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Discussion Starter · #1 ·
"Hard" and "Soft" mean different things to different tire manufacturers. I wanted to start a thread where we can share data to understand how compounds compare between brands. If you have a durometer please share your readings and we can create a master list.

BrandModelSizeCompoundDurometerWeight (lb)Notes
MRFZDM3175/70R15Soft62A23New at 65F
PirelliK175/70R15Medium (K4)60A28New at 65F
YokohamaA053150/625R15Soft (A50)75A24New at 65F

Durometer measurements are in Shore A. I also included weight measurements I have made.

The compound definitely gets harder after a number of heat cycles. I measured a well used Pirelli medium at 85A. Everyone always talks about how used tires lose grip because they lose their sharp edges, but I also wonder how much of that is the compound not being compliant due to heat cycles.

Post up your measurements below and I will add them to the master list. If I remember I will try to bring my durometer to the rallycross at Glen Helen on 4/25 if anyone wants to take some data.
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