Punctures with 21” wheels?

[Nuclear Nick]

I think we've been here before and I still disagree that the wider tyres increase the risk of aquaplaning. The extra area of the contact patch with the tarmac will reduce the risk of aquaplaning. On a slick tyre I'd agree, but on a treaded tyre the risk is lower.

I’ll have one more go at this, not for you jaffacake because I know you won’t change your mind, but I don’t want others to to be misinformed on a safety issue like this. It is a well known and long established fact that wider tyres increase the risk of aqua planing. The physics is primary school level. The greater the area of the contact patch of the tyre the less pressure per square millimetre exerted by the water film is required to lift the car.

The article you quote sadly has a misprint and is incorrect. Just search a wider selection of articles.

[bennachie]

As above................................

other inconsistences include 'high pressures' in F1 tyres; which nominally run at a minimum pressure of 23 psi rear and most teams will do anything to keep to that figure (or referably less)

[Toddie]

My 10p worth, I have 21” Pirelli P Zero summer tyres and 18” Pirelli Scorpion winter tyres and I can assure you that the 18” do not
Aqua plane but the 21” most certainly do. Both sets of tyres are nearly new and have 6mm plus tread depth.

No big surprise that a tyre specifically designed to prevent aquaplaning is not aquaplaning as much. I sincerely doubt this has much to do with the sizes but more to do with their ability to clear water.

The P-Zero is very much a summer tyre. It's hard rubber, difficult to warm up in winter and not brilliant in standing water. I doubt an 18" P-Zero would be much better. I can't wait to get rid of mine in the next month or so.

So I understand that you obviously have an intense dislike for Pirelli tyres, that is your prerogative and also your problem.

Having raced 210 National & 250 international Karts in my younger days, I very quickly discovered the reason that the wet weather tyres were so much narrower, it was so that they bit through the water, rather than float across it. Exactly the same principle is used through out the world on winter/snow tyres, it is so that the tyres cut through the water/snow/slush, yes the compound may be softer, and yes the tyres might have more sipes to help but the fundamental principle is still the same.

Also if Pirelli P-Zero is such a hard rubber, then how come that they wear much quicker that Michelin? or are you saying that Michelin are even harder?

[bigbaldybloke]

Got a GTS on order with its standard 20 inch wheels, current petrol S has 19” wheels with all season tyres. I live in deepest Lincolnshire where the roads are rough and pot holed badly and have had no problems. On previous Merc with big wheels and 30 profile tyres I got a puncture on day three of ownership and after about a year need a complete new front wheel plus a pair of tyres after hitting a pothole, so best part of £1000. Talking to the drivers at the PEC at silverstone they pointed me to the 19” and all season tyres for best all round road use, as who in their right mind would do a track day in an SUV was their thinking. I think they were about right, but will see how the 20’s fair on the GTS.

[SAC1]

I had 19" Michelin O.E. on my SD and ran it on no.2 one light PASM setting and were excellent in similar rural road conditions. I now have the standard 20" Goodyear O.E. on my GTS. This set up on the GTS, with its lower ride height, does produce a firmer ride. My fix is PASM on the no.1 no lights setting. After 7 months no issues with this set of 40 / 45 series tyres.

[jaffacake]

I’ll have one more go at this, not for you jaffacake because I know you won’t change your mind, but I don’t want others to to be misinformed on a safety issue like this. It is a well known and long established fact that wider tyres increase the risk of aqua planing. The physics is primary school level. The greater the area of the contact patch of the tyre the less pressure per square millimetre exerted by the water film is required to lift the car.

The article you quote sadly has a misprint and is incorrect. Just search a wider selection of articles.

Happy to review anything you care to link me to, I simply can't find anything that claims narrower tyres are better than wider tyres on standard road cars - the only claims relate to lightweight track cars which clearly need all the help they can get in standing water.

The Macan is over 2 tonnes, the pressure per square millimetre is significant even with the 295 wide tyres.

Like I say, happy to read anything that confirms otherwise. I've browsed numerous articles and none of them claim wider is worse - quite the opposite on some.

[jaffacake]

As above................................

other inconsistences include 'high pressures' in F1 tyres; which nominally run at a minimum pressure of 23 psi rear and most teams will do anything to keep to that figure (or referably less)

Yes, and 27psi at the front...where it's needed more.

[jaffacake]

So I understand that you obviously have an intense dislike for Pirelli tyres, that is your prerogative and also your problem.

They're actually really capable tyres, when warm, they just take far too much warming up and this doesn't work well for a day to day road car. It has similar characteristics to a Michelin Pilot Super Sport - great on a warm dry day with a longer journey, but not particularly good for a cold run around. They're not particularly bad in standing water though, with regards aquaplaning, just hard to keep warm.

Having raced 210 National & 250 international Karts in my younger days, I very quickly discovered the reason that the wet weather tyres were so much narrower, it was so that they bit through the water, rather than float across it. Exactly the same principle is used through out the world on winter/snow tyres, it is so that the tyres cut through the water/snow/slush, yes the compound may be softer, and yes the tyres might have more sipes to help but the fundamental principle is still the same.

I fully acknowledged above the need for this on lightweight track cars, no doubt at all. Likewise for snow. For a 2 tonne SUV, no.

Also if Pirelli P-Zero is such a hard rubber, then how come that they wear much quicker that Michelin? or are you saying that Michelin are even harder?

Michelin have always have the best wear characteristics, it's why they can charge the prices they do.

With the Pirelli I find them very hard at legal public road temperatures. They need to go quickly to get to decent, sticky, operating temperatures. Until they do, you get more wheel spin and more wear as a result. I've got a car with a top speed of 169mph and need tyres to match that. Even half that speed is still illegal, which means you need a very wide operating range for temperature. I find the P-Zero hard to get warm and in the wet they are hard to keep warm. i thought I was aquaplaning a lot when I first got the car, why I did some research, but since discovered they were just cold. When they are hot they are more than capable in lots of standing water, it's just my wife will never get them that warm and I'd prefer her to have a car with a tyre that gets sticky with more relaxed driving styles.

Porsche fit winter tyres with a limited top speed which obviously means the operating temperatures suit the conditions better. They don't N rate a 21" tyre though, so I need the best for all year usage. P-Zero certainly isn't it.

[bennachie]

OR a set of 19 inch winters....................

[Toddie]

So I understand that you obviously have an intense dislike for Pirelli tyres, that is your prerogative and also your problem.

They're actually really capable tyres, when warm, they just take far too much warming up and this doesn't work well for a day to day road car. It has similar characteristics to a Michelin Pilot Super Sport - great on a warm dry day with a longer journey, but not particularly good for a cold run around. They're not particularly bad in standing water though, with regards aquaplaning, just hard to keep warm.

Having raced 210 National & 250 international Karts in my younger days, I very quickly discovered the reason that the wet weather tyres were so much narrower, it was so that they bit through the water, rather than float across it. Exactly the same principle is used through out the world on winter/snow tyres, it is so that the tyres cut through the water/snow/slush, yes the compound may be softer, and yes the tyres might have more sipes to help but the fundamental principle is still the same.

I fully acknowledged above the need for this on lightweight track cars, no doubt at all. Likewise for snow. For a 2 tonne SUV, no.

Also if Pirelli P-Zero is such a hard rubber, then how come that they wear much quicker that Michelin? or are you saying that Michelin are even harder?

Michelin have always have the best wear characteristics, it's why they can charge the prices they do.

With the Pirelli I find them very hard at legal public road temperatures. They need to go quickly to get to decent, sticky, operating temperatures. Until they do, you get more wheel spin and more wear as a result. I've got a car with a top speed of 169mph and need tyres to match that. Even half that speed is still illegal, which means you need a very wide operating range for temperature. I find the P-Zero hard to get warm and in the wet they are hard to keep warm. i thought I was aquaplaning a lot when I first got the car, why I did some research, but since discovered they were just cold. When they are hot they are more than capable in lots of standing water, it's just my wife will never get them that warm and I'd prefer her to have a car with a tyre that gets sticky with more relaxed driving styles.

Porsche fit winter tyres with a limited top speed which obviously means the operating temperatures suit the conditions better. They don't N rate a 21" tyre though, so I need the best for all year usage. P-Zero certainly isn't it.

Maybe there is a good reason Porsche don't N rate a 21" Tyre? perhaps they don't work too well because they are too wide?