Yokomo 138G's
The Yokomo 138G's are indeed one of the best Rough asphalt tires availible. The "F's" work when the track temperature exceeds 100.F and the "H's" 120.F and above. The "F" & "H" compounds work really well in Nitro cars because they tend to heat tires up more than an Electric car.
For Smooth/sealed Asphalt; Sorex's are the way to go. The 36R's are the best all around for cool to hot weather (65.F to 120.F).
The other Sorex compounds don't seem to have as much grip as the 36R's when used on a Nitro car.