2010 FX Nytro XTX rear springs
Part 64
8HL-47473-00-00 SPRING, REAR 1
Part 65
8HL-47474-00-00 SPRING, REAR 2
2009 FX Nytro RTX rear springs (including optional springs)
Part 67
8GL-47473-00-00 SPRING, REAR 1 (K=1900NMM/DEG) | AP
8GL-47473-10-00 SPRING, REAR 1 (K=2100NMM/DEG) | AP
8GL-47473-20-00 SPRING, REAR 1 (K=1400NMM/DEG)
Part 68
8GL-47474-00-00 SPRING, REAR 2 (K=1900NMM/DEG) | AP
8GL-47474-10-00 SPRING, REAR 2 (K=2100NMM/DEG) | AP
8GL-47474-20-00 SPRING, REAR 2 (K=1400NMM/DEG)
Looks like the XTX has the 1900 NMM/DEG springs on from the factory (comparing part numbers), and you acan order stiffer 2100NMM/DEG springs (optional for the RTX) since the original XTX spring part can be used on the RTX (same part numbers). The price from the dealer in the states that I use is less than $60 per spring.
Another option is to buy for the rear suspensions is the Hygear torsion spring spacers (
http://www.hygearsuspension.com/Product ... rings.html). They stop the springs from twisting, effectively making the springs stiffer.