26 year old spare tyre replacement

Smudgemanuk

Smudgemanuk

Zorg Guru (II)
British Zeds
Joined
Dec 1, 2024
Points
104
Location
Bicester, Oxford
Model of Z
2.8l TU pre-facelift z3
I took my original spare tyre and wheel down to my local tyre shop

They said if they were me they would not get the tyre replaced, it looks in perfect condition, no cracks and no wear on the tread

But still, it seems a bit crazy to rely on such old rubber

What would you do in my situation?

Thanks Chris
 
Smudgemanuk said:
I took my original spare tyre and wheel down to my local tyre shop

They said if they were me they would not get the tyre replaced, it looks in perfect condition, no cracks and no wear on the tread

But still, it seems a bit crazy to rely on such old rubber

What would you do in my situation?

Thanks Chris
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Does it look like it would get you home or to a tyre repair shop at low speed in an emergency? If so, I'd put it back under the car.
 
Remember that spare should also be at 60psi..You can pick up newer ones from a 1 series on eBay cheap enough. Be at least 10 years newer.
 
Smudgemanuk said:
But still, it seems a bit crazy to rely on such old rubber
Click to expand...

a few years ago i raced a 1948 BSA at Pendine sands, as part of historical racing, the bike was exactly as was in 1948, including the tyres, rode that bike all over for many years, no tyre issue at all.

funnily though, watch the film, ''worlds fastest indian'' with Anthony Hopkins, top 10 movie for me, and theres a scene where hes cutting the tread off his tyres, and putting boot poilish on them to pass the scrutineer, before he heads out and makes 180mph runs.
H
 
ChrisD said:
These appear to be a different size. Do they fit in the carrier?
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Spare wheel was available in 15 and 16” ..both fit in the carrier 👍
Old..less old from a 1 series
IMG_9066.webp
 
Smudgemanuk said:
I took my original spare tyre and wheel down to my local tyre shop

They said if they were me they would not get the tyre replaced, it looks in perfect condition, no cracks and no wear on the tread

But still, it seems a bit crazy to rely on such old rubber

What would you do in my situation?

Thanks Chris
Click to expand...

Leave it well alone.
 
Smudgemanuk said:
I took my original spare tyre and wheel down to my local tyre shop

They said if they were me they would not get the tyre replaced, it looks in perfect condition, no cracks and no wear on the tread

But still, it seems a bit crazy to rely on such old rubber

What would you do in my situation?

Thanks Chris
Click to expand...

I just replaced my spare. It was original from 1999. I can tell you that after 7 years, the elastomer materials used in tire (tyre) manufacture do deteriorate and are at end of life. I have a degree in Elastomer Technology so know what I am saying. I would 'stretch' this may be by a year, perhaps two but no more. Combine this with the higher pressure (60 psi), replace it. Don't rely on the looks! FYI, I purchased a 125/80/R15 (Kumho this is a Continental brand) for $94. I can now drive and rest assured that if I need to use it, I can and not worry.
 
TexasZ3 said:
I just replaced my spare. It was original from 1999. I can tell you that after 7 years, the elastomer materials used in tire (tyre) manufacture do deteriorate and are at end of life. I have a degree in Elastomer Technology so know what I am saying. I would 'stretch' this may be by a year, perhaps two but no more. Combine this with the higher pressure (60 psi), replace it. Don't rely on the looks! FYI, I purchased a 125/80/R15 (Kumho this is a Continental brand) for $94. I can now drive and rest assured that if I need to use it, I can and not worry.
Click to expand...
Would the fact that the spare tyre (when stored) is hidden away from UV light make any difference to the elastomer life, or is that irrelevant? Always wondered, so good to have some one who knows about these things
 
GZed said:
Would the fact that the spare tyre (when stored) is hidden away from UV light make any difference to the elastomer life, or is that irrelevant? Always wondered, so good to have some one who knows about these things
Click to expand...
That is a great question. In part, the answer is yes. Direct sunlight/UV does break down the Carbon-Carbon links between the long chain polymers. Keeping tires out of direct sunlight will slow down this process but not significantly enough to extend the life by several years, The tyre manufacturers do include various UV protections/additives in their elastomer formulations that delay the effect of UV degradation (evidenced by surface crack) on the polymer chains but only to get them to about 7~9 years of active life. Here are some of the other reasons elastomers deteriorate over time. Apart from UV attack being a big one, all the factors discussed below each contribute to a continuous degradation of the elastomers. Tyre manufactures do run excellerated life cycles on the products that provide data to determine the expected working life. They add a factor of safety and that is how the 7 years is arrived at. When I said I would extend the 7 years to 8 or 9, I am eating in to that safety factor.

Hope this helps and apologies if the explanation became to technical.

. Oxidation:
  • Elastomers react with oxygen in the air, leading to chemical changes in their structure.
  • This process can cause the material to become brittle, lose elasticity, and crack.
  • Oxidation is accelerated by heat, light, and certain chemicals.
2. Chain Scission:
  • The long polymer chains that make up elastomers can break down over time, especially when exposed to heat, light, or mechanical stress.
  • This weakens the material and reduces its ability to stretch and recover.
3. Crosslinking:
  • In some elastomers, additional chemical bonds (crosslinks) can form between the polymer chains over time.
  • This can make the material stiffer and less flexible, eventually leading to cracking.
4. Environmental Factors:
  • Exposure to extreme temperatures, humidity, and UV radiation can accelerate the breakdown of elastomers.
  • Contact with certain chemicals, oils, and solvents can also cause damage.
5. Mechanical Stress:
  • Repeated stretching, bending, or compression can fatigue the material and lead to cracks and failure. The spare Tyre in our case is pressurized to 60 PSI so putting the elastomer under constant strain.
6. Ozone Cracking:
  • Ozone in the atmosphere can react with certain elastomers, causing surface cracks to form. We discussed this factor above.
7. Hydrolysis:
  • Some elastomers can react with moisture in the air, leading to degradation of the polymer chains. The plastic tray that the spare sits in does provide some protection from road spray but humidity is a factor.
 
TexasZ3 said:
That is a great question. In part, the answer is yes. Direct sunlight/UV does break down the Carbon-Carbon links between the long chain polymers. Keeping tires out of direct sunlight will slow down this process but not significantly enough to extend the life by several years, The tyre manufacturers do include various UV protections/additives in their elastomer formulations that delay the effect of UV degradation (evidenced by surface crack) on the polymer chains but only to get them to about 7~9 years of active life. Here are some of the other reasons elastomers deteriorate over time. Apart from UV attack being a big one, all the factors discussed below each contribute to a continuous degradation of the elastomers. Tyre manufactures do run excellerated life cycles on the products that provide data to determine the expected working life. They add a factor of safety and that is how the 7 years is arrived at. When I said I would extend the 7 years to 8 or 9, I am eating in to that safety factor.

Hope this helps and apologies if the explanation became to technical.

. Oxidation:
  • Elastomers react with oxygen in the air, leading to chemical changes in their structure.
  • This process can cause the material to become brittle, lose elasticity, and crack.
  • Oxidation is accelerated by heat, light, and certain chemicals.
2. Chain Scission:
  • The long polymer chains that make up elastomers can break down over time, especially when exposed to heat, light, or mechanical stress.
  • This weakens the material and reduces its ability to stretch and recover.
3. Crosslinking:
  • In some elastomers, additional chemical bonds (crosslinks) can form between the polymer chains over time.
  • This can make the material stiffer and less flexible, eventually leading to cracking.
4. Environmental Factors:
  • Exposure to extreme temperatures, humidity, and UV radiation can accelerate the breakdown of elastomers.
  • Contact with certain chemicals, oils, and solvents can also cause damage.
5. Mechanical Stress:
  • Repeated stretching, bending, or compression can fatigue the material and lead to cracks and failure. The spare Tyre in our case is pressurized to 60 PSI so putting the elastomer under constant strain.
6. Ozone Cracking:
  • Ozone in the atmosphere can react with certain elastomers, causing surface cracks to form. We discussed this factor above.
7. Hydrolysis:
  • Some elastomers can react with moisture in the air, leading to degradation of the polymer chains. The plastic tray that the spare sits in does provide some protection from road spray but humidity is a factor.
Click to expand...
So to sum up.......don't use 26 year old tyres! :p
 
OP.
I have a spare wheel for a Z3 going begging. It's only 24 years old, so a relative youngster! ;)
 
A long time ago when I was a student at what was then called the National College of Rubber Technology in north London (now subsumed into the University of North London), we had an accelerated life test apparatus called an oxygen bomb. If my memory serves me right it was a pressure vessel with water in the bottom which was heated to humidify the atmosphere inside, and that atmosphere was pure oxygen under pressure. The rubber samples were suspended in this chamber above the hot water. It didn't take long for some rubbers to be badly affected.

My employer was a domestic appliance manufacturer and we tested competitors' machines and their components.
 
motco said:
A long time ago when I was a student at what was then called the National College of Rubber Technology in north London (now subsumed into the University of North London), we had an accelerated life test apparatus called an oxygen bomb. If my memory serves me right it was a pressure vessel with water in the bottom which was heated to humidify the atmosphere inside, and that atmosphere was pure oxygen under pressure. The rubber samples were suspended in this chamber above the hot water. It didn't take long for some rubbers to be badly affected.

My employer was a domestic appliance manufacturer and we tested competitors' machines and their components.
Click to expand...
This is an important test and quickly shows how Oxygen and humidity combine to damage the long chain polymers. Add mechanical strain and then bad things start to happen pretty quickly. Thanks for this additional piece of information.
 
It's interesting, TexasZ3, just how image and quality are not always closely related. Without naming brands, one of the most prestigious brands both in the late 1960s and now in the 21st century, used a particular rubber compound in their washing machines tub/shell gaskets (the horse collar shaped 'bellows-like' gasket that seals off the static outer tub and the casing of the machine in front loading designs). This component is critical in not only making sure that the water remains inside the machine and doesn't leak out in use, but it comes into intimate contact with the wash load inside. Any decomposition will mark the clothes as they rub against it during the wash cycle. My company's product used compounds that had been thoroughly tested both in our laboratories and in field trials and, unsurprisingly, the gasket on our machine scored very highly in durability tests. This other brand, one from a European manufacturer, was so badly decomposed that it was semi-liquid on completion. My subject is principally synthetic polymers commonly called plastics and the design and materials thereof so I can only speculate on this material, but I assume it had de-polymerised back to its tree sap origins.
Many 21st century products use a rubberised tactile coating. Binoculars, cameras, small electronic gadgets, all are given this surface finish. Who hasn't found an MP3 player, or pocket video camera, for example, that has lain idle in a drawer for some years and found it now coated in a sticky, glue-like substance? This ruins a perfectly useable item in the name of point-of-sale quality feel.
 
  • Wow
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motco said:
It's interesting, TexasZ3, just how image and quality are not always closely related. Without naming brands, one of the most prestigious brands both in the late 1960s and now in the 21st century, used a particular rubber compound in their washing machines tub/shell gaskets (the horse collar shaped 'bellows-like' gasket that seals off the static outer tub and the casing of the machine in front loading designs). This component is critical in not only making sure that the water remains inside the machine and doesn't leak out in use, but it comes into intimate contact with the wash load inside. Any decomposition will mark the clothes as they rub against it during the wash cycle. My company's product used compounds that had been thoroughly tested both in our laboratories and in field trials and, unsurprisingly, the gasket on our machine scored very highly in durability tests. This other brand, one from a European manufacturer, was so badly decomposed that it was semi-liquid on completion. My subject is principally synthetic polymers commonly called plastics and the design and materials thereof so I can only speculate on this material, but I assume it had de-polymerised back to its tree sap origins.
Many 21st century products use a rubberised tactile coating. Binoculars, cameras, small electronic gadgets, all are given this surface finish. Who hasn't found an MP3 player, or pocket video camera, for example, that has lain idle in a drawer for some years and found it now coated in a sticky, glue-like substance? This ruins a perfectly useable item in the name of point-of-sale quality feel.
Click to expand...
motto. Your comments are spot on that visual quality does not represent functional or product quality. I have experienced first hand the sticky mess that some products experience after time. It can be removed by using denatured alcohol or petrol but what the heck...Tire design and manufacture have come a long way since the 1990's ~early 2000's but there are still limits to product life that must be followed. Look at the many plastic parts in our car that easily crack or just fall apart after 20~25 years. Tires manufactured in that time period should not be used under any circumstances no matter how good they look.
 
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