> I have 185/15 on the car now. I was lead to believe that this
> size converts to
> 205/70 15.
They are roughly the same diameter, but the 205/70 is almost a full inch
wider.
While we're on the subject, can someone tell me what the "engine rpm per 10
mph" figure for a TR6 is ? It's usually in the handbook, which I don't
happen to have.
> I don't even know what the numbers mean and how a
> 205/55 differs from a 205/70.
The first number is the approximate tread or "section" width in millimeters,
the second number is a measure of the sidewall height, expressed as a
percentage of the first number. A 205/55 has a sidewall height of roughly
55% of 205mm, which is 112.75mm or about 4-7/16". A 205/70 has 70% of 205,
or 5-5/8" Thus, a 205/55 is roughly the same width as a 205/70, but is a
much "lower profile" tire, slightly under 24" diameter; while a 205/70 is
over 26" in diameter.
> Is there an objective source for tire performance out there?
Test reports abound, but there are so many other factors that affect tire
performance and overall handling, it's hard to know if the test results will
match your car. There's lots of good information on the web, one of my
favorites is Tire Rack's web site (I also buy most of my tires from them).
http://www.tirerack.com
NFI, except of course I hope they stay in business so I can keep buying
tires from them <g>
Randall
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