than 3mm and although grip is importent, the reduction in braking ability as the tread gets less is significant and there are graphs to prove it so it is not just a cunning ploy by tyre manufacturers tomake you by tyres more often.
I understand that bridgestone made a video that shows this . Has anyone seen it and how can I find it

[Gareth]

Refering back to recommended tyre depth to replace, I was recently informed that on the continent, the legal limit his 4mm

Are you sure that's not the suggested limit for winter tyres? I've seen many recommendations to the effect that they are less effective below 4 mm.

[apple tango]

Regarding tyre depths I found this article this morning:



Taken from the ROSPA site:

In 2003, the British Rubber Manufacturers Association (BRMA) commissioned MIRA to study the effects of tread depth on stopping distances. The study was carried out on MIRA's test track in Nuneaton, and 5 different tread depths were tested - 6.7mm, 4.1mm, 2.6mm, 1.6mm (the legal minimum) and 0.9mm.
...
The stopping distance from 80kmph [~50mph] was recorded at each of these tread depths and the points plotted on a graph of stopping distance versus tread depth.
...
From the graph of results, it can be seen that the stopping distances in the wet start to increase dramatically at tread depths of below 3mm.

[Gareth]

It struck me the graph doesn't provide enough information to make an informed choice ... for instance, in the same conditions how would a premium tyre compare with a budget brand, (could you say that a premium brand at 1.6 mm is as effective as a budget brand at 3+ mm?), or how a premium brand from 10 years ago would compare.

Thing is, the amount of grip available appears to vary moment by moment as we are driving, because of changing road surface and different weather conditions, and somehow we mostly manage OK. I tend to think that, as drivers, we generally have an awareness about roughly how far it'll take to stop in the conditions we encounter, and adjust our driving accordingly. Yes, there'll be slight surprises, but provided we've left sufficient margin then those surprises just become data points that we use to adjust our driving.

[jcochrane]

I think you may have a point regarding tyre type/manufacturer, Gareth. In the Formula Ford racing championship regulations the competitors were only allowed to use a particular Dunlop tyre. It was claimed, by Dunlop, that a tread depth of 1mm was still good and was thus written into the regulation as the minimum tread depth. This is in opposition for most other racing championships regs. which allow minimum tread depth down to 1.6mm.

[Astraist]

That is my point as well. The tyre's abilities depend on more than the tread depth. It's also a matter of the tread pattern as a whole (directional tyres, for instance, are more ressistant to aquaplaning than most none-directional tyres), width of the tread voids and the shape of their sidewalls, application of sipes, use of different rubber compound with different textures and working temperatures, the age and milleage on the rubber, causing it to degrade, etc.

The state of the surface also has a big impact, depending on the type of tarmac at use (abrasive tarmac has higher skid ressistance than tarmac that appears "shiny" and slippery, or concrete), the depth of the water film, the temperature and the presence of slippery agents like leaves, mud, oil, tar, etc...

In the weather conditions in countries such as the UK - I would replace tyres once they reach a depth of four millimeters, again, if the age or milleage limit are not exceeded even earlier and if no damage appears on the tyre itself.

[stefan einz]

That is my point as well. The tyre's abilities depend on more than the tread depth. It's also a matter of the tread pattern as a whole (directional tyres, for instance, are more ressistant to aquaplaning than most none-directional tyres), width of the tread voids and the shape of their sidewalls, application of sipes, use of different rubber compound with different textures and working temperatures, the age and milleage on the rubber, causing it to degrade, etc.

The state of the surface also has a big impact, depending on the type of tarmac at use (abrasive tarmac has higher skid ressistance than tarmac that appears "shiny" and slippery, or concrete), the depth of the water film, the temperature and the presence of slippery agents like leaves, mud, oil, tar, etc...

In the weather conditions in countries such as the UK - I would replace tyres once they reach a depth of four millimeters, again, if the age or milleage limit are not exceeded even earlier and if no damage appears on the tyre itself.

That would be a challenge for me, given that the tyres on my GT3 come with around 4.5mm when new!

Seriously though, the data from the TRL tests was fairly clear - significant wet weather performance deterioration does not occur until 3mm or below; I think changing at 4mm is rather over prudent.

I do agree that tyre age is important. I have a 4 year rule, which I need to apply since in some of my cars I do insufficient mileage in that period to wear the tyres out. I recently acquired a 2004 NSX which was on its original Dunlop tyres. The tread depth is over 5mm, but the tyres feel lacking in grip and flexibility. I shall be changing them.

Perhaps the most important point not mentioned is to be aware of the state of one's tyres at all times. At lower tread depths, be more cautious in heavy rain where there may be standing water. I also think it is wise to use, as Astaist says, a really high quality pressure gauge to ensure correct inflation. Finally, be sure that the car's tracking (preferably the via a full 4-wheel alignment) is checked annually to avoid premature wear or even dangerous levels of wear due to excess camber, toe etc.

Cheers

[Astraist]

That would be a challenge for me, given that the tyres on my GT3 come with around 4.5mm when new!

That's different. Unlike perfomance tyres, road tyres come with 8 to 8.5 millimeters of tread depth. So we see eye to eye. Four years are a good maximum age limit (including storage time), but some tyres age within three and a-half, three or even two and a-half years. They will probably last a bit longer in the UK than under the mediterranean, where most tyres dry out after three years.

I also agree that awareness to the state of the tyres is important, so I have the habit of checking the tyres visually (by a brief walk around the car) each time I enter the car. The alignment is something I check each year, or after 6,000 miles, when I get the tyres removed, inspected all around and rotated.