Category: Atomic

I’ve been running the latest incarnation of Atomic’s ball diff since the release of the MRV and was happy to see that the company is now including a machined spur and a set of aluminum dust guards with the MRX Ultra v1.1 kit. These are welcome upgrades that turn an already good diff into an excellent one.

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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.

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When I was building the MRX Ultra, I noticed something was a bit off with the caster on my car. No matter what, the two sides were not the same. After tearing everything down again, I found that this problem was caused by the knuckles. Long story short, the two threaded bits did not line up, causing about a degree of difference in caster.

Fast forward to today when I received a box of goodies from Atomic that included a new set of knuckles, knuckle ball shims and a set of tuning springs.

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Like most MRX Ultra owners, I’ve been waiting for Atomic to release springs for their flagship car. While we are getting new springs for the sides, the company said this week that Ultra owners should use the rear springs from the MRX Master.

The Master springs are longer and wider than the stock spring so I was curious to see how well they would work.

Right off the bat, I had some issues getting the Ultra’s ride height down to where I had it before, which was around 2mm. The only way I was able to come close was to barely screw on the spring tension nut.

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If you’re like me, you probably built your MRX Ultra, mounted up a set of fresh front tires on your favorite wheels, gave them a spin and was surprised to hear a rubbing noise. The reason for this is that the car was designed to be used with Atomic’s own wheels which have a fairly narrow inner bearing hub.

With other wheels, like those from Reflex, the hub is a bit wider and may rub on the ball cups. Here’s a picture below of a wheel rubbing on the bottom ball cup.

The fix here is pretty easy and that is to take one of the extra silver 0.5mm shims that come with the kit and put it between the knuckle and the bottom ball. You may also need to place a shim above the knuckle if you’re experiencing rub up there. You’ll want to check this with your wheels straight and when turning.

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My MRX Ultra was delayed due to Chinese New Year but it finally arrived late last week. Like the MRX Master and MRV, the car comes in a small black box. Inside, you’ll find twelve bags with an assortment of parts. I’ve included pictures of the bags below.

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Atomic has posted what appears to be the final version of the manual for the MRX Ultra online. It has some great pictures showing how the new trailing axles and rear damper work.

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The big news over the weekend was Atomic’s latest pan car, the MRX Ultra. Featuring an extremely low center of gravity, the MRX Ultra comes with an integrated aluminum chassis and one piece motor mount. To further lower the CG, the mid damper has also been moved to the rear of the car and there is an opening on the chassis to allow the servo to sit lower.

There really isn’t much that carries over from the MRX Master. Even the front end has been updated with new lower arms that mount from the bottom like the BZ Master and knuckles that allow for 2 axle positions.

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