For what it's worth, K series S3, weather equipment,no heater ,leather seats, powerspeed exhaust, 6 speed manual ,weighed 560 kg with about 25 kg of fuel R500D with weather equipment ,heater ,leather seats and six speed manual weighed 580 kg ,again with about 25 kg of fuel . Both weighed on same Trading Standards certified weighbridge without driver . As always more than Caterham would have you believe.