I’ve been racing the MRX Ultra on and off for the last few months and, with the release of the new knuckles and tuning springs, its replaced the MRV as my car of choice for my local track’s 2500kv spec class. With this in mind, I wanted to share some tips and my current setup.
The brass balls on Atomic’s Double Wishbone Suspension (DWS) are one of those things you either love or hate. When setup correctly, they are great but it can take a bit of work to get everything moving without binding or being too loose.
With the Ultra, Atomic used brass balls on the top arms as well as the bottom and, for awhile there, I felt like all I was doing was adjusting screws. Another Atomic driver (thank you Michael) at my track suggested that I try some higher quality screws. The theory here was that with tighter tolerances, the screws would sit in the center of the ball, which in turn would fit better in the arms.
So far this theory has been true and I’ve found that in most cases I can just tighten the screws down and not spend another 5 minutes messing around so they’re not too tight or loose. Just remember to put some thread lock on the screws so they don’t back out during a race.
On the rear of the Ultra, I’m now using two 0.5mm shims above the white plastic ball like its shown in the v1.1 manual. This raises the height of the motor pod by 0.2mm so that it articulates better. If you decide to do this, make sure that you also insert a shim or two between the carbon wings and the chassis. If you don’t do this, you will have some unwanted preload on the side springs.
Using two 0.5mm shims above the ball also lowers the rear ride height a bit, which allowed me to go back to the stock, black bearing hub. Even with the purple rear spring, there were no issues getting the ride height below 2mm.
Right now my biggest challenge has been to keep the rear pod moving smoothly. For whatever reason, the front screw likes to loosen up after awhile and I have to keep checking to make sure that the pod is not moving in directions its not supposed to.
The rear damper also attracts a lot of debris. Putting a very light coating of grease on the kingpin screw will help keep it clean. However, you will still be tearing this damper down and cleaning it fairly often. With the damper being in the rear, there really is no way around this.
