Optima Mid Modern Race Build

[j0pp3]

No holes to mount shocks, hinge pins, etc.?

Maybe that's part of the new design. Everything holds up via electromagnetism

[Seabass]

Ok parts are coming in and everything was great until I tried putting the car together. I ordered a couple sets of Lazer ZX-5 hweels prior to doing reserach and then learned about the offset issue. I also ordered 65.5mm swing shafts. Once the shafts came in I learned 65.5mm is definately too short in the front, and too long in the rear. For the heck of it, I threw the ZX-5 wheels on the car and there is not that much of an issue with the front track being narrow than the rear. So iu fixed the offset issue with the wheels without knowing it.

So what am I doing wrong since this seems to be different from everything else I have read. The arms are not the same length but there is not that much of a difference in the length to make up that much distance (or at least I didn't think so). Could the reason be because I picked up ZX-5 hubs and carriers? Some clarification would be helpful. I am glad the newer wheels fit anyway because I prefer the newer wheels VS the ZX-R wheels.

What are you thoughts on this? I also need to find some black 62.5mm swing shafts but that is proving to be difficult since Kyosho is only showing silver RB5 shafts. What gives?

[RichieRich]

Ok, what exactly is your question? I know Kyosho made CVDs in several lengths. I think I used the standard RB5 CVDs for my Ultima build but that was with standard length arms.

[Seabass]

I have read in numorous places even here that state you must use the older Lazer ZX-R wheels because they have the same offset between the front and the rear wheels. The newer ZX-5 front wheels have a different offfset than the rear wheels which make the car have different track widths (front being considerably narrow than the rear).

I bought ZX-5 wheels prior to learning this and now that I got a chance to put the car together to check fitment, the ZX-5 wheels on my car have the same track width which is totally different than what I have read. I also figured since the off set would be the same on the wheels, the same length swing shafts would work, definately not the case here.

Here is my part breakdown:

ZX-R front and rear arms
ZX-5 Rear carriers
ZX-5 Front hubs and steering arms
65.5mm Front swing shafts (3mm too short)
65.5mm Rear swing shafts (3mm too long)

Why are my front wheels the same track width as the rear when everyone else has experienced the narrow front track? I am puzzeled by this and hope someone with knowledge can help explain why. Hope that helps, maybe not. I must say figuring out what parts to use and not use for this build is really starting to get aggravating .

[RichieRich]

Ok, now this makes sense. I ran into the same thing adapting my Ultima to use RB5 wheels. I don't have any experience with the ZX-R so I don't have any specific ideas to help. The only thing I can think of is that the arms are longer/shorter? and it makes up for the offset on the ZX-5 wheels.

[jwscab]

kyosho makes 68m shafts and 62mm shafts for various cars, along with the 65mm ones. I don't know enough about them to know what fits what. sorry not much help.

[Seabass]

Thanks guys, I have the shafts figured out, its the wheels that are throwing me off. I have to send the swing shafts back and get the right ones. I also purchased two sets of Lazer ZX-R wheels I probaly will not need either. Nothing like spending money on stuff you don't need.

Anyone else feel free to chime in if you can help answer the wheel question.

Jake

[j0pp3]

Interesting topic! I'll have to deal with this too in near future

Is there a good alternative from using ZX-R front and rear arms? They ain't very cheap for a runner right? Any modern arms that might fit?

/j0pp3

[Mr. ED]

I admit not having read the full thread but I'll do a throw at it:
The ZX-5 was originally released with a simalar fornt end to the TF5 = traditional C-arriers with the steering knuckles going inside. The front wheels of that car were the same as the old lazer => good for a mid also.

Then the ZX5-SP1 was released : this one having the more modern style front set up with slightly shorter arms and the steering kunckle going around the top and bottom of the 'c-carrier'. All later version have this same design.

If you got the old ZX5 front wheels they will cone out from the center to the rim.
The later wheels are lightly bulging from the rim to the center.

And then much later the ultima RB5 SP2 or something introduced a new rear wheel where the nut sits under the surrounding surface. I believe that's now used in the rear of the latest ZX5's also.

[Seabass]

The parts saga continues. I got my chassis in and the belt I purchased is wayyy to long, $20 down the drain. Why do people sell stuff marketed as a LWB Optima Mid belt when it doesn't even come close to being the right size?

So I did some searching and found the thread regarding the belt length, pitch etc. I am ready to place an order through SDP-SI but I need to confirm the proper belt length for this car. Looks like you guys were saying 129 teeth and a length of 25.4 inches. SDP-SI has a belt with 127 grooves that is 25.4 inches. The 129 grooved belt is 25.8 inches.

So which one do I order, the 127 grroved or 129 grooved?

Jake

[Mad Racer]

Don't know if I can help.

Part Nu OT89 is the original Mid belt.

Part Nu OTW7 is the Lwb belt that I got from Tough Racing on the Bay.

Cheers
Mark

[Mr. ED]

Are you sure that's a lwb chassis? Did you compare the wheelbase against that original alu chassis of the first pics?

[DennisM]

Meassured between the 2 nearest mounting holes on the front and rear gearboxes.

LWB has app. 238mm between the rear and the front gearbox mounting holes.
SWB has app. 220mm between the rear and the front gearbox mounting holes.

[Bo Wallen]

Hey !!!
Flip the old chassis on the back of the new one....check how much it is off. that will give how long belt you need.
I got 4 different chassis and 4 different belt. Super short, original, extra long, super extra long wheelbase.
Good Luck Sir

[Seabass]

This is a LWB chassis. Compared it against the old aluminum one and it is at least 20mm difference in length (I will measure the difference tonight). I also counted the teeth on the LWB belt I got and I counted 132 teeth. With the 5.08mm pitch, this belt is going to be at least 1 - 2 inches longer then needed.

I just ordered a 127 grooved, 25.4 belt from SDPSI. Hopefully this will correct the problem. I am trying to return the belt I got from eBay since it is definately not right.