RC10Talk - The Net's Largest Vintage R/C Community

Im re building an old race used zx5. Its mostly new parts, but much of the internals are used. Specifically, the diff balls and parts are used. So, I rebuilt the diffs, very clean, fresh grease.... Very nice and smooth. But, when I go to adjust the slipper clutch, I get diff slip,, so I tighten the rear diff, then tighten the slipper a bit more,, and its a tug of war between the diff and the slipper. I need to tighten the slipper enough so it slips just a little,, but that level of tightness forces me to tighten the rear diff untill its very rough. I go way past the smooth area in diff adjustment, and deep into the gravel grinder zone in the rear diff adjustment, just to be able to run the slipper at what my hands tell me is a good base line adjustment.

Any tips? I thought maybe rebuild diff using all new internals,, but honestly,, I think it still would be a salt grinder.... A bit confused.

I guess the first question here is what surface are you running on? I used to have a Lazer ZX5 FS2 SP and ran it indoors on a high bite but slightly dusty surface for a full indoor season this past winter. With brand new parts, I was able to set the diffs smooth and the slipper at the stock setting and not worry about diff or slipper slippage. You may end up having to get new slipper pads, so check the pads for wear/glazing. The Lazer slipper pad has a relatively small amount of surface area, much like the B44 (pre-VTS) if not worse. The slip "window" on those types of slippers is not that large when you run them in 4wd mod buggy, and I have found especially on my B44 that there is almost zero room for slipper adjustability, and so I keep it fully locked or very close to locked. It eats gears on high grip tracks, but I just deal with it.

Generally, for most of my diffs across brands, I set the diff to fully locked minus 1/8 turn as a starting point. The diffs should be able to handle this with a mod motor (8.5t or 7.5t is the range I use for 4wd buggy), but again it comes down to the surface. I don't run on super high grip, so it's not a problem for me.

Ill just be running on asphalt, but it will be brutal traction, with about 8.5 turn motor. I think the diffs need new internals! I used to run an original zx5 when they first came out, and dont remember the diffs being any kind of issue from new. Sometimes it dosent work to recycle balls. Do you think that perhaps sanding with 600 grit on the diff pads might freshen them up?

Another issue I just noticed. WOW this thing has alot of bump steer, and, the stock hubs severely limit over all steering throw on the inside wheel. Going to dremel the c hubs to allow more throw, and then experiment with shims to reduce bump steer.

On the bright side,, this stock zx5 weighs less than just about anything else, and the drive train is sooo free,, much better than the belt buggies it shares a shelf with.

These fiber reinforced plastic fantastic buggies really impress me. Im hoping to have the mr4bc back running along side the zx5 for some raucus street racing fun.

if diffs are gritty when (reasonably) tightened, new balls/plates (both thrust and main) is the only way to go that will allow you to safely move to the next step without any afterthought. All this is usually rather inexpensive (find OEM parts, Kyosho usually rips their customers off).

Go ceramic on thrust and carbide on main.

Paul

rccars4sal wrote:Another issue I just noticed. WOW this thing has alot of bump steer, and, the stock hubs severely limit over all steering throw on the inside wheel. Going to dremel the c hubs to allow more throw, and then experiment with shims to reduce bump steer.

I also had a major bump-steer issue with my Barney Turbo Optima car. Maybe this will help you solve yours or give you some ideas; it might be useful as I built that car with long Maxxum front arms and Lazer C-carriers. I simply mounted the tie-rod outer ball-cups beneath the steering knuckles instead of on top, which got the tie-rods parallel with the control arms, and all but eliminated the bump-steer.

http://www.rc10talk.com/viewtopic.php?f=30&t=21530&start=108

As for the steering throw, is the problem with the inner hub or is the problem that there is too much ackerman in the steering rack? With less ackerman, for the same throw in the inner hub, the outer hub will throw more. This will give you more mid-corner steering. I ask because there must be a reason, either good or bad, why the hubs were designed the way they are.

The newer plastic buggies are very light, but also brittle. It is not difficult to break front arms...

I think the problem is not enough akerman. The way it is now, the inner wheel has roughly the same throw as the outer, because the steering arm runs into the c hub before the whole system is at full throw. It could be wrong c hubs... The car was built from a pile of parts out of package. The c hubs fit perfectly,, but could be from another model.

rccars4sal wrote:Ill just be running on asphalt, but it will be brutal traction, with about 8.5 turn motor. I think the diffs need new internals! I used to run an original zx5 when they first came out, and dont remember the diffs being any kind of issue from new. Sometimes it dosent work to recycle balls. Do you think that perhaps sanding with 600 grit on the diff pads might freshen them up?

Another issue I just noticed. WOW this thing has alot of bump steer, and, the stock hubs severely limit over all steering throw on the inside wheel. Going to dremel the c hubs to allow more throw, and then experiment with shims to reduce bump steer.

On the bright side,, this stock zx5 weighs less than just about anything else, and the drive train is sooo free,, much better than the belt buggies it shares a shelf with.

These fiber reinforced plastic fantastic buggies really impress me. Im hoping to have the mr4bc back running along side the zx5 for some raucus street racing fun.

On my zx5 I run 1 gray washer and 1 blue washer under each ball stud on the steering knuckle side, that completely eliminates bump steer, I think it adds up to about 1mm but don't quote me on that, once you get rid of the bump steer it helps a little but it still has a huge turning radius. However today I was talking to kyosho's customer service about an order I placed, and we got to talking about the zx6, he said that you will be able to run the zx6 c hub and knuckle on the zx5 to decrease your turning radius and it also gives it a better overall feel. As of right now I like the rear end of my zx5 slide semi easy so I can flick it around in the tight corners on our track.

A few close-up pics of the steering knuckle area, and one from directly overhead, would be helpful.

The steering knuckle touching the c hub at full throw.





Overhead at full throw.




Something a bit newer with more modern geometry(refinement of xx4 steering design IMO).

Not quite sure but I think the c-hubs are backwards the right and left are reversed. My zx5 has aluminum upgrades so I can't compare directly

Ill check the arrangement of the c hubs today. In normal rc car design, the c hubs will have a slight rearward vertical tilt, for castor?

No designs would tilt the c hubs forward to counter the upward angle of the inner hinge pins?

I'll have to look at mine tonight but I think the steering knuckle might be the wrong one, I think mine only has one position, I'll talk a pic tonight and post it

Kyoshojoe wrote:Not quite sure but I think the c-hubs are backwards the right and left are reversed. My zx5 has aluminum upgrades so I can't compare directly

That's exactly what I was about to suggest yesterday. It's physically possible to install the C-carriers and steering kncukles on the opposite sides, but it'll affect the geometry and caster angle, and could cause steering to bind up too. Both sets of parts are usually labeled "L" and "R" to prevent mis-installation, even the Optima's knuckles and carriers were labeled to distinguish L & R sides.

Ive got the c hubs installed in the classic fashion, with castor angle rearward. They have a 7 molded into the side. so 7 deg castor angle.