Rare Upgrade for Mini-Z MR-03: Inner Tube Shocks (MZW416B)

One of the most important tuning tricks on an RC car is suspension dampening. Slowing down shock rebound increases stability. In the back of a Mini-Z, an effective dampening mechanism is using damper disks, which are easy to tune with tension and grease. The front suspension is not so easy. Some people grease the bottom of the king pins, but there's not a lot of surface area. Today I will do an uncommon upgrade that many people do not know about. It should be a fun one!

Kyosho makes this MZW416B upgrade option, the Inner Tube Shock Set, for MR-03. It adds a pair of pistons and tubes inside the same front springs. Grease can be applied inside to dampening the suspension. Let's see how the stock suspension behaves in slowmo. As you can see, the chassis bounces up and down quite a few times. The bouncing makes handling less predictable. If we look at a more advanced chassis, such as this GLR-GT, the front suspension is a double wishbone setup with coilover shocks. I applied shock grease onto the pistons to dampen the bounces. I haven't serviced the shocks in a while but they still do a good job of settling down the bounces.

Let's install the inner tube upgrade. The pistons and bottom spring holder are made of metal. Here's the instruction manual. Please note that the front suspension arms are different vs stock. The piston is attached to the suspension arm via a tiny 1.5mm ball stud. One side is nice and free, but this one is stiff. Making ball joints work is part of RC life. When the ball is extra small though, it's pretty annoying. I ended up using a 1.3mm dremel engraving cutter to remove some material from inside the ball cup. Making sure the new suspension arms swing freely. With the rest installed smoothly, we can see the white inner tubes inside the springs now. I guess they are made of delrin.

I've kept the same purple springs (medium soft), and I haven't applied any grease yet. Let's do the bounce test. With no grease as a dampening agent, the bounces remain.

Let's try the Atomic 35000wt first. This might be too thick. Luckily, with MR-03/PN25W, the front shocks are easy to access. With 35000wt grease applied, the degree of bouncing has decreased significantly. It's not surprising but still super cool to see.

The dampening is looking good, but I feel the suspension is too stiff after adding grease. Let's try softer ones. I replaced the MR-03 medium soft purple springs with GLR's medium black ones. They are softer than Kyosho's. After switching to softer springs, shock rebound seems too slow. Let's apply a lighter grease. This time, I will use Kyosho's 15000wt grease. This combination of lighter grease and softer springs feels better. The real test is on the track, of course.

Serious racers of MR-03 will opt for something like a PN Double A-Arm frontend, but I think Kyosho makes some fun upgrades too. The idea of adding dampenable inner tubes to the front shocks is sound. The simplicity is part of the Mini-Z charm. Kyosho is rolling out the new MR-04EVO2 as we speak and my guess is MR-04 will soon replace MR-03. Let's hope Kyosho continues to release cool upgrades!

This is Sammy and thanks for watching!

Music: "Instructions for Living a Life", Savfk (   • Instructions for Living a Life by Savfk  )