42384 Tamiya TRF421 Build Review and Set up Tips

A Tamiya TRF release is always something special, and the TRF421 caused a massive stir once it was presented to the world.

As Tamiya Racing aficionados, we have seen a lot of development prototypes since the release of the TRF420X. Tamiya have explored a range of new ideas such as the mid pulley layout, revised suspension arms, shorter shocks and other minor developments. So the general consensus was that we would get a TRF420XR or similar at some point.

So when Tamiya announced the TRF421 at the start of 2024 it was a much bigger jump than we anticipated. It was very different to the preceding car and featured a wealth of changes. Some did instantly proclaim it as a Blue MTC2R, however you don't need to look too hard to see the differences. Tamiya always go their own path on lots of important design decisions, so as we look closer at this kit we can explore some of these in greater detail.

The Tamiya TRF421 has seemed to take an age to arrive after its announcement at the start of 2024. I managed to get my hands on mine in June and it was an antagonising wait. 

The TRF421 comes in the now customary hard plastic case. Its great to have the kit come in a hard plastic box. The box is much larger than the parts included, this acts as a great place to store you TRF421 once assembled, or any other RC bits and bobs you have lying around. 

TRF kits are different to most manufacturers, in that they provide a full option race package. You wont find things like plastic steering arms and a huge list of additional recommended hop-ups to purchase additional to the kit. When you buy a TRF kit, you do not need anything else to hit the track, although you will benefit from using springs and oils that suit your local race circuit.

Saying that, any regular reader will know that I will add a few minor options, even though they are not needed, because well why not. I will use a combination of Tamiya Hi Grade screws (More blue bling, and a little weight reduction), alongside the excellent Moodyfools Titanium screws. I will also replace most of the steel ball nuts with the Tamiya fluorine alternatives as I like the smoothness and (cough), the colour. 

The TRF421 is built on a 2.25mm carbon chassis. It is 1mm narrower than the TRF420X, measuring in at 84mm. It is the same length and is approximately 3g lighter.  The profile is slightly softer than before, more rounded but still quite conventional. 

Unlike the TA07 MSX and TRF420X you do not get an aluminium chassis also included in the kit. Probably to save initial costs for the racer, the main issue for me is that it means there is no aluminium chassis option available at launch. 

The four lower bulkheads are all the same. Cut from 5mm thick aluminium and weighing in at 6.8g. They look quite simple compared to many of the former cars as the stabilizer bars are now mounted low on the chassis. 

Starting at the front the damper mounts are now also made from aluminium and are attached to the lower bulkheads. The horn style damper mounts have been experimented with on various TRF cars at race events for many years. I even remember seeing TB Evo6's with these mounts. The main advantage is that it is very easy to make changes to the damper angle, and can provide some very fine adjustments with small thin shims.

They attach to the bulkheads via two 8mm screws. Here you can see how well machined the part is with the smooth edges.  The 10mm grub screw is there to attach the dampers at a later stage.

Once mounted you can see that there is quite a distinctive look to the new 'Horns'.  Like the TRF420X The bulkheads are 20mm apart from each other. This makes it easy to use both droop blocks together to make a simple jig to ensure they are not twisted. Personally I would have liked a couple of locating pins on the lower bulkheads to make the assembly even easier to be perfect. 

The exquisitely small stabilizer mounts are small and weigh in at a fraction less than a gram.  They are mounted low on the chassis with a single screw, but stay perfectly aligned thanks to a locating pin. Once attached they are firmly locked into position.  Here you can also see the new steering posts. Tamiya has long changed the overall design these posts to have a hex design, to allow you to easily attach and remove them. 

The rear damper stays are larger and are less erect than the front ones. This ups the weight slightly to 2.3g. When measured against a regular shock tower the weight of these horns is actually very close TRF420X rear tower is 6g

At the heart of the chassis is the new motor mount. It looks resplendent in the classic Tamiya Blue. It is mounted centrally on the chassis with an option of up to four screws to change the flex characteristics. As it is quite a large piece of aluminium at a length of 82mm and height of 27.5mm, it suitably is quite heavy, weighing in at 23.8g. It is still very narrow and the motor is only 7mm offset from the centre of the chassis once installed.  The motor is also around 0.5 - 1mm higher than other brands. This is noticeable as there are no cut-outs on the lower deck. The TRF engineers have found that this can provide greater mechanical traction. This design trait is carried over from the TRF420X.

The TRF421 has now adopted the centre pulley design that other manufacturers have used for several years now. I don't know why it has taken the TRF team so long to return to this layout, especially as the TA05 had this layout in 2005. Still, high end touring  cars have  been  quite conservative until the last few years, so it is good to see Tamiya now following suit.  With a centre pulley you will have equal length belts. The theory is that this will make the car pitch and dive less on and off throttle.

The hard anodized 20t centre pulley is only 8.5mm wide. It's mounted on a short steel shaft that is keyed into the motor mount. Once attached it spins smoothly on two bearings. The narrow pulley is key to the two belts being as close as possible to the centre line of the chassis. Essential to ensure not unnecessary overhangs.

The battery standoffs are installed above for standard square packs. There are two 730 bearings for belt tension. A nice touch is that Tamiya provide titanium 18m screws for this part of the assembly.

The upper bulkheads are quite different to other manufacturers, and you can see the Tamiya philosophy come out here. Even though this is a high end racing kit, they want set-up and maintenance to be accessible for everyone. Once assembled you can simply unscrew the two retaining screws and slide the upper bulkheads to set the caster that you require. Even though the front and rear upper bulkheads are the same, they will provide different caster settings. You can select any position between the markings, but in reality you will mostly just use those as the main settings. 

• The front markings are 3.0, 4.0*, 5.0 degrees (* Kit settings)
• The rear markings are -0.5*, -1.5, -2.5 degrees (*Kit settings)

In use these are really easy to adjust. After seeing Tamiya experiment with a double turnbuckle upper arm I am glad they went for this more costly to manufacture, but simpler for the racer to use approach on caster adjustment.

The spool is very similar to the TRF420 series. The main difference is that the 37t pulley is is more central. It's a strong and lightweight part and weighs only 9.4g with the two 10mm titanium screws holding in the aluminium outdrives.

The  differential is technically also new for the TRF421. The only real difference is that the 37t pulley casing is different to bring the belts closer to the centre of the chassis. The internals are exactly the same. I have found the latest 420 diffs to be very good at holding oil, although the Axon G2 rubber o-rings are an excellent substitute. 

The differential can take up to 1.4g of oil. I usually fill the differential to 1.35g to avoid any mess.  The kit oil is 3K.

Here you can see the differential and front spool. The outdrives are slightly longer on the spool so there is an overlap. When mounted they are very closely aligned and the 3mm belts have minimal play between each other. 

Tamiya has included the aluminium 0.8mm offset diff bearing holders in the kit. These are a great update over the plastic versions that came with the earlier cars. They are even more precise and ensure the bulkhead is even more rigid. There is an additional set (22079 Aluminium Differential holders 0.5mm Offset), that you can purchase for fine tuning.  

The default settings for the car require you to mount the differentials low, this provides more grip, especially on power. Rotate the diff holders 180 deg to go higher and the car will be more reactive. This works well on high grip circuits.

As the TRF421 has a centre pulley you have equal length belts front and rear. These are 116t (348mm) in length. 

Tamiya has included the super smooth blue shielded bearings again in this package. I think these are an improvement over the fluorine coated ones that used to be standard. On my TRF420X they were strong and remained very smooth despite many runs. 

With both front and rear upper bulkheads attached I noticed a little lateral play with the spool and differential. Initially I thought I might shim them out with 10mm shims, however I had been informed to run the car as per kit as the slight movement will help facilitate chassis twist and flex whilst keeping the drivetrain free.

The front bulkheads have a 2mm carbon stiffener that is attached. It will allow you a simple flex option to remove this, or to try different thickness stiffeners down the line. 

The kit comes with a 116t 0.4 module spur gear. I have substituted this for a 100t 64dp spur gear. I will be running 17.5 blinky and this allows me a good range of gearing options for my local tracks. In reality changing the spur is really simple now as it sits beside the belts and is held on to the pulley with this special aluminium spur gear retainer nut.

To attach and remove the spur you use a 2mm hex driver. Just tighten the nut, and the O-ring will grip the spur and take away any potential movement. I cannot think of any chassis I have ever raced that is so easy to change spur gears.. excellent :)

The TRF421 has totally new suspension arms adopting a double A-arm layout. Whilst this is new for a TRF car, Tamiya has already created earlier versions with the TC-01 and TA08pro. The ones here are much more refined and also they are significantly longer than the TRF420 style suspension.

The other significant point of interest is that the arms are made from Glass reinforced plastic. Other manufacturers that have this style of suspension use carbon lower arms. There isn't any real advantage other than it makes the initial cost of manufacture cheaper as they do not need to make moulds. Tamiya turns this on it's head and invests in these moulds and the result are tough parts that whilst expensive to initially manufacture, are much cheaper for the consumer to purchase. 

The lower arms come on a sprue with  one front and rear. Left and right arms at each end are interchangeable so you wont need to carry many spares. 

The suspension arms still use aluminium bushings for the lower damper adjustment. These are held in place with a grub screw and you can swap them out easily if you wish. 

Above you can see the new fluorine stabiliser ball mounts. These these are a big step up from the older plastic balls that were on the TRF420 suspension arms.

The lower kingpin is a new short 5.8mm long part, and it's not the easiest to fit. I used the Tamiya 42276 damper pliers to hold the kingpin straight. 

Then using my other soft nose pliers I would squeeze them in. The plastics are so precisely moulded that once it is attached they move freely with no slop. 

The front arms weigh in at 11.1g and they are approximately 59mm pivot to pivot. This is 4.5mm longer than the  TRF420 arms

The rear arms have the suspension bushing in a more inward position. They weigh a little more at 11.5g and have 58mm between pivot points, 5mm longer than the equivalent TRF420 arm.

The longer lower arms are too long to retain the conventional suspension pin designs from all previous TRF (and other Tamiya onroad cars). The front arms are mounted inline with the bulkheads at 20mm apart, the rear are slightly more inwards at 19mm apart. 

The arms swing on 5x7x5mm fluorine ball nuts and they are that are attached to the chassis from underneath via four countersunk screws. This is a potential weakness, I've seen many X4 have the screws come through the chassis on a large hit, especially when racing indoors with solid track markers. A good way to protect the chassis is to dab some CA glue on a cotton bud and smear it on the inner countersunk holes on the chassis for extra strength. Also I would recommend to use slightly softer screws such as Titanium or maybe aluminium ones. In a large crash there is more change that they will snap and not the chassis. 

The TRF421 comes with four stabiliser bars in the box for a range of tuning options. They are totally interchangeable as they are the same front and rear. You will find the following in the box:

• 1 x 1.0mm (Green)
• 2 x 1.1mm (Black)
• 1 x 1.2mm (Red) 

These are the easiest stabiliser bars I have ever mounted. I got equal lift from both arms on my first installation. The entire movement is very smooth thanks to the 630 bearings. The stock settings suggest the soft (Black) on the front of the car. 

The rear it is recommended to fit the super soft (Green).

The double bell crank steering assembly carries over many parts from before. The only significant change is the revised steering bridge that now positions the steering links higher to clear the lower stabiliser bars. It comes with the 8mm pivot insert from the earlier TRF420 steering set, you can  swap it out for the less aggressive 8.5mm insert if you order the part, but I never used it before on the earlier cars.  This kit also now provides steering limiter spacers. I mounted mine with the smallest one (6.5mm). the kit also provides a 7.5mm one. You can also use a std 5.5mm Tamiya spacer that is in the kit which is not listed in the manual, but seems to be spare after the build is complete.  

The front double cardan driveshafts are very similar to those that are found in previous cars. They have proven to be almost bulletproof and very smooth so I am glad they have retained this design. They are made from the latest spec parts such as the Low Friction coated steel drive shafts and aluminium joint pipes and cross shafts.  The main changes are that the drive shaft is now 45mm long (TRF420X was 44mm). The axle is also revised as the bearings are 0.5mm closer to each other in the steering knuckle. With these lightweight parts the driveshafts weigh in at only 8.2g 

The steering knuckle will take a lot of load in an accident. So I always make sure I thread them with a Tamiya 54232 thread forming tap. It also ensures that your kingpins will mount straight and true. This is especially important with this ball type suspension as a wonky kingpin will change your caster values.

The knuckle arms are made from 2.5mm aluminium. They are not too heavy at 1.8g although I do worry about durability on tight indoor tracks. They are quite thin at places so may twist in a hard crash. The convention is to use carbon here, and I already have drawn up to try on my car for indoors running. 

Here you can see the arms mounted on the knuckles. The final weight is 16.5g. The upper kingpin is a standard 5x8mm ball connector. I use the fluorine coated alternatives (54208)

The rear axles are also revised. They come with 45mm rear aluminium drive shafts (TRF420X had 43mm ones). The other change is the axles. They are also modified for the closer bearings, but are now just attached with a grub screw. Personally I like the retaining pins of the older design. These will be fine, but I used some red Tamiya AG thread lock on the grub screw to ensure it would not come loose.

The Rear axles are now assembled weighing in at 14.1g each. The only real difference is that the knuckle arms have 3mm as opposed to 2mm shims under the ball connector. This is to ensure that the rear Toe Gain will  be 0 degrees when attached to the turnbuckles.

The upper arms are next. You get two on a sprue and each is able to work in the opposite side and end. These arms are very lightweight compared to other brands so it will be interesting to see how they fair over time. The camber adjustment follows the same style as the  TA08 etc. You have a titanium 18x4mm turnbuckle in each arm. 

Use an M3 Allen key to rotate it to slide the outer ball end inwards or outwards. 

When you mount the knuckles there is a little tip to make them less resistant to breakages. Swap out the kit included 0.5mm shim with one that has a wider outer diameter. Luckily most M3 washers are 0.5mm thick and have an outer diameter of 7mm. This extra surface diameter spreads the forces when the front end is in a collision. We have tested this method out and it has made a noticeable impact on the resilience of the front corners to resist a crash

The upper arms are now installed. Some people find a little resistance when lifting the suspension arms and dropping them. This is down to the upper arms binding on the balls. I usually ream my suspension ball ends for super smoothness anyway and the arms fell under their own weight. 

I have seen other drivers cars and some definitely do have a slight amount of binding. I don't think it is the balls themselves that cause the binding, but the thin bar across the top of the upper arm. It is slightly grabbing between the two balls (Ahem). If you cut the bar then it alleviates the tension. The result is a slightly softer upper arm, which does provide a different steering feel. In any case a few runs with the car seems to loosen up the arms with everyone. 

The rear suspension arms are now installed unlike the TRF420/X where you had to purchase an extra system. Here you can see the rear turnbuckles that connect the knuckle to the rear lower bulkheads. It's good to have this installed as a standard feature of the chassis. 

The kit settings provide for zero toe gain in the corners. Simply reduce the shims to add more toe gain. A useful set of spacers for any Tamiya car are part number 53539 5.5mm Aluminium spacer set. This will provide you with a range of spacers to change your roll centres, shock positions, toe gain etc.

The shocks are drastically different for the TRF421. The USBB (Ultra short big bore) dampers are 5.5mm shorter than the SSBB's. (well the  rears are 5.0mm shorter as they have a longer lower ball connector. 

The shock shafts are 20mm long and they mount in new recessed pistons. The actual fit is so precise it can actually cause a little bit of stickiness. Thanks to TRF Glazzer a simple solution was found. You should not assemble the pistons as per the instructions. Instead flip the piston around so the recess is at the top. To make this easier to achieve you want to place the top e-clip on the shaft, slide up the piston and then attach the lower shaft e-clip

I've revised the shock assembly instructions to make the shocks feel much more free.

Tamiya 74032 E-Ring tool will be a godsend for damper assembly.

Here you can see the final piston shafts ready for assembly.

The damper cylinders are have the same internal diameter, but they are now shorter with a length of 17.75 mm

When assembling the shocks, take care to notice that the front and rear lower ball connectors are different lengths. The rear connectors are 0.5mm taller, if you look at them closely you will see one set has two circle markings to help identification. 

The TRF damper tool made mounting the ball ends really easy. At this stage you must remember to fit the 0.5mm shim as per the instructions. This helps the kit included Lo-Mount aluminium lower retainers clear the lower arm on full suspension movement at certain shock angles.

The dampers how have a recess for the new bladders. They sit inside the cylinder and there are small holes at the top to let any excess oil escape when assembling them. The kit includes 400wt oil.

I drilled a 1mm hole in the upper cap as per the instructions. TRF dampers have always been high quality, but these were so easy to build with zero rebound. 

The dampers are attached via the excellent 5.8mm fluorine coated ball nuts. To change the  shock angle you simply add or reduce the shims on the damper horn. The kit default is 1mm at the front and 2mm on the rear.

It is good to see that these new dampers are able to still use 20mm springs. Some manufacturers have gone even shorter on the shocks and these require you to purchase different springs. Tamiya includes the 'Green' super soft springs in the kit. These are rated at 2.06 N/mm, very soft for the average racer, although with slower motors and low grip surfaces they can be useful. I will run Axon springs on my car.

The servo mount pushes the servo even more forward (Approx. 1mm). It is a beautiful piece of blue bling with the TRF logo etched on top. It is mounted with three screws along the centre of the chassis. Tamiya also includes the option stepped screws to ensure the servo mounts precisely. 

There are 4 ballast weights included.

They are slightly raised so as to have minimal effect on the chassis flex. They are low profile and provide you with a good amount of control on where you want to place the weight.

The battery mount system is new. It's great to see that it's plastic so it weighs very little compared to the aluminium and steel parts that have been supplied before. As you can see on the photo, you are also able to mount shorty packs in the TRF421. 

We finally get around to the upper decks. Tamiya has been generous and included two options for a wide range of flex adjustments. The single piece weighs in at 7.1g and the combined weight of the two piece deck is 6.1g. Both are made from 2mm carbon fibre.

The single piece top deck provides you with a range of different flex positions. You fit a 630 bearing in the hole and then secure it with a screw.

The dual deck configuration provides two mount positions front and rear. Here you need to attach some Tamiya step screws to secure them. There are four holes and two screws included, so you can experiment with different holes to change flex.  Note: Make sure to check the tightness of these each run, they are quite hard to replace and can come loose.

As we are looking at flex options. Here are the lower motor mount flex options.

The plastics for the bumper assembly are the same as the TRF420. The TRF421 does have a new bumper support made in 2.0mm carbon fibre. The new support rests against the front bulkheads for added strength in a collision. The front posts carry on from the TRF420 so you can rotate them to move the body 2mm forward for more steering. (Note this is only possible if you use rear horizontal posts).

The rear bulkhead is stiffened by the rear bodymount stay. This is a large piece of 2mm carbon fibre. Tamiya has provided a wide range of options here to allow you to use horizontal or vertical bodyposts. In the photo above I have assembled one of each to show you the options. 

In the box you get 8 body post extenders.  I will be using the standard horizontal mounts as I want the option to move my body forward and like the idea of reducing any unnecessary weight.

The last little touch is the included fan mount. This allows you to mount any size fan. 

Here is the final assembled chassis.. It looks spectacular.

Let's hope it goes as fast as it looks :)

You can  never have enough blue anodising. The quality of all of these components is superb.

Here you really get a sense of how low profile this chassis is.

The drive train is very light and free, the TRF421 keeps rolling around when I'm trying to take some of the photos :)

The final chassis weighs in at 493g with the slightly heavier single piece top deck, and including the 4 x 5g weights attached. With the lighter two piece top decks and no additional weights it would be 472g.  This brings it in at around 9g lighter than the TRF420X.

It's incredible to see how far Tamiya's TRF chassis have evolved over 25 years. Here is the TRF421 next to the TRF414X. If you want more comparisons read our article in the link  (Click Here).

Steering arm strengthening

Some racers have bent the aluminium steering arms on the TRF421. This will only be with a large impact, but you can strengthen them further by adding the following parts

Tamiya 54155 3mm Thin aluminium lock nuts and a packet of 54156 3mm Aluminium Countersunk washer.

As you can see on the photo above, the countersunk washers are wider and they add more strength to the thinnest part of the arm. This is the part that usually twists. There are other makes such as 1up racing that may even have a wider outer diameter for the washer, which will help further.

At the Track (s)

Now this was the moment I was waiting for. I still felt that my TRF420X was competitive, especially with the changes that I had made along the way. Yet when I sat in the pits, I was conscious that my fellow racer's chassis had started to feature some quite different design principles, I felt I might be  missing out, so was keen to see what the new TRF421 would bring to the table.

On its first shakedown I was struck at how the Tamiya TRF421 was a fundamentally different car to any of the previous generations of TRF race cars. The throttle response was quick and felt more direct, probably down to the reduction of pitch under acceleration. The other thing that I noticed was just how stable the car was. 

I found the car initially quite resistant to rotate in the corners. I was  able to quickly surpass the pace of my TRF420X even with a car that felt quite lazy, but very easy to drive. The longer suspension arms are going to contribute in some part on how the car feels in the corners. I was happy with the speed but I just wanted to experiment with different settings. 

A change of springs and a slight tweak of the upper shock mount positions and the car came alive. I was really encouraged on how reactive the TRF421 was with even small set-up changes. My concerns that this car was going to be quite numb were soon alleviated with only a little experimentation. I was feeling excited about the potential. 

I was happy with the progress I was making with the chassis. Along with other TRF421 racers we spotted some potential tweaks to the car to make it even more reliable. I personally have not broken or damaged any part of the car, even after hundreds of laps. 

One significant race was the excellent EWS international. It is always a fantastic experience. I pitted with some fellow TRFUK racers and we set about working on set-ups together. Again the car was so much easier to drive quickly on the large open track. It was  also good to actually run the car on the ETS style black carpet. There are not many clubs or events that run this surface, so it was a learning experience for most of us, but we soon found set-up tweaks that helped the car to really feel alive 

Unfortunately an incident in  my seeded qualifying heat put me at a slight disadvantage in my qualifying sessions, with only one clean run. I still managed to move up into a final to race alongside some good drivers and the car never missed a beat. I experienced a very large impact with a backmarker and suffered no breakages. Even when I checked the car out on the set-up table I had no tweak. I came away from the event, excited about the potential of the chassis, but I still wondered how I could unlock even more speed.

I had a small break from  racing and it made me contemplate on how to make the car feel more reactive.  Then it struck me that it was not necessarily the set-up of the chassis, but down to a  fundamental change in how much speed I could now carry into the corners with the TRF421.  I am a smooth, consistent driver, my consistency is usually my strength over a race. One of the key factors to achieve this is the ability to stop the car from being  on the edge unless absolutely necessary. This translates to monitoring my corner speed to ensure the car is within it's safe levels of grip. The thing is, the TRF421 can take much, much more corner speed than any car I have raced before so I realised I had to change my own driving parameters. 

From this revelation I had a few test sessions where I made no real changes to the car. I just wanted to learn more and more about it. I was learning and adapting and changing my own personal expectations of the best way to approach a corner. 

Time came for me to go to one of the larger clubs near me for a winter special GP. I was keen to see how I could perform against drivers that I knew were fast. 

I made no set-up changes for this track. I just gave the chassis a once over to check everything was still straight and placed the car down for it's first qualifying heat.

Unluckily for me, I had not got my tyre preparation right and the first 30 seconds of the qualifier the TRF421 felt fine, although I knew I had to wait for the tyres to start working before I was able to push. As the temps got higher the grip came up and I became more accustomed to the track. I was a slight disadvantage to many of my competitors as there was a four hour testing session before the race that many had attended which I was unable to make. So other than a few warm up laps I was still trying to find good lines. It was a great layout, with a wide variety of corners. As my confidence rose, I went closer to the corner markings with absolute confidence that the cars precision would keep me away from the barriers. I was pleased that I was third overall after this round.

This is how you get to the grub screw to remove a pinion

The second qualifier was a wash out.. I still hadn't got my tyre prep working that well, but I was already setting a quicker pace. I was really getting into a groove but as I slammed on the brakes at the end of the main straight, I felt that they were softer than  the  previous lap. On the next lap the brakes were even worse, and as hit the throttle towards the technical infield I heard the signature sound of a spur gear shredding its teeth.. Gutted..

The cause was simply user error, I had changed my gearing as I was running way too high compared to some of my competitors. I simply hadn't tightened the motor screws enough one I meshed the 64dp gears..  At the end of this round I had dropped to 7th place overall.  This mishap did allow the TRF421 to show off it's quick and convenient spur gear system. It literally took 1 minute to swap out the stripped spur gear to a fresh one. 

For the third and final qualifier I was keen to put in a clean run. It was frustrating that I still hadn't got my Volante 28's working from the start, but as the grip was coming up anyway it took less time before the grip felt fine. The TRF421 was so easy to drive it soon became easy to get into a groove. The car was able to hug the inside of wide sweeping corners at immense speeds, and even on the difficult infield chicane I was able to stay on the throttle and lightly flick the steering to avoid brushing against the barriers. I'm still learning this car and I became more and more confident. I made one mistake by driving a little too close to a tight sweeper. It span me around but I quickly recovered and posted my time.  I had improved by a considerable margin, now it was a waiting game to see where I would end up after the other rounds. 

I managed FTD so was going to sit on Pole for both finals.. To say I was happy was an understatement. I was racing against some very good drivers with a range of different  chassis. So to achieve this with the new car felt satisfying. The good thing was I knew I could have actually improved even further without that mistake and  getting the tyre preparation spot on. 

The first final wasn't the best.. I took a different direction with tyre prep.. (I totally forgot to do it as I was chatting with friends.. whoops).. So as soon as we approached the first corner I could see second and third place chasing me down. I tried to keep a cool head but the car was lacking in those first few laps, and the drivers behind could smell blood. I tried to withhold the pressure, hugging every apex as closely as possible, I went too close though and collided with the track edge, spinning around and falling instantly to third place. The rest of the race I followed behind but made a few too many mistakes pushing to catch up and crossed the line in third. 

For the second Final I took a different direction with tyre prep and as the field charged off at the sound of the tone it was evident that it was working well. The TRF421 was so easy to drive, I started to push harder and it was taking everything I threw at it.. I started to make a decent gap from the rest of the field and was feeling confident that I could retain this position. I exited a corner on the infield, taking a wider line as I was passing a backmarker and the car seemed to behave like it was literally on a rail line and then flipped over into a section of the track which I had already driven. It looked like there was a gap in the carpets and unluckily for me I had found it. I was now down in 5th position. I was gutted to say the least, but I pressed on. I soon made up good time and caught up with second and third place who were in their own battle.  

I joined in the affray and I had a great battle with the drivers. At one point I made it to third, but was not able to shake them for the final three laps. We traded places, with each of us scraping on the inside of an different apexes grabbing third place from one another. on the last lap I was at the end of a rather (cough) robust attempt which span me out and the third place was lost. I was disappointed at losing first place, but was buzzing after this battle, it was great to be scrapping on equal pace with all of these fast  drivers. 

I ended up third overall. My qualifying time remained the fastest time of the day and I really felt like I had moved up another step forward when racing my new car.

Set-up

Here is a solid base set-up for carpet. Thinner oil for smaller tracks (5k or 3k). 

Over the last few months I have been discussing set-ups and trading tips with other TRF drivers. Some have kindly offered their opinion on the TRF421.

Robert Clark

After running TRF cars for many years I was very excited to get the new 421. I had enjoyed running the 420x for about 18months and had some success nothing like A finals but some podiums in lower ones. 

Instantly the car felt easier to drive and had far more corner speed  than the previous car. Running it now for several months I have gotten very comfortable with it and my times have massively improved. 

I have had a couple of breakages mostly from pushing to hard in the early days but those were both of hubs. I know of other that have had more serious breakages but touch wood nothing bad my side.  Also in kit setup it wears tyres very fast the ring of death appeared within a couple of weeks at my Club. 

Moving forward I will keep playing with setup and see where it takes me.

Andy Travis

Having campaigned the 420x for a while, I was very keen to see what the 421 was capable of.

I was immediately impressed by the feeling that the car very much up to date. A lot of contemporary concepts have been refined with the usual Tamiya quality. I was immediately on the pace as soon as I hit the track and setup changes definitely made a difference that pushed the car forward. I've already had decent results and very excited to see how far I can push this car

TRF Glazzer

Life with the 421 has been a new learning curve, but very quickly found myself faster than the 420x. Small margins at first, but constantly improving.  So much so I replaced my 420x backup with another so now I have 2. 

Racing along side TheRcRacer I have learnt a few new tricks with setup, and the car is very easy to work on with quick access to most parts needed.

As with all cars there is an Achilles heal, might just be our track being wooden framed but hubs seemed to break and I bent a couple of the aluminium steering arms. TheRcRacers tip of using a slightly wider steel shim either side to match below the hubs helped stop the ball nut digging in causing the damage.

TheRcRacer also suggested countersink head washers for the secondary screw on the hubs and these help massively.

The car is very easy to drive, handles very well and has great turn in ability, sits and grips well on medium and high grip carpet, and I’ve found no issues with grip roll despite being a carbon chassis. 

All in all even as a novice racer, I’ve found a lot of gains making the change to the new platform and look forward to seeing what updates may arrive in due course..

Overall

I'm always going to be excited about a new Tamiya TRF car, but I find it quite remarkable just what a jump forward the TRF421 is after having spent a time with it on track. 

The quality of this kit is superb, I have not suffered any damage to the car at all. It might be a combination of luck, and also probably because I have been making little tweaks to parts based on feedback from other TRF421 runners. 

Having the two options for the upper deck is great for tuning options. I found the single deck made the car much easier to drive but it felt a little too calm for me on carpet. If I was running on lower grip tarmac, the single deck would be my initial starting configuration. 

In fact, Tamiya has been very generous with the tuning configurations with the TRF421. Providing a range of roll bars is good, especially as changing them on this car is really easy, and getting them to work well is simplicity itself.

The plastic A-Arms are another massive bonus. They are much more durable than the carbon arms of many of the competing chassis based on the fact that I've not broken any yet, despite giving them a thorough test at times. My rival drivers have suffered breakages with very similar collisions, and their spare parts are considerably more expensive. The other benefit, is that Tamiya can supply the same arms with different composite plastics to provide a range of different stiffness as a tuning option. Hopefully these will appear soon.

If I was to have any gripes, I would have liked driveshaft blades to have been replaced with ball bearings. It is worth mentioning that the included blades for the front spool are actually a little too large and bind when you fit them. I gently sanded them to fit smoothly. The same blades that are included with the replacement diff outdrives fit perfectly.  I wonder if  this is because the material has changed? I would sometimes go through quite a lot of these blades when racing, I am  still running the kit blades and they have not worn at all.

Other than the diff blades the quality of the rest of the components is superb. There are coated metals in all the critical places to promote strength and smoothness. You also find that you do not need to by any additional hop-ups. Steering components are alloy and even the diff holders are now precision aluminium parts. It's a very high specification kit.

The TRF421 has taken a lot of inspiration from other brands and blended it with Tamiya's own learnings to create something that fits comfortably in the competitive landscape of 1/10 electric touring, whilst still maintaining some original Tamiya design.

In conclusion, I the TRF421 presents a noticeable jump in performance over the previous cars. Importantly it sets a new path for future TRF chassis development. It's great to see that Tamiya is still committed to investing in creating cars that can compete at the highest level of competition.

The really exciting thing for me is that I know there is so much more potential in both the TRF421 and myself going forward into 2025.

Useful links 

Editable TRF421 setting sheet (Click Here)
TRF 421 Set-ups (Click Here)

Moodyfools (Click Here)

TRF Onroad Facebook group (Click Here)

Kentech Blog TRF421 presentation (Click Here)