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Old 5th October 2016, 10:00   #31
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Default Re: Tyre life: Monocoque vs ladder-on-frame cars

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Originally Posted by vipinendran View Post
Sad that many people in this thread have even boasted of 1,00,000 km with their tyres. I feel they are lucky to be alive driving around in those tyres. The tyre may look fine but are extremely susceptible to blow out under high speeds when going over sharp objects...
100,000 km is not a dangerous situation per se, provided other factors such as tread depth, number of years since manufacture (5 years is the general concensus), driving style & experience, presence of TPMS etc. are favourable. Driving a vehicle does not have any luck factor involved - which is why, internationally, vehicle damage-related incidents are not called accidents any more, but are termed crashes.

For example, I covered 100,000 km in ~4 years, my vehicle has TPMS, and I trained to be a low-risk driver.

Last edited by SS-Traveller : 5th October 2016 at 10:02.
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Old 5th October 2016, 10:49   #32
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Default Re: Tyre life: Monocoque vs ladder-on-frame cars

High speed heats up tyres a lot and tyres may burst due to the resultant high pressure. That is why when undertaking a long journey on roads which are conducive to high speeds, tyre pressure should be at the lower range when measured in a cold tyre. This is more so when the ambient temperatures are high in summers.

In most cases I have noticed that tyres that burst are nearly bald - less than 1mm average tread depth or have damaged sidewalls that bulge out, and that was one of my points for unsafe tyres. This is often the case in vehicles which are normally driven in urban situations and for relatively short distances - 10-20km in slow moving traffic. The bald tyres may last in these conditions but on a highway at high speed they are a recipe for disaster.


Urban drivers venturing on highways once in a blue moon are at times a source of trouble to others as they are used to heavy and at times B2B traffic where speeds are nominal most of the time.

Once they hit an open highway, the lack of experience and sheer joy of open vistas raises the vehicle speed. In most cases the drivers are not even aware of the dangers of high speed and in emergencies loose control.

These drivers are very easy to detect and when on highway, I am wary when they are around.

Last edited by Aroy : 5th October 2016 at 10:51.
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Old 5th October 2016, 10:56   #33
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Default Re: Tyre life: Monocoque vs ladder-on-frame cars

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Originally Posted by vipinendran View Post
Sad that many people in this thread have even boasted of 1,00,000 km with their tyres. I feel they are lucky to be alive driving around in those tyres. The tyre may look fine but are extremely susceptible to blow out under high speeds when going over sharp objects which includes small stones too ( our Indian highways are littered with these).
Thankfully, the 85,000 on my tires have come in under 2.5 years. I am not here to show off the tire's life at all as most of my driving is on the highways and with family. The important point to highlight here was that with proper driving and care, tires can last really long (For me long = Kms and not years).

A rare case that we will have folks here who will drive all the way till the treads are bald completely and only then change.

A tire that has run 80-90K Kms for one might look same as 30-40k kms for someone else - It totally depends on the Tire make, the driving style, the terrain used and usage patterns. Referring to that as dangerous or lucky holds no real logic unless you actually bother to check these tires yourself.

Last edited by paragsachania : 5th October 2016 at 10:58.
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Old 5th October 2016, 10:58   #34
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Default Re: Tyre life: Monocoque vs ladder-on-frame cars

One more reason I could think of.

Most passenger cars with front only independent suspension have only the front toe-in as adjustable whenever wheel alignment is done. The rear wheels are non-adjustable even for toe.

But in case of SUV's like the Fortuner and the likes, the rear wheel alignment parameters like toe-in are also adjustable, which means uniform and even wear ensured.
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Old 5th October 2016, 12:02   #35
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Default Re: Tyre life: Monocoque vs ladder-on-frame cars

The chassis although has a bearing on the tyre life, is not the primary factor affecting wear and tear.

Tyre wear primarily is affected by the compound, driving style and surface the vehicle is being driven on.
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Old 5th October 2016, 12:09   #36
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Default Re: Tyre life: Monocoque vs ladder-on-frame cars

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Originally Posted by paragsachania View Post
Thankfully, the 85,000 on my tires have come in under 2.5 years. I am not here to show off the tire's life at all as most of my driving is on the highways and with family. The important point to highlight here was that with proper driving and care, tires can last really long (For me long = Kms and not years).

A rare case that we will have folks here who will drive all the way till the treads are bald completely and only then change.

A tire that has run 80-90K Kms for one might look same as 30-40k kms for someone else - It totally depends on the Tire make, the driving style, the terrain used and usage patterns. Referring to that as dangerous or lucky holds no real logic unless you actually bother to check these tires yourself.
If you have read my post fully I have mentioned that the replacement has to be 50k km or 5 years whichever is earlier. No tyre manufacturer in India has manufactured tyres which will function to its FULL ABILITY after 50k km. (this taking into account the average use of a car in typical Indian conditions). It would still roll on, you could still drive on it with your family and still get away with it only if you are lucky .

Your usage of the tyres inspite of it clocking 80k is what defies logic, and when you say "a tyre which looks good to the eye is good enough to ride" is completely unscientific as we all drive on Indian roads which has some of the most treacherous surfaces in the world, and tyres are made of rubber ( the main component) and usage ( heat, weather, exposure to different temp.pH of Asphalt and Road tar) takes its toll, resulting in rubber becoming hard ( Shore Hardness ) and can only be measured with a durometer and never visually. I have a few students of mine who work for the best tyre companies in India and they where aghast when I mentioned 80k - 90K numbers to them, Inspite of the fact that they were maintained well and with immaculate driving.

If you still feel you can use the tyres after its stipulated life period of 50k/5yr, please go ahead, but it is Sad that many drivers and automobile users in our country feel that safety can be compromised and sometimes learn it the hard way.

Last edited by vipinendran : 5th October 2016 at 12:10.
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Old 5th October 2016, 12:25   #37
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Default Re: Tyre life: Monocoque vs ladder-on-frame cars

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Originally Posted by vipinendran View Post
Your usage of the tyres inspite of it clocking 80k is what defies logic, and when you say "a tyre which looks good to the eye is good enough to ride" is completely unscientific as we all drive on Indian roads which has some of the most treacherous surfaces in the world, and tyres are made of rubber ( the main component) and usage ( heat, weather, exposure to different temp.pH of Asphalt and Road tar) takes its toll, resulting in rubber becoming hard ( Shore Hardness ) and can only be measured with a durometer and never visually. I have a few students of mine who work for the best tyre companies in India and they where aghast when I mentioned 80k - 90K numbers to them, Inspite of the fact that they were maintained well and with immaculate driving.
And we have had cases where tire surfaces have cracked more due to age and less due to running. Taking into consideration all your scientific logic, ultimately you will have 2 types of drivers, those who would care less on the usability aspects of the tire itself (Grip levels, Traction, Dry and Wet performance, Ride comfort etc) but still want only one thing - LIFE (of the tires of course) and the others to whom all these parameters are utmost important.

And when the second category of drivers manage to get more life out of it, it is not because their only motto was to get there but it is only because of proper care and driving. The same drivers will also not be too careless to ignore the usability aspects of their car's tires after clocking 80-100K kms.

My 16,000 kms run stock Good Years are biting dust at home. No one wants them mainly because the profile is not friendly with most of the cabs as well. I had made up my mind that I will lose a lot by not getting anything out of it but will gain a lot (in terms of driving dynamics, grip etc) by investing in better tires due to my usage.

To me, at this age of the tires, my main worry was how these can be vulnerable to damage/punctures when hitting sharper objects or driving on bad roads that off late I have only been anticipating puncture during every drive but thankfully there has been just one among all these 4 tires and that too in the last month.

Quote:
If you still feel you can use the tyres after its stipulated life period of 50k/5yr, please go ahead, but it is Sad that many drivers and automobile users in our country feel that safety can be compromised and sometimes learn it the hard way.
I have to agree here when you say one has to "feel" if the tires are doing their job. Who else but the sole driver can confirm this better?

I have my own examples (and no hesitation there) of 2 set of tires from 2 cars but of the same make. The only differentiating factor between them is their age - One is now in its 5th Year while the other is still less than 2.5 Years and I don't deny that there is a "Huge" difference in how they appear or perform today. Needless to say that age is a major differentiating factor here. The other car runs only inside the city now and the fact that the steering had gone hard and so has the ride quality is a good reason to replace them now.

The point here simple - 50,000 kms cannot be the upper limit for usable life unless one factors the age, even after factoring Indian driving conditions and terrains. It all boils down to the usage patterns. For rest of your points, I have to agree!

Last edited by paragsachania : 5th October 2016 at 12:33.
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Old 5th October 2016, 12:57   #38
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Default Re: Tyre life: Monocoque vs ladder-on-frame cars

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Originally Posted by paragsachania View Post
And when the second category of drivers manage to get more life out of it, it is not because their only motto was to get there but it is only because of proper care and driving. The same drivers will also not be too careless to ignore the usability aspects of their car's tires after clocking 80-100K kms.
I have to agree here when you say one has to "feel" if the tires are doing their job. Who else but the sole driver can confirm this better?

The point here simple - 50,000 kms cannot be the upper limit for usable life unless one factors the age, even after factoring Indian driving conditions and terrains. It all boils down to the usage patterns. For rest of your points, I have to agree!
Agreed buddy, Yes the driving style is very important in enhancing the life of a tyre within the limits I had mentioned. One must keep in mind that most of the tyre bursts do not often happen on rough roads but on the so called well laid out smooth highways, where even a very sedate and careful driver would maintain speeds of 50 to 70km/hr. However great a driver I am, I would never be able to spot a small extremely sharp stone or nail on the tarmac at that speed. A tyre ages both by usage and/or time. A good under 50k tyre will immediately absorb the impact very well but a 50k+ well maintained and well driven tyre will not be able to do so because of its increased hardness wherein the hole created would immediately spread and result in sudden loss of air pressure.

Just imagine the consequences if it is an SUV or a tall boy hatchback. Well one can use a tyre beyond the 50K mark, but it is a compromise a very large compromise indeed.
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Old 5th October 2016, 13:22   #39
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Default Re: Tyre life: Monocoque vs ladder-on-frame cars

Quote:
Originally Posted by vipinendran View Post
...the replacement has to be 50k km or 5 years whichever is earlier. No tyre manufacturer in India has manufactured tyres which will function to its FULL ABILITY after 50k km.
...when you say "a tyre which looks good to the eye is good enough to ride" is completely unscientific...
I am curious to know, what exactly can go wrong, in your opinion, with a tyre which is, for example,
- 2 years old,
- has run 50,000 km,
- has ~50% tread depth still remaining, and
- has no nicks, cuts or other damage to the tread / sidewalls / beads.
By your description, one has to compulsorily change such a tyre. But should it be changed? Why?

I am also curious to know whether, in your opinion, one should or should not change a tyre which is, for example,
- 2 years old,
- has run 10,000 km,
- has tread depth worn out to 1 mm over 20% of the tread surface (the remaining tread area has about 80% depth of tread), and
- there is no visible sidewall damage, but 5 puncture repairs have been done during the period of use.
By your description, one does not need to change such a tyre. But should it be changed? Why or why not?

Last edited by SS-Traveller : 5th October 2016 at 13:24.
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Old 5th October 2016, 13:57   #40
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Default Re: Tyre life: Monocoque vs ladder-on-frame cars

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Originally Posted by SS-Traveller View Post
I am curious to know, what exactly can go wrong, in your opinion, with a tyre which is, for example,
- 2 years old,
- has run 50,000 km,
- has ~50% tread depth still remaining, and
- has no nicks, cuts or other damage to the tread / sidewalls / beads.
By your description, one has to compulsorily change such a tyre. But should it be changed? Why?

I am also curious to know whether, in your opinion, one should or should not change a tyre which is, for example,
- 2 years old,
- has run 10,000 km,
- has tread depth worn out to 1 mm over 20% of the tread surface (the remaining tread area has about 80% depth of tread), and
- there is no visible sidewall damage, but 5 puncture repairs have been done during the period of use.
By your description, one does not need to change such a tyre. But should it be changed? Why or why not?
Second question first, I have not advocated anywhere that if a tyre has 5 punctures and is just 2 years old and is in a bad condition ( tread wear etc., ) one should not change it . 50K or 5yrs is just the max limit sir and not that every tyre should last that long. It is just a limit like the max speed limit on the road. Well fatal accidents have happened at lower speeds too but it is just that the probability of a fatal accident is higher when we cross specified speed limits.

I shall try answering the first question with my limited knowledge. A tyre is in constant contact with the road surface. The tyre which is just 2yr old and has covered 50K km and still has tread depth left, with no punctures would still run on the road and look good visibly. But the tyres rubber would have been subject to (1) High temperatures due to constant running. (2) Less cooling of periods (3) Constant exposure to pH - acidic or alkaline - depending on the road surface - Asphalt, Tar or even melted plastic used on modern roads. All this would increase the hardness of rubber by about 60% making it less flexible and more brittle, BUT completely invisible to the naked eye and to any hand feel over the tyre rubber.

Now when the tubeless tyre undergoes stress during a highway drive the rubber is unable to take in the sharp object like before as the adjoining areas of the impact immediately crack resulting in a sudden loss of pressure which is catastrophic. ( Remember the tubed tyres) Something similar to that. Hence it is ADVISABLE to change the tyres. So ageing of rubber is not just because of the time factor alone but the exposure and stresses it undergoes too.

Last edited by vipinendran : 5th October 2016 at 13:58.
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Old 5th October 2016, 18:23   #41
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Default Re: Tyre life: Monocoque vs ladder-on-frame cars

As long as the tyre compound has not deteriorated and is soft (and of course has 3mm+ tread depth left), there is not much danger in using it.

A tyre whose compound has gone hard due to UV will be susceptible to frequent punctures. Frequent punctures also damage the sidewalls which results in higher probability of blowout at high speeds. One factor that I use to determine the end of life of a tyre; even when it has 3mm+ tread left; is to change it when punctures start occurring frequently.
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Old 5th October 2016, 18:49   #42
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Default Re: Tyre life: Monocoque vs ladder-on-frame cars

Quote:
Originally Posted by vipinendran View Post
...the tyres rubber would have been subject to (1) High temperatures due to constant running. (2) Less cooling of periods (3) Constant exposure to pH - acidic or alkaline - depending on the road surface - Asphalt, Tar or even melted plastic used on modern roads. All this would increase the hardness of rubber by about 60% making it less flexible and more brittle...
Tyre technology has come a long way from the early 20th century, and the points above make no significant difference to a running tyre's performance over 50,000 km.

I am now curious to know the information/data source when your students working in Indian tyre companis inform you that 50,000 km of usage over 2 years will increase the hardness of rubber by about 60%. An increase of 60% in rubber hardness will cause very perceptible difference in the ride and handling quality of any tyre, which any driver or passenger will be able to translate into harsher suspension characteristics, but more importantly, much higher road noise - and paragsachania has correctly stated:
Quote:
Originally Posted by paragsachania View Post
I have to agree here when you say one has to "feel" if the tires are doing their job. Who else but the sole driver can confirm this better?
AFAIK, the increase in Shore A values of the tread material is in the range of 15-30% over a 10-year period while usable tread depth is retained (>2mm). The change in hardness of the sidewalls is comparatively far less because there is lesser exposure to (as you correctly pointed out) - high temperatures, repeated heating and cooling, pH changes, and organic solvents from road construction material. You may confirm this with your students working in the tyre companies (I hope they work in R&D, and not in marketing).

Incidentally, all tyres manufactured in India use summer compounds, which are far more resistant to changes in hardness with use than winter tyres. The accepted operating temperature for Indian tyre rubber compounds is ~65*C at least, but a properly inflated tyre will not usually exceed this temperature even in peak summer - my own TPMS readings have often supported me, and a summer run on the YEW at noon (>44*C ambient) at 100 kmph keeps tyre temperature below 60*C.
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Originally Posted by Aroy View Post
High speed heats up tyres a lot and tyres may burst due to the resultant high pressure. That is why when undertaking a long journey on roads which are conducive to high speeds, tyre pressure should be at the lower range when measured in a cold tyre. This is more so when the ambient temperatures are high in summers.
A fallacious reasoning. Underinflated tyres generate more heat quickly due to ply shuffle, and tyres run hotter when underinflated to begin with. Reducing air pressure in a hot tyre has even worse effects, due to higher generation of heat subsequently.

By now, I think we are completely off the main topic of this thread, but then again, this is an informative debate nonetheless. Thanks for starting this, @vipinendran.

Anyone on this forum who works as an R&D engineer in the Indian tyre industry? It would be very instructional to have inputs from such a person directly.

Tyres & oils - the two least-understood parts of any automobile, where marketing spiel obliterates hard data!
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Old 5th October 2016, 19:32   #43
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Default Re: Tyre life: Monocoque vs ladder-on-frame cars

Most passenger tyres have a limit to air pressure inside the tyre. Over inflated tyres running at high speeds on a surface that at times melts the tar can build up pressures very fast, and with slight imperfection can result in a tyre burst.

The recommended running air pressure is published by many manufacturers for most of their tyre ranges, but more so for those used in high performance cars.

Here are a few references
http://www.carbibles.com/tyre_bible.html
http://www.tirerack.com/tires/tirete....jsp?techid=35
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Old 5th October 2016, 21:33   #44
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Default Re: Tyre life: Monocoque vs ladder-on-frame cars

Have gone through the various view points on what is actual life span of a tyre and when it should be replaced.

I have worked in a well reputed tyre company (Amongst the top 3 in India) for a little less than 10 years. Not in R&D, but on the shop floor production. With that little knowledge, let me tell the following points. (Not technical points which needs much intense deliberations and time).

There is not really a clear way to tell how long a tyre lasts. It depends on many variables such as design / driver habits / road conditions / the environment / inflation pressure etc etc. So, the question of how long a tyre can last is not having a definite answer.

Now, coming to the second question. When a tyre should be replaced?. There are various measurable parameters which can be assessed for arriving at an answer for this question. Most of the points like, tread depth (Can be assessed with the TWI - tread wear indicator), visible damages, sidewall cracks, blisters/bulges, punctures, age etc are already discussed at length in the above posts.

The industry consensus is that the safe average to be considered for replacement of a tyre is 50000 KMs / 5 Years. The tyre can very well go beyond the 50000 KM limit and can be used if it is maintained perfectly and runs on better surfaces with good habit driver. Of-course, within the permissible speed limits.

But that is not the case with ageing. If a tyre is more than 5 years old and even though have enough tread depth and in good condition (as appears to the user), still it has to be inspected by a tyre professional for the road worthiness and then only it can be used.

If you are not able to get a professional advice (beyond 5+ years), PLEASE REPLACE the tyre. Your life / your family's life as well as the life of people on road is much more valuable than a set of 5+ years old tyres. DO NOT go by just the appearance and continue with the 5+ year old tyres.

On a lighter note, less than 50K KMs /5 Year old tyres are like boy/girl friends whose behaviour can be predicted by the other half to a great extend.

But, alas... Once the tyre crosses 50K KMs / 5 years, it is more or less like a wife. You can seldom predict how she is going to behave in various circumstances. Since you have a choice to replace the tyres, go ahead and replace.
May not be lucky enough with the other, so mend your behaviour, be an obedient partner, listen carefully, talk slowly and continue gracefully with all the calculated risk factors.

Happy motoring on good condition vehicles with good condition tyres.

Last edited by Sree73 : 5th October 2016 at 21:40.
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Old 5th October 2016, 22:21   #45
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Default Re: Tyre life: Monocoque vs ladder-on-frame cars

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Originally Posted by Sree73 View Post
There is not really a clear way to tell how long a tyre lasts. It depends on many variables such as design / driver habits / road conditions / the environment / inflation pressure etc etc. So, the question of how long a tyre can last is not having a definite answer.
...
The industry consensus is that the safe average to be considered for replacement of a tyre is 50000 KMs / 5 Years. The tyre can very well go beyond the 50000 KM limit and can be used if it is maintained perfectly and runs on better surfaces with good habit driver. Of-course, within the permissible speed limits.

But that is not the case with ageing.
Thank you. That sums it up very succinctly.

Quote:
Originally Posted by Sree73 View Post
Once the tyre crosses 50K KMs ... it is more or less like a wife. You can seldom predict how she is going to behave in various circumstances
After 20 years of blissful wedded life, I beg to differ. I guess the ability to predict the wife's behaviour needs life transformational training over 2 decades.
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