Tire rubber durometer rating -- stability

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SUMMARY

The discussion centers on the durometer rating of karting tires imported from Taiwan, specifically a discrepancy where a sample tire measured 60-65D instead of the specified 65-75D. The factory claims that the tire compound remains unchanged, attributing the hardness increase to transportation conditions. Factors such as UV exposure and temperature during shipping are noted as potential influences on tire hardness. The conversation highlights the need for traceability and proper inventory control, suggesting that the timeline of shipping may not justify the observed change in durometer rating.

PREREQUISITES
  • Understanding of durometer ratings and their significance in tire performance.
  • Knowledge of the effects of UV exposure and temperature on rubber compounds.
  • Familiarity with tire manufacturing standards, including DOT regulations.
  • Basic principles of inventory management and quality control in manufacturing.
NEXT STEPS
  • Research the impact of UV exposure on vulcanized rubber properties.
  • Learn about the ASTM D2240 standard for measuring durometer hardness.
  • Investigate best practices for inventory control in tire manufacturing.
  • Explore case studies on the effects of transportation conditions on tire quality.
USEFUL FOR

This discussion is beneficial for tire manufacturers, karting enthusiasts, quality control professionals, and anyone involved in the importation and testing of rubber products.

gusss
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Hello; I import karting tires from Taiwan , while reviewing a sample tire sent for inspection for our order, I noticed a change in spec. of Duro rating . We spec. them at 65-75D ,this sample came in at 60-65D ..here is the factory response=
Hi Gus,

The tire factory explained that the tire compound is no changed so far. But the tires are getting harder after by sea. One month transportation under the Sunshine and the tires are harder. This time, you received the tire which is by air and just several days to arrive to your hand. Please kindly understand it. The tire factory has no change for spec of the compound. Please don’t worry it. Thanks

Please some Poly engineer, give us some ammunition to call this "bull"
any help much appreciated , gus.. (www.vintagespeedtires.com)
 
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If you don't get a good answer here under materials, I'll move it to M.E. Automotive. Perhaps better answers there.
 
Can you read a date code, or other traceability mark on the tire that indicates its manufacture date? This would clarify the timeline. DOT (US Department of Transportation) requires this, and most race car tire manufacturers (Goodyear, Mickey Thompson, Hoosier, Firestone, Goodrich, etc.) do this as well. I'm not sure non-DOT imported tires are handled like this.

Tire temperature, UV exposure, O2, O3 can influence hardness over time, among other things. https://pubs.acs.org/doi/abs/10.1021/ie50360a009?journalCode=iechad I'm having trouble finding a good article on vulcanized rubber oxidation that isn't behind a pay wall. Tires will degrade faster in the sun, or at elevated temperature, so there's at least a grain of truth there.

As far as ammo--I wonder how much sun those tires see while in a closed container in the middle of a container ship. More likely, the inventory control is poor, especially if they have no traceability or date codes on the tires. It seems unlikely the tires were cost-effectively transported by plane, but I could be wrong. You may be able to ask a few questions about the shipper to see if the story holds up, and learn if they are going to keep shipping by air in the future, or if it will be random as required to explain QC issues when they occur.:smile:
 
Wait a month and test again? Inventory is expensive, but you could easily use up that month arguing about it. And I would start looking for a different supplier.
 
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Thanks ChemAir; Yes these tires have a date code ..The sample tire airmailed to us was just made, normally we ocean ship, and that time line is about one month, this was airmailed for a OK to expedite production.. I find it hard to believe one month in a container would raise the Duro 10 points on Shore A scale..
These tires go on vintage racing karts, and because of earlier frame designs, a to soft compound will incur frame binding, and karts can flip over.. I've had other problems with this factory ,and usually with enough counter ammo they rescind. I'm not a Poly chem guy ,so I was looking for some good data to counter . Being such a niche market I'm limited for small production..thk/u. for your info and time ..gus..