Right front ball joint

[45mod]

I run a long ball joint in the lf and a short ball joint in the rf upper as I know a lot of people do. My buddy who is a very successful driver runs the long ball joint in the lf AND the rf. He got this car from another very successful driver. What does this do? How does this affect the car long ball joint versus short ball joint in the right front (upper)? Thanks

[HEAVY DUTY]

Long LF upper will raise roll center and move it to the right. More importantly it will add camber gain. You will have to reset the bump steer.It is probably a good thing unless the roll center gets too high. It might create shock clearance problems.

[MasterSbilt_Racer]

I believe HD mistyped and meant to describe the RF.

[Fraley Racing Ent.]

always remember if your changing ball joint lengthe to adjsut roll centers that it affects caster, camber and bump steer. you have to check and/or rest all of these things

[HEAVY DUTY]

Your right Mastersbuilt, I did mean RF. Glad you caught that

[45mod]

Thanks for the info guys. One more thing will this make my spring act stiffer or softer or no affect?

[HEAVY DUTY]

RF spring should act stiffer, because the roll center will be higher and farther right, which will resist body roll some.

[Fraley Racing Ent.]

it will make it "stiffer" but it wont be that much of a change. dont start changing springs to compensate for the movement of the roll center .... you will end up back a square one or not knowing what made the change in the car.

[Lizardracing]

Is the wheel rate and roll center location linear?

[HEAVY DUTY]

The wheel rate is linear, but the roll center will probably move right, and maybe up more with the long balljoint than the short one. Raising the roll center will shorten the moment arm causing the car to roll less. ( will act like lowering weight in car)

[Lizardracing]

Does the RC move right in linear fashion to the increase in RF spring rate? Do the front springs affect RC at all? Where does the RC go is I take out the RF spring and replace it with a solid spacer?

How can graph paper and a ruler on current theory accurately calculate RC if the springs are partly responsible for RC migration using just mechanical attachment points without springs?

[HEAVY DUTY]

I do believe springs play a part in the roll center. If you had a solid bar, the roll center would be at the contact patch of the tire with the solid spacer I am assuming. I personally believe that the roll center is one of the least important things in a front end. Camber curves, caster gain, and bump steer all are more important than where the roll center is. There are a lot of theories on roll centers, and a lot of money being spent on programs that tell you that roll centers are the most important thing in a front end. What are your thoughts Lizardracing?

[jsf74]

That's funny I've talked to several very good drivers and a few chassis builders and they say the same thing. While it's good info to know the roll center its not the be all end all. It's more of a tuning tool and helps sell magazines.

[speedbuggy]

I don't think a stiffer spring changes roll center (if you agree that roll center is just a geometric expression of suspension behavior). Roll centers are calculated without regard for spring stiffness. For any given suspension configuration. there is a path that the roll center will migrate along. The spring just helps dictate how far along that path the roll center travels.

......Camber curves, caster gain, and bump steer all are more important than where the roll center is. There are a lot of theories on roll centers, and a lot of money being spent on programs that tell you that roll centers are the most important thing in a front end......
?

I agree with this.

That's funny I've talked to several very good drivers and a few chassis builders and they say the same thing. While it's good info to know the roll center its not the be all end all. It's more of a tuning tool and helps sell magazines.

and this...

[Lizardracing]

Lets say I get 4" of up travel on the RF and 4" of down travel on the LF as measured from the end of the spindle. For theory discussion, this was quantified by data acquisition during testing day. If I took my car home put my car on jack stands and took the springs out, lowered the LF 4", raised the RF 4", remeasure the mechanical pivots points to come up with a RC location and migration pattern, does that change when I place the spring back in the car while still on jack stands?
RC location theory is usually referred to in about two dimensions as viewed from the front/back. Measurements are noted from the upper ball joints, lower ball joints, inner mounting points and the tire contact patches. The vectors are to be averaged of the front and rear inner mounting points of both upper and lower controls arms.

Does the front roll center have to be located in two dimensions or can it migrate front to rear as well? If I have a car that gains/loses caster and the Instant Centers now move forward, does that change the Roll center and the moment arm lenght? If a line is drawn from the CG of the front and rear and that line is a angle is not parallel to the ground but slants downward toward the front(front is lowe) does that also mean wheel base lenght is a factor in where the RC/ Moment arm lenght should be located?

Maybe I think too much.....