Outcast Curious about Differential weight in the center and rear

[adidas303]

Will heavier weight oil in the diffs limit air control in a 6s Outcast? Not sure if Center diff and rear should be lighter or how heavy an oil I can go, maybe?

Thanks in advance for your time and info!

 

[jym73]

Will heavier weight oil in the diffs limit air control in a 6s Outcast?

I would say no. The heavier weight in the center diff. will give more traction to the rear wheels when the car is on the ground and even when it does wheelies. More the center diff. oil is heavy more the front and rear wheels will turn at the same RPM.

When the car is in the air, the oils in the diff. have almost no effect.

This table explain shortly how oil affect car behaviour :

You can find information in these threads :
https://www.arrmaforum.com/threads/outcast-diff-oil-setup-discussion.4497/
https://www.arrmaforum.com/threads/diff-oil-recommendations.3107/
https://www.arrmaforum.com/threads/outcast-oil-recommendation.5066/

Or even search in this google result : https://www.google.com/search?newwi...hUKEwiwz46W44vlAhWC5OAKHSjGA2AQ4dUDCAs&uact=5

Diff. oil weight is something "personal", not everybody use the same weight, it depend on how you want the car's behaviour will be. It is something to test before find his own setting.

 

[olds97_lss]

I ran 100/500/100 in my outcast when it was 4S, but when I started running 6S, I changed to 100/300/100. Made it a bit less wheelie happy and easier to drive.

 

[adidas303]

Thanks @jym73!! Yea I knew the Oil weight I would need to play with some, was trying to verify if I should start heavy in weight or light.


Also, Thank you @olds97_lss! I was guessing the heavier oil would tone down the wheelies, trying to learn if the Diff oils can mess with the Air Control with jumping it. Trying to learn how to be a @Rich Duperbash or @RC DUDE81 Basher! Haha

 

[olds97_lss]

Heavier/lighter in the center does change the launch off a ramp a bit, since the front tires leave the ramp a split second before the rear. I didn't run stock oils that long, so I can't compare too much to that. I just remember the first arrma I saw was a v2 talion that a "newbie" had clearly been beating on for quite a few months. It unloaded the front tires constantly on him, so much so that they were basically bald down the middle. I suggested he increase the weight in the center diff to calm it down a bit and after he learned a bit more trigger discipline, he was much happier. I think he changed to 500k, which may be ok on 6S in the kraton/talion, but in the shorter outcast, it makes it wheelie way too easily. On 4S, it was great though. Now on 6S, 300K seems to be a happy medium for me running the 3.8" trenchers that are strapped.

 

[Reubydoobe]

I would say no. The heavier weight in the center diff. will give more traction to the rear wheels when the car is on the ground and even when it does wheelies. More the center diff. oil is heavy more the front and rear wheels will turn at the same RPM.

When the car is in the air, the oils in the diff. have almost no effect.

This table explain shortly how oil affect car behaviour :
View attachment 50238

You can find information in these threads :
https://www.arrmaforum.com/threads/outcast-diff-oil-setup-discussion.4497/
https://www.arrmaforum.com/threads/diff-oil-recommendations.3107/
https://www.arrmaforum.com/threads/outcast-oil-recommendation.5066/

Or even search in this google result : https://www.google.com/search?newwindow=1&rlz=1C1PRFI_enFR860FR861&sxsrf=ACYBGNQjtPVKKH7XtpGoFPP-fCaUNCKE6w:1570507183081&ei=rwmcXfC7BILJgweojI-ABg&q=site:arrmaforum.com+differential+oil+weight+outcast&oq=site:arrmaforum.com+differential+oil+weight+outcast&gs_l=psy-ab.3...65235.67525..67828...0.0..0.76.510.7......0....1..gws-wiz.QQa2h9MqWgc&ved=0ahUKEwiwz46W44vlAhWC5OAKHSjGA2AQ4dUDCAs&uact=5

Diff. oil weight is something "personal", not everybody use the same weight, it depend on how you want the car's behaviour will be. It is something to test before find his own setting.

When the car is in the air the oils in the dif have little affect ????? are you serious? Of course they do. It's so much easier to flip my outcast with 500 in the center than it is with 150.
250 or 300 is enough to give you air control but if you want to flip like mad go thicker. Ten rear 50/60 up front

Thanks @jym73!! Yea I knew the Oil weight I would need to play with some, was trying to verify if I should start heavy in weight or light.


Also, Thank you @olds97_lss! I was guessing the heavier oil would tone down the wheelies, trying to learn if the Diff oils can mess with the Air Control with jumping it. Trying to learn how to be a @Rich Duperbash or @RC DUDE81 Basher! Haha

Thicker oil will make it wheelie more not less. ? 150 in the center it won't wheelie to much.

 

[bicketybam]

When the car is in the air the oils in the dif have little affect ????? are you serious? Of course they do. It's so much easier to flip my outcast with 500 in the center than it is with 150.
250 or 300 is enough to give you air control but if you want to flip like mad go thicker. Ten rear 50/60 up front

Thicker oil will make it wheelie more not less. ? 150 in the center it won't wheelie to much.

That's interesting. I would think the center diff unloading to the front wheels would make it rotate better. That was my experience with my Rock Rey.

 

[adidas303]

When any car is in the air rotating, I can understand the weight of the oil will limit or not limit the wheel spin. Is most of the rotating power in air coming from the Rear or Front wheels? Or is that where it depends on the oil weight, example: 10k up front 50k in the rear and the rotating power in the air now comes more from the front wheels? or vise versa

or is it, the majority of the power always goes to the rear anyway and that is the driving factor with rotating in the air?

 

[Mr.Duke]

The power will alway travel the path of least resistance. Each of the 4 tires holds the kinetic energy ultimately responsible for air control as they increase or decrease in rpm. Running higher viscosity fluid in the center splits power more evenly front to rear whereas, the front and rear diffs split power left to right.

 

[olds97_lss]

The power will alway travel the path of least resistance. Each of the 4 tires holds the kinetic energy ultimately responsible for air control as they increase or decrease in rpm. Running higher viscosity fluid in the center splits power more evenly front to rear whereas, the front and rear diffs split power left to right.

When the tires are in the air though... does it really matter what's in the center diff? With all things being equal, there's the same energy needed to spin both the front and rear tires in the air, so does the oil weight really have any impact if the tires are off the ground?

For the launch, the center weight will alter the initial weight transfer and the initial start of the rotation, but as soon as the rear tires leave the ramp, the front and rear would require the same amount of energy. Right?

I feel like I'm working my brain too hard on this... now I need a nap.

 

[adidas303]

Appreciate the insights from all who replied, I'll pick up some 300k diff oil, @olds97_lss was stating in a previous post as it seems like a good middle ground start. Get the feel for how it acts and look into any changes from that point. Just checking if there was a setup that is used by the majority for this type of bashing. Like most other aspects of this hobby, still seems to be a personal preference! Thanks!

 

[bicketybam]

Fronts are first to come off the ground under power and I believe they unload immediately to help rotation. That's my theory and my experience!?

 

[jym73]

Take any car with a center diff. and a little bit of grease inside, so not that much resistance, almost nothing from the grease. Lift the wheels from the ground and push the throttle, all the four wheels will spin at the same RPM. The resistance is equal on front and rear input gear and crown gear and bearings, the only difference would be with the center shafts weight, the rear shaft is often longer, but it is negligible. Keep your car with the wheels lifted, add a little bit resistante on front or rear wheels, the opposite two wheels will spin more fast, release the resistance, they will come back to the same RPM, equal on all the four at the same RPM. It is same when you are in the air, the air resistance, which is the same on all the wheels, make them spin at the same speed.

When you take a bump or ramp, the last impulsion given to the car will be from the rear wheels as they are the last ones which are on a surface to push the car. When the oil is thicker in the center diff. this will give a bigger impulsion from the rear wheels at the last moment (as a thicker oil help to do wheelies because there will be more traction on the rear). So the car will flip more if you keep the power and push it more just before the last wheel left the ramp, this will give a movement of rotation on the car (i don't talk about the rear shock absorber which also give a movement to the car when they are released, the spring and oil in the shock absorber will also influence the movement the car will take and also how the weight is distributed on the chassis and the curve of the ramp). Once the fours wheels are in the air, they will return at the same RPM and the car will keep the rotating movement given by the rear wheels (and shock absorbers). But, if you give the same amount of power all along the ramp, if you stay linear on the power you give, and use the good amount of power to keep the car flat in the air, and at a moment you want to make a backflip, you give more power to the wheels, the whole car will rotate, with all the wheels at the same RPM. Thick or thin oil will change nothing to this. So, the control of the car in the air isn't influenced by the oil thickness. But the movement the car take in the air just after it has left the ramp/bump can be more influenced by how the power was when it left the ramp/bump, so influenced by the center diff. thickness, as it is the rear wheels which will give the last impulsion and the difference of spin speed between the rear and front wheels.

I found more annoying a car which does wheelies too easily, so with too thick oil in center diff, when you want to jump. If the oil is too thick in the center diif., a little bit more power will make the car does a wheelie on the ramp, it will loose speed, won't have a good position and the jump won't be as big, worst, we lose the control of the car more quickly and it is more hard to control. Take a buggy, with small wheels compared to a MT (and also a lower gravity center), you can push the power at the last moment, the buggy won't do a wheelie as easily as a MT and will do a big jump. Do the same with an Outcast, it will directly do a wheelie and spin on itself on the ramp, and the jump is lost. With a SWB truck with big wheels like an outcast you must be linear on the power/acceleration from the beginning and until the car left the ramp. That's why we advise a Kraton instead of an Outcast for a beginner, the throttle control is really important with an Outcast to do great jump with it, more than with a Kraton. For me the center diff. thickness influence how you can take the ramp, from the start until it left the ramp, the center diff. oil thickness will more influence how the car will be more or less easy to control for taking the ramp in good condition and keep the control while in the air, not to control it while it is in the air, but to manage/control it to go in the air, in the way you want it will going.

The speed of the chassis rotation movement will be faster with a SWB than a LWB chassis. It is same than the experience you can do on a spinning chair, extend your arms on left and right, you will go slower, put your arms on your chest you will go faster, as already said it is due of the keeping of kinetic movement. Heavier wheels will give more rotation to the chassis than lighter wheels.