The Next TRF: A Racer’s Perspective

The TRF421 has been my main car for a long time now, and over that period myself and a close group of TRF racers have pumped in thousands of laps across a wide range of conditions, predominantly high-grip carpet. It’s a car I know well, and one that continues to perform at a very high level.

With that level of familiarity also comes perspective. Small traits become clearer, workarounds emerge, and you start to see where subtle evolution could push an already excellent platform even further. None of what follows is about fixing problems, it’s simply a racer’s view on where the next TRF could take things.  

Upper Arms

I primarily run on carpet, and one of the areas I’d most like to see addressed is the upper arms. The kit arms are absolutely fine in low to medium grip, but once grip ramps up the car can start to feel a little vague at times.

Many of us TRF racers have already found workarounds. arm stiffeners (Free download here), or third-party upper link conversions, but ideally this is something Tamiya could address directly. I don’t think the arm mould needs changing; simply offering the arms in a harder material would go a long way.

I’ll admit, I’m a bit lazy at the track. The convenience of sliding a caster plate and tweaking camber via the turnbuckle is a huge plus with the current design. Compared to traditional upper link setups, where turnbuckles constantly move and need checking every run, it’s just simpler and more consistent. That said, if the choice was between no alternative and a Tamiya-designed upper link kit, I’d take the latter. At least caster would remain fixed and repeatable.

Thicker Aluminium Steering Arms

The aluminium steering arms look fantastic, but they can bend after impacts. Outdoors this is less of an issue, but indoors, where track markers are far less forgiving, it becomes noticeable.

You can mitigate this by running larger shims on the arms, but ultimately aluminium will still bend given enough abuse. Unsurprisingly, TRF racers quickly started producing thicker carbon versions, reinforcing the key areas. A factory option here would make a lot of sense.

Active Shock Towers

Rear active towers would be a welcome option. Having made these myself on everything from the TRF417 onwards, I know how useful they can be in certain conditions. It would be great to see this option officially supported on the TRF421 platform, or its successor.

Going Low

One of the biggest performance jumps for me came from moving first to the Tamiya aluminium chassis, and then to the Wierc aluminium and steel chassis. As with all chassis plates, flex characteristics change, so that always needs factoring in—but the standout difference was height.

The 1.5mm and 1.2mm Wierc chassis sit noticeably lower than the standard car, and that fundamentally changes how the car feels through the corners. I’d be very surprised if the team drivers haven’t reached similar conclusions.

Whether that’s achieved through a thinner chassis, shorter shocks (although I really like being able to run 20mm springs), or a combination of both, I do think bringing the centre of gravity lower is an area worth exploring.

Simultaneous Chassis Options

Waiting for the aluminium chassis release was frustrating. Ideally, I’d like to see Tamiya offer both chassis options from day one, either as two separate kits or, even better, both included in the same box.

This approach worked brilliantly with the TRF420X (and the TA07MSX) and feels very much in line with the TRF philosophy. Personally, this would be my preferred solution.

Revised Differential Internals

The TRF421 differential uses the same internal gears as earlier designs. To be clear, they’re excellent—very smooth, durable, and even with motors faster than 17.5 blinky, they’ve required virtually no maintenance.

The only downside is occasional weeping around the outdrives. I’d consider myself a very experienced builder, and most of my diffs don’t leak (I rarely run below 5k oil), but every now and then you’ll get a small amount of seepage. It would be good to see this area refined further.

On the subject of outdrives, most touring cars now run bearings on the driveshafts. I’ve actually done this on my TRF420X using a few Axon parts. It’s beautifully smooth, although in all honesty I didn’t notice a real performance gain.

The potential benefit is reduced long-term wear compared to the pin cushions Tamiya still uses. That said, pin cushions are cheap and easy to replace, whereas tiny driveshaft bearings can be fiddly, and plenty of racers already complain about how awkward they are. As with most changes, there’s a balance to be struck.

It’s worth saying that none of the above takes away from just how strong the TRF421 is as a complete package. It’s reliable, beautifully engineered, and still very much at the sharp end of touring car racing.

These thoughts are simply the result of long-term use, high-grip conditions, and the natural desire to see Tamiya keep refining the chassis and moving forward. If history is anything to go by, Tamiya will already be exploring many of these areas. Whatever form the next TRF takes, it’s exciting to think about where the platform could evolve next.