Tamiya RM01X Build and Review - Part 1

Background Tamiya's RM01X is the company's current offering for competition 1/12th scale. It is based on the RM01 chassis with...


Tamiya's RM01X is the company's current offering for competition 1/12th scale. It is based on the RM01 chassis with many upgraded components included, to change it from a scale model into a full blown racer. I'm a sucker for buying something different with my cars, so decided to take the plunge and get hold of one. My current car is a Speedmerchant Rev 7, which is unsupported in the UK. My previous car's have been a V-Dezign, with limited UK support, and my own home builds. So the choice of a Tamiya, probably the biggest RC car manufacturer in the world, would seem like a 'sensible' choice.

Fear not. After contacting my local model shop in Macclesfield, who used to support the Tamiya Eurocup and has a good relationship with the UK distributor, the car was unavailable in the UK. The distributor would only import a minimum case load, and the same for spares. So yet again, I was after an unusual car.

A search of the internet revealed my best option was Stella Models in Hong Kong. The shopping list below outlines the puchases. The Tamiya and 3Racing components are available through Stella Models and are under £150. Postage was just under £30, which brought the cost of the car into the lower end of the UK 1/12th scale market. Other components would have to be purchased, but they are readily available in the UK. I will mention those at the relevant points. The order took 6 days to arrive.

The only other shop I used overseas was Banzai Hobbies in Japan. They have bent over backwards to source a set of rear ride height adjusters that allow me to adjust the ride height in 0.5mm steps, and also run smaller diameter rear tyres.

Shopping List

TA84335       RM01X Chassis Kit

TA54367       Rear Tread Spacer Set

TA54352       Roll Spring Set

TA54359       Pitch Spring Set Since discovered the option springs are too hard for UK racing

TA54366       Front Upright Shaft for 1/8x5/16 Bearing

F103RM-11   64 Pitch POM Gear Ring Designed for different diameter axle

TRG5029       Rear Axle Ride Height Adaptor

The Build

This has to have been one of the nicest 1/12th kits I have ever assembled. Everything was a perfect fit, and the instructions gave small details that are lacking from other manufacturers in the class, who expect you to know already. I would recommend it as a first time 1/12th car on the build alone.

Basically, follow the instructions and you can't go wrong. I will add a few extra pointers though which will help in building the best car possible. I also made a minor modification to the front suspension which I will detail, as it allows the car to run smaller front tyres.

The instructions recommend superglueing the edges of the chassis and other carbon fibre components. This prevents the carbon fibre layers delaminating in a heavy accident and is worthwhile taking the time to do.

Before glueing, sand the sharp edges off all the carbon fibre components with some fine wet and dry. It is also beneficial to sand a small radius on the underside of the front edge of the chassis, so it doesn't catch on the carpet. We used to sand the sides of the chassis too for the same reason, but now the cars are narrower and very unlikely to roll enough to catch the carpet.

To glue the edges, have a handful of cotton buds nearby. Put a few drops of glue along one side of the chassis edge and then spread it with the cotton bud. Spread the glue as far as it will go before adding a few more drops. Do not use too much at once, and be careful disposing of the cotton buds, as too much superglue will combust if exposed to air. the cotton buds keep your fingers out of the way and ensure a neat finish without the glue running on to the finished surfaces of the carbon fibre.

From the photo, you can see there are a number of holes at the front of the chassis. As standard, the car comes with Tamiya's own version of the 'old school' front end used on the Speedmerchant cars. However, the chassis is pre-drilled and countersunk to take the Associated 12R5 front suspension. the chassis is also drilled to accept either a standard size steering servo (handy if migrating from another class) or a full blown 1/12th servo.

Side Links and Centre Pivot
These are fully interchangeable with the Associated 12R5 components. Tamiya do produce graphite versions which are stiffer than the standard parts, but the Associated parts are readily available in the UK.

Since completing the car I have fitted the Associated parts as i had a spare set from somewhere. Serpent or X-Ray links will also fit. CRC are imperial and although the links are the same length, the ball joints are different.

Rather than go into the best way to build a differential, it is best to look here:

The basics are the same regarding sanding of the diff rings, and using grease sparingly.

The kit comes with a mod06 spur and pinion, which is fine to get you going. It is best though to upgrade the diff at this point to a 64dp spur. The kit axle is 6mm diameter, whereas the industry standard is 1/4". This is where the gear ring from 3Racing comes in. It acts as a spacer to increase the axle diameter to 1/4" at the point where the spur gear bearing fits.You will need the following in addition to the adapter:

64dp spur gear - I used a Schumacher 78t spur which will allow the correct gear ratio for running a 13.5 motor. If using a Kimbrough, you cannot run below 80t as the Tamiya diff rings are a larger diameter than standard and will foul on the moulding. The Schumacher gear is flat on the side, so this is not an issue.

1 off 1/4" x 3/8" ballrace.

12 off 1/8" diff balls.

My car is actually assemble slightly differently as I found out about the 3Racing adapter too late. I have reamed the centre of the spur out to 10mm and used a 6x10mm bearing. I still need the 1/8" diff balls. I now have the adapter and will use it in future as I can then share components with my other car.

Front Suspension
As standard, the front suspension will allow you to run a minimum tyre diameter of 45mm whilst achieving the minimum 3mm ground clearance. This is not much use as the majority of 1/12th tyres are 45mm to start with, so you'll be done by the end of a run. This issue is a result of Tamiya producing their own wheels and tyres, which aren't much good for UK 1/12th classes (and I believe the wheel diameter is above the max allowed by the BRCA. I need to check this as I'm the BRCA 1/12th Section Technical Officer) but were fine for the scale cars they have come from. A one make series is run the the US (and Japan I believe) where these tyres work well on tarmac. The Tamiya wheels and axles also accept metric bearings, so standard 1/12th wheels will not fit as they use imperial bearings.

Tamiya produce a 1/8" axle which allows standard 1/12th wheels to be used. You will also need four 1/8"x5/16" ballraces.

To increase the ride height, I removed the moulding from the underside of each steering arm. This lowered the arm by 1mm, which would allow 43mm tyres to be run. I then carefully sanded the underside of the arm to remove a further 0.5mm. So now I can run 42mm tyres. This process is a bit painstaking as I had to keep checking the arm by sliding it on to the kingpin with a 1.5mm spacer on top (to replace the material removed beneath) and try to fit the both e-clips. I wanted to remove the bar minimum of material so there was no slop.

The suspension was then assembled following the instructions, and you have the result shown above.

At this point you fit the wheels and find that they now rub on the top of the kinpin thanks to the mod. To rectify, use a permanent marker and colour in the exposed part of the kingpin above the suspension arm, then remove the kingpin. You then chop off the coloured portion of the kingpin with a dremel and cutting disc which will leave the top of the kingpin flush with the suspension arm. You can now fit the wheels without them rubbing. DO NOT cut the king pin in situ on the suspension arm. It will heat up and melt the suspension arm!!!!

Just as you think you've finished you fit the radio gear, turn the steering, and find the wheels now rub on the forward edge of the upper suspension arm! AAARGH! A bit of careful filing with a needle file will resolve this though.

And finally, the car will start to look like this. i still need to tidy up the wiring as the electrice were lifted straight out of the Speedmerchant. With the bodyshell on it tips the scale 2grams over the minimum weight limit.

Body Posts
The only weak spot on the car. The screws did not tighten up in them, so I have now taken then off and fitted a set of Associated 12R5 items that again were lying around from somewhere.

Testing and Future Changes
The car arrived the night I broke up for my summer holiday, so I have not run it yet. First run will be tomorrow at Crewe car club, so I will write again about that.

I am running it initially with the Tamiya front suspension, just to see how the car is as standard. As mentioned before, the 12R5 front bolts straight on. It does cost over £60 though! I have a complete CRC front end lying around, but the hole spacing are different and it will not mount on the chassis. that is unless you bribe someone who has a milling machine with copious amounts of beer to make an adapter. I will provide an update on this once the bits are complete.

Part 2 will cover the basic setting up of the car - choice of damper fluid, setting the tweak and ride height, how to set front camber/castor etc.

You can see it here RM01x Build and Review part 2

tamiya 2000996654358171504

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