I had been running Dunlop SP4n's on my car until they went out of
production. I put a new set of Dunlop SP20's on my car before the Alaska
trip. Good news: They seem to handle at least as well as the SP4's.
It's hard to say how far they _should_ go before they're worn out. The
Alaskan roads are very hard on tires, having eaten up four sets of tires
on my trailer during the trip. The SP20's took a beating on 5000 miles
of gravel. Today I had them off the car for a good look while swapping
out the race rubber. The fronts look about 60% worn after 20,000 miles,
the backs about 80% worn.
The big thing is that the tread shows a lot of shallow chunking from the
gravel roads, notches 1/4" to 1/2" across but only about 1/16" deep. But
the notches cover at least 60% of the surface, and a lot of them overlap.
!/4 of the travel miles on these tires were on those gravel roads, so
lots of rubber was removed that way.
The other good news, obviously, is that these tires took all that the
Alaskan roads could dish out for two months and came back in one piece,
no flats. I don't know that it's anything special in that respect about
these tires. I suspect that any steel belted radial might do as well.
The only flats (on cars) recorded during Brit Run To The Sun were on the
Morgan from Dallas. One took a nail in a campground, but the other two
were caused by wrinkles in the inner tubes, the fault of the installers.
I still like my Dunlops. I will buy another set when these are used up.
Barney Gaylord
1958 MGA with an attitude
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