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Author Topic:   car rolling over too much
sixwillwin
Dirt Full Roller

Total posts: 35
posted May 30, 2000 09:00 AM
OK jammin and others, reference my "scaling" post below to get up to speed on my chassis. Car is much better now, no more tight on entry, two feature wins, however the car is rolling over on the right side too much and staying over there too long, not transfer the weight to the LR quick enuff, I feel this is limiting my forward bite off the corners. Otherwise car feels good. Cross is 50.8%, LF 900, RF 1100 with easy up shock, LR is 200 with tie down shock, RR is 225. RR is ahead 3/16". Is there something that can be done with springs to help keep weight on the left rear? Or is it as easy as increasing the cross? Any knowledgable suggestions and ideas welcome. Thanks sixwillwin

jammin
Dirt Administrator

Total posts: 3279
posted May 30, 2000 09:17 AM UIN: 16262997
Have you plotted out the roll center of your car? What kind of offsets are you using? How is your rear suspension set up on this?

sixwillwin
Dirt Full Roller

Total posts: 35
posted May 30, 2000 11:16 AM
No idea on the roll center. 2" offsets on front. 3" offsets on rear. IMCA tires. Stock four link rear suspension. RR slightly forward of LR to help with rear steer. Rear trailing arms are mounted to help with anti- squat, but may not be enuff. Any ideas?????

jammin
Dirt Administrator

Total posts: 3279
posted May 30, 2000 11:43 AM UIN: 16262997
Running a panhard or a j-bar?

sixwillwin
Dirt Full Roller

Total posts: 35
posted May 30, 2000 01:53 PM
No panhard bar or J bar, only the stock 4 link.

jammin
Dirt Administrator

Total posts: 3279
posted May 30, 2000 01:56 PM UIN: 16262997
How heavy is the car? What is the left side percentage. Usually, in the heats when the track is tacky, your better off to transfer a lot of weight, but to make the car stick in the feature, you need the left rear to stay down. Depending on your leftside numbers, you can add weight before the feature to the left rear, this will affect the left side weight and the rear percentage, but not the cross, so it will basically keep the LR down longer. I think this is what your searching for. I would try about 30 lbs or so first and if you see that it helps, go to 50. Then you should be flying.

[This message has been edited by jammin (edited 05-30-2000).]

CHASSISCAT
Dirt Full Roller

Total posts: 58
posted May 30, 2000 08:01 PM
Depending on the width of your rear end, we used to run a wierd wheel offset which seemed to work. This was on an 82 cutlass with street tires,9 in Ford, and stock rear end mounting, but if could work for you also.
LF 3 off,RF 2 off, LR 4 off And RR 2 off. On dry slick we added 55 lbs of lead to left rear. The wheel offset tended to keep the rear tucked under as the driver liked to keep the car under him.Our class of car required a weight limit of 3400 lbs, we had 51% rear and 52% left. Can't remember cross,sorry. I hope this helps.

sixwillwin
Dirt Full Roller

Total posts: 35
posted May 30, 2000 09:57 PM
More info for ya. 53.6 % Left; 50.0% rear with 110# lead ballast mounted with 55# behind LR and 55# behind RR. 3000# even race ready with driver fuel and 110# ballast. Any other thoughts now with this additional info?? What about spring changes or would this not effect forward bite?? Thanks. Keep the ideas coming, I'll try anything once. Also, I am very fast at both tracks, but the racer in me is always searching for just a bit more, with more forward bite I could get more quickly to the front. Thanks again.

jammin
Dirt Administrator

Total posts: 3279
posted May 30, 2000 10:07 PM UIN: 16262997
You don't have enough rear percentage. I saw this on another car also. He thought it was the actual tires going away. Not enough weight on the rear. When the track is tacky, it will run good, but dry slick is another story. I would say that you would need at least 1 more probably 2 more percent on the rear. There are several ways to do this, but you have to find a way that is suitable for your rules.

CHASSISCAT
Dirt Full Roller

Total posts: 58
posted May 31, 2000 09:05 PM
Jammin,you can reply to this,. If the pinion angle is too high it will also take away foward bite,correct?

jammin
Dirt Administrator

Total posts: 3279
posted June 01, 2000 07:04 AM UIN: 16262997
You know, I have heard all types of stories on the pinion angle, but can you tell me one thing. The power goes into a rear end in one place and comes out in another. I look at pinion angle only as a way to keep my drive shaft in under acceleration.

sixwillwin
Dirt Full Roller

Total posts: 35
posted June 04, 2000 09:59 AM
Hey jammin:
One more question for ya'......I currently have an 900 # LF spring and a 1100# RF spring....I want to increase the RF to 1200#(I'm getting too much shock travel on RF).....what would the effect on the car handling be if the LF spring was 1100#???......so the front split was only 100# instead of the current 200#??? I have either a 1000# or 1100# for the LF. Of course, I will reset the ride heights and get back the same cross weight. Thanks again.

jammin
Dirt Administrator

Total posts: 3279
posted June 04, 2000 12:21 PM UIN: 16262997
You will notice that when you increase the RF spring rate, the car will be tighter all the way through the turns(in, apex, out) This will keep the cross in tune and will not let the LR lift as much. The left front spring will help you on weight transfer, it will keep the weight on the rear where it should be. It will help RR bite. If the spring you are replacing the current one with is the same height, your weights will not change.

sixwillwin
Dirt Full Roller

Total posts: 35
posted June 04, 2000 05:04 PM
OK I understand the heavier RF spring will tighten up that the car thru out the corner, but what about my question on the LF spring?? I currently have a 200# front spring split, if I decrease that to only 100# front spring split, what effect would THAT have on handling?????????? Thanks again

jammin
Dirt Administrator

Total posts: 3279
posted June 04, 2000 05:59 PM UIN: 16262997
It will keep weight transfered back to the RR on exit and will not unload it as much on entry. It will add back to the roll over problem, but it will not be as bad because of the increased pressure on the RF. You can also run a smaller offset on the RF and this will change your rollcenter and help it to keep from rolling and you can increase the LF and this will help also.

spanky
Dirt Newbie

Total posts: 3
posted June 12, 2000 09:15 PM
I think I would just try to adjust it by putting two turns in the right front and put one turn into the left rear. You can keep doing this until you feel the car getting to tight or pushy, I had the same problem and did this it seemed to work just fine

Rick
Dirt Newbie

Total posts: 1
posted July 23, 2000 08:48 PM UIN: 333
I think I'd look at playing with a front sway bar, even if you had to lighten up your springs in the front particularly the RF. The idea of the bar is to control roll and should plant the LR coming off.Rick

RickP
Dirt Roller

Total posts: 17
posted July 24, 2000 12:11 PM
Sixwillwin,
You mention having too much roll over on the RF. How close are you to bottoming out and are you? As long as you aren't hitting the bump stops I'd leave it.

One thought on the spring split the rear is low around 25#/in. I think by increasing the RF and not doing anything on the left making the front split greater is going to upset the car. What effect would raising them both the same have?
RP-02BB

RickP
Dirt Roller

Total posts: 17
posted July 24, 2000 12:12 PM
Sixwillwin,
You mention having too much roll over on the RF. How close are you to bottoming out and are you? As long as you aren't hitting the bump stops I'd leave it.

One thought on the spring split the rear is low around 25#/in. I think by increasing the RF and not doing anything on the left making the front split greater is going to upset the car. What effect would raising them both the same have?
RP-02BB

CHASSISCAT
Dirt Full Roller

Total posts: 58
posted July 24, 2000 09:00 PM
Remember:
Stagger gets you in.
Wedge gets you out.

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