KYOSHO OPTIMA CS BUILD - Optima + Options = Competent Vintage Class Carpet Racer?

Wait, what? But, David you already have an Optima I hear you say. 😁

That is correct! 😅 But that one was my first 4WD Legendary Series build and something I wish to keep completely stock. This one is being built solely for the purpose of indoor carpet track use and vintage class racing.

I love the Vintage Series from Kyosho - some of the best RC's ever produced(IMHO). But like most vintage designs, they're not really suited for use on high grip carpet tracks. Not without some modifications and tuning. Hence this build. In this video I finally put together my Carpet Spec Optima.

*Addendum. Since completing the build I've picked up a few more of the more costly alloy options, which will be added to the buggy when (and if) the original plastic parts fail. A full option Optima would be nice...but, oh so very expensive. 😬

After a shakedown and testing day at Carnosa RC Park I'm very pleased with how my initial setup performed. See below for details.

Ultimately, the question I want to answer is: Can the Optima take on the mighty Dog Fighter?

To answer that I guess I'll need an 834B...😁


OPTIMA CS INITIAL SETUP

Diffs have 10,000 weight oil front and rear. Normally I'd go with 7,000 front, maybe 5,000 rear, but I was curious to see how it would respond to thicker oil. Also, having the diffs leak would be a major PITA! 😩 So thicker = less likely to leak.

I opted to use the standard Optima belt as the low friction one is slightly longer. This might make it more prone to skipping on carpet under hard braking etc. Belt tension is (supposedly) adjustable, but to me the range of adjustment, if any, is minimal.

The hard suspension arms require slightly longer dog bones to work best. Otherwise you'll need to add an o-ring to the drive cups. Without them they may pop out of the axles on cornering. See the Turbo Optima manual for more details.

The wider hubs helped with cornering stability, as did the sway bars. I'd like to lower the Optima further, but that isn't straight forward without resorting to third party parts. I'm by no means a suspension guru, but to my mind the main issue is the limited mounting points for the stock dampers and the Kyosho front springs are perhaps too long for carpet use.

With the pre-load adjuster all the way to the top, the springs remain under compression even at full extension. Removing the internal spacer (OT210 - 2) will allow for more extension (droop) and take a bit of tension off the spring, but I don't think it would much to change the ride height. Add some more internal spacers and it will lower the buggy at the expense of suspension travel.

Selecting the right springs is also tricky. Go soft and the buggy will sit lower under its own weight, but roll too much in the corners and bottom out badly on the jumps. The chassis hitting the jumps makes the handling very unpredictable. Go stiff and it's better for larger jumps, and although the chassis doesn't roll as much in the corners, the higher COG will lead to more traction rolling.

To be fair, this is a problem that most vintage buggies suffer from. With the 870c I went through numerous shock mounts, pistons, springs, oils etc to get the suspension setup right (for me). The best setup I had used Unfair RC Big bore shock towers and YZ-4 big bore dampers. They transformed the handling! Happy days! The 870c could fly with the best of them! Now to sort out the chassis balance - relocate the battery, servo, update the steering linkages and...

hold on a second.

In my goal of making the 870c handle as good as a modern day machine I felt that I'd lost sight of the whole purpose of racing vintage class - to race a vintage machine! With each step my "vintage" 870c was less and less" vintage".

So, with the Optima I want to try and stay as true to the original as possible. No third party shock towers, big bores, or custom fabricationOn the day I switched between 43mm kit wheels/tires, 50mm Turbo Optima wheels/tires and 2.2 wheels with carpet spec tires. The 2.2 were the most consistent, but surprisingly the 50mm soft compound tires on Turbo Optima wheels. I ran both heavy nimh packs (less roll in the corners, but harder landings) and light weight lithium batteries (more likely to traction roll, but better landings).

Anyways, enough of my waffle. Here are the initial settings I went with.

Camber: FRONT 2º / REAR 2º
Toe: FRONT 1º out / REAR 2º in
Dampers: #300 + yellow springs FRONT / #300 + blue springs REAR.
with the spring adjusters set as low as possible
Ride Height: ~32mm without battery and 23 ~ 25 with.
weight ~ 1,280g without battery.