The last while I have been working on the Serpent 4X making changes to a mid alloy car and developing parts that have made this car a very good car for me. I, previously had the original X20, which worked well, but left some room for additional tuning wants. Then I ran the X20 '21, which is a nice car, and a lot of people have had success with it, unfortunately not myself, having durability issues. My test track is a pretty small bullring, so it really tests the durability of the cars.

So, now the story continues. Unfortunately, the Serpent manual is sparse on text, and if there are YouTube videos they are in Chinese, and do not transfer over very well.

I will attempt to go thru the manual and cover the areas that I feel may help with either the assembly or durability or tuning of the car.

Let’s begin. I will forgo the first 3 pages of the manual as its pretty straight forward and really has not changed in the Serpent world for a very long time.

Page 4, Step 1.1, right off they put a warning up showing the diff housing and the outdrive? Not sure what the warning is about so I will give my 2 cents.

The very first thing I do is look at the seals, if they are not the green seals #401784, I replace them. If not, be prepared to have a wet diff. I wish they would just include the green seals form the beginning.

I cannot emphasize enough the use of thread lock on the M2.5x5 screws that secure the outdrive to the crown gear drive, these take a lot of shock and are a item that even after being built should be checked regularly for loosening off.

There should be a little bit of float between the outer bearing and the outdrive. This is determined by the 12x15x.025 shims that go on the back side of the crown gear. So check to make sure you have a little float, not tight and causing a bind. This will ensure that you will have a very smooth diff. * Personally, this is probably one of the nicest Serpent diffs I have had.

Step 1.2, the amount of diff oil. They suggest that “Differential weight with volume compensators = 8.4 grams” I'm not sure what “volume compensators” means, BUT, the amount of oil for the diff housing as shown is 8.4 grams. That’s 8.4 grams with the housing, not as a zeroed out scale reading, if you are used to the old way that the diffs used to be built.

The rest of the steps are straight forward till we get to,

Step 4.1/4.2 the FF and RR lower arm inserts. If you are running on black carpet I would suggest starting with Front 1 degree toe out. This makes the car feel a little smoother. Take note that the pills have a 0.05mm relief machined into them, I guess that so it locks in the lower arm ball so you dont need a wrench to keep them from rotating while you tighten the screw. The bad part about this is if your raising the roll centre with shims there is a chance that they will distort as the screw pressure is applied. I made some 0.05mm shims that fit in the machined void to give me a flat surface to adjust on. Just something to watch out for, perhaps Serpent will make a insert that is flat instead.

Step 5.1/5.2, the only thing I will add here is that the car is 1mm narrower that the previous model.

Moving onto Step 6.3, I change out the C-clip to a cir-clip, so I can use pliers to remove the clip.

Step 7.1/7.2, pay attention to the diagram, if you have set your RR arm insert to 0 toe in you use the left side of the diagram. If you set the car for 1 toe in, use the right side of the diagram. This setting is less of a caster setting than a wheel base setting. Just watch to make sure that if you play with this that you have proper clearance between the top of the shock body and the upper arm. The stock suggested setting is pretty good.

Step 7.5, take note that the front bearing insert is different than the rear, the front insert is 1mm wider than the rear. The difference is the offset built into them. The axle up/down is the same between both but the amount of spacing from the hub to the edge of the bearing is different. This is a area that can get confusing, and I've read a bit about this adjustment. The easiest way I can describe it is by saying that if you make reference to the axle height as you lower the axle, you will lower the roll centre. Then apply what you know about roll centre.

Front

Rear

The in/out of the insert can be used to change the wheel width of the car without having to change hexes, to a point. If you do this make sure that the end of your drive axle is still adequate in the plunge of the out drive. Too far and a lot of pressure is put on the tip of the out drive and can break the cup. * If you run USVTA and have wheel rub you could do this for better clearance.

It should be noted that the front and rear steering levers are the same, so cuts down on extra parts.

Steps 8.1/8.2 again, making reference to the chart, (see above in reference to the rear setting), pay attention to your FF arm insert setting, if you set the lower arm insert to 0 toe, you use the left side of the chart to set your castor. A lower arm insert set at 1 toe, use the right side of the chart.

Step 12, something that is not shown but should be mentioned, is the shock top have a arrow indicator molded into them so that when you build the shock you can rotate the top to keep track of what weight oil you have put in them. The other item about the shocks is that they are made with a progressive inner body, so no insert. They build quite nice.

Step 13, the shock towers. The towers can be built either solid or floating. Here is a little tip about them. If you build the car with the towers set as floating, but use a 6x3x1 shim you can run the car either solid or floating without having to flip the towers around. If you want to go from floating to solid, just install the shims on the screws and it will lock the tower in place. This something to play with on black carpet. I find that letting them float takes a little abruptness out of the car, sort of numbs it down, takes the edge off, less direct feel.

Step 14.4/14.5, the rear body posts. This is another area that you should play with. I know the trend is to go to the horizontal body posts, which sort of help body tuck issues, but they also lock the rear of the body to the chassis, and in some cases this will make the car unstable, or cause other issues. If you have a setup on your car where it rolls a lot in the corners, without some body float it will create some instability.

The rest of the car build is straight forward. The final product makes for a fast, durable car, the corner speed is crazy fast.

To summarize the changes of the new car compared to the old;

1. Narrower bulk heads

   

2. Improved differential
3. 2 piece top deck
4. Centralized belts, spur gear on the outside for ease of changes
5. Outer hub roll centre adjustments front and rear
6. Spring loaded battery holder clamp system
7. Short lower sway bar mounts, ball bearing mounted.
8. Very lite assembly
9. All bearing DJC, and CVD
10. Floating shock towers
11. Multiple lower arm inserts for stiffness.
12. Progressive shock bodies, oil weight indicators.
13. Longer rear arms
14. Longer upper arms front and rear