moving roll center

[thinkstomuch]

lets say I'm was going to take a scientific wild a** guess and move my roll center to the right. how could I do this with just ball joint lengths?

[speedbuggy]

Longer on the right...shorter on the left...

Consider changing uppers only. If you put longer lowers in, you will have to lower your ride height by the same amount to get the correct angle back in the lower control arm. But if you want to lower your ride height anyways, then it would work fine. Just keep any eye on your LCA angles.

[adamsraceshocks]

It is more complicated than this but generally the lower ball joints have more impact on rc height and uppers on lateral placement. Longer right side upper ball joint stud will move rc to the right

[JR. MECHANIC]

It should be noted that you will also affect camber curves....

[Dirtrunner35]

why do you want to move it ? and how do you know where it ends up in the turn ?

[thinkstomuch]

thanks for the input ya'll. Why do I want to move it you ask. Well I suppose as a racer I cannot leave well enough alone, this is why I'll try spring, shocks, tire etc whenever just to see if it works. I wont know where it ends up, call me low tech but I trial and error until I like it. If it works it doesn't matter to me how just as long as its working

[bobdoo]

By making the ball joint changes as suggested and moving the r.c. to the right, how does it affect/what does it cause the chassis to do.

[speedbuggy]

By making the ball joint changes as suggested and moving the r.c. to the right, how does it affect/what does it cause the chassis to do.

Take a look at this first...

http://www.circletrack.com/chassiste...y/viewall.html

[HEAVY DUTY]

A taller balljoint on the right front will make the instant center of the upper and lower a arm shorter, which will make the tire gain more camber during body roll. It will also change the bump steer, because the spindle is working at a tighter arc, because of the shorter instant center ( called the front view swing arm) . If you put a taller upper balljoint in, it will make the bump steer bump out and you will have to either shorten the bump steer spacer ( run the tierod uphill towards the spindle, so it pulls the steering arm in during bump travel), or shorten the tie rod to compensate ( make the tie rod run at a tighter arc). More camber gain is usually good on a 4 link car that is hiked up a lot on the LR, but might cause shock clearance problems with the RF upper ball joint. Conventional roll center theory will tell you that a longer RF upper balljoint will move the roll center up and right, if you don't make any changes to the left side. Remember that the roll center theory, is just the average heights of the left and right instant centers where they intersect each other.

[thinkstomuch]

you say the tire will gain more camber during body roll...... is this only true for the tire where the ball joint gets changed? i would assume

[Dirtrunner35]

you say the tire will gain more camber during body roll...... is this only true for the tire where the ball joint gets changed? i would assume

Do you think your car is not turning good enough ?

[HEAVY DUTY]

you say the tire will gain more camber during body roll...... is this only true for the tire where the ball joint gets changed? i would assume

Yes, whatever wheel you use a longer balljoint will have more camber gain on compression.

[thinkstomuch]

are dirt cars typically designed with the roll center to the right or to the left of center?

[HEAVY DUTY]

are dirt cars typically designed with the roll center to the right or to the left of center?

They are all over the place. Most, if not all are to the right of center after roll if they have any camber gain on the RF. The only way to keep them centered is to run the same size uppers and lowers, at the same angles, side to side. It is waaaaay more important to get your camber curves, caster gain and loss, and bump steer right on the car than worry about where your roll center is at.

[thinkstomuch]

your persistence has me sold that roll center can be moved further down the list. I'll have to search around the web to find info on camber curves & caster gain. i'm sure these are very much variable too on what works and doesn't