INTRODUCTION : Volvo enthusiasts at some time or another consider bigger brakes. Disc Rotors are a component needing understanding. Rotor measurements have been made for ventilated discs 240 / 740 / 940 Turbo, with a 'scale relationship' drawing for easy understanding.

NOTES: The 240 rotor is more inboard The 740 rotor is larger in dia than the rest, but note its still the same thickness as a 240. With the tall, slim disc warpage is a risk so make sure the wheel nuts are torqued up very evenly. Volvo learnt a brake lesson with the 740 rotor and hence the Jumbo rotor was designed with a proper width to diameter ratio, meaning wider and less tall. One upgrade out there is Mazda RX7 Turbo brakes onto a 240. The upgrade uses the 740 rotor which you can see is outboard 11.5 mm. Therefore Volvo factory 240 rims (including 5 spoke Gemini 16x7") will interfere with the RX7 / 740 setup as normally on a 240 the rim sits very inboard, hence very close to the standard caliper. Solution is aftermarket rims.     VOLVO DISC ROTOR BASIC DIMENSIONS - by Anthony Hyde 240 Std OD=263.3 mm (10.36") 22 thick, Hat 150 OD (4 piston caliper)            240 Rear Discs = 281 mm 740 1988-95 OD=286. 7mm (11.28") 22 thick, Hat 160 OD (double piston caliper, smaller pad than jumbo) 940 Jumbo OD=280 mm (11.033") 26 thick, Hat 150 OD (smaller OD, but thicker, single larger dia piston caliper, larger pad than 740) Biggest difference is in hat diameters. The Jumbo is the same design as the 240 rotor hat design plus same inside ventilation system, the difference being a much thicker rotor thicker and larger outside dia 280 vs 263 = 23.4 mm). The 740 has a larger hat and outside ventilation. Thanks to Peter Linssen & others on Turbobricks for discussion on Jumbo 940 brakes.

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