[Sn1p3r]

^ I agree that you need to be in the right gear at the right speed and I agree that brake fade should always be a consideration but still I insist, that engine braking should not be a priority. Peace

[vina]

Found this while researching for another thread:


Tyre use in Formula One - F1technical.net

Originally Posted by http://www.f1technical.net/articles/1

A dry-weather racing tyre in Formula One generally operates at an optimal temperature of around 100° C. In contrast, intermediate spec tyres are operate at between 40°C to 100°C, depending on the wetness of the track, while full wets approximate 30°C to 50°C. All heat that is created due to the tyre's friction with the surface should, in theory, be ideally distributed between the outside, the centre and the inside of the tyre tread (a bad distribution is often adapted to by changing camber). This temperature should also be identical from left to right, and from the front to the rear of the car. Too much heat at the front tyres will cause understeer while non-optimal temperatures in the rear tyres will result in oversteering.

temperature increase of a mere 30C can lead to very different traction/wear results. Road cars are off course no F1 cars, but then in road cars we are talking about wear over thousands of km, not just a few hundred.

[Sn1p3r]

Originally Posted by vina

Found this while researching for another thread:

Tyre use in Formula One - F1technical.net

temperature increase of a mere 30C can lead to very different traction/wear results. Road cars are off course no F1 cars, but then in road cars we are talking about wear over thousands of km, not just a few hundred.

But does this not raise the question on how tyres gain temperature? F1 car doing 300 km/h and the braking to 100 km/h within a few hundred meters and then going back to 200+ is operating in some tight range then how our car tyres have their operating temperatures dictated.

Thanks for the information. Cheers!

[sagarpadaki]

How hot does a typical road tire get when we are cruising at 100-120 kmph for say 50 kms?

[vina]

Originally Posted by sagarpadaki

How hot does a typical road tire get when we are cruising at 100-120 kmph for say 50 kms?

I don't know about highways - but coming from Ooty to Mysore in the Mudumalai ghats I have twice had the tyres so hot - it was enough to burn fingers.

Speed was may be 30-40 each time.


BTW where in India can you cruise at 100kmph for 30 straight minutes? Is the Pune-Mumbai highway so good?

Originally Posted by Sn1p3r

But does this not raise the question on how tyres gain temperature? F1 car doing 300 km/h and the braking to 100 km/h within a few hundred meters and then going back to 200+ is operating in some tight range then how our car tyres have their operating temperatures dictated.

Thanks for the information. Cheers!

F1 tyres are designed for this performance - so they (along with the rest of the car) are also designed to lose the heat very fast.

Normal tyres one the other hand give very good grip from cold start onwards, so I would think that once the temperature rises even a little bit, they would have a tendency of excessive wear - though raising temperature for road cars should take more time.



On how tyres get hot in the first place - if car is driven with lots of start/stop and turns - then sliding friction (and the scrubbing tyres get) generates the heat. On a normal cruise, internal friction of the tyre (the chords in the carcas and the different layers inside the tyre rubbing with each other) generate the heat.

[sagarpadaki]

Originally Posted by vina

I don't know about highways - but coming from Ooty to Mysore in the Mudumalai ghats I have twice had the tyres so hot - it was enough to burn fingers.

Speed was may be 30-40 each time.


BTW where in India can you cruise at 100kmph for 30 straight minutes? Is the Pune-Mumbai highway so good?

You can cruise at 100-120 for extended periods on NH7(Bangalore-Hydrabad).

I have also touched the tires after extended periods of high speed running but havent felt them hot enough to burn the fingers! Maybe your tire pressure was low so tires got overheated

[vina]

Originally Posted by sagarpadaki

You can cruise at 100-120 for extended periods on NH7(Bangalore-Hydrabad).

I have also touched the tires after extended periods of high speed running but havent felt them hot enough to burn the fingers! Maybe your tire pressure was low so tires got overheated

I have heard NH7 was really good, but didn't know it was this good. Unfortunately twice I have planned Hyd-Mysore and twice it had to be shelved.

The tyre heating thing I was referring to was with taxis both times - first time a Sumo, second time an Indica. There is a roughly 30km long section which is very steep downhill when coming from Ooty to Mysore. I have seen several smoking tyres at the end of it, not just on our vehicles but on other vehicles as well.

I'm not sure this is relevant to highway driving.

[sagarpadaki]

Originally Posted by vina

I have heard NH7 was really good, but didn't know it was this good. Unfortunately twice I have planned Hyd-Mysore and twice it had to be shelved.

The tyre heating thing I was referring to was with taxis both times - first time a Sumo, second time an Indica. There is a roughly 30km long section which is very steep downhill when coming from Ooty to Mysore. I have seen several smoking tyres at the end of it, not just on our vehicles but on other vehicles as well.

I'm not sure this is relevant to highway driving.

NH7 is Sierra Nevada of India .The only fly in the ointment is the village intersections that you get typically every 2-3 kms! There you have to slow down since the people wont have traffic sense.I have seen the tata magic cabs crossing from one side to another rashly!

Are you talking about the route with 36 Hair pin bends?.Maybe due to the excessive use of brakes while descending the ghats the heat got transferred to the tires i think.

[dhanushs]

Originally Posted by vina

but coming from Ooty to Mysore in the Mudumalai ghats I have twice had the tyres so hot - it was enough to burn fingers.

Originally Posted by vina

There is a roughly 30km long section which is very steep downhill when coming from Ooty to Mysore.

Vina, during ghats, its not really the tyre that heats up, its the discs. The temperatures easily go 100+. Hence, the tyre absorbs some amount of heat.

Also, this is the primary reason why it is advised to drive down a hill, in the same gear you drive up. If the drum's heat up, it jams, and if the discs heat up, it fades.

[AvonA7]

Originally Posted by vina

I don't know about highways - but coming from Ooty to Mysore in the Mudumalai ghats I have twice had the tyres so hot - it was enough to burn fingers.

Speed was may be 30-40 each time.

BTW where in India can you cruise at 100kmph for 30 straight minutes? Is the Pune-Mumbai highway so good?

Hi Vina,

Just posting this out of curiosity - do you mean touching the tire (rubber part ?). I may sound stupid here ... but I touched my tire after more than 01 hour drive on highway 70 - 120 km/hr and I could still touch it, not so hot to have burning sensation.

Considering the air temperate at Mudhumalai ghats with speeds at 30-40km/hr ( I guess the distance covered in ghats will be in the range of 30-40kms), sounds interesting, any other external factors might come into play here.

In Pune-Mumbai expressway one can drive with speeds at 130km/hr and still can find vehicles overtaking with ease, but as you rightly said - 100km/hr for 30mins. hhmmm too difficult IMO. But, concrete roads results in more friction (rolling/sliding) resulting in more noise and increased tire temperature compared to good old black tar roads.

[vina]

Originally Posted by sagarpadaki

NH7 is Sierra Nevada of India .The only fly in the ointment is the village intersections that you get typically every 2-3 kms! There you have to slow down since the people wont have traffic sense.I have seen the tata magic cabs crossing from one side to another rashly!

Are you talking about the route with 36 Hair pin bends?.Maybe due to the excessive use of brakes while descending the ghats the heat got transferred to the tires i think.

That's the route we took each time - and the taxi drivers drove they way they always drive so yes lots of braking. The sumo guy's tyres got so bad, we had to get some water and throw over the tyres. The guy was a bad driver to begin with, so we were worried for our own safety.

In city driving tyres on my Figo get mildly warm to touch within 10km of city driving (and I don't like to use brakes - I take foot off the pedal the moment I see a chance that I may have to apply brakes further down the road) - given that tyre is an insulating material the temperature must surely be in 70s.

[Chewbacca]

Originally Posted by sagarpadaki

How hot does a typical road tire get when we are cruising at 100-120 kmph for say 50 kms?

There are too many variables ..... ambient temperature, road surface temperature, laden weight, type of road (tar/concrete), undulations of the road, type of tyre (Nylon/Radial/Tubeless/tyre width), tyre pressure etc.

Twisty roads, concrete roads and ghats will heat up the tyre to the max.
Combine this with lower than normal tyre pressure, extra laden weight and the humidity of the air inside the tyre will further help in raising the temperature. Note that the rim too heats up due to braking and will pass on the heat to the air inside. The natural air circulaton will keep the rim/disc temperature under control but the same is not true for tyres.

Originally Posted by vina

BTW where in India can you cruise at 100kmph for 30 straight minutes? Is the Pune-Mumbai highway so good?

Pune-Mumbai expressway: 120 kmph but is a concrete road, thus more friction. Ensure tyre pressure is correct, preferably with Nitrogen filled tyres.

NH-4 Pune to Kolhapur: 100 to 120 kmph. The only obstracles are 5 toll booths and few towns enroute that do not have a bypass.

NH-4 Kolhapur to Hubly: 100 to 140 kmph. Excellent road with properly demarcated lay-by's for trucks.

NH-17 Karwar - Honavar - Udipi - Mangalore: 80 - 100 kmph. The road is so scenic that you won't feel like driving above 100.

NH-8A Baroda to Amhedabad: = 100 kmph
NH-7 Bangalore to Hyderabad = 100 kmph
SH-57 Hassan to Belur, Karnataka = 80 kmph

Originally Posted by AvonA7

In Pune-Mumbai expressway one can drive with speeds at 130km/hr and still can find vehicles overtaking with ease, but as you rightly said - 100km/hr for 30mins. hhmmm too difficult IMO.

The speed drops when the expressway curves but for a seasoned driver with a good car that has hydraulic steering, the same speed can be maintained.

Originally Posted by vina

given that tyre is an insulating material the temperature must surely be in 70s.

Sumo, Indica and Figo being heavier might explain why you feel the tyre hotter than others. Also, the problem is with the air inside that is also hot and the insularing properties of rubber prevents it from cooling. Try filling Nitrogen, it prevents the side-effects i.e. expansion of air.

[vina]

Originally Posted by Chewbacca

...



Pune-Mumbai expressway: 120 kmph but is a concrete road, thus more friction. Ensure tyre pressure is correct, preferably with Nitrogen filled tyres.

NH-4 Pune to Kolhapur: 100 to 120 kmph. The only obstracles are 5 toll booths and few towns enroute that do not have a bypass.

NH-4 Kolhapur to Hubly: 100 to 140 kmph. Excellent road with properly demarcated lay-by's for trucks.

NH-17 Karwar - Honavar - Udipi - Mangalore: 80 - 100 kmph. The road is so scenic that you won't feel like driving above 100.

NH-8A Baroda to Amhedabad: = 100 kmph
NH-7 Bangalore to Hyderabad = 100 kmph
SH-57 Hassan to Belur, Karnataka = 80 kmph



The speed drops when the expressway curves but for a seasoned driver with a good car that has hydraulic steering, the same speed can be maintained.



Sumo, Indica and Figo being heavier might explain why you feel the tyre hotter than others. Also, the problem is with the air inside that is also hot and the insularing properties of rubber prevents it from cooling. Try filling Nitrogen, it prevents the side-effects i.e. expansion of air.

I'm sure there are other roads you haven't mentioned where touching the above speeds is possible. The question on the other hand is can you really do 100kmph+ for 50 straight km?

That will require unusual luck IMHO given that most highways almost go through towns and there is low speed traffic on almost all roads.


If nobody is literally claiming 100kmph for 50km, but more like an average speed of 100kmph over 50km (with sometimes slower and most of the time fast thann100kmph) - that is also very difficult but probably possible on many roads.







Regarding tyres feeling hotter - Figo is 1ton and most cars are within 10% of it, so I don't think weight has much to do with Figo. Sumo on the Ghats section does probably have to do with the weight - but the driver was bad too - he was trying to do high speeds and obviously had to brake a lot.


also it is not just the rim an air that generate the heat. More heat is generated right inside the tyre - rubber requires more energy to flex it than it gives back when it unflexes - hence the rolling resistance. All of this heat is generated inside the tyre and it it very hard for the heat to escape.




BTW I have no experience with Nitrogen filled tyres - do they matter so much? I mean 80% of air is nitrogen anyway; even or very humid days air doesn't have more than a couple of percents of water vapour. While the latter will expand a lot, can having pure N2 make a huge difference?

[Chewbacca]

Originally Posted by vina

....that is also very difficult but probably possible on many roads.

Once the road becomes familiar it is not so difficult. I frequently do Kolhapur-Belgaum (115 kms) within an hour. This stretch has 2 minor ghats where speed drops to 60 kmph, no toll booths and the small towns are completely bypassed. This stretch of NH4 is truly world-class.

Originally Posted by vina

BTW I have no experience with Nitrogen filled tyres - do they matter so much? I mean 80% of air is nitrogen anyway; even or very humid days air doesn't have more than a couple of percents of water vapour. While the latter will expand a lot, can having pure N2 make a huge difference?

A tyre gains approx 5 psi for every 25 degrees celcius increase in ambient temperature. This is a enough to adversely affect handling, traction and milage!!! That is why it is advised to check air pressure when the tyre is cold (normal temp). An increase by 5 psi later (when hot) is acceptable but not the other way around !!

With Nitrogen you eliminate the remainder 22 % gases that expand more than N2, it makes a difference on highways since there is minimal variation in pressure due to temperature.

[vina]

Originally Posted by Chewbacca

...


A tyre gains approx 5 psi for every 25 degrees celcius increase in ambient temperature. This is a enough to adversely affect handling, traction and milage!!! That is why it is advised to check air pressure when the tyre is cold (normal temp). An increase by 5 psi later (when hot) is acceptable but not the other way around !!

With Nitrogen you eliminate the remainder 22 % gases that expand more than N2, it makes a difference on highways since there is minimal variation in pressure due to temperature.

Going by the Gas Law, assuming air (or N2) is an ideal gas, and gas voulem doesn't increase (tyre carcass will ensure that to some extent):

% increase in temperature = % increase in pressure

I think whether you fill air (80% N2 to begin with) or N2 the gas law will still be followed to a great extent given that we are not working on extreme temp and pressure and N2, O2, CO2 are near perfect gases.

Following is from my studies on the internet:

All gases, CO2, O2, N2 behave similarly under temperature increase as far as pressure goes.

What does change in H2O -> the "vapour" is actually suspended droplets which truly vaporize as temperature increase leading to a liquid to gas phase change - hence faster increase in pressure. This leads to unpredictable pressure rise with temperature for racing conditions where 0.5psi can matter. Hence it is avoided like plague.

N2 dispensers get rid of H2O to a good extent, thus reducing the unpredictable part of the equation. The rest of the temp rise-pressure rise is avoided by pre-heating the tyres (from the same F1 article I quoted earlier) - that way temp doesn't change much when gas is filled vs. in actual usage.

O2 is avoided because it can oxidise tyres in the long run - though F1 allows N2, air and CO2 (another inert gas) to be used.

Another thing - N2 is lighter (very slightly) than air, so that in theory can help. In practice the difference is insignificant (N2 has a molecular weight of 28, air about 29, and mass of air in tyres is not much to begin with).