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Author Topic:   Roll Centers
lil'blue
Dirt Roller

Total posts: 25
posted June 10, 2004 05:38 PM  

How critical do you feel roll centers are? We got some software and from what it's telling us we are way off on height and offset. From my understanding the offset should lean more to the driver side, we are a little over ~8.0" passenger ande about 4 in height. But we would have to make some major modifications to get it close to where it should be, the next problem is the car is real driveable and we wonder if we're thinking too deep.............

juliaferrell
Dirt Freak

Total posts: 370
posted June 10, 2004 06:23 PM  
Once you take a certain setup to its limits * in your mind * always remember that there are many approaches to making things work. Roll centers and there affect on racing is very, very, very, critical. That is why if you buy a late model or such most guys never mess with that ride height stuff *rollcenter*. Although not the same but have very similar concepts. That's the norm, well I always wanted to go faster than the norm so if I have a good explanation for what I'm doing..............the **** with the NORM!!!!!!!!

NJantz
Dirt Forum Champ
Total posts: 755
posted June 11, 2004 06:23 AM  
On a scale of 1-5 with 5 being very important, I'd call roll center a 4.

Last winter I figured out where my front roll center was and made some ball joint changes as well as moved some a-arm mounts to get things corrected. I feel it was well worth the effort.

I was very suprised to find out that the roll center location that my car left the chassis builder with was no where close to what you'll read in books about the proper location.

What is the roll center height the software is telling you?

Coleman has an adjustable ball joint that makes life easy when it comes to correcting front roll centers.

JuliaFerrell is right on, why be happy with just the "norm"? If you want to be faster than the others, you need to do things they aren't doing. And I'm pretty confident there are very few modified people that know the exact location of their front roll center and how to find it. It's just not really looked at. So make the changes and see what happens.

juliaferrell
Dirt Freak

Total posts: 370
posted June 11, 2004 07:55 AM  
Something else I always thought about:
How could you ever learn what really really works unless you climb the mountain and fall back off the ledge. Bet you would know why you fell?

lil'blue
Dirt Roller

Total posts: 25
posted June 11, 2004 08:11 AM  
What the software is telling us is the car was built more as an asphalt car than a dirt car if the information they supplied is correct. Thanks for the input, we'll look into the adjustable ball joints.......

lil'blue
Dirt Roller

Total posts: 25
posted June 11, 2004 08:24 AM  
Is there a specific starting point that you would shoot for with the left to right and can you give me your theory on why? We can get height changes really easy its the getting it to the left with out having a flat right upper control arm angle and a steep left side upper angle that also seems to get the ball joint extremely high and possibly weak. Earlier I said we are about 8" right of center and from what we are told by others it should be about 4" left. How much of a change do you feel is needed before the driver would feel a change?

Iowamod20
Dirt Full Roller

Total posts: 73
posted June 11, 2004 09:23 AM  
Keep the roll center height between 3" and 5", and close to the centerline of the car, maybe a little the the left. This would imply a slightly flatter RF upper compared to the LF upper.

The static location isn't as important as keeping the range of change as the car rolls more consistent. Making the front end symetrical, except as I noted above, is what your aiming for. Remember, the car doesn't actually roll about the "roll center".

If the car is drivable now, I would question all the work.

[This message has been edited by Iowamod20 (edited June 11, 2004).]

UNVRNO
Dirt Maniac

Total posts: 136
posted June 11, 2004 03:32 PM  
3-5 inches high

2-4 inches right on a banked track and centered to 2 inches left for a flatter track.

centered and or more to the left allows more front end roll to the right front, which may be needed on the flatter tracks.

I use front end pro computer geometry to work on mine, and its made a world of difference by getting it in the ballpark.

fastow
Dirt Maniac

Total posts: 168
posted June 11, 2004 09:08 PM  
Iowamod20 if I understand what you are say correctly you are talking of the roll center being consisant when the chassis rolls. I have seen where different length control arms can effect this. getting roll center correct at a static state would be one thing making it consistant would be another. lil'blue what software are you using and does it go into all this. I believe this is important to making a better handling car but I would bet if you got to know the low down alot of the cars put out by some of these builders I wonder how many has this all figured out. I have studied these cars for years and maybe I am slow but this gets really complex for me and seeing all the different front end setups out there I would bet not all of them are setup with this in mind.

lil'blue
Dirt Roller

Total posts: 25
posted June 12, 2004 09:03 AM  
fastow were using Autoware http://www.auto-ware.com/software/asgp/asgp.htm
It shows you the static and then allows you to measure the centers at different travel giving you a curve allowing you to try to make for "nuetral" through the suspension travel.
With ours being 8" right does this effect weight to transfer, will the driver feel a big difference in the car if we get it more to zero?

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