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Tamiya 54886 TRF419 Suspension Upgrade Set Review


After the inception of the TRF414 Tamiya has released over 20 different chassis variations, however over this period there have only been 4 different types of suspension designs. The new TRF420 introduces a totally new suspension set, which is also available as an upgrade set so other Tamiya racers do not need to feel left out, so let's take a closer look.

You get the above parts included in the set. This provides you with most of the parts needed to upgrade your existing Tamiya (Compatibility list later in the article). The main parts missing are the four droop screws and the lower shock mount balls. If you do not run a chassis with the TRF418 style suspension you will need to source four 4x8mm grub screws.

All of the plastic components are carbon re-enforced plastic and the webbed design ensures they are much stiffer than the current arms. 

The arms have a slot that takes an aluminium bushing. This allows you to tune the lower shock mount position to fine tune the suspension settings. They are asymmetrical so you are able to set them to an inner position (A) or an outer position (C). 

The inner position is the same as the TRF418 suspension arms lower mount. The C position is further out than the TRF419 arm mount position. The TRF420 comes with the (B) mounts (Tamiya part no 54942) which are not symmetrical, but at the same position as the TRF419 arms, so more suited to some of the wider suspension blocks.

In reality you just want to set these to help fine tune the angle of the damper. As a general rule:

  • Shock more upright: Makes the damper feel harder. The stiffer it feels providing a more direct feel, less lateral grip.
  • Shock more inclined: Makes the damper feel softer feel initially and it gets progressively stiffer as it compresses, helping to achieve more lateral grip.
The new front arms are 0.85g heavier than the TRF419 versions
As you would expect the new arms do weigh slightly more than the existing arms because of the extra webbing and the aluminium bushings.
The rear arms are 1.3g heavier than the TRF419 versions
Overall you are adding a negligible 5g (approx) more weight. 

The new arms are also slightly wider than the previous arms my measurements are approx 0.5mm. This is worth considering when tuning your car, as 0.75mm is the difference between each suspension block iteration (i.e From 1A to 1B). (More info in the suspension mount guide here)

Also they are 0.5mm more narrow on the inner width. So you will need to adjust your wheelbase accordingly at the front. 

When considering the rear wheelbase, the new arms swing back 3mm. This is down to giving the TRF420 a shorter lower deck for better flex characteristics. Again if you want to maintain the same rear wheel position you will need to remove 3mm from the RF suspension spacers. 

The other change is that the lower anti-roll bar ball mount on the front arm is more frontward than the original. It is not a bit deal, but another thing to adjust when rebuilding your Tamiya with the new suspension kit. 

Regarding the plastic ball ends for the anti-roll bars. They are not a great fit, they are far too large so you will need to file them down. The tight fit is amplified by the inclusion of the new Tamiya adjusters. These are a great fit on the proper suspension balls but they have very little slop and are stiff so you cannot squeeze them with pliers to loosen them a little.

The best way to shave your balls (So to speak) is to get a thin piece of sandpaper and place it over the balls and squeeze on a ball joint and wiggle it around for a few seconds. It is not a big job, but I was a little disappointed that I had to do this with a Tamiya part. 
Tamiya sells a very high precision reamer drill chuck (42303). I found this makes the arms really smooth, without any slop.

Final preparation for the arms is to ensure that they are all reamed and free. This is something that is much more important if you use the new adjustable suspension mounts as they do not use suspension balls. 

Reaming the arms just ensures they are perfectly free. You can now ream the outer holes as well as Tamiya has moved to 3mm outer shafts to replace the 2.6mm arms.

The new outer shafts will be much stronger and have a continuous groove in the middle to ensure that they are easier to fasten. They are made of steel, although I would expect titanium ones would be a good upgrade in the future. 

The front upright is now a 2 piece design. This is to allow other arms to be fitted to the bearing holder change the ackermann angle or the steering response feel. The TRF420 comes with carbon arms that provide a more aggressive steering feel than the plastic parts. The arms are attached with a screw (I used a lightweight one, not the kit steel one), and the fit is very snug. The flange bearings included also are now the same length (About time). 

This is the big one.. the C-hubs are totally re-designed. At last!! Tamiya's are great, but the previous C-hubs were the single worst part for any serious indoor racer. It became so drastic that I even tried to use aluminium versions despite knowing the perils of an unnoticeable bend. 

I am glad to say that these new parts feel much more chunky, they weigh in at 0.5g heavier, importantly the design is thicker at the lower section where the previous arms would always break. There is a lot riding on these.. this could be the single biggest reason to upgrade.

The front arm assembly all assembled feels nice and free with very little lateral movement. The flange bearings have very little movement and also you do not need to fit the 0.7mm shim between the upright and the upper flange bearing anymore!

The rear assembly also has very little lateral movement. I did have to very lightly file the rear hubs to move freely in the arms. The rear hub is exactly the same dimensions as the previous hub but with a 3mm shaft hole as opposed to 2.6mm.

Track test

I've been running these arms for a while now indoors on carpet. The first thing I noticed was that they are much more responsive because of the more rigid arms and lack of lateral movement. This feel is very different than the previous arms. It did seem to come at the cost of grip initially, however I tweaked the roll settings to be closer to an outdoor setting and the car felt much better. 

Importantly, once the grip comes up the car feels much more alive than before. It feels more responsive, whist also providing me with more grip. 

The change in feel is most apparent when entering the corner, the chassis is able to rotate harder but still maintain grip. Once I realised this extra potential was available from the chassis I was able to improve my personal best (Oh and track record) by over 6 seconds. This was with the same chassis, same electrics, same batteries and tyres that were older. 

The other big improvement is the durability. Obviously I never hit the barriers (Ahem!) but as I like to give everything a good test I thought I would clip my fair share of barriers over the last 4 weeks. The great news is that the C-Hubs are still perfectly intact without any breakages. To provide context to this I am running blinky 17.5 at these small and technical tracks, so the hits are still hard and they destroyed many C-hubs over the last few years of running.
Clockwise tracks leads to a lot of spare Left hubs :)


Compatibility chart


Overall

This new suspension set is a good option for racers that want a more responsive handling feel thanks to the stiffer arms, along with more tuning possibilities thanks to the adjustable lower shock mounts.

It is also more durable, saving not only money, but as a racer it allows you to feel more confident to push harder in the pursuit of speed, as you have the security that the C-hubs are not going to fail randomly.
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