XRAY - Model racing cars

was wondering when you guys change your setup, in what order do you change something?

i know that tires is the biggest thing but what do you change next?

what does the spring rate do?

what does the viscosity of the oil do if you go lighter? heavier?

diffs are always confusing to me so this i will just do a search for and read the manual.

Yeah thats what it means, 5k, 7k, 3k for Front, middle, rear.

I read about people using that 777 or 555 as well but it doesnt make sense to me if you understand how diffs work.

Real quick:

When you enter a turn the inside wheel has less traction and the outside wheels have more traction due to weight transfer and some chassis roll. A diff will unload ts power to the wheel with least traction which would mean both inside wheels which are with the least traction in a turn.

To tune this scenario you use oil in the diffs to control the effect they have when on or off traction. In a turn you want the front wheels to pull through the turn so you want the outside front wheel to remain on power and not allow the inside wheel to receive all the power or you wont pull through the turn that well. This would mean that you want thicker oil up front to help limit the amount of power being sent to that inside front wheel which has no traction.

When you do this you gain traction to the front wheel which will pull you through a turn. Now when you consider the back tire you have to decide which tire you want on power, inside or outside. If its the outside just like the front then you have one side of the car on power and it would favor a spin out. Therefore you use a lighter oil at the rear then the front to create a contrast front to rear and let the front outside tire do the work of pulling through a turn. The opposite effect at the rear will keep the car stable and not want to spin out by allowing more power to be sent to that inside rear tire.

This is why I dont understand why people run the same oils front to rear but you can try it and see what you notice.

Now that you understand how diffs work you will know why you put lighter or heavier oil in the center diff. Under hard throttle the rear will naturally squat and gain more traction then front. Lighter oil in the CD means more power sent to the front wheels and heavier means more equal distribution of power or an all wheel drive effect

I know use 755 and its much better so I dont suggest 7k in the CD, I tried it and it was very hard to drive.

For your oils the thicker oils will slow down the shock action and thinner speed them up. This is also based on your piston sizes which will also do the same as thicker or thinner oils. Larger holes would be like using thin oil and small holes like thicker.

Its not that easy since other factors come into play like turbulence or what we call "pack". Thick oils resists this and you will have less pack but thats not so good since you want them to pack (lock) up landing from a jump so you dont bottom out. However if you run too thin of an oil it will be bouncy and hard to drive so there has to be a balance.

This is why many are trying to run thicker oils in the EC shocks with smaller pistons. Some of us have moved over to the Big Bore trend and it allows for a much better balance between all of this. A larger amount of oil in the shock allows for a thinner oil to be used but at the same time not making it too bouncy and still allowing for the right amount of pack.

For your setup I would go from Jason Branhams setup and practice a ton then decide what you want to change when you learn more. I still run his base setup because I am not good enough to notic a degree of change here or there. For the most part the car handles better then I can drive it and until its the other way around I wont change all this settings.

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whitey thank-you for the book. just joking with you. i appreciate the explanation of the diffs as i seem to now have a better grasp on what they do. i will go with jason's setup and see how i like it. the one thing is, we are running indoor right now and there is a ton of traction. this is why i am asking about changing things.

anymore suggestions that you can give i will appreciate.

180 booker I would advice to run jasons setup then come back & say what you felt the car is doing for you. From there we can advice on what way to go & what do to get what you want this as every one drives different & its easyer from a known setup.

Bren

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this set up was completely awesome. i had done a few minor changes while i was at the track and will post that setup very soon. will link it and you guys let me know what you think would be even better improvement.

one question i do have is about the anti-roll bar. what does moving it in on the suspension arm do? moving it out or flush with the outside?

its good you liked the setup, if your looking for more in certain areas just ask & will try to help.
As for moving the ball joint on the roll bars, this will have little affect on the xray as there is very little room for adjustment. your better of just changing the roll bar either thicker or thinner to get the affect you want.

Bren

In that setup i don't understand why the ackerman shim is put under the knuckle. Would that not give more bump steer?

Also does he really mean the ball stud ?