I've got a set of Cooper Sportmaster Metric tires on my TR4A IRS. These look
pretty good on the 4A, they have an aspect ratio of 82. Here's my question.
In looking at the TR4/4A factory manual, I see that Michelin "X" radials
should run a pressure of 17/24 (front/rear). Dunlop radials are listed at
24/28. Well, these Coopers have probably the softest sidewall of any tire
ever. At 24 lbs, you can push your thumb WAY into the sidewall. The contact
patch looks like a banana slug, with the sidewall bulging out. I am currently
running 28/32 on the 4A, and the car seems to sit right and tires don't bulge
out as much; the scraping problems that I wrote to the list a couple weeks
back are much improved. But, I think I could go a few pounds higher. The
tires have a max pressure of 44 psi. I'm thinking of going up to 32/36.
Question to the list: I'm baffled by "recommended tire pressures" since surely
the recommendation is a combination of what is best for the car and best for
the tire. My "Tire Guy" has me run my P4000 Pirellis at 40 psi all around on
my Audi A4, which is quite above what the owners manual states.
My question to the list: Should I run 32/36 on my TR4A with these Coopers?
Anyone else running these tires?
Thanks,
Chris
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1964 TR4A (running well, looking sharp)
1959 TR3A (in for heavy maintenance)
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