Car tyres, interesting article.

[HF2300]

[QUOTE 4678184, member: 9609"]generally 8 ton per axle on fully freighted lorries but an unloaded flat bed triaxle would not be much more than a ton an axle.[/QUOTE]

Typical car probably 0.8 to 1.2 tonnes so 0.2 - 0.3 tonnes per wheel. Range Rover 2 - 2.5 tonnes so around 0.5 - 0.6 tonnes per wheel. Tri-axle flat trailer probably 6 - 8 tonnes unladen so 1 - 1.4 tonnes per wheel.

Ground pressure is related to contact patch size and inflation pressure as well, though. Not sure what the contact patch sizes are but I'd guess a modern Range Rover has a contact patch larger than a single or twin truck wheel (and a different shape) but not as large as a supersingle.

The car tyre regulations haven't always been that way. Having said all this, my recollection is that the car tread depth went up from 1 to 1.6 mm due to harmonisation with EU regulations specific to car tyres. Where you have to have the minimum, and what the rest of the tread can be like, has changed over the years as well.

There was a bit of a spat about this last year as several tyre manufacturers wanted EU laws to change to a 3 mm or even 4 mm tread depth. They claimed this was for safety though I can't help feeling their motivation might have been the increase in sales.

Michelin held out, saying that they saw no link between tread depth and braking performance and that modern premium tyres were designed to ensure maximum effectiveness down to 1.6 mm. They also said they saw no relationship between tread depth and increased accident rate. Interestingly though they also said that in recent years tyres have entered the market that are specifically designed to do well in tests rather than real world conditions, and that these can lose up to 30% of their effectiveness as they wear.

This from a Tyresafe survey on illegal tyres last year:

Illegal tyres by city

Bristol 46.20%
Birmingham 42.00%
Manchester 35.40%
Cardiff 31.80%
Cambridge 29.50%
Liverpool 26.00%
Leeds 24.40%
Newcastle-upon- Tyne 21.40%
Edinburgh 20.60%
Greater London 13.80%

Region Share of illegal tyres

Northern Ireland 36.50%
North West England 31.20%
South West England 29.80%
Wales 29.10%
Scotland 27.40%
South East England 27.30%
Midlands 26.90%
England (total) 26.80%
North East England 25.80%
East England 14.40%
Greater London 13.80%

 

[Lancsman]

[QUOTE 4678184, member: 9609"]I thought the 1mm depth was just for vehicles above 7.5 GVW, did not know it extended to cover mini-buses - completely barking[/QUOTE]

Just to confirm my previous comment,because I was beginning to question myself, "1.0mm minimum tread depth applies to:• a passenger-carrying vehicle with more than 8 passenger seats excluding the driver’s seat• a vehicle first used before 3 January 1933." That is taken from the testers manual. It applies to class 3,4, 5 and 7 vehicles

 

[HF2300]

[QUOTE 4678522, member: 9609"]A proportion of the weight goes through the pin (sits on the tractor/unit) a skelly type logging trailer with short rear overhang may sit on the scales at 1200-1500 per axle (huge variances though from trailer types and overhangs)

so 675kg per wheel ~385/65 super single = 1.75kg per mm tyre width
RR + passengers = 2630kg
so 657kg per wheel ~ 265/50R19 = 2.48kg per mm of rubber = 42% more
(not sure if footprint and width are directly proportional with width though)[/QUOTE]

As the area of an ellipse is proportional to its radius you'd expect the width to relate to the contact patch size though there are other factors.

I suspect this is all getting a bit off topic and angels dancing on the head of a pin though; for example, you could make the Range Rover look bad by picking an empty short overhang skeletal and a loaded late model Range Rover, or make the Range Rover look better by picking a long overhang low loader trailer, hiab stepframe (or reefer!).

If anything, probably demonstrates why it's unlikely the law was based on ground pressure calculations and more likely it was something like EU harmonisation or average accident rates (or industry lobbying).

From experience with old low mileage vehicles you can get multiple tyre issues. The rubber compound can deteriorate with age making it less compliant and reducing grip. At extremes the rubber starts to decay. Exposed sidewalls can weather and perish causing cracks and splitting which itself exposes the tyre carcase to damage or perishing. Tyres that sit for extended periods can go permanently out of round. The older a tyre is the more it's been exposed to damage, and the damage can increase aging effects; and so on.

 

[Drago]

The vehicles with the highest ground pressure are also those with the greatest mass, and therefore the biggest levels of intertia - all the more important to keep the tyres tip top.

 

[Deleted member 26715]

How many folk used to buy remoulds?

All the F1 & BTCC teams

 

[Deleted member 26715]

[QUOTE 4676534, member: 9609"]A newer tyre will have a slightly bigger diameter so your apparent mpg will go down, you always need to calibrate your milometer with known a known journey distance.

lets take a tyre size of 185/50R17 ie radius should be about 308.4 mm when worn out radius 301.4 therefor mileometer would be 2.3% out therefor new to old mpg could go from 48mpg to 49.1mpg.

also since there can be a bit of a differance (up to 5% I think) between different batches your lower mpg could well just be down to inaccuracies in your mileometer due to different tyres having different diameters.[/QUOTE]
Unfortunately you haven't taken the car weight & therefore tyre deformation into account

 

[Deleted member 26715]

From my experience of 40 years in the motor trade town driving does kill tyres. We maintain lots of local private hire vehicles and they go through front tyres at a very high rate. It is the constant full lock turns they go through.Toe out on turns can cause massive slip angles on outer tyres. Yes they are high mileage vehicles but they go through more tyres than similar mileage vehicles used on motorways etc.

Normally driven by people who don't give a monkeys about the vehicle they are in, hard acceleration, hard braking, get the person there, get them out of the car & get back to the rank.

Also from my experience tracking doesn't go out. Suspension joints and bushes wear components get damaged, but tracking very rarely goes out there is usually an underlying reason .

Hitting kerbs, bouncing up & down kerbs tend to be the main reasons

 

[Levo-Lon]

When I had my Fusion it came with a new MoT. Unbeknownst to me Arfur Daley at the second-hand dealers had replaced a failed tyre with a part-worn. Come the next MoT, I was told that one of the tyres, while legal, was older than the car! I then and there told him to replace the worst two tyres - all my budget could spare as it also needed an exhaust, and I generally replace tyres in axle pairs. All the tyres on the Clio are new this year, replaced prematurely due to sidewall damage on one and a puncture on another. It's got Landsail all round. Although they're a cheaper brand, they were recommended by the chap my dad knows at the tyre fitters.

unfortunately that's the rub with dodgy Daves car sales....
I bought a cbr 1100xx super blackbird with a new 12mth mot from wheels motorcycles. Peterborough areas biggest and a main dealers. . 170 odd mph motorcycle "fastest bike on the planet at the launch"
It had so many unchecked faults I was lucky to get it home..rear chain adjuster siezed and the chain was almost dragging the floor..lethal. .just shoddy crap dealers after your money

 

[Tanis8472]

unfortunately that's the rub with dodgy Daves car sales....
I bought a cbr 1100xx super blackbird with a new 12mth mot from wheels motorcycles. Peterborough areas biggest and a main dealers. . 170 odd mph motorcycle "fastest bike on the planet at the launch"
It had so many unchecked faults I was lucky to get it home..rear chain adjuster siezed and the chain was almost dragging the floor..lethal. .just shoddy crap dealers after your money

That used to be Taz didnt it?

 

[Levo-Lon]

That used to be Taz didnt it?

yes and it was Taz i bought it from

 

[oldfatfool]

You would have had to do those sort of trips just to get to the 70mph bit. Far more about size, quality etc.

Not really. To put it in even more perspective, my octy estate that does mostly loaded trips of 50 miles + on generally free flowing A roads is about to have 2 new fronts at 25k miles the rears are still fine, post office vans which I used to drive regularly about 5 - 15 miles a day and you would be lucky to get 4k miles out of a set.
Alterntively took a car abroad on new rubber and upon returning home after 3k miles that needed new fronts, but had been on the autobahns, nurburgring and round the alps.

All of these have been on premium tyres.

 

[Levo-Lon]

Premium doesn't mean big miles though..it may be a long life or a wtf wheres the tread gone super grippy job.
front wheel drive usually eats tyres..rear wheel drive last longer as long as you dont do a Top Gear on them.
new car tyres seem to last longer for some reason..if you replace with the same they never last as long as the OE fittment

 

[PaulB]

I think the most interesting fact about tyres is the name of the company who makes more tyres than anyone else. Anyone know the answer to that? It's not a joke, it's genuine and quite amazing to discover who this actually is.

I'll park that here for a while and see if anyone can come up with the answer. NO GOOGLING!

 

[wheresthetorch]

I think the most interesting fact about tyres is the name of the company who makes more tyres than anyone else. Anyone know the answer to that? It's not a joke, it's genuine and quite amazing to discover who this actually is.

I'll park that here for a while and see if anyone can come up with the answer. NO GOOGLING!

Lego!

 

[Levo-Lon]

Lego!

yeh but their cars are so friggin plasticky