BGTV8

With 3.9 ratio
Holinger: with 265/650R18 slick @ 8500rpm limit

Ratio Diff Mph Kph
2.570 3.909 8500 64 104 Dia 25.6in 650mm
1.990 3.909 8500 83 134
1.600 3.909 8500 103 166
1.350 3.909 8500 123 197
1.140 3.909 8500 145 234
1.000 3.909 8500 166 266

Holinger: with 280/655R18 or 310/655R18 slick @ 8500rpm limit

2.570 3.909 8500 66 106 Dia 26.1in 663mm
1.990 3.909 8500 85 137
1.600 3.909 8500 106 170
1.350 3.909 8500 125 201
1.140 3.909 8500 148 238
1.000 3.909 8500 169 272

Holinger: with 290/675 slick @ 8500rpm limit
2.570 3.909 8500 67 108 Dia 26.6in 675mm
1.990 3.909 8500 86 139
1.600 3.909 8500 107 173
1.350 3.909 8500 127 205
1.140 3.909 8500 151 243
1.000 3.909 8500 172 277


With 4.08:1 ratio
Holinger: with 265/650 slick @ 8500rpm limit
Dunlop 265/650R18 Slick
2.570 4.083 8500 62 99 Dia
1.990 4.083 8500 80 128
1.600 4.083 8500 99 159
1.350 4.083 8500 117 189
1.140 4.083 8500 139 224
1.000 4.083 8500 158 255

Holinger: with 280/655 slick @ 8500rpm limit
Dunlop 280/655R18 Slick and Dunlop 310/655R18 slick
2.570 4.083 8500 63 101 Dia
1.990 4.083 8500 81 131
1.600 4.083 8500 101 163
1.350 4.083 8500 120 193
1.140 4.083 8500 142 228
1.000 4.083 8500 162 260

Holinger: with 290/675 slick @ 8500rpm limit Dunlop 290/675R18 Slick
2.570 4.083 8500 64 103 Dia
1.990 4.083 8500 83 133
1.600 4.083 8500 103 165
1.350 4.083 8500 122 196
1.140 4.083 8500 144 232
1.000 4.083 8500 165 265

There is a good spread of speeds available for the circuits we visit. Philip Island is without a doubt the quickest apart from Bathurst, with Sandown and Sydney MotorSport park the next quickest and Winton and Mallala are the slower tracks.

I probably won't bother with 675 tall tyre and use the 655 diameter tyre as the standard (280 on the front and 310 on the rear, both on 10.5" wheels), and use 3.9 FD ratio at Philip Island and Bathurst, and the 4.08 elsewhere. Using a smaller diameter tyre helps lower CoG without having to raise suspension pivot points.