WeiRC Tamiya TRF421 Steel chassis review

There is no escaping it, if you race 1/10 onroad the rise of steel chassis has been something you cannot ignore. The first chassis I recall seeing on for was the Awesomatix, but now they are available for a wide selection of chassis.

This is in part thanks to Wei RC, they have been making option parts for a few years now, and they were quick to bring steel chassis to the market.

 
I have had the TRF421 steel chassis for several months, however I've been so pleased with the performance of the Wei RC 1.5mm aluminum chassis that I have been loathe to go to the hassle of swapping it over to the steel one, but what's the point of buying it if I didn't try it.

So why would you want a steel chassis? Well the obvious advantage is that it moves the weight of the car down lower to the ground, hence giving you a lower centre of gravity. This is usually a good thing with grip based racing.

The other advantage is that it lowers the mass within the car as well. In the example of the Wei Rc steel chassis, your motor / mount / bulkheads / shocktowers etc are all 1.05mm lower that the base TRF421. This makes the chassis 'shorter' vertically.

There a lots of impacts on a cars handling that this has, but the largest is that the lower CoG reduces the leverage of the chassis, this means.

• Less body roll in corners
• Less nose dive under braking
• Less rear squat under acceleration

This increases overall tyre contact as you are less likely to overload tyres as the weight moves. So if you are on high grip will find that the car will feel more precise and have more mid speed corner steering. 

When you take the chassis out of the packet it's evident that it has been made to a great standard. The shape is similar in profile to the Wei RC aluminium chassis, but there are many more cut-outs as you would expect.  There is also no nice bevel at the bottom of the chassis, as the steel is even thinner at 1.2mm so it would be almost razor thin at the edge, which could potentially be a hazzard for marshalls. 

The chassis is 84mm wide, and it's heavy.

• WeiRC 1.2mm Steel chassis - 142g
• WeiRC 1.5mm aluminium V1 - 79.6g
• WeiRC 1.5mm aluminium V2 - 69.7g
• Kit Carbon TRF 2.25mm - 68.6g
• Tamiya Aluminium deck (2.0mm) - 91.7g

One thing I really do like on this chassis is that it has the balance pin holes.. I still find these the best way to balance a chassis and I have missed them on the Tamiya chassis plates for the TRF421. (I hope the 421X brings these back). 

The other very noticable thing is that these steel chassis are not annodised black. I actually don't mind this, and it reminds me of the silver carbon weave we ran on the TRF414m2 and TA04 TRF cars back in the day. It also doesn't clash with the Tamiya Blue.. infact it compliments it rather well :) 

Before you install the chassis, it is essential you purchase the screw kit for the chassis. As it is so low profile the screws are 110 degree. I had worked with WeiRC to ensure that there is a TRF421 screw kit that has all of the needed screws for the chassis (along with a few spares). The screws are made from hardened steel, and I had no issues with the quality of them with my high quality tools. I would recommend you do have a good 2mm hex for these screws though. 

Swapping the chassis over is quite simple, and I was able to do it in a couple of hours. There are some things that you need to adapt. 

The roll bar mounts have a locating pin that is a little deeper than 1.2mm so you either need to shim them on the chassis to elimate this, but you may find the front steering links could rub them. I opted to file them down a little so they were perfectly flush with the bottom of the chassis. 

The other part that also needs modifying is the lower front bumper mount. You can shave that down, which is way too much effort, or fit 1mm shims to raise it. This is a little bit of a pain, so I made a simple bumper plate that you can 3D print. (Dowload here) This makes installation nice and easy and also makes the bumper more solid than using the shims. Download it free here (link). 

Once installed, it was time to actually feel how much the chassis flexed. In hand it was surprisingly compliant, slightly stiffer than the WeiRC aluminium chassis, but broadly similar in feel to the Tamiya aluminium lower deck. Of course, any subtle differences would only really reveal themselves once it hit the track.

Race day arrived and I was looking forward to giving the chassis a proper run. I hadn’t made any setup changes other than removing a few weights.

As soon as I ventured out onto the track one thing became instantly apparent—the car felt very, very lazy. It had a huge amount of understeer in the sweepers and even on the infield the car felt so locked-in that I had to slow down far more than I wanted just to load up the front tyres.

I started working to dial this out, but it took longer than I would have liked. Interestingly, the TRF421 was incredibly easy to drive, almost startlingly so. I was able to match my fastest lap several times in a row simply because the car was so predictable. However, I couldn’t really push it, which made it clear that there was still pace being left on the table.

To free the car up I began making adjustments. I increased the bump steer by adding more shims, reduced the rear toe-in, and also backed off the rear toe gain.

Gradually the car started to come alive. It was running well, although it still felt a little too easy to drive. I began to wonder if that was simply a side effect of having so much weight positioned low in the chassis.

By the end of the first race meeting I came away with a respectable A-final result, but I still wasn’t completely convinced.

For the next outing I decided to go a bit more aggressive and switched to the split top decks. This made a noticeable difference and the car was immediately around 0.3 seconds per lap quicker. It still felt very planted, but I was now able to attack the corners more aggressively and the car started to feel much closer to my preferred balance.

The next big change was moving to a stiffer rear differential. Previously the car was so locked in at the apex that I could almost see time slipping away as I waited for it to rotate. The stiffer diff helped significantly and the car began to feel sharper again.

One thing worth mentioning is how resilient the chassis appears to be. I’ve had several fairly hard hits, yet every time I’ve placed it on the tweak board it has remained perfectly straight. Considering it’s only 1.2 mm thick, the durability is genuinely impressive.

Comparing it to my 1.5 mm WeiRC aluminium chassis, I’d say that on the medium-grip tracks I typically race, the aluminium option remains a very strong choice. I really like the way the car feels with it, although that’s undoubtedly helped by the amount of time I’ve spent refining that setup.

What’s impressive with the steel chassis is that, with only a handful of outings, I’m already able to match those lap times. As the grip level increases, it really starts to come into its own, the car stays incredibly consistent and flat, and grip roll is a non issue. If you are racing at medium to high-grip venues I’d have absolutely no hesitation to recommend this chassis.  Personally I find both the WeiRC chassis to give a performance gain over the std chassis, I primarily think the fact that the motor is lower really changes the feel of the chassis to my liking. I am keen to see how the new TRF421X will feel as it seems the factory drivers have also preffered the feel of this, and moved the motor lower in the car. 

For me, well, I’m still planning to tune the steel chassis further, partly because swapping chassis plates is a bit of a pain ;), but also there are more things I can do to make the car feel more alive, changing roll centres etc.. So I will update you on the progress.