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Author Topic:   Left side % ??
Kromulous
Dirt Forum Champ
Total posts: 796
posted July 25, 2005 01:15 PM  
Would a Mod with a low left side % cause the car to have excessive side bite? I am thinking it would, but i need a 2nd opinion.

Were running on some outlaw Mod tires, and they produce some some serous grip / side bite and i just cant get the car to loosen up on entry and in the middle. My J-bar is flat, almost running down hill, so i am running out of ideas on loosing it up.

We scaled the car out last week before race night and found out the left side % is low, its at 51%. I was thinking of moveing some stuff around and getting up at least 53% or maybe higher.

Scale numbers were 53% rear, 51% left, and 52% cross, at 75lbs LR. I am also thinking about upping the LR bite to 150lbs, but i already got to much bite coming out now.

Any help would be appreciated.

Krom.

leapinlizard
Dirt Freak

Total posts: 402
posted July 25, 2005 01:35 PM  
As I understand it, left side weight determines how much weight is transfered to the right. If the left side is heavy, it's much harder to ge the body to roll(transfer). Without the transfer of weight, no other additional weight other than track banking providing a weight increase to all four tires, the right side tires will not be able to dig in, and stop he car from sliding. Increasing the left side, especially higher mounted weight, will transfer weight to the right side. This increases side bite but will aso introduce roll steer as opposite affect.
If I'm right, adjusting shock timing can help. Maybe try lowering the weight so the car isn't as sensitive to the weight change. Less body roll, less side bite, less roll steer, more tight on the gas.

wfoondirt
Dirt Forum Champ
Total posts: 505
posted July 25, 2005 03:24 PM  
Is this on the 25 degree bank you wrote about in another post?

Kromulous
Dirt Forum Champ
Total posts: 796
posted July 25, 2005 03:31 PM  
Well, we got this issue on 2 tracks, both very steeply banked. I would say 25* plus, both tracks are similar.

This problem has been haunting us all year. I believe the majority of the trouble is with the rear. Not sure if its the swing arm - z-link or what.


dluna
Dirt Freak

Total posts: 334
posted July 25, 2005 06:33 PM  
How do your tires look after the feature? Any feathering / tread wear patterns you could mention?

If you are tight on entry and you like your exit, you could lighten the LF spring. Moving the RR out with a different offset wheel could help as well.

Add stagger in the rear if you can for the middle.

dexter
Dirt Roller

Total posts: 19
posted July 25, 2005 08:55 PM  
I believe low left % can cause the right side tires to grip better than the left side and cause a tight condition on corner entry. I also feel you can soften the left front spring to get less weight transfer to the left front and more on the right front and keep more on the left rear. This would cause dynamic wedge and loosen entry.

Kromulous
Dirt Forum Champ
Total posts: 796
posted July 26, 2005 06:52 AM  
Just slight feathering on the RF, brand new tire last saturday night. The RR & LR tires are wearing but arnt feathering at all.

Heat wise RR was a touch hotter than the LR, and RF was hotter than the LF.

I think i am going to up that left side %, i cant help but to think thats at least some of our problems. Raising it to 53%, for these high banked tracks we run.

dluna
Dirt Freak

Total posts: 334
posted July 26, 2005 07:42 AM  
Earlier in the year, I was overloading the RR tire, causing it to slip out instead of create sidebite...this produce a lot of feathering in my tires.

I'm up to 54.8% LS with me IN the car right now. The car is really fast and free on a tacky track. I'm still working on the slick setup. I drop the LS just a tad as the track slicks off.

wfoondirt
Dirt Forum Champ
Total posts: 505
posted July 26, 2005 07:45 AM  
A couple notes about setting up for a high speed/high bank track. Depending on track configuration and the racing line they may not all be applicable but still is something to be aware of. First off ls spring changes can work backwards especially on late entry/midcorner due to the fact that the ls springs will compress due to the banking. Also there is not as much lateral weight transfer due to the banking.

We run a high bank track weekly and run a much stiffer spring package than we do on a flat track.

If you already have you j-bar high and flat I would suggest stiffening both rear springs 50-100lbs. This should loosen transitional handling without effecting steady state much. I also would definately up your ls%, even though high banked tracks don't require as much, you are still pretty low.

The biggest thing to keep in mind is that alot of tuning techniques change once the track reached ~18 degrees of banking. You really need to watch the car and see what each corner of the car is doing to be able to estimate dynamic wheel loads.

Kromulous
Dirt Forum Champ
Total posts: 796
posted August 09, 2005 09:36 AM  
Finnally got the car to turn well, went to a new 1000lb RF spring, and a new 275lb spring on the LR. Added LR bite, its at 140lbs right now.

Our scale numbers are 55% rear, 53% left, and the cross was like 54%, with the 140lbs LR.

The car was really close, Only a high speed push in the tri oval area, very slight. We should have a great base line set up now to work off of.

Thanks for the help.

Krom.

wfoondirt
Dirt Forum Champ
Total posts: 505
posted August 09, 2005 11:50 AM  
A little more ls% and a little less diagonal will help that high speed push.

Kromulous
Dirt Forum Champ
Total posts: 796
posted August 09, 2005 12:19 PM  
More left side, and less diagonal.

So i need to raise the LF's numbers, right? or take some off the RF, transfer it to the LF.

I think i had like 60lbs split across the front RF heavier. That was with a 1000lb RF and a 850 LF. I could change to a 900 LF that would help to, wouldnt it?

Generally i dont like running that much spring split but i didnt have a good 900lb spring.


wfoondirt
Dirt Forum Champ
Total posts: 505
posted August 09, 2005 01:44 PM  
Well changing your springs won't change the wheel weights if you reset your ride heights if thats why you suggested the spring change.

And to answer your question yes you will end up with less front split. You will need to physically move some weight to the left then set your crossweight a little lower (53.5ish). Your lr bite will remain about the same.


On a high bank track the lf spring doesn't have much effect anyway so you can probably get away with that much front spring split. Being that its tight in the trioval (I'm making an assumption that its more of a dogleg than an actual corner) a change in static wheel weights will have a greater effect than spring changes will.

Kromulous
Dirt Forum Champ
Total posts: 796
posted August 10, 2005 09:26 PM  
I got ya on the spring change Wfoondirt, i am in the process of replacing all my old springs with new Hypercoils. Plus i dont like the 150lb split on the front, it just bugs me. So i thought i would put on a fresh 900lb when i try to get these numbers on track with your suggestions.

I got another questions for ya, what would putting a 25lb lighter RR spring on this car do?

I got it in my head its what the car wants, but i have no idea why. Sounds crazy i know but other than the scale numbers i really have no idea what to change next.


wfoondirt
Dirt Forum Champ
Total posts: 505
posted August 11, 2005 10:47 AM  
It really depends upon driving style/track configuration. Typically on a 4/z car it will loosen entry and tighten exit. That is unless you drive in on the gas, or the rr lifts under power or a million other variables that are car/track/driver specific. You really have to watch the car and see what each corner of the car is doing to beable to accurately predict what a spring change will do.

25lbs isn't much of a change especially if its mounted on the arm. That small of a change is really hard to predict unless you can actually see the car. I hate to say it but alot of times when you get down to such fine adjustments its almost a try it and see what happens deal.


Kromulous
Dirt Forum Champ
Total posts: 796
posted August 11, 2005 11:25 AM  
That makes total sense, thanks for the insight.

The track is big, i dont really ever let off all the way, just roll back a little, and roll on (the throttle) alot. Usually i am consceince of how fast i let out of it, trying to be as smooth as possable.

Turns 1 & 2 (i dont count the tri-oval / dog leg) its best if you stay on the power and let the RR carry itself on around, then slowly back off until you clear the apex, usually about 1/2 to 3/4 throttle, then your off agian.

Turns 3 & 4 is best if you run high down the back stretch and late apex and dive down off the bank low into 3, or into the apex. Then let the car drift up high out 4 and thru the tri oval turn.

Going into 3 is super fast, and you usually let out the most there, and it hurts the car if your tight in.

Gonna try it to see, if it loosens entry and tightens exit i'll be happy, if not oh well. Nothing ventured nothing gained as they say.

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