Race Preparation
How to Race Prepare a Tamiya M03 Mini
This is not necessarily the definitive “How To” guide, but a collection of hints and tips on how I prepare my car “The Leighton Buzzard Way”, taken from cars that work seem to work well when raced in our series, and, using information from www.rc-mini.net simply the best Tamiya Mini based website on the net. Follow this guide and your car will work. Then it’s just practice, practice, and practice.
The Basics
An out of the box standard kit can be made to work, and although for the inexperienced this can prove difficult to achieve, with a few optional extras and some simple modifications, a race winning chassis can be built. Where to start, and with which kit? Although called “The Tamiya Mini Series” the Leighton Buzzard race series is in fact open to any Tamiya M03 Chassis. Tamiya M03 Mini, M03M Suzuki Swift, M03L BMW Mini and the M03R Chassis are all eligible to compete. However, these notes will focus on the more popular Mini bodied short wheel base car. So, what do you need?
Bearing Set
The standard M03 Mini part #58211 is supplied with “Plastic Bushes”. While they do the job, the friction they cause dramatically slows the car down. Number one purchase should be a bearing set. Tamiya can supply a set, part #53348, but they are slightly more expensive. Many local hobby shops can supply bearings sold loosely, and at a better price. If yours doesn’t, a search on ebay should find you a set for under £10.00. You will need 12 – 5x11x4mm bearings and 2 – 5x8x4mm bearings. These can then replace the plastic bushes as you go through your build process.
Dampers
The kit supplied friction dampers can be made to work, but for the inexperienced (and experienced for that matter) they can be difficult to set up. Number two purchase should be some oil filled dampers. Tamiya part #50746
Mini CVA Plastic Damper set works very well, and they are reasonably priced. Tamiya can also provide some threaded alloy bodied dampers, and while they are widely recognised as amongst, if not the best, dampers money can buy, you really don’t need them on a Mini.
For those with more money than sense, part #52102 Hard Black Coated Dampers, part #59355 Fluorine Coated Dampers or the new M Chassis Dampers, part # 54000 will all fit. There are also many other manufacturers that produce alternative dampers for the M Chassis cars. Tech Racing, 3Racing, Topcad, Yeah Racing, GPM and Exspede to name but a few. But be warned, some of the far eastern produced accessories are of a very poor quality.
Springs
The kit supplied springs are too long for carpet racing. You will need Tamiya part #53333 Short Spring Set, or #53340 Short Spring set. As well as being shorter, the optional spring set allows you to fine tune the suspension settings. The #53333 set comprises of Blue 15.27lb, Orange/Red 13.24lb and Yellow at 12.90lb. There is also a further optional White Spring, harder than the Blue at 17.24lb, which is included in the #53340 set. You don’t need the White Springs, but if funds allow, they are a worthwhile purchase.
That’s it. That’s all you really need to buy to make the Mini work. There are hundreds of optional “Hop Up” parts available, from a myriad of manufacturers. Most of which are just bling and a complete waste of money. Some will offer a performance enhancement, some will offer strength or durability, and they’ll get a mention as the build is completed.
Building Your Race Winning Mini
The tricks are now how you put it all together, and how you set it up. I’ll go through the build manual in page order. Just build it as Tamiya states in the manual, with the following suggestions. If you’ve already built your car, take the opportunity to strip it completely down, give it a good clean and check it for any worn or broken parts, and then rebuild it this way. It will work.
Differential
Firstly, our regulations dictate the use of the kit supplied geared differential only. Build it as the manual states on step 1, and to be honest, you’ll have a reliable and strong diff that should last you a long time. However, I’d strongly recommend some minor modifications as you put together the gears. Before you place the Planet Gear, #MA22, on to the 3 pronged gear holder, #MA20, place a small 0.1mm or 0.2mm shim, from Tamiya part #53585 Shim set. The manufacturing tolerances are not that accurate, and the shims help seat the planet gear on the holder, taking out some “slop”. The build manual suggests you use a thin coat of grease on the metal components. This will help with longevity, but, ultimately, it will slow the car down ever so slightly. I use a dry PTFE Lubricant (from the Cycle department at Halfords) to avoid any additional friction.
It is possible however, to tune the diff, altering its action by stiffening it. This can be done in one of two ways. The first, is to place a second shim after the planet gear is fitted to the holder, again, 0.1mm or 0.2mm, and, then place a larger shim, I use an AE product, part number #3911, underneath the main thrust washer, #MA9, before you put the main gears into the diff holder. This effectively locks up the diff. You can also build the diff as above, but before you put the gear cover on, completely fill the diff with a heavy grease. Again, this helps lock up the diff.
The locked diff will give you more traction pulling out of turns, but you will lose some steering action. You will also see a significant increase in tyre wear. Having tried both methods, neither offers any increase in overall lap times.
You can also purchase an aftermarket Speed Tuned Geared diff casing and spur gear set made from Delrin, produced by both Eagle RC and Nikis. Don’t bother. They will spin slightly smoother, but they are not as durable, and will need replacing on a regular basis. The same can also be said of the aftermarket metal spur gears. A footnote on gears. While we allow the use of aftermarket gear sets, you must retain the original gear ratios.
Front Chassis Section
Following steps 2 and 3, the diff’s are fitted to the casings by way of two solid steel shafts. A Hop Up option, of lighter Carbon or Alloy shafts is available. I will admit, I use them, but there really is no need, so save your money.
Not forgetting to install the battery holders (please, don’t waste your money on any of the optional quick release battery holder, just use the kit supplied parts) fit together the two front chassis halves. A quick note here on screws. You can buy Alloy, Titanium and Stainless Steel screw sets. You don’t need them, however pretty they look.
Build the front arms as instructed in the manual, and attach them to the chassis, shown in steps 4 and 5. As our regulations give you complete freedom in respect of suspension arms, I’d better run through the options available.
- Alloy Wishbones. Very shiny, very pretty and possibly the biggest waste of money on a Mini. Apart from the extra weight, the stronger Alloy Wishbones will put a tremendous strain on the wishbone screwpins, and worse, on the chassis if you have a heavy impact, and if you’re new to Racing, you will have some heavy impacts.
- After market plastic, or Delrin Wishbones are also now available from a few manufacturers. They offer no advantage, other than when and if you need to replace the standard front arms through breakage or wear, they are a bit cheaper. I use Delrin Arm’s from Yeah Racing (pictured) with their optional Titanium pin’s using the more common “C” clip fixing method. Their design does offer a slight increase in travel, allowing some Droop adjustment, although this is restricted by the overall length of the damper shafts.
You have a number of choices of upper camber links available. The kit links are fixed in length giving about 1.5 degrees of Camber. You can buy some aftermarket alloy links, another complete waste of money. It is possible to make some adjustable turnbuckles, which will give you another tuning option. (This method can also be used on the rear links) You will need some 10mm Turnbuckles, Tamiya part #53892, and some 5.00mm Ball Ends, Tamiya part# 50797 and a 5.00mm Spacer. The Ball Ends will need 4mm cutting from their length (please be careful when handling sharp knives) then simply attach a Ball End joint to each end of the 10mm Turnbuckle. As the original camber links are offset, you will need to place the spacer under the Ball stud on the front hub carrier to provide an equivalent offset. You can now adjust the front Camber. I have found running the car with zero front camber gives you a bigger contact patch (tyre to surface) and gives improved drive out of corners, and from a standing start.
While on step 5, a very worthwhile Hop Up is to fit Tamiya part #53218 Hard Outdrive Cups. No performance gains, but as the name suggest, they’re made of a harder material, and will last much longer than the kit outdrives, #MA17 and #MA18.
Step 6. Building the front axles. This can be a weak point on the MO3 Chassis. The Hub Carriers, part #B1 and especially the steering knuckle, part #B9 are prone to breakage. You do have some options however. You can replace both assemblies with the equivalent assemblies from the M03M Swift models. These have been slightly redesigned making them a bit stronger. You will need Tamiya part #51238, which is the F Parts spruce from the M03M Swift kit. Be warned, the bearing sizes on the M03M are a different size. There are Alloy Knuckles made by a number of companies. As the weakest link in this instance, the Alloy knuckle is a worthwhile purchase. Once again, the quality of some manufacturers components is questionable. I can only recommend Tamiya’s own, part #53523. So far, they have been bullet proof! Replacing the kingpins, MA1 in the manual, is another option. Alloy, Titanium, Steel, Blue, Red etc etc, are available. They’re not really needed, so save your money unless you have an abundance to spare.
Step 7. I prefer at this point, to replace the kit Dogbones with a set of Universal Joints. As ever, a huge choice is available. Save yourselves time and ultimately money, and buy Tamiya #53597 Rebuildable Assembly Type Universals. They are the most expensive from the outset, but will outlast all alternative at least threefold.
Steps 8 and 9. These cover the motor, and I’ll cover this in more detail later. While on step 8, I’d recommend you replace the kit pinion with Tamiya’s optional Hard Coated variant, #53509. Please remember, we only allow the kit gear ratio’s, using a 20 tooth pinion. The kit pinion’s can “hook” through use. This is where the leading edge of the teeth gets slightly worn through contact, eventually resembling a hook shape. A hooked pinion will cut through a spur gear like the proverbial hot knife in butter.
Rear Chassis Section
Follow steps 10, 11 and 12 as per the manual. As with the front end, you can replace the Suspension Arms, Upper links, screws etc etc, as described previously.
You have some optional parts worth considering. To give the car a bit more stability, replace the rear hubs, part #B4, with the optional 2 degree rear toe in hubs, Tamiya part #53345. Also, recently made available following the launch of the M03R Chassis, are some 1.5 degree rear toe in hubs, produced Alloy only, they are very expensive.
When you’ve completed step 12, do not attach the two chassis halves to each other yet. Loosen the screw that holds the chassis halves together that’s found at the lower part of the chassis, nearest the centre of the car, by a few turns, just enough to be able to gently pull open the two halves a few millimetres.
We’re now going to try and fit your electronics inside the rear chassis. Receiver first. This is not always possible, as some receivers are simply too big. It’s not too important, as receivers are generally very light anyway. If it does fit, push it as far to the rear of the chassis as you can.
The kit supplied Electronic Speed Control, is a great bit of kit, and more than good enough to win you races. Please, don’t waste money buying a high end ESC, you will not notice any difference. The ESC is next, and it will fit, just. You will only squeeze 75% of it in, but don’t worry, when the two chassis parts are joined, there is just enough space in the front chassis section for the remaining 25%. By squeezing all the electronics into the chassis, and not mounting them where the build manual suggests, you are lowering the centre of gravity by quite a considerable amount. This will noticeably improve the chassis handling characteristics. Fit the two sections together, oh, and don’t forget to re-tighten the screw in the rear section.
Dampers
Build the dampers as recommended by the manufacturer in their supplied instructions. I smear some Associated Green Slime on all the O-rings and on the damper shaft during assembly. Take your time, checking that the shafts are the same length when you screw on the lower Ball Ends. I slightly overfill the dampers with oil, and then compress the piston a few times, turning the shaft at the same time, to ensure you remove most of the air trapped in the damper body. I then leave the damper for at least 10 minutes to let any smaller air bubbles get to the surface. Screw the top on a few turns, and very slowly, fully compress the piston. Any residual oil will escape from the top as the pressure builds, and you should end up with an air free damper, that has a small amount of rebound, where the damper will slowly extend on it’s own. I use either 50 weight Silicon Oil in the front with the Blue Springs, or 60 weight with White Springs, and 40 weight at the rear with Orange Springs. When attached to the car, the shorter springs should mean that the lower suspension arms are at least level with the floor.
Follow steps 18, 19 and 20 where applicable. Step 20 covers the fitting of a servo. A couple of tips here. You will note that the manual shows the servo posts, #C12 in step 20, as having one hole to mount the post to the chassis and one hole to mount the servo to the post. Using a small drill, I recommend you place a second hole in the post, allowing you to use both the upper and the lower mounting lugs on the servo. This will greatly reduce the risk of the servo coming lose during a race. While we’re on the servo, please don’t waste money on a super quick, high specification servo, it really isn’t needed. The servo in my car is pushing two years old, gets used every week, and cost under £5.00. Another worthwhile purchase is a combined transponder mount and servo (see photograph above) plate that fits across the top of the chassis. It helps clamp the uppermost part of the chassis together, at the points where the servo is attached, and greatly reduces flex caused by the servo.
Tyres
We are nearly there. From step 21 onwards just follow the manual. However step 22 covers the fitment of the tyres. Probably one of the most important little tricks that’s used to dial out grip roll, is to Superglue the tyre walls. Take a look at the photo. Notice the beads of Superglue around the edge of the tyre. You only glue the front tyres, and I promise you, this will do more to take out grip roll than almost any other changes you make.
The kit tyres work well enough on our carpet. They can suffer from glazing on the rear tyres. This is caused by the undriven rear wheels, not working hard enough, and picking up residual tyre additive left on the carpet. This will form a hard surface, and the rear end loses all its grip. Simple to cure. Scrub each rear tyre before you start the race meeting with a medium or course Emery or Wet and Dry paper to remove the glaze. While we’re on the subject of additive, try and use it. LRP produce an additive especially for carpet racing in an easy to use applicator. Coat the entire treaded surface on all the tyres during practice, and then just the inside halves during the racing. I usually find I don’t need any additive for the final round, as the grip levels increase significantly through the evening.
Our regulations stipulate we can only use a Tamiya D60 Radial tyre. These are available in three specifications. Standard, M Grip and Super Grip. Although the latter can cost anything up to 30% more, I would strongly recommend you use them from the outset. I have nearly a years worth of racing out of one set, and they still look and grip as if they were new. Hard driven standard D60 tyres would last me 2 months maximum, before they lost their grip.
The Silver Can 540 Motor
Our regulations allow the use of the Mabuchi or Johnson RS540SH, J or SF Motors only. These are fixed timing, sealed endbell 540 size motors. In general, the Johnson motor has a dull finish to the can, and the Mabuchi a shiny finish. It is widely recognised that the dull Johnson motors have more power and it’s pot luck as to which manufacturer's motor you get.
One thing is certain, you will not get the SF motor in the kit. This, if you really want one, you will have to buy, and it’s tricky to track down.
But don’t worry; there are a lot of tricks that are supposed to increase the Silver Can’s performance. Some are mythical, and some genuinely work. The following article was published on the Hobbyworks website, and gives an insight into how to race prepare your Silver Can motor.
The Sealed Endbell Conundrum
After years of working with sealed endbell motors, I can tell you for a fact that they do not all perform equally. Among long-time Tamiya aficionados, the Johnson and Mabuchi motors are known to have very different power levels. Even Tamiya, the sole US distributor of these products, acknowledges that the matte finish Johnson has a distinct horsepower advantage over the much more glamorous chromed Mabuchi. That’s why they hand out Johnsons at their annual National event in Los Angeles. Unfortunately, there seems to be no rhyme or reason as to which motors come in which kits, so you’re pretty much in the hands of the Japanese motor gods when you open the box containing your new pavement weapon. Don’t get me wrong - the Mabuchis are just fine for practice, and their slightly lower power output will give you more control on days when the asphalt is particularly slippery - but grab the opportunity to pick up a Johnson if your only legal motor is a Mabuchi. In the long run, your car will simply go faster.
The good news here is that the motors are very consistent from example to example, so you don’t have to buy a dozen Johnsons to find a fast one.
Here’s another great truth: proper break-in really improves the performance of any sealed endbell motor. For years, racers simply oiled the bushings, slapped the motor in their car, and figured that it would break in with use. Then a few of us started to experiment with different break-in methods and discovered a series of steps that made these motors spin faster and produce more power. We’d show up at the track with cars that were supposed to be equal, but ours were quicker out of the corners and had a higher top speed at the end of the straightaway. Not only that, but these faster motors seemed to hold their edge for a long, long time. Like the sound of that? Follow these three steps with your next new Johnson and I think you’ll agree that the performance advantage is worth the extra time.
- Before ever running your new motor, lubricate the bushings at both ends with lightweight oil like Mobil 1 5 weight. Do this three times, allowing the oil to soak in for several hours between applications. To enhance the flow of oil into the bronze bushings, place the motor in a warm, dry place like a sunny window or the top of the refrigerator. Do this once in the evening before going to bed, again in the morning before leaving the house, and once more when you come home. By the second evening, your motor will be fully lubed and ready for the next step.
- Unlike their hotter stock and modified siblings, sealed endbell motors experience very low levels of internal stress and are manufactured using very hard brushes and fairly soft springs. This combination makes seating the brush face fully against the commutator a difficult task. Simply putting a fan on the motor and running it for awhile on a four cell pack or low voltage power supply will cause the commutator to become significantly worn before the brushes are broken in.
That’s why these motors should be water dipped. Simply fill a medium sized plastic or paper cup (fast food soft drink cups work well for this task) with clean cold water from the tap. Connect the motor to a low voltage power source (use either a four cell pack or the low voltage tap on a power supply - never use a six cell pack or AC power for this) and lower the motor into the water. Yes, I know it sounds weird, but trust me here. After the motor has spun fully submerged for a minute or two, you will notice that the water is starting to get dirty and grey colored. Pull out the motor, dry it off, and place a few comm drops - any good brand will do - on the commutator where the brushes rub. Put a small plastic fan blade on the motor and run it for two or three minutes (the fan blade keeps the motor cool and puts a slight load on it). Then remove the fan blade, empty the cup, refill it with clean water, and repeat step one for another minute or so. This time, the water will be less dirty, but that’s OK. Dry off the can, lube the bushings again, and run the motor with the fan blade attached for four or five minutes until it’s warm and dry. - I will add one further tip, recently published in a UK magazine, but completely missed by most readers. Once you have water dipped your motor, and re-lubricated the bushes, put one small drop (an applicator can be purchased from any good model shop) of WD-40 on the comm before you start your race meeting.
So, paint your shell (try and use a bright colour that’s easy to pick out against our Grey carpet) and get booked in. You are ready to race.
Additional Information
LBMCC Tamiya Mini Series Regulations
Any Tamiya M03 derivative. M03, M03M, M03L and M03R.
1700 mah (maximum) Sub C Sized Cells, factory produced in a stick format.
RS540J, SH or SF Silver Can Motors only.
Standard kit supplied spur and 20 tooth pinion only.
Tamiya D60 Radial Tyres – any derivative - only.