XRAY - Model racing cars

In the xb8 instruction manual it says that if you raise the front upper arm you will get a lower roll center in the front, and if you lower the front upper arm you get a higher roll center.

It also say the a higher postion will give you more on power steering, I havn`t had the chance to try it out. Does anyone else tried this tuning on the car?

From my thinking I would have thought the opposite, lower the arm will give more roll, better grip and a lower roll center. A higher arm will give less roll, less grip and higher roll center. Am I thinking wrong??

I was actually discussing this with that Ralph Burch guy when we were racing offroad a couple weeks ago and what I had observed and the manual says is correct. the lower you go with the front upper pin, it will make the front end more 'grabby' if you know what I mean. Going in the corner when you get that weight transfer and the car begins to roll, it will give the front end more traction.

Similar to the back, the lower you go on the shock tower, it should increase camber gain slightly giving you more sidebite as the car rolls.

The manual is correct, if you lower the top arms you raise the roll centre and vica versa. Roll centre and its effect on any vehicle is a complicated subject but in short the roll centre is an imagianary point in space determined by the relationship in the angles and length of both the upper and lower arm. This point then has a torque effect on the vehicle when rolling depending on the length of the roll moment which is the distance between the roll centre and the centre of gravity of the vehicle. A vehicles roll centre can be placed in many different positions including under ground.
Follow the manual or better still try the different positions and see which you like because as always no matter how much you understand suspension the effects of any adjustment will always be affected by the rest of the suspension system and your driving style.

Rocco's on fire!

Just don't ask me to transfer a phone call... Haha

I have been playing around with the front roll center a little bit as well.

When I was running 3 degrees of kick-up, I ran .5's down on the front and 0's in the rear for the upper arm roll center. I did this to prevent binding according the article in the Tips n Tricks forum.

I went back to 4 degrees of kick-up and I went back to 1's up for front roll center. The car feels a little bit more balanced and secure in the corners now. I am running 17 degrees of caster (total - so 16 at the hubs) and with the front roll center back to 1's up it feels a bit more stable in corners. The front was grabbing a little bit too much in the corners with the lower roll center and high caster position.

Sorry if this is a bit confusing but its the best way i can explain it.