58738 Tamiya XM-01 Pro Chassis kit Review Build tips

The Tamiya XM-01 Pro is an all wheel drive M-Chassis. This isn't a first for Tamiya, they have released the M-Four chassis which was quirky, and a crushing disappointment as it was designed around the 380 motor, even  though it was a derivative of the excellent TA05 chassis. 

The great thing about M-Chassis cars is that they are a great size for a smaller indoor track, when you couple that up with a 4WD drive train it looks like a recipe for a lot of fun. So with that in mind, let's take a closer look

The box card gives you a brief overview of the main components. This is a pro level kit. These are made for more advanced enthusiasts of the hobby. With that in mind you get any electrics (Motor / ESC), or bodyshell included in the kit as you will want to source your own.

As it is a pro kit you will get hex head hardware (2mm hex), along with plastics of the highest quality, bearings and a selection of hop-ups.

Unlike some of my reviews, I intend to build this kit with very few additional extras. Yes, anyone that follows this site will know that they will come at some point in the future, I'm an addict for blue aluminium and carbon fibre. However this is a pro level kit so it should provide a very good experience out of the box. So lets see what it has to offer.

The chassis is a top quality piece of Tamiya's moulding. The best in the business and it's evident here with the quality. It's made from glass fibre re-enforced plastic, very stiff and quite difficult to twist.

The chassis as you would expect is the core part of the XM-01 pro. This is a M-Chassis car so as you can see the front diff moulding is built in, however there is nowhere for the rear differential. That is because there are two separate sections that you will need to choose between depending on the wheelbase you wish to use.

The XM-01 Pro allows you to choose between Short (210mm), Medium (225mm) and Long (239mm) wheelbases. So you will choose the suitable part for the build (there is also an additional spacer which  is needed to achieve 239mm). Luckily everything is included in the box so you can swap between wheelbases when you choose. 

For this build I intend to build to the long wheelbase. Even though my local track is very tight, I was keen to have something stable and easy to drive. It would be racing against TT02's so it would still have a shorter wheelbase.

Starting the build and you already notice something quite different to most chassis. The steering posts are mounted far forward. It's always good to see a bit of blue bling this early on. 

The shock tower brace is mounted by the screws into some M3 lock nuts that are mounted underneath.

The steering assembly is very smooth with the steering arms rotating on 850 bearings. As you can see about they are not like standard arms. They slope down along the profile of the diff housing to grab the  steering bridge. The attachment is friction free because of the bearings. There is a little movement (Slop). Not enough for me to be overly bothered with. 

This design is similar to that of the TB EVO8 and the TB05, it allows more flexibility for the electric placement in the chassis. It does look a little unconventional, but I have had experience with it on the TB EV08 and it worked well. 

Time to build the differentials. The XM-01 pro provides you with three differential ring gears. Two are 39t (Same as the TT02 etc). You also get an additional 40t gear. This allows you to create overdrive at the front or rear of the car.  

The manual contains info on what this achieves. As you can see spinning the wheels faster at the front will give a little more stability, and spinning faster at the rear will make the  rear of the car more lively around  corners and give a 'slight' amount of extra pick up from standing still on  acceleration. 

The XM-01 is rally focused, so this is a great tuning option for running on dirt or loose traction. I will be however racing this car on medium / high grip carpet so will run the standard 39t front and rear.

The differentials are included here were introduced on the XV02-PRO (The XM-01's big brother). These are also compatible with the TT02. They are available separately as part no 22049, and replace the older gear differentials (Tamiya 54875) that were available in the SR model. 

The differential shares parts with the TRF gear diffs and importantly they do away with the metal internal gears that  were in the earlier differentials. This makes the differential lighter, and helps improve the throttle response of the car. Steel gears are really not needed unless you are running a big heavy basher truck, there is absolutely no need for them on onroad or rallying. 

The new differentials are are a big improvement, the tolerances on how it fits  together are nice and snug. I've made a lot of gear differentials over the years, and these are simple and easy to assemble. 

One of the main reasons why differentials can seem to leak is  because they are  overfilled. I would  aim to fill these with 1.2-1.3g of oil as a maximum. 

The end result are two very smooth differentials. I used  10k oil in the front and 3k oil in the rear for this build. This is a good setting for an easy handling car, but if I wanted  to go faster I would look at 100k in the front. 

The suspension arms are a new part for the XM-01. It's great to see that they have an attachment point for Stabilizer bars (although none are included in the kit). I ream out the 3mm holes to ensure they are super smooth. 

The new arms are stiff, they swing on 3mm suspension pins balls on the end that fit into the suspension  mounts. 

These attach to the lower differential casing. Here you can see the inner split blocks and the one piece front suspension mount.

The rear suspension arms are very similar. You can see there are holes to mount 5mm ball connectors on both sides, you can use these to change the lower shock attachment points. I went for the ones that  are furthest out. The most important thing is to ensure that you mount both in the same hole on either side.

Here you can see the arms mounted to the lower differential cover.

Before fitting the output shafts, ensure you choose the correct bevel gears. Simply choose the ones that have the same number that correlates to the amount of teeth your differential has. So in this case, I used two 39t gears.

The steel input shafts feel very sturdy. You have a shorter one for the front and a longer one for the rear which you can see above. The foam bushings are there to ensure the drive shafts stay in place, as this car has variable wheelbases, it is essential. 

The  front differential is now positioned into place.  Everything moves nice and smoothly.  

Attaching the lower diff mount involves a little bit of screwdriver gymnastics :) Luckily this is a Tamiya kit, and everything fits into its aligned place so the screws easily attach.

You have two lower rear differential mounts. I went for the longer one as I am building the long  wheelbase.

The rear section of the XM-01 is now ready to be mounted onto the main chassis.

You have to fit a spacer before mounting the rear differential section if you wish to run the 239mm wheelbase.

To mount the rear section on, you align it and guide two 40mm long cap screws into the main chassis.  

Once set in its place you attach six more screws on the upper section to hold it firmly onto the main chassis. 

Time for the centre mounted spur gear assembly. The XM-01 pro comes with a direct centre pulley, with the option to fit a centre differential or a slipper clutch. This is very rare in an onroad orientated RC car. Clearly Tamiya have set their rally aspirations high with this and the XV02 chassis. I am not taking this car on the dirt, so will use the direct pulley set-up that is included in the kit, its the most efficient and lightweight option.

I didn't use the kit 70 tooth spur gear, instead I mounted Tamiya 51356 TB03 64 teeth spur gear. This is to give me a chance to get a low FDR that is needed to compete with the other Tamiya's that I will be racing against. 

The motor mount looks resplendent in it's chunky blue aluminium glory. It weighs in at 15.5g and the machining is spot on. 

Now we come to fitting the centre spur gear into the chassis we need to choose the correct propeller shafts. There are three in this kit so you can swap them around for your desired wheelbase. They are 54mm, 45mm and 30mm 

Once mounted everything feels nice and smooth. The good thing about this kit is you can actually change the spur to any you have in your pit box, including 64dp. The only thing is that once you build the car, it is quite difficult to align the motor because of the tight space. I used the 0.6 mod as it is for the Tamiya class at our club.

The spur gear cover holds the bearings in place and should keep the muck out if you want to race it on a dirty car park.

The front and rear shock towers are chunky and TALL! Again the rally DNA of this chassis is quite evident to see. The tallness of the towers might limit some of the shell options for this car, but there is a lot you can choose from.

If I enjoy racing this car I will draw up some new towers that can lower things a little. You can also see that both front and rear towers have three settings for the roll centre height.

The rear tower offers three upper shock settings. I also attached the upper (18mm) turnbuckles in the middle position. 

The front tower offers two settings. The front bumper / skid plate is also attached. 

As this is a pro kit you get 30mm universal drive shafts for all corners. Tamiya's drive shafts are probably the most robust out there. The only thing you need to take notice of when building is the orientation of the axle ring. Always ensure that when rotating clockwise, the leading edge is the part that has the hook that fits into the hole.

Whoops, here is a hop-up.. the kit includes plastic hex's. I prefer to run aluminium ones that I can clamp down on the axle. This ensures that I can tighten the wheel nuts without the hex rubbing against  the bearings. The Tamiya 53823 Hex 5mm wheel hubs are my preferred option, I find some of the cheaper ones do not seem to clamp the hex very well. 

Now starting on the four corners of the chassis. First up it's time to work on the front caster blocks. They have two different positions (High and Low), so you need to use a 2.5mm pin vice to ensure that you can mount the grub screw through to grab the suspension shaft.

The options to run high and low just shows how versatile this chassis is.

The caster blocks require you to use a shorter 5mm ball connector if you want to run the XM-01 in the lower position. This isn't included in the kit, but you can swap the ball connectors used on the front uprights (5mm), with the 8mm ones used for the caster blocks in the higher position.

The front uprights and caster blocks are now assembled. I opted for the low position.  Yes you can see  the bearings popping out from the upright, I don't really know what the benefit of this is, but it shares this with the M07. Each of the front  corners weighs 22.7g

The rear uprights also allow two height positions. These are a really nice part, you have the ability to change the length of the rear turnbuckles by adding shims to the upper section to push it more inwards. 

The axles spin in the kit included 1050 bearings. Again poking out.. Each of the rear corners weighs 18.9g 

It's all starting to take shape now, the suspension arms move really freely and fall quickly under their own weight. 

The shocks are the classic TRF Special dampers. These have been refined slightly over the years, with better pistons and rod guides. The o-rings included here are the clear type, these are thicker than the blue VG ones that are in the onroad race cars, these have a little more friction, but they will be more robust if rallying.

The damper cylinders are threaded to allow fine adjustments. 

The pistons have three holes, and I included internal limiters for the front and rear. The manual says to not fit these in the low position, but I can only assume that is because it's for rally and you would want the arms to fall further. I ignored this as this will mostly be on a flat surface and I want to limit roll. The two with the single o-ring will go in the front shocks, and the two with the o-ring and the spacer will go in the rear. This is a good base set-up for internal shock movement, and you can always swap front to rear if you want to change the amount of droop.

The now obligatory shocks in the Tamiya took holder.. I used the kit 400 oil as that is ok for the track surface I will be racing on. 

Whilst the bubbles were releasing from the shock oil, I used the pin vice to make a 1mm hole in each of the upper shock eyelet. This is not in the manual, but I like to build shocks with zero rebound and this helps achieve that. 

The final shocks all assembled with the kit included springs. They are 25mm black shock springs (so medium strength). I will be swapping them out for 20mm springs at a later date as with these springs the car will be too high. 

The front shocks are mounted.

And the rear :)

We are basically finished now,  added the front and rear stabiliser mounts on the chassis. None are included in the kit, I assume the M07 parts will fit, but I will check that at a later date. 

Now we get onto one of the more 'Quirky' parts of the build. The battery compartment requires you to place the battery on its side👀.  Tamiya has always been keen to challenge convention, and it's going in strong here. It's easy to understand why this is needed because of the available space. It will also make the chassis keen to roll, so not maybe the best for a grippy onroad race track.. but that's not going to deter me :)

The chassis is now finished. It looks fantastic and it was an enjoyable build. 

The chassis has a Lexan dust tray and wheel well covers. The car also comes with the Rally style tyres. I didn't fit these for my build as it will be raced not rallied.. yet

The quality of the components is great. I cannot wait to take this to the track. 

It's tiny but not slight. Weighing in at 635.6g it weighs approximately 172g more than a Tamiya TRF421 :) There however is a LOT of weight saving that can be performed on this car with a good selection of hop-ups. I'll take a look at these over the coming weeks / months once I start racing the car. 

The 21t brushed electrics were installed for our class. Here you can see the battery mounted on its side. 

Square case lipos do fit in this battery compartment. You may need to do a little bit of trimming on the  retainers to  get  to the battery holes. I made a simple extension and kept the deans connector. This provided a neat and more versatile set-up.

Here is the car prepped for the race track.

The internal ratio of the chassis is 2.6. The same as the TT02 etc. I wanted to get as low an FDR as possible to compete with the 1/10 TT02-SRX. I had a 29t pinion so had a F.D.R (Final Drive Ratio) of 5.74.

Now I just had to choose a race shell.. luckily Tamiya has a lot of very nice bodies to choose from.. I have a full and exhaustive list of every Tamiya M-Chassis body here (Click the link).. 

Let's go racing!!

The car was prepped and ready to race at my local club. It's a small technical track, some call it the Monte Carlo of Manchester.. 

This week the field consisted of TT02's (RR's / S/SR/SRX), and a M-07. The rules are loose, you just have to run a Scale body, and the core 21t motor and a Tamiya Tub chassis. Nice and simple and a lot of fun. 

Time to unveil my body.... 

The NSU TT 😂😅ok not exactly the smartest move for bodyshell choice.. Its high, long and isn't renowned for it's aerodynamic efficiency. However I was able to pick it up for cheap so the wallet made the decision.

As we began qualifying I had no idea how the XM-01 would perform. As I throttled away I was going to be interested in how the night would progress. As I approached the first corner the car rolled into the corner, and then rolled a little bit more. I didn't think it was going to end but after what seemed like an age the car was fully loading  the outside wheels. I was surprised it hadn't continued to roll onto its roof but the car gripped well and I made it around the corner with ease. As I accelerated from the apex the 4wd drive train gripped up and the car moved away at a good pace. My FDR was higher than many of my rivals so I had a little more zip out of the corner but it soon became evident that on the main straight that I was at a disadvantage.  Luckily the cars fondness to lean hard on it's tyres in the corner worked well on the lower grip surface (It's a temporary track, and the first run is always low grip until the racing line forms).  At the end of the run I was actually fastest in the class. This was down to just how precise and grippy the car was. 

For the second qualifier I decided to tweak the roll centre a little to try to stop the car leaning quite so much into the corner. It worked well enough to keep the XM-01 on all four wheels. I was really happy with how sharp the cornering was with the car. I really do think that the super tall bodyshell was exaggerating  the actual amount of roll.  It did help give me a lot of feedback on how the car was handling but my heart was in my mouth every time it leaned into the corner. I was expecting the car to grip roll so I was not pushing as hard as I should. I still managed second fastest in class in this round.

Third round and I played with the springs. A harder rear and softer front were mounted to change the balance. This would help the car have a bit more steering out of the corner and free the rear a little. The XM-01 was still on the pace, it was superb on the infield, the combination of it's diminutive size and the great throttle response of the drive train gave me the confidence to almost rub the inside corners. The lack of overall speed was my weakness' so I had to make every corner count. There were a few close calls and the occasional bump but I was still second fastest at the end of this round. 

The final round of qualifying and I was still second overall. I tweaked the front and rear camber in anticipation of experiencing traction roll as the grip was now very high. The higher grip worked well and the car was on three wheels on most of the corners.. I was pushing hard as I had nothing to loose. Everyone was watching the car going around, expecting it to roll, but it held on. I was more confident  with the car and was throwing it more aggressively into the corners to make it rotate even harder. It  was great fun. The steering was so sharp and precise I was able to pass backmarkers with ease.. squeezing past in places that I might have struggled with if running a 1/10 Tamiya. In the end I managed to qualify first by less than a second.

I lined up for the final knowing that second and third were faster cars, with lap times around 2-3 tenths quicker than mine. Luckily I had been consistent, and now I was at the front of the grid I was able to control the pace.

We all charged off from the grid on the sound of the tone. The five Tamiya's thundered down the track. I was holding off the two faster challengers nipping at its heels of my XM-01. The drivers were close behind and we battled fiercely through each corner, each twist and turn testing everyones nerves and skill. 

I was hugging the apex, blocking every attempt to overtake. We were all maintaining our positions by a hair's breadth. It was stressful, but everyone was clean and it was fun being in  this train of competing cars. Halfway through the race, a backmarker unexpectedly collided with me as I passed, sending me spinning off track.  The car rolled and once it came to a stop it was back on it's wheels so I could quickly regain control. I now found myself in third place, the sweet taste of victory slipping away.

Determined to reclaim my position, I pushed the XM-01 and my thumbs to the absolute limits, every ounce of focus and skill channelled into making up lost ground. I had nothing to lose so I drove with renewed vigour, and  the XM-01 devoured the distance to the second-place racer. For two gruelling laps, I studied my rival's every move, searching for the perfect opportunity to strike. On the next lap, with a bold, calculated manoeuvre, I managed to squeeze past on the way to the apex of a tight infield corner, reclaiming second place and setting my sights firmly on the lead. Unfortunately the gap was just too far and the leading driver was on top form, not making any mistakes so I crossed the line in second place. 

Overall

I always get excited with any new Tamiya chassis. The XM-01 pro is a very interesting addition to the Tamiya line up. It obviously shares a lot of DNA with the XV-02 but I am amazed at how the Tamiya designers have crammed it all something so small. 

The quality of the parts is superb as you would expect from a Pro level kit. I didn't shim anything on this build and there are some parts that have a little bit of movement, but nothing that in any way impacts the handling of the chassis. 

The electrics install is snug, and you do have to take your time if you want to make it nice and tidy. The front motor position really helps the handling balance of this car. Having the battery on it's side is something that very 'Tamiya' Obviously if this chassis was a pure onroad racer it wouldn't have been designed around this layout. As it stands though it is very neutral and and easy to drive. Out of the box it is more than capable enough to race around the track in the Tamiya class at our track. 

The other thing I must talk about is how robust this car is. I've raced it several times now and I have had some heavy collisions with the boards, sometimes launching the car in the air. Absolutely nothing has broken or bent. I can only imagine that the rally DNA though the design of the car is responsible for this. 

Going forward, I'm looking forward to seeing how much I can push this little car. Roll bars (Stabilizers) and a low bodyshell, maybe a 225mm wheelbase will really improve the handling. I will cover it's progress over the next few months.

Tamiya has managed to do it again, a versatile fun chassis that's an enjoyable build but even more run to drive. Great stuff :)  ☆★

Tamiya M-Chassis Body guide (Here) 

Tamiya XM-01 Setting sheet (Here) - Coming soon