Roll center?

[tstiles]

I would like some input on this subject, as far as gathering the measurements to conduct the equation, I know how to get that. My question is what's right or what is ideal? And if I should have to make an adjustment, what do I do? What changes it? Thanks in advance.

[richardpetey]

Paved track front suspension roll centers(for a full bodied stock car) usually are located between 3" and 4" above the ground and offset approx. 3" to the right of the racecars centerline.......................... :cool:
To measure roll center you have to project lines through the right upper and lower control arms until they intersect(instant center), then draw a line from the instant center to the RF tire centerline(swingarm length), perform the same measurements to the left side suspension and where the swingarms for the L & R front intersect is the true front roll center............ :confused:
Because of the rules in the trux and the cars, very little can be done to adjust roll centers ........................... :help:
You would need to change spindles, A arms and there pivot points, springs, ball joints or a combination of all four for your front suspension. In the rear(with coil spring suspension) you can control roll center with a panhard bar.................... :rolleyes:
With all this said, the purpose of obtaining a lower front and rear roll center height is basically to distibute the weight on your tire patch vertically and create more downforce in the turns................................. :D
I could go on forever about front and rear roll centers, roll moments, camber curves, roll axis and center of gravity heights but on the kind of cars/trucks we run most of it is non-adjustable........................ :eek:
UNCLE PETEY................. :wave: :wave: :wave: :wave: :wave:

[tstiles]

Well thanks mr. Pete, you are the man!. Do rollcenters change when you change tire size? you referred to the center is to the right 3'' approx. but is that where you want it? or should it be on the left of center? and my last question; why would you want to change the roll center on a car? i know from what you said before that the object to getting a good roll center is to achive maximum vertical force on the tire patches.

[kleilamotorsports]

Any change you make to the height of the chassis, spindle height, tire size or camber change has an effect on the roll center.

[tstiles]

ok thanks. how do you know if it is wrong?

[richardpetey]

If you are referring to your truck, its built into the stock suspension geometry................... :disgusted
You can lower your roll center by using smaller diameter tires, smaller spring heights, etc., but you have to keep the same roll center relationship front to rear or you will experience a real loose or tight condition, depending how much you change the ratio front to rear(front should always be lower)........... :rolleyes:
Whats a good roll center for your racecar? It depends on the track banking, weight of racecar, driver, etc...................... :eek:
It is such a complicated subject that we could go on forever with these Q & A's .................................... ;)
I'll try to put together some stuff that will better illustrate what we can do to our trucks to better the roll centers(within the rules, hehe)..................... :applause:
UNCLE PETEY....................... :wave: :wave: :wave: :wave: :wave:

[tstiles]

So, is it possible to be too low? or is it fine as long as the front and rear are close? thanx mr. Pete.

[NEETS-1]

My Street Stock roll center was 6" below ground, hehe. (Stuck like glue). :D

[richardpetey]

Your roll centers on a high banked paved track should be lower so the camber change curve is less, and a little higher for a flat or mildly banked track........................... :D
The front roll center should always be lower than the rear roll center.......................... :cool:
If the front roll center is too low in relation to the rear roll center it will most likely cause a push...................... :help:
On the other hand, if the rear roll center is too high in relation to the front roll center it will tend to stray towards a loose condition............. :*-(
Wheelbase is also an important factor effecting roll centers, the shorter the wheelbase the more critical the front and rear roll center relationship becomes................................... ;)
Hope this helps a little, like I said before, in a division that dictates a stock suspension geometry, your reduced to springs, tires and camber adjustments to control the ROll......................... :disgusted
UNCLE PETEY.................... :wave: :wave: :wave: :wave: :wave:

[tstiles]

In the past race season I have gained interest in the set up on a front suspension and I'm having fun learning, so this is just for me to broaden my horizons in stock car racing.
Besides, no one uses this tech forum, so I figured I would start one up. Thank you on all the info guys. and did i hear right? did billy b say his roll height was 3'' below ground?
And if so, then is it fair to say that roll centers are like the limbo game??
the lower the better?? just kidding

[richardpetey]

Actually, billy musta had a SS "freak of nature" because you want a slightly higher roll center on dirt to aid in horizontal tire slip, but some camaros have a naturally low roll center................. :help:
Your roll center is pre-determined on "stock" type suspensions, but on a racecar built to turn left it is tapered to the track surface , tire and banking you will race on........................... :rolleyes:
So NO! Lower isn't always better................................ :(
UNCLE PETEY................... :wave: :wave: :wave: :wave: :wave:

[RGeeProductions]

Just found this (http://www.ovaltrackdigest.com/issues/issue1/content/roll-center.htm) from another post.

[RGeeProductions]

From a different thread in our forum here. Was looking thru the site and the roll center article caught my eye.

[tstiles]

That's a good illustration.

[richardpetey]

Sleepy Gomez writes many articles for Stock Car racing magazine.............. :cool:
He's kinda like a backyard, do it yourself, make your own tools type of raceguy you would pit next to every week................................. :D
UNCLE PETEY.................... :wave: :wave: :wave: :wave: :wave: