WEIRC Tamiya TRF421 1.5mm Aluminum lower Deck Review

2025 is shaping up to be an exciting year for touring car chassis development. Manufacturers are clearly experimenting with unconventional materials and surface thicknesses pushing boundaries beyond what’s traditionally been considered standard.

One standout area of testing is the use of 1.5mm thick aluminium chassis on both high-grip carpet and asphalt tracks. While aluminium on carpet isn’t particularly new, what’s interesting is its emerging use outdoors—an area typically dominated by carbon fibre.

WEIRC Enters the Scene

WEIRC has entered the market with a range of 1.5mm aluminium chassis designed for a wide selection of current touring cars. Fortunately, the Tamiya TRF421 hasn’t been left out so I promptly placed an order to give the chassis a test.

Design

The chassis comes in a sleek, black anodised finish, with lightly chamfered edges to reduce the risk of snagging when cornering. 

It follows the same contours as the original TRF421 carbon chassis, with some alternate cutouts to improve flex characteristics and reduce weight.

Previously, I’ve run the Krazed Builds 2mm aluminium chassis during winter. It’s narrower and features far more cutouts. Despite being unfinished (natural metal), it weighs slightly more.

A Different angle?

Switching to 1.5mm aluminium introduces a new issue: the standard TRF screw countersink angle is too steep. Using the kit screws will result in them not being flush with this thinner chassis.

To address this, a 110° low profile countersunk screw is needed to fit snugly in the chassis and better distribute the load. WEIRC offers a 50-piece 110° screw kit that, while not manufacturer-specific, should suit a wide range of cars.

After a quick teardown, I was ready to fit the new chassis :)

Building

This chassis has been very well designed. I encountered no issues with fitment in any area and all the measurements from the original chassis are accurate so no geometry has chang

Here are the weight comparisons using corner scales

• WEIRC 1.5mm aluminium - 79.6g
• Kit Carbon TRF 2.25mm - 68.6g
• Tamiya Aluminium deck (2.0mm) - 91.7g
• Krazed builds 2mm aluminium 83.8g

These weights are pretty much where I would assumed they would be in comparison to each other

Build Notes
Screw Kit: The WEIRC screw set is designed to be universal. 

The TRF421 primarily uses 6mm screws, but I came up short, some 8mm screws are included, which I used for securing the bulkheads. I checked that they didn’t bottom out, and they seated correctly.

Lower Suspension Mounting: On some TRF421s, the lower suspension arms have pulled through the carbon chassis. I’d previously tried an 8mm screw here but had no way to secure the nut. With the new 110° screws, this issue seems resolved.

Roll Bar Mounts: The mounts include alignment pins that now stick out slightly due to the 0.75mm thickness difference between the new chassis (1.5mm) and the original (2.25mm). I initially added a 0.5mm shim to raise the mounts, but this caused the steering ball joints to rub.

Instead, I removed 0.5mm from the pins—allowing the mounts to sit flush. It may seem minor, but on a high-speed car, avoiding even slight contact can prevent damage to the track or chassis.

Front Bumper: Now sits slightly lower. I may trim it later but left it as-is for testing.

The chassis is all installed, ready to race. 

Track test

I’m not a fan of running major upgrades at competitive events without prior testing. With the next round of King of Clubs coming up, I headed to Cotswold Model Car Club for a shakedown session the weekend before.

Cotswold is my local track—ideal for testing in a race-like environment without the pressure. The forecast was warm with increasing track temps throughout the day, which typically slows lap times—but it’s the same for everyone.

I kept my previous setup, with only two changes:

• Installed a 1-piece top deck
• Removed rear toe gain

From the first few laps, the car felt more responsive, quicker to rotate and more planted through corners. The improved stability gave me the confidence to run thicker rear diff oil, helping to push more power out of corners.

By the end of the day, I had:

• Broken into the 17-second lap range
• Beaten my personal best by 4 seconds

A significant gain. :)

As the weather warmed, times crept up for everyone, but the car remained consistent and responsive to setup tweaks.

What about on Carpet?

The Rc Racer here..  

I’ve also been giving the WEIRC chassis a proper shakedown, this time on carpet. As a big fan of Tamiya’s aluminum chassis, I was really keen to see how this one stacked up.

 

The first thing that stood out was how similar the flex feels, it's remarkably close, in fact. The big difference, is that the roll center is dropped even further. On high-grip carpet, that’s a real advantage.

I've made quite a few tweaks to my setup, but right now the TRF421 is the best it has ever felt for me on carpet. The corner speed is outstanding, and I’m able to hold my own against some very quick racers.

Full disclaimer: I’ve gone down a slightly different setup route with this car, so it’s possible that if I’d done the same with the 2.0mm chassis, I’d be seeing similar results. That said, the WEIRC chassis is definitely worth considering for indoor racing. And with a steel version also on the way, things are about to get even more interesting.

Overall

I was initially sceptical about running aluminium outdoors, but I’m glad I gave it a shot.

The WEIRC chassis is beautifully made, with perfect fitment—no need for fettling. I particularly like the profiled side edges, which help prevent catching on curbs or rough edges.

Yes, the black anodising is scratched after outdoor use—but honestly, it’s no different from the wear you’d get on carbon.

This has been an eye-opening test. I’ll definitely be ordering another chassis to try indoors next.

Note : Due to excessive demand. WIERC has stopped taking orders until they catch up with the demand, and will then open orders again. 

WEIRC - Facebook (Please dont contact them until they say they are taking orders again)
WEIRC - Website