I often see customers make this error, using a 3x6mm screw instead of a 3x5mm (as per the manual) which won’t tighten down all the way in the front 2 holes of the rear topdeck mounting. The reason being, the rear ARS link ball studs being mounted from underneath and thus bottoms out against the top screw.
This will have a negative influence on the rear flex of the car, and will make the car less stable. Make sure that you use the correct screw lengths!
The Glassfiber topdecks are new option parts for the X4 platform. At only 1.5mm thickness, they do provide more flex than both the 2.0 and 1.6mm carbon topdecks. Since we first started testing with them in early summer, I've preferred them pretty much everywhere on asphalt. The only exception being the WC, which was held on a VERY high grip track. They do provide more mechanical grip. I've personally had good success with using the rear topdeck on the front as well, to help improve initial steering and response, at the expense of some mid corner steering. These topdecks also work great on low- to medium grip carpet.
Regarding the graphite hardness lower arms. They've been on my car for every race since I first received them (on asphalt). They do provide better consistency and response, especially in hot conditions. Keep in mind that they work the tires a bit harder, so tire overheating may increase - and they do give up a bit of overall grip. But - the benefits usually outweigh the disadvantages. I've loved running them outdoors. I even like them for certain carpet conditions, especially for higher grip levels. The difference is the composite plastic material, which is a graphite mixture instead of pure composite, making them stiffer. The arms were used by the team at the recent IFMAR World Championships!
