Kyosho Optima Mid Part 5 "Koswork Shock Absorbers"

Kyosho Optima Mid Part 5 

"Koswork Shock Absorbers" 

Hello fellow RC enthusiasts from around the World and thank you for joining me. I hope you are all well.

In this post I will be building and fitting some new shock absorbers to the Kyosho Optima Mid. 

Since buying the period correct OT-66 tyres for the Optima Mid, I have decided to spend some more money on her, as she is at the moment a completely standard buggy.

Some people may think I am crazy for fitting new shock absorbers to an RC car that will never be used, and I would agree with them for a couple of reasons, this will of course include that the car is not going to be used (at this moment in time). The other main reason is that I cannot compare these new shock absorbers with the original ones as the car has not been used, nor have the original shock absorbers been filled with oil. However, there is a little method in my madness as the shock absorbers that I will be removing from the Optima Mid will be fitted to a future project ("Kyosho Javelin") that I am saving up for. To be honest, although the standard shock absorbers were never filled with oil, the operation of original shock absorbers was clunky and not smooth at all. I can compare that fact with many other non filled shock absorbers in my collection that indeed feel smooth without the need for being oil filled.

Although I cannot compare the original shock absorbers to the new shockers, I know that the new ones will be better as they have a bigger bore size than the standard shock absorbers. The new shock absorbers are in fact "Koswork" 12mm Big Bore shock absorbers finished in gold. 

The picture above shows the Koswork 12mm Big Bore shock absorber fully assembled. When the new shock absorbers came, they were in kit form and need to be assembled as shown in the picture below.

I ordered the Koswork 12mm Big Bore shock absorbers from Wheelspin Models with the part number of kos04901 and they cost me £80.74 (including delivery as I ordered the stabilizer kit also for the Optima Mid which took the bill over £100 and qualified me for free delivery) for the full set, which I think isn't too bad considering that a PAIR of standard Kyosho shock absorbers cost £57.59 excluding delivery.

The picture above shows the Koswork shock absorber kit.

Time to start assembling the shock absorbers.

When I opened the bag of the shock absorbers, I was horrified to find that there were no instructions in the bag. However, there was a QR code to follow and it gave me the perfect diagram to follow.

Time to follow steps 1 and 2.

The picture above shows assembly up to step 1 and it was quite the challenge fitting some of the rubber "O" rings.

The picture above shows the shock assembly up to step 2. 

The picture above again shows step 1 on the rear shock.

Above is another picture of step 1 on the rear shock absorber.

After a couple of hours (yes it took me that long), all four of the shock absorbers are up to step 2 of the build instructions. 

I will be filling the shockers with genuine Kyosho shock oil as can be seen in the picture above.

The picture above shows the "bleed hole thread". This allows you to bleed the air out of the shock absorber.

The latter half of step 2 tells me to fit the turnbuckles and on my first piston I seem to have crushed the shaft. You can see the marks on the shaft on the closest shock absorber in the picture above. It may not look very much but you can feel the crush points when you slide the piston up and down. These crush point will eventually wear the piston seals away and will leak oil.  After crushing the piston with the pliers I have managed to buy a new pair from Germany at a cost of 21 Euros. The shafts themselves were only 9 Euros and the postage was 12 Euros. Since I crushed the shaft I decided not to fill the shock absorbers with oil until I can do all 4 together.

I did however fit the other three turnbuckles successfully.

A picture of the shock absorbers with the turnbuckles fitted.

The above picture shows the spring seats which are actually aluminium and are of a high quality. I am very impressed with them.

Although the shock absorbers are not filled with oil, I decided to fit the springs and I can report that the operation of the shock absorbers is really smooth (apart from the one I crushed with the pliers DOH). I can't wait to fill them with oil and fit them to the car.

After a little thinking, I decided to fill the shock absorbers with oil, however I forgot to take any pictures.

The above pictures show the difference in the diameter of the new Koswork shock absorber to the original Kyosho one. The difference is quite a few millimeters. 

With the oil in the koswork shock absorbers, the smooth operation is superb and a lot better than the original Kyosho shock absorber.

With the oil filled into all four Koswork shock absorbers, I quickly fitted them to the car and the difference in the stance of the car is very noticable, it looks race ready now. The Koswerk shock absorbers move under the weight of the very light car that. The Kyosho shock absorbers never moved. There is still a lot of adjustment in the shock absorbers if the car was populated with it's full complement of it's electronics to ensure the car will handle perfectly.

The only tricky Koswork shock absorber to fit was the back right one (pictured above), as it was right over the pinion cover. I had to take the bolt out of the upright/shock tower and then refit it with the shock absorber in position. Other than that, the shock absorbers fitted without issue.

A view of the front shock absorber.

Well that is the shock absorber project complete and I can say, the shock absorbers were easy to build and the performance of them is silky smooth. In my humble opinion they were worth every penny/cent/euro. If you are looking to buy some shock absorbers for your RC car or buggy, I would seriously consider the Koswork ones, they are beautifully smooth and easy to build.

With this post now complete, I hope you will join me for future projects. 

Take care, continue to enjoy your RC hobby and be kind to other people.

7/8/26

catxls.com

Small Update 26/8/2026

The shock absorber piston shafts were delivered a couple of days ago.

The picture above shows the new piston shaft replaced with the new one, which means I now have a spare front shaft in case I need one in the future. Hopefully, you can see the old damaged one in the bag with the new one alongside it! It's the top shaft that it the damaged one!

catxls.com