May be there is something already here but I haven't found it. I recently changed tyres on my Floride S because they had reached 10 years. They have had very little use. My understanding is that it is recommended by manufacturers that tyres should be changed every 6 years. But general consensus seems to be every 10 years. The reason given is that the tyres will have become hard by the heating and cooling cycles. The Qld Govt has no ruling regarding tyre change times. Recently did some hardness tests on new, used and very old tyres. The very old Michelins were not as hard as other brands of new and and used tyres. So my question is, if hardness is the problem why aren't use by times based on a hardness measure not age? Interestingly one tyre manufacturer claims their tyres do not go hard over 10 years despite number of heating cooling cycles. One for you Peter.
Tyre Hardness
- Thread starter Sunroof
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As I understand things, there are two issues.
The first is wet grip. The channels in the tread (longitudinal & lateral) are meant to clear water & get the tread in contact with the road. Sipes play a minor role here as well. The road is not then dry but, at best, slick wet. This film is overcome in two ways. If present, sipe edges can cut through the film, store a bit of water & mechanically interlock with the road. Of increasingly greater importance, though, is the "rubber" deforming & moulding itself around the micro peaks & valleys of the road surface. This mechanical interlocking is the final source of wet grip.
Obviously, that tread to road interlocking will work variably well as compounds vary in their capacity to mould to the surface irregularities.
This is basically a matter of chemistry (no I'm not a chemist, but . . .) & that chemistry can vary by design (not all tyres are created equal here) & in response to various environmental influences. One of these is, indeed, the heat cycles of use. Another is ambient temperature (compounds work best within a design range). Others are exposure to oxygen & light. Some are, though, I gather, simply the result of time passing & various chemical lattices not being stable enough to resist detrimental change.
Although we speak of increased hardness as the issue, I gather that there's more to the chemistry than that.
The upshot of all of this that the rule of thumb that I've been told is that at around five years of age one should be experiencing noticeably diminished wet grip even in merely slick conditions where tread wear is not as important. This is but a rule of thumb & the history of the tyre's use & the detail of the manufacturer,s chemical expertise can shift things in either direction.
The second issue which arises from chemical changes is structural failure of various sorts. Most notable is belt separation. As the tyre rotates, its bits have an inertial tendency to not rotate but fly off at a tangent. One such is the package of steel belts. These tensions place considerable stress on the bond of belt to "rubber" in the carcass. Partly that stress has been counteracted by wide use of Pirelli's invention of the zero degree nylon (usually) constraining "bandage" belt between steel belts & tread. But stress on the steel to "rubber" bond is not thereby eliminated & the strength of that bond is degraded by some of the chemical changes mentioned above. Bonding among other elements of the carcass is also affected.
Again, I gather that there is more to the chemical story than just hardness.
The upshot is that the usual "rule of thumb" concerning such risks of structural failure is that chemical changes would have occurred to such a degree at around 10 years of age that considerable risk of structural failure obtains. Same caveats as before about different tyre histories & different original manufacturer chemistry varying matters.
I'd be curious to learn who the manufacturer you mentioned is. I wonder what trade-offs there are elsewhere in the spread of type performance parameters to achieve that.
The first is wet grip. The channels in the tread (longitudinal & lateral) are meant to clear water & get the tread in contact with the road. Sipes play a minor role here as well. The road is not then dry but, at best, slick wet. This film is overcome in two ways. If present, sipe edges can cut through the film, store a bit of water & mechanically interlock with the road. Of increasingly greater importance, though, is the "rubber" deforming & moulding itself around the micro peaks & valleys of the road surface. This mechanical interlocking is the final source of wet grip.
Obviously, that tread to road interlocking will work variably well as compounds vary in their capacity to mould to the surface irregularities.
This is basically a matter of chemistry (no I'm not a chemist, but . . .) & that chemistry can vary by design (not all tyres are created equal here) & in response to various environmental influences. One of these is, indeed, the heat cycles of use. Another is ambient temperature (compounds work best within a design range). Others are exposure to oxygen & light. Some are, though, I gather, simply the result of time passing & various chemical lattices not being stable enough to resist detrimental change.
Although we speak of increased hardness as the issue, I gather that there's more to the chemistry than that.
The upshot of all of this that the rule of thumb that I've been told is that at around five years of age one should be experiencing noticeably diminished wet grip even in merely slick conditions where tread wear is not as important. This is but a rule of thumb & the history of the tyre's use & the detail of the manufacturer,s chemical expertise can shift things in either direction.
The second issue which arises from chemical changes is structural failure of various sorts. Most notable is belt separation. As the tyre rotates, its bits have an inertial tendency to not rotate but fly off at a tangent. One such is the package of steel belts. These tensions place considerable stress on the bond of belt to "rubber" in the carcass. Partly that stress has been counteracted by wide use of Pirelli's invention of the zero degree nylon (usually) constraining "bandage" belt between steel belts & tread. But stress on the steel to "rubber" bond is not thereby eliminated & the strength of that bond is degraded by some of the chemical changes mentioned above. Bonding among other elements of the carcass is also affected.
Again, I gather that there is more to the chemical story than just hardness.
The upshot is that the usual "rule of thumb" concerning such risks of structural failure is that chemical changes would have occurred to such a degree at around 10 years of age that considerable risk of structural failure obtains. Same caveats as before about different tyre histories & different original manufacturer chemistry varying matters.
I'd be curious to learn who the manufacturer you mentioned is. I wonder what trade-offs there are elsewhere in the spread of type performance parameters to achieve that.
Yes unfortunately I didn't keep a note of which tyre companies said what but I'll go through browser history and see if I can find it again. Unfortunately almost all the information on the net is from tyre companies that of course want to sell more tyres. I am not driving competition cars but old cars that I do not drive hard. That being said safety is still the issue. Thanks Peter good clear explanation.
It seems that modern compounds 'go off' a lot sooner than compounds used thirty or forty years ago. I can notice a loss of grip in modern performance tyres very early in their life. Part of the problem may be that the compounds are designed for best grip when very hot and those high temperatures result in accelerated degradation.
I have measured tread temperatures at sprints with an infra-red thermometer and typically adjusted pressures to achieve about 85 degrees C across as much of the tread width as possible. In less stressful situations I have monitored pressures using on-board tyre pressure monitor and then used Boyle's Law to calculate tyre temperature. With any sort of spirited driving on modern performance tyres, 80 to 90 degree C seems fairly common.
While all tyres generate heat with normal driving and more with spirited driving, my impression is that tyres used to run a lot cooler than they do now. It seems to me that it is the higher running temperature as well as the chemistry of modern compounds that cause the early degradation and loss of grip. Of course, even then they have better grip than their predecessors!
I have experienced tread delamination only twice. Once many years ago with a 155/80/13 XAS on my R12. Subsequent analysis suggests that the cause was a slow leak resulting in high temperature etc. The second was with an old* 135/80/15 ZX on my Dauphine. Luckily I stopped as soon as I noticed a vibration, so no damage resulted. The point is that the replacement 135/80/15 ZX did not have spectacularly better grip, either wet or dry. This supports my contention that modern 'sticky' compounds degrade a lot earlier than older ones. Of course, it is all fairly academic because tyres with the older compounds are now old enough to need replacing anyhow!
*The youngest that it could have been was about sixteen years old.
Modern compounds degrade so quickly but give amazing grip
20 laps of Albert Park circuit of 5.8 kms at 1 min 20 sec per lap and your tyres are shot
Pull in, 3 sec tyre change and off you go again
20 laps of Albert Park circuit of 5.8 kms at 1 min 20 sec per lap and your tyres are shot
Pull in, 3 sec tyre change and off you go again
Michelin and Continental both recommend as a precaution change tyres at 10 years. Some others start at 3 to 4 years many at 5 years and the remainder 6 years. I still believe that tyre manufacturers want to sell tyres and also avoid a being sued, so are generally over cautious. While I acknowledge Peters and Harrisoni's comments re chemical and technical design issues. If a tyre is still soft and has no side wall cracks it should continue to perform well. But do not take my word for it do as the manufacturer says.
Hang on - you average 261 km/hr, and have a pit crew that can change your tyres in 3 secs?
I'm far more 'age permissive' with a spare than I am with a full time road wheel, which is a bit perverse when you think about it!
My Michelins that are old as perhaps 15 years and are softer than the tyres I recently bought for the Fuego and show no side wall cracking. My recently discarded Nankangs are also softer. Neither have done many kilometres and have always been garaged accept when at motels or on the road. The Nankangs have done around 8000 miles. To discard tyres that may still be usable is bad for the environment as well as a waste of money.
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As observed, there's more to it than hardness/softness.
Interesting video on a guy that tries two sets of the same motorcycle tyres on on the track, one set new, the other set 7 years old.
He goes into the factors that effect tyre degradation, age is only a small part of it.
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He goes into the factors that effect tyre degradation, age is only a small part of it.
The insurance company wouldn't accept the argument that the tyre that failed was 'only the spare' I guess.... I'm equally guilty.
The R8 Gordini being assembled near me at present has an unused set of 145-15 Michelins that have never seen the road and have been kept in the dark. I'm not sure about hardness but you should see the cracks... I used to keep Michelins until the microcracking on the walls looked a bit ugly. Grip? Not good in the wet...
Nobody has mentioned the biggie of age and internal heat generation ... sudden delamination in steel belt radial tyres.
"lets see how they go with a bit of heat in 'em " .. seems a risky paradigm to me.
Having had a perfectly good looking 265/70/16 Bridgestone spare suddenly go bang after its first highway use was enough to scare me away from the "it is just the spare" argument.
"lets see how they go with a bit of heat in 'em " .. seems a risky paradigm to me.
Having had a perfectly good looking 265/70/16 Bridgestone spare suddenly go bang after its first highway use was enough to scare me away from the "it is just the spare" argument.
I've had 3 makes of brand new steel belted radial tyres have an unplanned disassembly.
Two out of a set of four Hankooks on an SD1, two out of a set of four Michelins on a MB, and two out of two LT Dunlops on a small caravan..
Might have to go back to crossplies.
I recently replaced the tyres on my lightweight single axle car trailer. It is kept out in the weather on concrete. It is rated to carry 1200Kg with 195/14C commercial tyres on it. This trailer may have done 10 000Klms in the 9 years since I fitted the tyres, maybe 1/3 of the time unloaded. Maximum load has been about 1050Kg with most of the Klms done with a 400Kg Historic Formula Ford onboard. I generally have 50 - 55 PSI cold in them to achieve the load rating.
On the last trip from Brisbane to Sydney to pick up a Clio, on the way home with Clio aboard both Chinese Maxtrek delaminated. I had been talking about replacing them a couple of months before. One tyre became about 25mm greater in diameter over about 1/3 of the tyre, where the other one maybe only 8mm out of round, but the whole centre of the tread had ballooned out looking more like a motorbike tyre. The rubber had become cracked in the tread grooves, but looked fine otherwise.
Now replaced with some Dunlops including the spare. Maybe I will change these at the 8 year mark.
On the last trip from Brisbane to Sydney to pick up a Clio, on the way home with Clio aboard both Chinese Maxtrek delaminated. I had been talking about replacing them a couple of months before. One tyre became about 25mm greater in diameter over about 1/3 of the tyre, where the other one maybe only 8mm out of round, but the whole centre of the tread had ballooned out looking more like a motorbike tyre. The rubber had become cracked in the tread grooves, but looked fine otherwise.
Now replaced with some Dunlops including the spare. Maybe I will change these at the 8 year mark.
I might have a better chance of achieving some actual wear on the trailer tyres - 15,000 km in less than three years! Something to do with geography. My Tiltatrailer has light truck tyres and the company insists on 60 psi. Everyone tells me it it too much but I reckon Tiltratrailer advice might be OK...
I admit I think my Tiltatrailer with the 400Kg Formula Ford can get away with 50psi, but yes the manufacturers know what specs need to be reached to get the load rating required. Just trying to give Jims little open wheeler a slightly smoother ride.
My experience is a set of Michelin XVS at 20 years old and 15,000 km.
I knew they were getting hard by the way they thumped over any small bumps.
One day travelling at 90kmh one simply flew to pieces on the freeway. It literally just broke up.
New tyres all around after that as I could never relax driving the car waiting for another tyre failure
I knew they were getting hard by the way they thumped over any small bumps.
One day travelling at 90kmh one simply flew to pieces on the freeway. It literally just broke up.
New tyres all around after that as I could never relax driving the car waiting for another tyre failure
Got a tyre hardness meter. Take 6 or more readings around tyre and on different sides and centre of tread. Then average the result. It is interesting to note that the hardness varies quite a bit around the tyre.
Some examples.
Vitoria City Life 7 years old 165 X 13 on front of R10 hardness 71.
Nankan 9 years old 145 X15 just removed from Floride S but kept as spare. Hardness 61.
Vitoria Work Life unused trailer tyre 175 X13 2023 manufacture. Hardness 58. Had the biggest variation around the tyre.
Michelin MXL 175 X 13 no date probably 20 years old on R15 off road for 12 years. Hardness 67.
Michelin Pilot 3 195 X13 of Fuego not registered. 15 years old but was used on the track. Hardness 89.
None of the tyres have done many kilometres as on old cars on club registration. None show any cracks. But some not used for some years so if put back on road who knows.
Some examples.
Vitoria City Life 7 years old 165 X 13 on front of R10 hardness 71.
Nankan 9 years old 145 X15 just removed from Floride S but kept as spare. Hardness 61.
Vitoria Work Life unused trailer tyre 175 X13 2023 manufacture. Hardness 58. Had the biggest variation around the tyre.
Michelin MXL 175 X 13 no date probably 20 years old on R15 off road for 12 years. Hardness 67.
Michelin Pilot 3 195 X13 of Fuego not registered. 15 years old but was used on the track. Hardness 89.
None of the tyres have done many kilometres as on old cars on club registration. None show any cracks. But some not used for some years so if put back on road who knows.