Buggy Diff Question
 

I am getting a 1/8th scale buggy soon and I have a few questions. Ive been watching this forum for a while (and Ive been RCing for 6 years) so I know most of the basics about 1/8th scale buggies (and all other land RCs for that matter). The center diff distributes power between the front and the rear right? SO if it tries to wheely, all the power will go the front and keep the fornt down right? Thats what Ive came up with about the whole 3-diff thing as opposed to to only 2 diffs on sedans and monster trucks. What does changing to different diff oils do? Also, how do sway bars work? I know they keep the vehicle from leaning in the turns, but how do that do that? Thanks.

RE: Buggy Diff Question
 

You have the basic idea of the 3 diff setup right. 1/8 scale buggies very seldom do wheelies. About the only time you will see that is if you land nose high while on the throttle. As for diff oils, they help determine where the power goes in different situations. If you use a heavy diff oil in the center diff, it will try to distribute power to both the front and rear evenly regardless of which wheels have the most traction. With a lighter oil, the diff will unload and send the power to the wheels with the most traction. Your best bit is to determine where you will be driving and adjust the diff oils accordingly.

As for sway bars, they reduce body roll when cornering because it is attached to both control arms. Sway bars make both arms work in concert with one another by tying them together and not letting one side do all the work. There are definitely more technical ways to describe the ways diff oils and sway bars work however this is just intended to show the basics.

RE: Buggy Diff Question
 

There are as many opinions on good diff oil combinations as there are 8th buggy racers. I know people that run 30,000 F, 10,000 C, and grease in the rear, while other folks will run 5,000 F, 3,000 C, and 1,000 R in the same car. I've even seen heavy shock oil used so it's one of those things you will have to experiment with. A good beginners oil setup is 5,000 F, 3,000 C, and 1,000 R. This will give most japanese buggies a very nuteral feel, but will cost you in both off power steering and straight line acceleration. Another very popular combination in Japanese buggies is 7,000 F, 5,000 C, and 3,000 R. With this setup your buggy will corner better off power and will also hole shot better, but it will also step out faster. The idea is to get you car to follow the front wheels so whatever oil you use in the center, use a heavier oil in the front and a lighter oil in the rear.
As for sway bars, if you are running a mild engine they won't do you much good front or rear. If on the other hand you are unning something hot, putting a sway bar on the rear will give you more steering. The general rule of thumb for sway bars is whichever end of your car needs more steering, put a bar on the opposite end.

RE: Buggy Diff Question
 

Then why do all diff setups I see reccomended have the highest weight in the center diff. i.e (5,7,1) (3,5,1) (f,c,r) etc... Am I backwards here?

RE: Buggy Diff Question
 

So the power is more evenly distributed between the front and rear. The idea is to get everything working in concert to achieve the best traction. The center diff will usually have the highest weight oil because you don't want a situation where the buggy is being pulled by the front wheels or pushed by the back wheels. A higher weight oil will make the front and rear diffs work together to find the best grip.

RE: Buggy Diff Question
 

That's kinda what I thought, the previous post had it backwards then by saying to have the oil in the front be heavier than the middle.

RE: Buggy Diff Question
 

i have 5000/ 100,000/ 3000. i absolutly love the way it handles.
ill give you a example of the good 100k in the center will do.
there has been a few time where i landed nose down, and was on the gas, instead of topping over, it rode forward for a few feet and i drove out of it.

personally i think the center should be way high. i cant be under alot of gas thru a sharp turn, but if you "pedal" it thru, and punch it, then you have all 4 pulling you forward.

another example: picture coming around a hairpin turn, you have to gas it to clear that tripple right in front of you. as you approach the lip of the jump, your rear wheels will still have power going to them, thus keeping your attiude in the air, if the diff unloaded quickly and sent the power to the front, you most likly would tend to nose down.

i think my front diff is more that 5k tho. if i take the rear wheel and spin it, they will spin in opposite directions for a few seconds.
and that has 3k in it, now with the car suspended, i can turn the front wheel, and all 4 will spin in the same direction. the front is alot harder to turn than the rears for only being 2k diff.

to show you how thick 100k is, i can hold both front wheels in my hands in a wheelie position and roll the backs on the table, they will sorta slide a little and roll a little too.

RE: Buggy Diff Question
 

You have actually locked the center diff... So you are getting 50-50 traction almost no matter what.

RE: Buggy Diff Question
 

Sorry, brain fart on my part, I was thinking unlimited monster trucks which we set up with the heavy oil up front to make the front wheels pull the truck through corners. You are correct, most buggy setups do put the heaviest weight in the middle. I just finished building a set of buggy diffs and used 5,7,3K F,C,R.

RE: Buggy Diff Question
 

I was under the impression that standard diffs will do exactly opposite of this. When you lose traction the diff can unload and when it does all the power goes to the wheel(s) with the LEAST amount of traction. This is the reason you use heavy weight oils in the standard diffs, because it keeps them from unloading longer. Torsen diffs are the ones that send the power to the wheels with the most traction and you do not need to worry about different weights in them. I'm definitely not positive on this, but this way it does make a little more sense to me why torsens are so expensive.

RE: Buggy Diff Question
 

You are correct about the difference between standard and torsen diffs. Heavy oil in a standard diff will delay the unloading action, the heavier the oil the longer it takes for the diff to unload. Torsen diffs do not use oil to control their action, but you must use some kind of grease (usually supplied by the diff manufacturer) to keep the diff from wearing out too quickly.