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!
XRAY X4 tech tip: 0mm hub height
You may have seen from team driver's set-up sheets that we sometimes use 0mm under the front (or even rear) hub/upright. As stated in the manual, less than 0.5mm isn't recommended to be used. It is possible however, with the following modifications:
Remove the outer screw that holds the hub plate to have clearance for the lower arm on suspension compression. Alternatively, use an aftermarket M3x4 screw with a low and flat head and thus, will have clearance. The hub plate can shift in a crash, hence why a 3rd option is to CA glue it to the hub.
The ball studs need to be cut 0.5mm shorter to have clearance for the driveshaft. This can easily and quickly be done using a Dremel tool with a cutting disc or such.
What's the benefit of such a low hub height? It can help to improve the car's traction on that end of the car, or the overall traction when used in front- and rear. This is especially recommended on low- to medium grip asphalt, and low grip carpet surfaces. The car will scrub more speed in the corner (will be less free) but will have more grip!
Keep in mind that when you lower the hub height, you need to use a 0.5mm higher downstop value to retain the same amount of droop, when using a HUDY downstop gauge.
