In the last couple of months I have gotten a lot of questions on how I build my cars and optimize some parts. After a short discussion with Xray we decided that it would be a great idea to build a new T4 2016 and post it on Facebook with all details and additions.
I will not go into details on all parts, as most is perfectly described in the manual but some things needs some special attention. I will also try to explain why I use some of the tuning parts find in my car. You can call this an Online Workshop if you will to help you to correctly build a Basis-Car.


Chassis and shock towers I grind in 4 steps.

First with a normal fine file then I start with sandpaper (80-100) until the edges are round. I then go to a finer paper (180-250) and to top it off I use a very fine sandpaper (800-1000). If you want you can even go down to polish paper to make it shine.

At the end all Carbon parts will look great and also feel good without any sharp edges anywhere. I do not use any superglue. Time duration should be approx 20min for the parts.

The top deck I work differently. I use a knife and scratch the edges with a 45 degree angle to make it slightly less edgy without changing the flex of the top deck. At the end I use a counter sunk tool to take the chamfers of in the bore holes. I do this per hand and very carefully.


My next step is A-arms. A-arms I always use the graphite. On both carpet and asphalt front and rear of the car. Due to the harder material you will get less flex in the suspension. The hinge pin holes which are 3mm I ream carefully. ONCE only as the graphite will open up faster the your normal plastic arms. When I have mounted all the A-arm holders and A-arm onto the chassis one always needs to make sure that all arms moves without any friction stops. They need to fall down on their own upon being raised from you. If this is not the case you need to unscrew one of the arm holders in the chassis. While securing them again, make sure to push them away from the A-arm which will make a small small gap and your arm will after this move freely. If the play is to much (perfect is about 0.1mm) then you need to do it the other way around with the arm holders. If this is not enough you can use small shims, however 99% you only need to use the above mentioned approach.

This should also be done during a race especially after being involved into a crash or similar. Check the play in your A-arms and redo if its needed. What is extremely important is that you have the same play on both sides of the car so please always check this.

Additionally I also always use the orange spacers in the car. To be able to make fine adjustments on the wheel base I use 0.5mm spacers instead of the standard 1mm ones.

#303169 Composite Rear Susp. Arm – Graphite
#302169 Composite Front Susp. Arm – Graphite
#303121-O Alu Shim 0.5mm orange (10)
#303122-O Alu Shim 1.0mm orange (10)


For the Spool build there is not much to add. I always use the steel outdrives with blades instead of the plastic outdrive. Their is nothing negative with the plastic outdrive however after a couple of batteries driving modified, especially on carpet you can feel that their is some play inside the outdrive. Also when hitting curbs on carpet tracks the risk can be that it breaks. The steel outdrives incl blades have a lot higher strength and also stays more constant over a longer time and thus most likely even cheaper in the long run.

When building the gear diff I first check the gears and take away any plastic leftovers from molding and then I put the parts together. When adding oil use a scale and add 1.3-1.4 grams of oil. For you guys who don’t have a scale fill the geardiff with oil until its 1mm above the X middle part. Then put it into a Air-remover to take out air to make sure that the correct amount is added. Important is when you rebuild the gear diff is that you exchange the black o-ring as it expands when you run it and when rebuilding the diff it won’t fit correctly again. Also please make sure to always use oil from the same manufacturer as there are differences in thickness between them. When cleaning the differential never use brake cleaner as this will ruin the sealing o-rings. Just put it upside down for 5 min and clean out the rest with a towel. 100% oil free you won’t get it.

Also always make sure that there is no dirt between the gears and belt, especially big problem when running carpet as the carpet hairs gets pressed into the teeth and you risk having the belt skipping over the pulley. You can easily clean the teeth with …yes you guessed it, with a toothbrush
#305137 Solid Axle Adapter – Spring Steel


Over the complete car I use screws from Hiro Seiko. All counter sunk screw for the bottom is titanium and for the top are made in aluminum. The quality is perfect and you don’t need to worry that they might break or get ripped out.
The last a long time just make sure that the 2mm driver is fresh and they will last at least as long as the steel ones. Lower weight (20-30grams) + lower CG + looks awesome!

As you can see on the pictures I mark my bulkheads. This way you always know where they should sit and and never build them incorrectly and always sit at the same place.

I only use the white low friction front and rear on all tracks. Personally I don’t think the low friction is the main difference, but that they last longer thus makes it safer to run. In Modified you can use the white belt longer then the standard one. How long time you can use a belt is always different and depends a lot on the motor you run and the grip level. When its time has come you can actually hear it.
In stock you can normally drive a complete season on 1 set of belts.

Belt tension is something very important but often not thought about.
Compared to the „Zero“ settings I almost always 1 position harder in the front and 1 position softer in the rear when turning the ballbearing/differential holders. The front belt I always test with a simple trick. I try to push the belt down onto the front hole in the Topdeck (see picture). You should be able to just such the top deck. When its to soft you will hear it when you drive. In Stock I suggest to go 1 hole softer front and rear then what I use in Modified.

#305882 Xray 64dp Spur Gear 112T
#305434 Low Friction Belt front
#305447 Low Friction Belt rear

Hiro Seiko #69924 Titan & Alu Hex Socket Screw Set Xray T4´15


The assembly of the driveshafts needs some extra care. Start with black Hudy grease in the round ends of the shaft. You only need a small amount to create a thin layer. Any additional grease will be pushed out anyway. On the outer part of the drive shaft put some black grease into the small holes as well. So far the same procedure front and rear. On the front ECS shafts I use Loctite. I actually very seldom take the drive shafts apart. Once they work one should not take them apart to often.

When I rebuild the car after a race or practice weekend I normally clean the outer dirt of the shafts with a cloth. If they afterwards do not move freely I use some brake cleaner to clean them roughly off. Do not overdo it with the brake cleaner though.
After that I use a Teflon spray (see picture) and spray the complete moving part of the shaft with. During a race or practice weekend, I always re-moist the shafts with a thick metal bearing oil, for both ECS and CVD shafts (see picture).

When it comes to the blades between the driveshaft and the outdrive of the diff or spool, I only use the optional orange blades. They are made out of a much harder and long-lasting material compared to the std black ones. In Modified on fast asphalt tracks, its only barely possible without the orange ones. After every 2-3 LiPo packs you need to check the blades to see if they are still fine, if not, you need to change them immediately. To get the blades to live slightly longer you can use some really thick grease, similar to the one we used in ball differentials and make a thin layer on the blades using your finger.

#305242 Drive Shaft Cap 3.5mm orange - Strong


I almost always use the original plastic parts when it comes to the C-Hub, steering knuckle and rear uprights. Very soldom I might put on the graphite C-hubs. Building the parts together is normally childs play. All parts fits almost always perfectly without any additional work. Only thing you might want to take away are leftovers from the mold process first with a knife and then with a sandpaper (600). On the rear upright I always use a set screw in the second unused hole to make it more rigid in case of harder impact.

Pressing the ballstuds into the ball caps I use an old bulkhead (see picture) this way its a lot easier and you also don’t kill your thumbs while doing it

All links, steering and camber ones, I only use the orange aluminum ones. No performance gain since the stock ones are also in aluminum but they look a lot sleeker

When screwing the links together I put a small drop of oil in the thread, this way its a lot easier to get them done. Also pay attention on the direction on the links (small line) put these all in the same direction then it will be a lot easier while setting up the car (see picture)

Additionally I use the titanium outer pins (not the longer A-arm mounting pins). They are lighter and also decreases un-dampened weight.

When securing the pins with the set screws, make sure that the are firmly secured, but do not over tighten!

#307222 Front Arm Pin Titan (2)
#307322 Rear Arm Pin Titan (2)
#303212 Alu Turnbuckle orange (2)


One of the most important things to take care about when building or rebuilding the car is to get it tweak free within the car itself (not talking about setup work, shocks, springs, etc etc)
All Bulkheads, Topdeck, Shock Tower needs to be mounted without having the rest of the car tweaked at the same time.

Step 1. All the following screws needs to be mounted however not tightened. There should be approx 1/2 of turn left before they are tight. This way basically the parts are loose and won’t cause any tweak. All top deck screws (8-12), shock tower screws (8), in the aluminum shock tower mounts (8), and all the bulkheads/motor mount screws in the chassis (for the spool, diff and motor) (12-14). The only screws which should be tightened are the ones to the A-arm holders-

Step 2. Tighten the bottom chassis screws, however only lightly using 2 fingers only. So still not finished.

Step 3. Tighten the top deck screws, also here using 2 fingers only and not tight yet.

Step 4. All screws in the shock towers and shock tower mounts, again with 2 fingers only.

Step 5. Tighten all screws in the bottom of the chassis.

Step 6. Tighten the shock tower mountings.

Step 7. Loosen up the screws in the top deck and shock towers (like Step 1.)

Step 8. Put the car on a absolute flat board (Hudy Setup board or on a glas plate) and tighten the shock tower screws.

Step 9. Tighten the screws to the top deck but diagonally. Front right, rear left and so forth.

Step 10. Check that everything is perfectly tweak free. Check all 4 corners of the car. Place the car on the flat board and gently push the car in the different corners to see if its tweak free or not.

This you need to do every time you rebuild your car as well as every time you might have a bigger shunt. At least Step 7-10

A tip in general is, to also use the 4 screws in the top deck which connects to the motor mount even if you will not use these later on. Its easier to get the car tweak free this way and when you are finished you can just take them out again. But it helps building a tweak free car.


To fix the battery I use 2 parts.

I use a 20g Xray screw on weight. I mount this on the centre line using 1 counter sunk screw and one allen screw without head. The latter I use loctite so that it does not fall out. The reason for this solution is to make a minimum of change to the flex of the car.
This 20g weight sit at the perfect place. Centre of the car for perfect weight distribution and at a position so the LiPo hits it and thus gives it the perfect distance to the middle.

For the perfect positioning front and rear of the battery, I use shortened Xray servo holders. Just use a Dremel and cut them down to the length you need. Use a file and sandpaper to make it smooth and nice. Then get a M3 Threader and get the holes done (2x one for the front and one for the rear) With the correct shims you can now individually fit any LiPo battery they way you like in any position. However always make sure that there is a minimum of 0.5mm play. Otherwise it will ruin the flex in the chassis.

#309853 Chassis Weights Center 20g
#306200-K Alu Servo Mount – Black (2)
#306200-O Alu Servo Mount – Orange (2)


With the bumper you basically only need to work on the lower part. From production you will notice that its slightly to thick and sits below the chassis line. Just use a sand paper and grind down until its level or even slightly about the chassi line (see picture). Make the tweaking of the car easier. Attention though if you use the Aluminum Chassis, you need to take away even more material.

I have gotten a lot of questions on how I grind down my foam bumper. Very similar to the carbon parts actually. At the beginning with a rough sand paper (80-100) to get the form. Then go to a finer paper (150-350). Then at the end very carefully use a lighter to burn off the remaining small fussle. I tried to use a Dremel, however it is extremely difficult to get a good result. You need to spend some time on this. In general, the more time you spend, the nicer it looks. Of course only for the optical performance. I also cut out a small square on the inside of the foam bumper to be able to put 10-15grams of weight there. Just use a cutter knife, cut nice and clean into the bumper and then pull the part out using a plier.

On the top of the bumper I use the carbon part. Again, only optic performance

The Body post are more important than most think, so follow carefully.
I always cut the body post at the same length. Front take away 4 holes and rear 3 holes using a cutting knife. Then use some sand paper to smoothen the edges out.
Don’t worry. With this length you will be able to use all meaningful bodies (Mazda, Nazda, Dodge Dart, LTC, LTC2.0, Silvy)

To be able to get the perfect setting I always use the Aluminum adjustable holders. This way you can get any setting done. Definitely recommended.

Now to the important part. I have seen so many bodies at race tracks being mounted completely wrong. This affects the handling and performance of the car massively.
I always have a pre set height which I use for my different bodies so that they are always mounted correctly. Most of the lines the manufacturers make into the molding are guidelines, but I don’t think they are optimized.
From the measurements I will mention, there might of course be some tolerances with 1 or 2 turns since the body might be mounted more forward or to the rear. The pictures should explain well how I mount the bodies.

Protoform Mazda Speed6: front = 58,2mm - rear: 35,2mm
Protoform LTC-R: front = 54,7mm - rear = 35,2mm
Protoform Dodge Dart: front= 54,2mm - rear = 35,2mm
Montech Silvy: front = 52.5mm - rear= 35,2mm

#301213 Upper Holder Bumper 2.5mm Graphite
#301351-O Alu Body Post Stop (2)


Building the shocks is very straight forward. Build them according to the manual. Use some silicon oil everywhere and take away any remaining plastic edges from the molding.

How to fill and refill the shocks them selfs is like a small project of its own. Everyone has there own way of doing them. I will try to explain the way I do them.

1. Fill the shocks with silicon oil. Move the piston up and down thru the oil 3-4 times to get the air out below of the piston. then put the shocks into a vacuum using a Air-remover (let it be for 4-5minutes). If you started out with a new shock or a completely cleaned shock then you need to do this 2 times. Otherwise 1 time is normally enough.

2. Push in the shock shaft until 2-3mm remains (tip, you can put shims between the shock housing and the plastic. This way it will always be identical, its more work but easier to get the same result)

3. Bladder and only the bladder ( no plastic or aluminum cap) should be mounted onto the shock body using your fingers but leave one side open at first. Then slowly get the bladder „into“ the shock and let the rest oil sip out until the bladder completely seals the shock body.

4. Put the plastic cap onto the bladder. Then use the aluminum screw cap and slowly tighten it as there will still be some oil going out. The cap should be tight but not over tightened as this will deform the bladder.

5. Double check that there is no oil inside the shock. If there is, start over with step 1.

6. Check the rebound. It should be about 1-1,5mm rebound. If there is more, then start at step 1 again and at step 2 make sure to push the rod into the shock slightly further (use less shims).
A good way to check the rebound is to push to shocks together and check if they go into the shock at the same speed. This way you can make sure they are the same. If all 4 shocks have the same settings you can select the shocks to get the pair which are the closest to each other and put either front or rear. If one pair have more rebound, use these in the rear.

7. Check the shock length before mounting the springs. Check the picture on how to do it. Additionally I make a small indicator on the spring collar to be able to check that all springs are equally tensed. When the shock cap is mounted tightly, screw the shock collars to the top of the shock. Then make the indicator at the same place on all 4 shocks, this way you will have a Zero position. From this position turn 5 turns down to put some pressure on the spring and this will be a good start before fine tuning the ride height.

If you do not understand everything 100% please feel free to contact me. Its not so easy to understand all the steps if you have never done it this way
If you have problems while rebuilding the shocks, especially with step 3, then exchange the bladder as this one tends to expand during use.

I always use the aluminum version. Looks a lot better and the also stay the same for a longer time.

To get the shock balls installed into the plastic parts, I normally just screw them into the plastic instead of using a plier. Check the picture. Its very easy. At the end you just screw on and all of a sudden its perfectly mounted

#308031-O Alu Shock Spring Collar orange (4)


I always use the optional aluminum steering. Its easier to setup the steering angle perfectly and it won’t get a lot of play as fast as the plastic ones.

To get away some play I use very thin shims with big outside diameter (see picture). With the help of a screw from the top I put some additional pressure on the bearing to get some of the up and down wobble gone.
If you should use 0.1mm or 0.2mm you need to test yourself as there will always be some small differences between different cars and different steering racks. The most important though is that the steering is smooth and friction free.

Always make sure that the steering linkage are the same length. When you adjust the toe in the front always make both sides either shorter or longer. How precise I measure this you can see on the picture. Additionally I always use the orange turnbuckles.

To setup the maximum steering output angle, I always use a shim as a limit. I have 3 different shims (see picture) The different diameters are from the left 7.5mm, 6.0mm 5.0mm. Normally I use the 6.0mm shim. For stock 7.5mm is almost always enough. The 5.0mm only on extremely! tight tracks. The thickness of the shim doesn’t matter only need to make sure it hits the steering arm. Setup the steering output on the transmitter so that the arm not only touch but slightly presses onto the shims. The advantage is that when you use full steering output is that the tires won’t wobble thru the corner. The handling improves ALOT this way. If the steering linkage are the same length and you setup your transmitter correctly you won’t need to use any setup systems to check that its the same right and left. I almost never check the steering output with any setup system.

Always use a aluminum steering horn. Its more precise steering and reaction and gives more steering. But don’t crash to much as it will either bend or break the servo.

#302525 Alu Dual Servo Arm
Alu Servo Horn #293503, #293502, #293501
#302612-O Alu Turnbuckle 39mm – orange (2)


I hope that my explanations the last weeks and days has been understandable and that I could bring my thoughts correctly to you. Still, if you might have any questions about anything, just let me know.
Here are some more photos of the completed T4´16 car. I have also made a list of all parts used.

I hope you enjoyed it

1x #300022 XRAY T4 2016
2x #303169 Composite Rear Susp. Arm – Graphite
2x #302169 Composite Front Susp. Arm – Graphite
2x #303121-O Alu Shim 0.5mm orange (10)
2x #303122-O Alu Shim 1.0mm orange (10)
2x #303123-O Alu Shim 2.0mm orange (10)
3x #301159-O Alu Countersunk Shim orange (4)
1x #305137 Solid Axle Adapter – Spring Steel
1x #305882 Xray 64dp Spur Gear 112T
1x #305434 Low Friction Belt front
1x #305447 Low Friction Belt rear
1x #305242 Drive Shaft Cap 3.5mm orange – Strong
1x #307222 Front Arm Pin Titan (2)
1x #307322 Rear Arm Pin Titan (2)
2x #303212 Alu Turnbuckle orange (2)
1x #309853 Chassis Weights Center 20g
1x #306200-K Alu Servo Mount – Black (2)
1x #306200-O Alu Servo Mount – Orange (2)
1x #301213 Upper Holder Bumper 2.5mm Graphite
2x #301351-O Alu Body Post Stop (2)
1x #308031-O Alu Shock Spring Collar orange (4)
1x #302525 Alu Dual Servo Arm
1x #293503, #293502, #293501 Alu Servo Horn
1x #302612-O Alu Turnbuckle 39mm – orange (2)

#69924 Hirso Seiko Titan & Alu Hex Socket Screw Set Xray T4´15
#69596 Hiro Seiko 4mm Alloy Wheel Nut orange (4)


T. Wahl