Aged tyres

[carl888]

Quite a nice little video from Porsche on the subject:

 

[tazzieman]

  And that's not correct about car companies trying to get money out of you, Porsche don't make tyres.

That's news to me. They sell oil too.

[ANF]

Have you read your owners manual?  The Porsche tyre life issue is addressed there

It's not unscientific, a tyre degrades whether you use it or not, that's a fact.  And that's not correct about car companies trying to get money out of you, Porsche don't make tyres.

I have and it is not in my 1983 owners manual. If it was it would have little bearing on todays tyres, tyre technology has moved on a bit in the last 33 years.

 

Michelin say 10 years maximum life with yearly checks after 5 years, that sounds like a plan to me

[tazzieman]

It's not unscientific, a tyre degrades whether you use it or not, that's a fact.  

Are you a scientist? Do you understand the broad nature of the comment?

I'm leery of "facts"

ANF wins the correct answer. Tyres older than 5 years , in general should be assessed by a tyre expert. A tyre expert told me this. Cracks are an unreliable sign of ageing , unless you are a human 

Oh and Porsche approved N spec tyres are soft , which gives them secret levels of grip and unprecedented wear out ability!

[SimonN]

This idea of the tyres being inspected by an expert is, I fear, a bit unrealistic, not least because I don't know how you would find such an expert. You certainly won't at any tyre shop I know. Yes, they can look at the tyres and see there are no cracks etc, but how many do you think can tell you what the rubber hardness actually is, never mind what it should be or what it was when new. I wonder how many have Durometers and know what Shore points to look for on each tyre, should be or is safe for that tyre? And I don't think there are any resources that give the information, 

Tyres degrade at different rates depending on usage, storage conditions, UV exposure and much more. I personally wouldn't use a tyre that is more than 5-6 years old, for the simple reason that when you consider the overall cost of ownership, tyres spread over that time makes them a fairly cheap part of the motoring equation, so why take any risks with one of the most important parts of the car? Depending on tyres, what are we talking about per year? $200? Seems like a false economy to be pushing the life of tyres.

[StevepGT3]

Thumbnail in the tread section and visual inspection between the tread blocks as well as the  sidewalls for cracks should tell you more than enough to make a judgement. Heat cycles as well as ultra violet effect tyres as much as time does 

[tazzieman]

By & large , tyres cop a lot. I hit lots of potholes and rocks , so that makes the decision easy - for me. The last tyre I had inspected had a 6cm tear in the inside tread,  but no symptoms other than a slow flat. 

[tazzieman]

There's always a few concours purists out there; mind you the original air is missing

http://www.ebay.com/itm/VINTAGE-MICHELIN-220-55-VR-390-TIRES-40-FERRARI-BMW-PORSCHE-MERCEDES-/302125496431?hash=item465815386f:g:ao8AAOSwXSJXOm-0&vxp=mtr

 

[TINGY]

Have you read your owners manual?  The Porsche tyre life issue is addressed there

It's not unscientific, a tyre degrades whether you use it or not, that's a fact.  And that's not correct about car companies trying to get money out of you, Porsche don't make tyres.

Are you a scientist? Do you understand the broad nature of the comment?

I'm leery of "facts"

ANF wins the correct answer. Tyres older than 5 years , in general should be assessed by a tyre expert. A tyre expert told me this. Cracks are an unreliable sign of ageing , unless you are a human 

Oh and Porsche approved N spec tyres are soft , which gives them secret levels of grip and unprecedented wear out ability!

Carl may not be a scientist Tazzie but most people would say say he is not far wrong, a broad comment it may be, none of us are experts tazzie.

Cracks are an unreliable sign of ageing , unless you are a human 

Is this a fact tazzie? I don't think so, i know lots of people who have had too much sun and look like they are in their 60's and are only in their early 40's.

It's a pretty broad statement wouldn't you say.

[ANF]

This is getting like a typical oil thread.......

[tazzieman]

 

Carl may not be a scientist Tazzie but most people would say say he is not far wrong, a broad comment it may be, none of us are experts tazzie.

 

Is this a fact tazzie? I don't think so, i know lots of people who have had too much sun and look like they are in their 60's and are only in their early 40's.

It's a pretty broad statement wouldn't you say.

Skin cracks are a very reliable sign of skin ageing and a direct risk of "failure" (disease) .

Hard (eg old style compound) tyres crack , soft ones not so much. Thin people wrinkle more than fat people. These are all general facts  

[Shady Speedway]

I was told to wear out my Toyo R888s in 2 years.

Any tread left after that is pretty much wasted.

Good job I live in the hills.

[Peter M]

This is getting like a typical oil thread.......

No, it's worse.

[Pork Chops]

I replaced the 6 year old P Zeros with heaps of tread on my 996 as soon as I bought it with PS2s. Transformed the car from both a grip and ride comfort perspective. 

Just replacing my 50% worn Pzeros with new ones on the GT3 as the old are really sketchy.  Old ones were new in 2010.

[JWM]

I had a very bad accident many years ago that can be chalked up mostly to old tyres. Don't risk it, even expensive tyres are cheap. 

[carl888]

I have and it is not in my 1983 owners manual. If it was it would have little bearing on todays tyres, tyre technology has moved on a bit in the last 33 years.

 

Michelin say 10 years maximum life with yearly checks after 5 years, that sounds like a plan to me

My apologies,  I assumed incorrectly it would be in your 1983 manual,  here's Porsche official position for the 1980s:

 

 

With regards to tyre technology moving on in 33 years:  When I was testing tyres annually from 1998 I determined approximately after 5-7 years of use the tyre maintained almost all of its elasticity (And therefore most of its grip) provided it still had 2mm of tread.  This was determined using the Shore Durometer ASTM D2240 Scale A standard.  The tyre was pretty constant starting fresh with a rating around 70-75 using tyres with a TWI of 140 rising to 73-78 after 5-7 years.  Back then that was the Pirelli P-Zero Giallo, Bridsgestone S-01 and a Continental I can't quite recall, a Sport Contact I think.  The vehicles I used for testing were a 1987 Carrera 3.2 and a 1976 Ferrari 308 GTB.  The advantage of these two cars was the fact they used the same size tyre, 205/55/-16 and 225/50-16 and both vehicles are particularly sensitive to tyre condition. 

From 7 years the tyre fell off a cliff with hardness increasing alarmingly and particularly wet braking distances increasing.  Tyres used aggressively or on the track hardened faster, but certainly 5-7 years was a good guide for street use.  This was (And is) a very easy parameter to test using a durometer coupled with a physical inspection of the carcas.  Tyre durometers are inexpensive and the only reliable way of determining the condition of the compound externally as it ages.  I do not recall ever sighting a tyre that showed any cracking during this period however so the crack test is of no consequence in this regard. 

Tyres from around 2002 (The date of manufacture) however began displaying weird results after only 4 years of use.  I found that the life of tyres in terms of going hard was decreasing by approximately 1-2 years.  When I took this up with the tyre engineers I was told it was because of the enormous pressure tyre manufacturers were under to reduce rolling resistance.  They blamed the addition of silica (Which was an additive designed to control hysteresis) prematurely ageing the compound. 

I don't test tyres like I used to, however I still use a durometer annually to note the hardness of the compound.  I find with tyres for the street these days,  I only get a maximum of 5 years out of them before the compound ages and sometimes as little as 4 years.  This is easily measured not only by the durometer but also by lateral acceleration tests and particularly wet braking results. Once the tyre passes 3-4 points on the durometer scale, I change them.

Incidentally,  Michelin tyres from China performed exceedingly poorly in maintaining grip over the life of the tyre when I tested them in about 2008.  They were on par with Maxis/Kumho/Other import rubbish.  Finally, be very wary of tyre tests that only test the tyre when new.  The tyre should be tested when new but also as it ages.

Tyres, like oil is subject to much conjecture and opinion.  It's really important when dealing with items of a safety nature to refrain from emotive and subjective judgements.

 

 

I just did a search via eBay under "Type A rubber tester" and came up with this:

http://www.ebay.com.au/itm/K1BO-Practical-Shore-Type-A-Hardness-Rubber-Tester-Tire-Tyre-Meter-Durometer-New-/181847421536?hash=item2a56f37260:g:dOMAAOSwECZUol4w

It's probably not the last word in accuracy, but I suspect it doesn't matter provided you get a reading off the tyre when new.

[TINGY]

That's great info carl, i would say that's definitive.

[TrevMcRev]

Who's back tyres last long enough for this to even be a discussion?!!

And you 928 guys got V8s too!  What's wrong with you?

C'mon ANF.  Just smoke those babies up and get some freshies.

 

[ANF]

My apologies,  I assumed incorrectly it would be in your 1983 manual,  here's Porsche official position for the 1980s:

 

 

With regards to tyre technology moving on in 33 years:  When I was testing tyres annually from 1998 I determined approximately after 5-7 years of use the tyre maintained almost all of its elasticity (And therefore most of its grip) provided it still had 2mm of tread.  This was determined using the Shore Durometer ASTM D2240 Scale A standard.  The tyre was pretty constant starting fresh with a rating around 70-75 using tyres with a TWI of 140 rising to 73-78 after 5-7 years.  Back then that was the Pirelli P-Zero Giallo, Bridsgestone S-01 and a Continental I can't quite recall, a Sport Contact I think.  The vehicles I used for testing were a 1987 Carrera 3.2 and a 1976 Ferrari 308 GTB.  The advantage of these two cars was the fact they used the same size tyre, 205/55/-16 and 225/50-16 and both vehicles are particularly sensitive to tyre condition. 

From 7 years the tyre fell off a cliff with hardness increasing alarmingly and particularly wet braking distances increasing.  Tyres used aggressively or on the track hardened faster, but certainly 5-7 years was a good guide for street use.  This was (And is) a very easy parameter to test using a durometer coupled with a physical inspection of the carcas.  Tyre durometers are inexpensive and the only reliable way of determining the condition of the compound externally as it ages.  I do not recall ever sighting a tyre that showed any cracking during this period however so the crack test is of no consequence in this regard. 

Tyres from around 2002 (The date of manufacture) however began displaying weird results after only 4 years of use.  I found that the life of tyres in terms of going hard was decreasing by approximately 1-2 years.  When I took this up with the tyre engineers I was told it was because of the enormous pressure tyre manufacturers were under to reduce rolling resistance.  They blamed the addition of silica (Which was an additive designed to control hysteresis) prematurely ageing the compound. 

I don't test tyres like I used to, however I still use a durometer annually to note the hardness of the compound.  I find with tyres for the street these days,  I only get a maximum of 5 years out of them before the compound ages and sometimes as little as 4 years.  This is easily measured not only by the durometer but also by lateral acceleration tests and particularly wet braking results. Once the tyre passes 3-4 points on the durometer scale, I change them.

Incidentally,  Michelin tyres from China performed exceedingly poorly in maintaining grip over the life of the tyre when I tested them in about 2008.  They were on par with Maxis/Kumho/Other import rubbish.  Finally, be very wary of tyre tests that only test the tyre when new.  The tyre should be tested when new but also as it ages.

Tyres, like oil is subject to much conjecture and opinion.  It's really important when dealing with items of a safety nature to refrain from emotive and subjective judgements.

 

 

I just did a search via eBay under "Type A rubber tester" and came up with this:

http://www.ebay.com.au/itm/K1BO-Practical-Shore-Type-A-Hardness-Rubber-Tester-Tire-Tyre-Meter-Durometer-New-/181847421536?hash=item2a56f37260:g:dOMAAOSwECZUol4w

It's probably not the last word in accuracy, but I suspect it doesn't matter provided you get a reading off the tyre when new.

Thanks for that. My manual has the first part but not the second part referencing 6 years.

Looks like you have done some tyre testing Is it worth getting one of those tester tings?

[Coastr]

Great info.  Maybe you could explain what a durometer does and how to use it effectively?

[firstone]

I promise to wear my tyres out quickly.

 

Decision easy. ?

 

[tazzieman]

928s go through back tyres quickly , and of course fronts if you like to "press on".

Now being the sort of guy who yawns at the usual line up of 911s and other Porsches in the club scene , I go around noting tyre dates. Anoraky,  but there ya go , gotta find something to educate and titillate the mind. Down in poor old ignorant Tassy , people do not replace on age; the guys who race replace when they wear them out,  the others treat them as weekenders , and I know some on 15 year old+ tyres. And horribly cracked drilled brake rotors.

Even if we had RWC here , I doubt whether that would enforce new tyres. There are classics kicking around with 40-50 year old tyres - seriously.

Yet I cannot recall a single accident in a classic of any brand attributable to old tyres. Nor indeed a modern Porsche. We must be good drivers down here,  or just wusses on public roads. Or my memory is piss poor.

So as usual , it's theoretical and anecdotal , and the internet is just like the village rector - good vs evil , black vs white.

Oils ain't oils and as the Chinese Michelin comment above alludes , rubber ain't rubber.

[KGB]

When was the last time one of your a.m. Tassie classic car mates had his house razed by fire?

[tazzieman]

When was the last time one of your a.m. Tassie classic car mates had his house razed by fire?

You tell me , comrade

I fought fires off in '97. What doesn't kill you...

[KGB]

My point is we're all insured for fire, no matter (nationally) how rarely it occurs.