275 Michelin pilot super sports

Do they?

 

I think so, at least that's what they told a friend... I argued it was too high, he agreed but this is what they told him apparently.

i ran them on track without dropping pressures, seemed fine..

 

On 19s I ran 30f and 32r expecting them to heat up a lot due to it being a hot day. In the end I CBA to mess about with pressures but the fronts lasted 3 laps of Bedford (about 12 miles).

 

Was it just the outer shoulders that went?

 

Cold pressures after track use are about as relevant as zebras and toasters.

 

The lower the cold pressure the hotter they will get and the pressure will rise more (by a bigger amaunt). If the tyre owerheats it is from low pressure not from high pressure (measured cold! )
The maximal tire load rating is acheived at the maximum cold pressure ! Then the tire will heat up least!

Sent from my LG-D855 using Tapatalk

 

Sorry but this simply isn't true. The ideal gas law governs the relationship between tyre pressure and temperature, and there is simply no avoiding this unless you use very special gases in your tyres (I don't mean nitrogen). Look at every motorsport formula where tyre heating is not allowed; they start with the lowest alowable starting pressure to keep the hot pressures as low as possible.

By driving a car in a certain way you put a certain amount of energy into the tyre, and the temperature rise associated with that energy increases the pressure in the tyre. If you start with a lower tyre pressure and do the drive you get the same percentage increase in tyre pressure as if you have a higher starting pressure.

The different tyre pressures however give the vehicle different dynamics, allowing you to put different amounts of energy into the tyres, and therefore get a different temperature and pressure rise.

The other consideration is that tyre pressure increases as a result of temperature are not solely as a result of the tyre temperature increase. The air inside the tyre chamber is also heated significantly by the rim, which is heated by the brakes, so the behaviour of tyre pressures on a handling circuit where you may not speeds, but there is a lot of braking (and therefore heat soak from the brakes into the rim and into the tyre chamber giving big pressure increases ) is very different to going out for a Vmax run (where you are not touching the brakes but getting very high speeds and surface temperatures, and massive cooling of the rims from airflow, giving no pressure increase during the run, but a very rapid rise when you lift off at the end).

 

Finally, some sense here regarding tyre temps.

Plus the road/circuit and ambient conditions also play a huge role in tyre temperature/pressure deltas.

 

Not quite true.. The lower the initial pressure the more the tire works and moves, and heats up more. The higher the initial pressure the less the tire will work and deform, and the rolling resistance will be lower.
Now the rollig resistance is transfered to heat and heat only. So the lower the initiall presure the tire will have bigger rolling resistance and will heat up more!
The higher the temperature is the pressure will slowly rise untill the pressure and heating "equlises" , this temperature will be much higher than on a tire that is at high pressure when cold.
The energy imput in to the tires IS NOT THE SAME when the pressure changes!!! The energy absorbed by the tires is only dependent on the rolling resistance (given the driwing conditions dont change, ie speed, cornering etc)

And in the end look at the recomended pressures for a single tires for diferent load and speed rating.
These are rarely given for a car tires but for motorcicly tires they are, and you can clearly see that the load rating for of the max pressure is less than half of a max rated load if you are looking at a maximum speed. However if you want the max load rating and you want lower pressure the max alowed speed is much lower!

Sent from my LG-D855 using Tapatalk

 

I'm not sure, I wasn't aware that the tyres had softer sidewalls, all I noticed was a drop in grip levels (prob not helped by a large amount of 'marbles' on the track - it was like an F1 race!)

 

So, MPSS tyre pressures on 19s should be what for road and what for track?

 

I had Super sports and moved to 595 rsr and now have just had a set of NS-2R delivered. I do miss the Michelin's for the daily use as they take away the harshness of crap roads.

The sidewalls on the Federals and Nankang ns-2r are stiffer than a teenager in a titty bar !

 

I'm not sure but if you email Michelin they'll advise.

They told my friend with a focus over 40 psi so will be interested to see what they say.

 

Ah ok. What did you mean when you said they only lasted a few laps of Bedford?

 

I follow, kinda, what both you and James are saying but I'm struggling a bit with one part of your explanation

To make it a bit easier to understand, can we try this with numbers?

Firstly, we all agree that if you take a car with 35psi and drive it on track, the tyre will heat up and pressures will increase - let's assume they increase to 40psi

However, if you drop the pressure of the tyres to 20psi (cold), and drive them on track, we are saying:

1. The pressures will still increase (everyone agrees)

2. MilosB is saying the pressures will increase more initially, and increase more because the tyre is deforming and moving around more because it's colder (something I understand and agree with)

Here's the question...

So MilosB, are you saying that if you start with a 20psi (cold) car and drive it on track, then it will still get to the point where it heats up to 40psi anyway, and therefore there's no point in over-working the tyre when it's at 20psi because it will heat up anyway?

Or, are you saying the pressure may only increase from 20psi to, say, 35psi but you don't think that's a good idea because it's increasing by 15psi, whereas if you start if off at 30psi and it increases to 40psi, then it has only increased by 10psi?

In my experience I aim to be running the 'optimum' tyre pressure when it's hot, but I do it gradually

I'll therefore go...

1. Leave the pits at 30psi, come in after a short session (say 10mins)

2. Reduce the hot pressures from 35-37psi back down to 30psi

3. Go out for a longer session (say 15mins), come back in

4. Check pressures. If pressures are higher than 35psi and tyres seem to be 'going off', i'll consider dropping them.

If they're at 35psi and seem fine, i'd leave them

At lunch, they will cool down (often as low as 24psi on whichever front tyre is being worked the most), so i'll top them back up to 30psi and repeat the process again

 

They lost grip essentially, the first 2 laps they were fine but after that I could feel them going off and the car starting to move around more. The Meg is not light and so I assumed the tyres were over heating.

 

Yeah this is normal. Once they cool the grip comes back and they're fine though

Hope you didn't bin the tyres after?

 

OK, from Michelin themselves today:

Road Use
The pressure on road would be: without load 34 psi front axle 30psi rear axle. With load: 37 psi front and 33 psi rear.

Track Use
For track use you should put the 4 tyres to 29 psi and start warming them up. Afterwards you should inflate or deflate looking at the wear of the shoulder. If there is too much wear on the center of the tread and not on the shoulder it means you should deflate. If it is the opposite and the wear is more visible on the shoulder you should give more pressure. You should not go over 36 psi when hot.

 

At £170 each??!! God no, I just came in after 3 laps, which doesn't sound like many but that was 12 miles.

 

Thanks for sharing this... I'll forward this on to my friend and let you know what his response is.

These are the sort of pressures I'd have thought were acceptable..

 

34/30 is what i am running, ps4 road driving

Sent from my SM-G920F using Tapatalk

 

Which dimension?

 

I assume you mean wheel size? This is for 19s with 235/35 profile.

 

OK then, those are correct pressures indeed.