Mr. Mike,
> What's the approximate profile number for a metric tire
> (tyre)? I've been running some numbers to see what I can fit
> on the TR4 with TR6 wheels, and I'm not sure what the original
> rolling radius was...
I went through this once about a year and a half ago. Fortunately, I had 2
cars worth of the original 5.60-15 tyres to check out carefully before I
chose replacements. The original tyres had an original radius of about 315
mm, really close to a "modern" 155/80-15, or the 165/75-15 you chose as
your reference.
> Specification Sidewall Radius Circumference Revs/Mile Difference
> 165/75-15 124mm 314mm 1974mm 815 0.0%
> 165/72-15 119mm 309mm 1943mm 828 -1.6%
> 165/70-15 116mm 306mm 1923mm 837 -2.6%
> 165/65-15 107mm 298mm 1871mm 860 -5.3%
> 195/60-15 117mm 308mm 1932mm 833 -2.1%
> 195/50-15 98mm 288mm 1810mm 889 -8.4%
> 205/50-15 102mm 293mm 1841mm 874 -6.8%
Actually, the "best" size tyre I found is:
Specification Sidewall Radius Circumference Revs/Mile Difference
185/65-15 120mm 314mm 1952mm 815 -1.2%
This tyre looks good on the TR4, gives a little wider contact patch, but is
just a tad bit too wide for the original 4.5" TR4 rims. But since you
mentioned you have TR6 rims (I didn't know you could do that!?!) which are
5.5" (?post '69?), they should fit perfectly!
Pat Vilbrandt John Fluke Mfg. Co., Inc. Everett, Washington USA
UUCP: pwv@tc.fluke.COM or: { uunet, uw-beaver, sun, microsoft }!fluke!pwv
|