Design Flaws in ZX5 and how to sort them

[SimonW]

Hi has anyone noticed that the car runs out of up-travel far to soon, i think its the main cause of the flipping as tiverton was very bumpy on sundays 1st round and the rear shock cups fill with dirt and make it even worse I've E-mailed atomic to see if they can help me with a different shock tower as for the cups i've cut slots in the sides to let dirt fall out. Stock up on spur gears too...

[OldTimer]

Simon, just sent you a email re the shock towers.

Cheers
Jonathan
atomic-carbon.co.uk

[paulj]

I noticed when building mine that the rear travel gets very stiff in the last 1/4, so much so I thought something was binding it.

What I've found is it's the rear dogbone drive shafts, remove them and it's fine no stiffening at all. Luckily I had bought a set of the optional rear CVD style shafts to try when I bought the car and with these fitted the rear suspension action is smooth through the full travel.

[jimmy]

I cant say i noticed that paul, are you 100% that you have them built correctly ? my dogbones dont bind at all. one did when i first built the car because i had missed out a spacer.

as you say though, doesnt matter now though with your fancy cvd's !

[paulj]

Originally Posted by jimmy

I cant say i noticed that paul, are you 100% that you have them built correctly ? my dogbones dont bind at all. one did when i first built the car because i had missed out a spacer.

as you say though, doesnt matter now though with your fancy cvd's !

LoL

I'm not certain if it was built right, it should have been for the time it's taken :wink:
Which spacer did you miss out by the way? I wanted to use the dogbones then switch to the CVD's to see if I could detect any difference on track but it was binding towards the end of the travel for no obvious reason so I switched them and it was much smoother.

[jimmy]

i think it was a little plastic cover for the diff screw i missed out that messed it up, it allowed the dogbone too much float and sometimes it would bind up
There are the little foam spacers also, i think i stuck one at each end of the dogbone to keep it in the middle

[paulj]

I know the ones you mean, little white plastic ones, nope they are in, the only thing I didn't fit were the foam spacers as the instructions only mention them for the one way. I'll try one of the rears again with the foam spacer to see if it helps and report back.

[niggs98]

Originally Posted by SimonW

Hi has anyone noticed that the car runs out of up-travel far to soon, i think its the main cause of the flipping as tiverton was very bumpy on sundays 1st round and the rear shock cups fill with dirt and make it even worse I've E-mailed atomic to see if they can help me with a different shock tower as for the cups i've cut slots in the sides to let dirt fall out. Stock up on spur gears too...

personally we found the car needed a touch off antisquat and once we added a spacer with two dimples the car was a lot more drivable across the bumps at tivvy,this may be a cheaper option to try instead off designing new shock mounts,

as for dogbones binding try extra foam or O rings in the drive cups,

[OldTimer]

I have drawn up a alternative shock bracket for SimonW,it does give you more options, anybody going to Baginton on the 27th Nov, nice bumpy astroturf, and if you break any shock brackets i will bring some carbon fibre ones with me :salut:

[BluesFan]

I personally haven't noticed any bind in the rear dogbones unless I accidently put it there. I originally tried to put too many 'fillers' in the outdrives and axle cups so there wouldn't be any 'float' in the dogbone at all (It's been awhile since I've had dogbones in a car). That of course didn't work and caused some major binding issues. I'm not too keen on getting the rear universals when they cost 37$ US (probably a lot more for you UK folks) so I figured I'd try to make the best of it with the doggies. I've found that if you stick only 1 Losi shock o-ring in the diff outdrive, it seems to give just enough float to the dogbone yet at the same time not bind the suspension at all, or at least while it is stationary. I'm not sure how much binding occurs when the car is actually in motion and the suspension is working. Also, using the Losi shock o-ring allows for for diff adjustments without taking them out since you can stick a wrench through the o-ring.
I still haven't gotten around to changing out the springs, but then again, the American tracks I run on usually differ a lot with your UK tracks. After changing the shock oil to 35wt in the rear and 40 up front, I find there is minimal body roll in the corners and the stock kit springs still have enough speed to return the tires quickly to the ground through the bumps without having the car getting tossed after the second bump or so consecutively. I'd like to pick up some stiffer springs though to try out different setups I might like a bit more from the current one I run.
Simon mentioned problems with spur gears. That is puzzling to me.... I haven't had any drivetrain problems other than the ones that have been caused by my own doing. I've unfortunately set my slipper too tight a few times and have blown out the rear diff gears, but I've yet to have a problem with the spur. In fact, I've been very impressed with the quality and precision of the drivetrain. It moves very freely and smooth. It's actually a lot more quiet running around the track than other 4-wheelers. Simon, if you don't already, I'd suggest checking your gear mesh all the way around the gear. I've noticed that the gear mesh is loose in some areas and tight in others. I try to find those tight areas and make my gear mesh adjustments there, and then work my way back to the looser areas to make sure it isn't too loose there once I've made an adjustment.
Lastly, I'd like to express my own personal dealings with "design flaws". It's been discussed many times already about the front brace so I won't get back into that here, but there are other things I thought maybe Kyosho could have done differently. The build of the diff cases seems a bit much. Too many screws and they aren't easily accessible. I'm also not a fan of the shock tower mount and camber link brace that both screw into the diff case. Seems excessive in my opinon. Why not just screw the shock tower and ball studs for the camber links directly into the bulkhead? Maybe I'm missing something? Also, changing the ballstud location for the camber links is a chore. you have to remove the shock tower to get to them... or at least I do to reach them with my current tools. I'd like to get the Losi titanium ball studs so that I can use my hex wrenches to reach them. Also, did Kyosho make a mistake by doing too good of a job in making the car so light? It hardly leaves room for optional carbon graphite pieces or the new woven carbon fibre pieces Jimmy just did a review on. The ROAR rules put 4wd max weight at 3lbs. 12oz. I have all stock pieces on my car with the exception of the titanium screw kit, and I'm at 3lbs. 12.1oz. Titanium turnbuckles or the new shock towers/center brace would put me under! I'm not a big fan of gluing or taping weights to my car to stay legal. I never know the best places to put them to keep things balanced. :wink:

[jimmy]

I'll have some 3rd party Alloy parts to review soon I hope which should beef up the car a little, and bring the weight back up a little!

I need to weigh my car, but with all the Ti screws, Ti Turnbuckles, Carbon fibre, it should be slightly over minimum weight, just.
With an airbrushed shell and tidy wiring I could see how it could be underweight though.

The camber link plates / bulkheads are a bit of a pain, You can adjust the rear ones with a long nut driver, but the fronts are impossible. Its a pain but for a new car its not bad at all, you seem to get problems like weak hinge pin braces / wishbones / shock towers etc crop up on new cars all the time, after all i guess these superstars that develop the cars probably dont crash like me and you! :wink:
I'm sure any weak bits will be ironed out if possible.

[OldTimer]

The way i look at it is the lighter the car the better, then i can add weight were i want it not were the manufacture puts it so he can make the kit cheaper.

If you look at F1 cars they are all built under weight, and they move lead ballast around on the car to improve the handling, the same as what we are doing.

Weight low in the chassis is always better than weight high up.

The Slim4 prototype is carbon and titanium (and turning into a labour of love lol ) but i will make it as light as possible then hopefully bring it upto weight with lead, this is why there is no top deck but a extra thick chassis, again all this weight is down low.

[BluesFan]

Oldtimer, good call. I didn't think of it that way. However, how do you know where to put the weight? I would assume all weights are fixed to the chassis plate, but where exactly? We all use different batteries, motors, speed controls, and receivers. They all weigh differently and are of different sizes. Is there a way to find out where to put the weights so that all 4 wheels are supporting equal amounts of weight? I'm assuming that is what we are all shooting for... to have a car equally balanced on all 4 wheels.

[paulj]

Hi Bluesfan, I'd start by fixing any weights to the chassis near the motor mount but to the outside of the chassis. This is something that BJ4 owners do, despite the car coming in way over the limit, to counteract drivetrain torque to make the car run true on the straights.

After that I guess you could move weight around to see what works, need more rear traction add the weight to the rear, more turn in move some weight forward. If you don't need to change the balance of the car add the weight as near to the centreline and as low as possible to minimise it's effect.

[paulj]

So far my ZX5 has only been across my garage floor so I've no idea how it handles on a track yet Traction was good across the painted floor but a little bit lacking under braking :wink:

But seriously how do you find the front shock travel? They seem quite short to me when compared to Losi fronts, there does seem to be scope for more travel as the driveshafts are nowhere near the end of the outdrives at full droop, front or rear. The rear is travel limited anyway as std but I suppose that increasing rear travel/droop will be useful on very bumpy tracks the trick will be to balance the extra chassis roll from more droop v bump handling :roll:

[jimmy]

Front shocks do look a bit limited, i've wound out the ball ends a little from the shock shaft to give it a little more droop, only a mm or so but it looks a bit better now.
have to see how it goes though..

[paulj]

Jimmy have you tried a front anti roll bar?

The kit rear version will fit the front as well as the rear, maybe this would calm the car down into the corner and combined with stiffer rear springs limit chassis roll problems? Plus the front one way diff is pretty aggressive for off power turn in so it would calm the car when entering the bend.
I know the XX4 is often run with a front bar, I'm pretty sure Doughty has said he wouldn't run one without it?

I presume the lack of stiffness with the kit springs is a cornering problem and not a problem on jumps and bumps?

[trekkker]

having found the front to have a lack of droop we spoke to mike craddock who sent us some la43's which are a longer shock bottom ball joint, we tried this at tivverton and both nathan and myself found this to be a major improvement, we trimmed 3mm off its lenth to get the desired droop so the chassis grounded out before the shock did and havent looked back, the good thing about this is that its a readily available kyosho part so no other bits need modification for fitment, if its ok jimmy i will post a pic of the 2 parts so everyone can see the difference

[trekkker]

Originally Posted by paulj

Jimmy have you tried a front anti roll bar?

The kit rear version will fit the front as well as the rear, maybe this would calm the car down into the corner and combined with stiffer rear springs limit chassis roll problems? Plus the front one way diff is pretty aggressive for off power turn in so it would calm the car when entering the bend.
I know the XX4 is often run with a front bar, I'm pretty sure Doughty has said he wouldn't run one without it?

I presume the lack of stiffness with the kit springs is a cornering problem and not a problem on jumps and bumps?

we are sticking with the oneway diff but are trying the 10 degree hubs at stotfold on sunday to calm the car down going in and give more mid corner steering either nathan or myself will post our findings

[jimmy]

yes mate post away on the photos, i think my droop isnt too bad now with the ball joints wound down a little but some proper ones would be better