Kraton V3 Kraton 6s troubleshooting

[Johnny Polpetta]

Hello everyone! As I have written in my intro post, I have recently bought my first Arrma: a brand new v3 Kraton 6s. So far I've been mostly happy with my purchase, although there are some things that have left me sort of a bitter taste in my mouth (the build quality being the biggest head-scratcher).

The truck in itself is a true beast: when I bought it, I had the plan all along to use it and abuse it, so I immediately chose two 3s batteries to run it on 6s. One thing I immediately noticed is that the motor tends to get quite hot very quicly, even though so far the truck has never really been pushed hard.

I tried mounting a fan on it (I even designed and 3d-printed a clamp-style fan mount to use) but it hasn't been a big help. On the last run, the motor got so hot, that the threadlock on the pinion's grub screw melted and allowed the screw to back out, making it gauge the red motor mount and allowing the pinion to move along the motor shaft, causing a bad mesh with the diff spur.

I read around the web that most people run a 14t pinion instead of the original 12t, claiming it is "the sweet spot", so I was wondering: will a 14t pinion help the motor run cooler, or will it just make things worse?

Another thing I need help for, is understeer: this truck has loads of it. To try and fight it, I have changed the diff oils (50k-100k-30k for front-center-rear), removed the sway bars and put the shocks in their softest settings, but the darn truck still won't turn right; sharp corners only happen at low speeds, but press the trigger slightly and they get very wide. The servo isn't to blame, and the tires don't feel too hard even though they're still the stock ones. Any of you guys had to fight this problem? How did you solve it?

Thank you in advance, any help is greatly appreciated!

 

[Primarrma]

Are you running the stock pinion? What terrain are you driving on? What style of driving are you doing?

Steering isn't always easy to get right, have you adjusted your end points and servo saver? If you're sure you're getting full lock and the servo saver isn't activating then, check your steering rack and make sure that the bolts are seated properly and not loose on the inner holes of the rack. Check your pillow ball's aren't too loose or too tight, ect...

Read up on how to change the steering characteristics on an rc under power or out of a corner it may help you achieve more steering, just remember this will make it feel twitchy at speed.

 

[Johnny Polpetta]

Yes, the pinion is still the stock one. Except the diff oils, the whole car is still stock.
The last runs I did were on tarmac, but I have driven the Kraton offroad on a dusty, loose surface and the motor still got hot rater quickly.
About the steering, all of the nuts and screws are tight (I have the compulsion to check my cars after every run I do) and the servo saver nut is tight all the way. I even removed the rubber grommets that come stock on the servo mounting holes, which helped the steering get more precise.
A few days ago I read a guide by one of Arrma's official bashers on how to set the suspensions in order to get either a more numb or more precise driving experience, and I tried all three setting holes on the shock towers both front and rear: so far, nothing has helped much. The softest setting made it more bearable, but the understeer is till there. The only thing I haven't tried yet is new tires.

 

[Primarrma]

Yes, the pinion is still the stock one. Except the diff oils, the whole car is still stock.
The last runs I did were on tarmac, but I have driven the Kraton offroad on a dusty, loose surface and the motor still got hot rater quickly.
About the steering, all of the nuts and screws are tight (I have the compulsion to check my cars after every run I do) and the servo saver nut is tight all the way. I even removed the rubber grommets that come stock on the servo mounting holes, which helped the steering get more precise.
A few days ago I read a guide by one of Arrma's official bashers on how to set the suspensions in order to get either a more numb or more precise driving experience, and I tried all three setting holes on the shock towers both front and rear: so far, nothing has helped much. The softest setting made it more bearable, but the understeer is till there. The only thing I haven't tried yet is new tires.

Sounds like you have done your homework then, the backflip tyres will definitely give you more traction, but won't help the heat issue. Are you running a lot of full throttle, I'm surprised you're getting things hot with a 12t pinion. Have you actually measured the temps? If you're not not getting up to 150-160f then you're ok, 120f is hot for the esc. Is the ambient temperature very high?

Anytime the front end is lifting up you'll push wide unless the car is steering with rear power(power sliding). If you're looking for a track setup the Kraton is not ideal, but with a bit of work it should be very driveable, I've run mine with truggy race tyres and it handles well, though you can't run those on tarmac or high speed for long. Have you tried lowering the car and stiffening the suspension?

 

[Johnny Polpetta]

Not a lot of full throttle, I still need to get used to the 6s power, although I have been trying to pull wheelies on the tarmac. Still, my driving is quite conservative: full throttle only happens for a very short time (less than a couple of seconds) and I don't usually slam on the brakes, I let the car gradually decelerate by itself, so the batteries don't suffer (matter of fact, they're still flat as a brick).
I never had the chance to measure the temps, but one thing I was taught early on is the general rule of thumb that if you can't keep your finger on the motor for more than a couple of seconds, then it's hot. Ambient temp is barely warm: here in southern Italy it's about 20-22°C (around 70°F).
Ride height is one thing I haven't dealt with. With the soft setting I'm running and the batteries strapped in, the car is quite low, the driveshafts are angled slightly up towards the tires, but the suspension still has all of the travel available. Do you think that by reducing the excursion using the droop screws can help the steering?

 

[Mad Man Slice]

Yes, the pinion is still the stock one. Except the diff oils, the whole car is still stock.
The last runs I did were on tarmac, but I have driven the Kraton offroad on a dusty, loose surface and the motor still got hot rater quickly.
About the steering, all of the nuts and screws are tight (I have the compulsion to check my cars after every run I do) and the servo saver nut is tight all the way. I even removed the rubber grommets that come stock on the servo mounting holes, which helped the steering get more precise.
A few days ago I read a guide by one of Arrma's official bashers on how to set the suspensions in order to get either a more numb or more precise driving experience, and I tried all three setting holes on the shock towers both front and rear: so far, nothing has helped much. The softest setting made it more bearable, but the understeer is till there. The only thing I haven't tried yet is new tires.

I use Robinson racing 16T Extra hard pinion, Yeah racing heat sink & duel fans..... even when I did not have the heat sink & fans, I don't recall any issues. Is it really hot where you live?

Also, what exactly does this mean?
servo saver nut is tight all the way.

 

[Johnny Polpetta]

Ambient temp is not a problem: as I mentioned in the previous post, it's around 70°F, so nothing to be worried about.
By "servo saver nut is tight all the way" I meant that I screwed the servo saver nut as much as it allows, making the spring as compressed as possible. I wanted to exclude the servo saver as a culprit for the understeer by making it virtually non-existent.

 

[Mad Man Slice]

I have always set my servo saver nut about 5mm above the chassis.... I don't think having it fully tightened will help much, it will actually make it more stiff to turn left and right.

 

[Johnny Polpetta]

I use Robinson racing 16T Extra hard pinion, Yeah racing heat sink & duel fans..... even when I did not have the heat sink & fans, I don't recall any issues.

What kind of surface do you usually run on? And how is your driving? I'm trying to figure out if the one true cause of my truck's problems might be me

 

[Notorious J]

What kind of surface do you usually run on? And how is your driving? I'm trying to figure out if the one true cause of my truck's problems might be me

Hey Johnny. I figured that the understeer problem was exclusive to the Notorious/Outcast platform because of the short wheelbase and excessive torque. Knowing your experiencing it in the Kraton was an eye opener. I too am trying different preloads on the rear shocks, hoping to balance it out, but the front end lift under acceleration seems to be impossible to eliminate. As a basher, I've learned to accept it as normal, and find myself tapping the brake before I need to make quick steering adjustments. It seems more obvious in high traction areas, as the lift is almost imminent. On loose dirt and gravel, there's more control as the rears don't bite in as well. Based on your attempted set ups, which do you find helps the most? Firm f/r, soft f/r, soft f firm r, or firm f soft r?

 

[bicketybam]

You can only do so much with the stock servo, or in @Notorious J 's case a servo with nearly identical specs as stock. I run a Savox 1210SG at 7.4v with a voltage hobbies aluminum servo mount. I don't have any issues. Does it handle like my Typhon? No, but I don't struggle with understeer.

 

[Johnny Polpetta]

Hey Johnny. I figured that the understeer problem was exclusive to the Notorious/Outcast platform because of the short wheelbase and excessive torque. Knowing your experiencing it in the Kraton was an eye opener. I too am trying different preloads on the rear shocks, hoping to balance it out, but the front end lift under acceleration seems to be impossible to eliminate. As a basher, I've learned to accept it as normal, and find myself tapping the brake before I need to make quick steering adjustments. It seems more obvious in high traction areas, as the lift is almost imminent. On loose dirt and gravel, there's more control as the rears don't bite in as well. Based on your attempted set ups, which do you find helps the most? Firm f/r, soft f/r, soft f firm r, or firm f soft r?

So after all it is a common thing, apparently. From what I noticed in my runs, my current setup is the one working better: inner shock tower hole on all 4 corners, with a preload of 5 turns on the rears and just 2 on the front (maybe a little more if the notorious/outcast is lighter, but I doubt it) and no droop limit. I put the anti-roll bars back on the truck, because on full throttle accelerations you can definitely notice some torque twist.
My next step will be reducing the caster angle of the front wheels to a minimum. If that doesn't help much, I'll get some new tires.
How about you: are you having heat issues with your motor? What pinion are you running? How's your typical bashing? I'm curious to see if it's just the Arrma electronics that like to run hot.

 

[Notorious J]

You can only do so much with the stock servo, or in @Notorious J 's case a servo with nearly identical specs as stock. I run a Savox 1210SG at 7.4v with a voltage hobbies aluminum servo mount. I don't have any issues. Does it handle like my Typhon? No, but I don't struggle with understeer.

The speed of my Savox is almost identical to stock, but that's not my issue. Yesterday while jumping in a grassy area, the front end lift was causing it to understeer pretty badly, slowing down kept it planted and turning well, but any acceleration would bring the front up and increase the radius of a turn. From a dead stop, punch set at 6, it just bites at the rear wheels and lifts the front. This is common for the swb, as it was intended to be able to back flip from a stand still or slow roll. Wouldn't expect the same problem with the lwb trucks. A faster servo would likely help, but the trucks should be able to turn better on stock specs.

 

[bicketybam]

Well I will admit most vehicles don't turn very well when the two tires that do turning are off the ground ?

 

[Notorious J]

So after all it is a common thing, apparently. From what I noticed in my runs, my current setup is the one working better: inner shock tower hole on all 4 corners, with a preload of 5 turns on the rears and just 2 on the front (maybe a little more if the notorious/outcast is lighter, but I doubt it) and no droop limit. I put the anti-roll bars back on the truck, because on full throttle accelerations you can definitely notice some torque twist.
My next step will be reducing the caster angle of the front wheels to a minimum. If that doesn't help much, I'll get some new tires.
How about you: are you having heat issues with your motor? What pinion are you running? How's your typical bashing? I'm curious to see if it's just the Arrma electronics that like to run hot.

I'm still running the stock (I think 12t) pinion, and have never thermaled. I run 50% in the grass and 50% loose dirt and gravel. Even at punch 4 with some pretty decent run times, never had an issue. Raising the punch to 6 has taken a bit of time off, but still averaging over 17 minutes. Not keeping my temp gun on hand, I'm able to touch the motor after a full pack and know it's easily out of danger. Temps here in Toronto are still fairly cool and I usually only run in the evening. I'm sure this all plays into it. Thanks for the tips on the set up. I'll give it a try and see how it feels.

 

[Primarrma]

The droop setting on these cars really is protecting your shock rod ends, if you have no droop adjustment you will end up stretching and braking your shocks, I run a little extra so I'm not in danger. I doubt the droop will effect the steering that much.

The temp thing has me confused, a 12t should be able to run flat out and not get hot. I run 16t and don't have any real issues, but if I run hard it will get hot. Have you checked your mesh between motor and spur isn't too tight? You should be able to rock it back and forth a tiny amount, about 1/2 a mm.

One other thing to try is your rear camber try a bit more negative camber it should help when it's under load. You can remove the top spacer on the front arm instead and try that? Change the front or the back not both, unless you do the opposite thing at the front to the back.

 

[Johnny Polpetta]

Thanks for the tips. My droop screws are set at the very end of the excursion of the arms, but it's still safer to reduce the travel a little bit more as you said, so I will check on that.
The mesh should be about right: the spur has that tiny amount of rocking you mentioned, and the truck doesn't make any weird noise as it runs. All the bearings in the transmission, from the motor to the axle carriers, are free-spinning, so there's no binding there either. At this point, the only problem left to investigate is the driver . Although I'm fairly certain the truck hasn't been driven that hard to explain the motor heating that much. I'll try and pay attention to my driving style next time. Unfortunately it won't happen sooner than a few weeks because of my commitments, but I'll keep you guys updated.

 

[Lazy Bushman]

I have a similar steering issue and I expect it has something more to do with me stuffing around with steering dual rates when trouble shooting another issue as I have only recently observed this. Prior to that my V3 Kraton turned on a dime on bitchumen. I haven driven on the road for a while now as 85% of my driving is gravel and 15% grass I reckon. I was really noticing the understeer yesterday on a short grass run actually. It is a bit annoying but I just haven’t had the time to look into it more deeply. When I do, I will be starting with steering dual rate.......I also run backflip tyres.

The hot motor thing seem extreme for a stock setup, that one is puzzling and would cause me greater concern if it was my truck.

Sorry to here you’ve had such an ordinary start to what is normally a great truck

 

[nino]

I think a truck set up for stunting (limited droop, stiff suspension, thick diff oil) is bound to turn and handle worse than stock.

 

[bicketybam]

I think a truck set up for stunting (limited droop, stiff suspension, thick diff oil) is bound to turn and handle worse than stock.

This is true especially of you go with heavy fluid in the front diff. On order for it to turn, one wheel has to turn faster than the other. Heavier diff fluid makes it more difficult for that to happen. The heaviest I go in the front is 50k.