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Author Topic:   Side Bite and Chassis Roll
leapinlizard
Dirt Freak

Total posts: 402
posted September 20, 2004 10:09 AM  
This weekend we started with a great car and expected to finsh well. With about 3 laps to go we were running 10 and a little tight through the center. I kept feeling a hole devoloping into all four turns. After we took the checkered and got back to the pit's We relized the chassis was rolling over to the right so far on the really tack track it was hitting the track and upsetting the car and the car was snapping tight at the beginning of the center and I would have to fight it all the way through, making our exit terrible. We had a little rear end wiggle which agian affected the next corner exit and forcing me to find a higher line to the point I left he racing surface on one occasion. I feel we need to reduce side bite through the center so the rear will stay at yaw longer hoping to be faster through the center so we can reduce average laps times. What is the most effective way of going about reducing side bite and chassis roll? Raise panhard or take out a few turns on the left side? Either way I don't want to affect entry. Entry is really good. Better when the track is slick but still okay when the track goes tacky. We are losing 3/4 per lap when the track goes tack. We are slightly under powered right now while I build an engine. We already have all the wieght on the left side(56%) I'm new to the driving thing so if anyone has comment's on how to compensate for an under powered car...

Thanks,

dirtywrench13
Dirt Freak

Total posts: 324
posted September 20, 2004 11:53 AM  
FOR GOD SAKES, MOVE THE WEIHGHT TO THE RIGHT AND THE REAR.THE MORE I MOVE THE WEIGHT IN OUR CAR TO REDUCE THE LEFT SIDE %, THE FASTER IT GETS! IT ENTERS WELL AND COMES OFF WELL, NOW WE ARE WORKING ON CORNER SPEED. GOING TO THE NEW CAR NOW SO THE RESEARCH WILL CONTINUE.

START BY MOVING THE BALAST AROUND AND THEN TRY DIFFERENT WHEEL OFFSETS.

300 LB DRIVER AND ONLY HAS 53% LEFT SIDE WEIGHT.

leapinlizard
Dirt Freak

Total posts: 402
posted September 20, 2004 12:35 PM  
Increasing right side wieght would further hinder the problem with chassis roll. That's why I have such a high amount of left side weight mounted low(below the centerline of the chassis). Simply put. I need to reduce the amount of chassis roll when the track get's sticky. Something I can do between heats and feature. About ten min.

[This message has been edited by leapinlizard (edited September 20, 2004).]

PEwaste
Dirt Roller

Total posts: 14
posted September 20, 2004 01:11 PM  
its not going to affect chassis roll, it will just make it bite harder
you need to lower the car down a little and raise the panhard bar up an inch on each side and go from there... also stiffen up your right side springs if they are rolling over that hard they are the wrong spring

chapa73
Dirt Maniac

Total posts: 169
posted September 20, 2004 01:16 PM  
im new to mods,so dont take my advice!!
but I read on here daily,and the left side % seems really high.
I think raising the parnhard bar on the rear end side and chassis side will reduce chassis roll.

less angle on the panhard bar will reduce side bite.

This may be a shot in the dark,but if your springs are really soft that could couse the exesive body roll.

hopefully somebody will correct me if im wrong,and if im right then,Thanks Dirt Forum!!!

I wish I typed faster,he said everything I was saying!!

[This message has been edited by chapa73 (edited September 20, 2004).]

leapinlizard
Dirt Freak

Total posts: 402
posted September 20, 2004 02:21 PM  
Left side is a little high but I don't consider it to be the main problem right now. For all the weight is below the CG.

I did think about springs being too soft and came to the conclusion with only one night left this year I'm not going to buy new springs yet. I don't want to make huge chassis changes untill I get a better feel for the car and what it means to be loose out and tight in ect... This winter will the engine building winter so things will change agian next year. We are only making around 400 horse from our current two barrel engine and we need around 550 to stay up front. One of the problems I see from being under powered is the inability to drive the car with the throttle on super tacky tracks. It's tacky enough most drivers use little front brake with a brake shutoff right front to get the thing to yaw on corner entry. Sometimes I feel like it going to throw me out the seat and through the right side window! With the belt's as tight as I can get them and still breath I still get slammed agiast the right side interior hard enough to briuse my knee and arm. Every race night. Maybe it gives an idea about how sticky it get's. Most front runners have enough power to back it in, then rocket off but we don't so I have to be faster through the center to keep up. If it ever goes dry I got'em easily. So my way of thinking goes if I can reduce the chassis roll to keep from bottomng out than I can average faster through the center to keep up with the mid pack. Make sense?

Kromulous
Dirt Forum Champ
Total posts: 796
posted September 20, 2004 02:33 PM  
Without changing anything else, and you want less side bite, i would raise the panhard bar on the frame side. That should do it, or raise on both ends.

BigBlueFord
Dirt Full Roller

Total posts: 44
posted September 20, 2004 02:42 PM  
Trying raising both end of the panhard bar a half inch for your heat race. If it's still rolling over too much then raise the panhard bar another half inch for the feature.

good luck!

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted September 20, 2004 02:43 PM  
What kind of panhard bar and where is it mounted?

What suspsension? 2 link 4 link etc?

What srpings are in the car?

How does the car scale out?

With a limited HP engine on tacky 2 things that will hurt you are being unnecessarily overweight and having the car too tight.

rocket36
Dirt Freak

Total posts: 209
posted September 20, 2004 02:58 PM  
we suffered a similar problem for most of the season in our latemodel at one track in particular which is extremely tacky. we tried all sorts of different spring, bar angle,and corner weight combinations. high wedge, low wedge, dummy shocks, ballast, fuel loads, wheel spacings, compounds and stagger. and after running bad for 10 shows at this track, we ended up raising our j-bar up to the top hole on the pinion mount (leaving the frame mount as high as it would go) and all of a sudden our under powered car was running with the front runners.
so i guess i would have to say, try a similar adjustment. make sure you maintain your correct side - to - side measurement though (adjusting j-bar length).
adjustments to the j-bar make a real noticable difference that you can genuinely feel, not just dream. most of the others are a lot finer tuning adjustments once your in the ball park.

leapinlizard
Dirt Freak

Total posts: 402
posted September 20, 2004 03:01 PM  
Yes we are under wieght by 250 pounds. Don't tell anyone! hehe. As I said before, we do really well all through hot laps and we are the first class out after the the LLM(1 heat) so the track is still pretty wet and slick. It's just we are the first class out of the gate at the feature time. Just when the track goes super tack and before it takes rubber.

Three link mod with 15" panhard bar mounted all the way down on frame and set level. Behingd the rear end on the left side. 750 RF, 650 LF, 225 LR, 150 RR. Weight's are posted in previous post by me

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted September 20, 2004 03:19 PM  
If it really is as tacky as you make it sound I think i would stick a jbar on it and set it about 1" higher than the pinion and give it about 3" rake to the frame. or even a longer straight bar across the back. At the very least you need to raise the bar that you have which should raise the roll center and help free the car through the turns.

Is it tight just rolling into the middle or does it get tight when you pick up the throttle?

leapinlizard
Dirt Freak

Total posts: 402
posted September 20, 2004 03:35 PM  
Throttle. If I can keep the chassis off the ground.

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted September 20, 2004 03:54 PM  
Then it sounds like you have too much LR bite in it. I couldnt find the post with the scale figures so i am just guessing. If its only tight from the middle out then i would take some LR bite out and see what it does. Or even trail the RR 1/4" or so and see if that frees it up for you. Raising the panhard could still help as well.

leapinlizard
Dirt Freak

Total posts: 402
posted September 20, 2004 05:23 PM  
The post with percentages was deleted by my boss at work by mistake. Anyhoo, Left is 54 and rear is 52 with 51 cross. I don't want to change entry at all but I need ot free up hte car through the center, I'm not woried about exit because I think once I fix the tight/center deal loose out will get better because of the higher exit speeds from a better center speed. This weekend I will try raising the panard 1" in the heat and see if it's better. If it is, I will go up 1/2 in the feature. Maybe 1" if it's a lot better. If that don't work I will move down a lane where the banking is flat and float the throttle till she hooks. Maybe I can catch them goin in.

Thanks to everyone and there knowledge.

Ego Racing
Dirt Forum Champ
Total posts: 724
posted September 20, 2004 08:39 PM  
I would see if I could borrow a 175 right rear spring or try a stiffer right rear shock to try to keep the right side up. &5lb spring split is more than we run on a 1/3 mile FAST track. Also the 150lb spring is softer than we run on our 2200lb SLM.

ctfarm
Dirt Freak

Total posts: 206
posted September 21, 2004 06:31 AM  
I'm with EGO,if you can't get a spring,try a stiffer shock,more air in rr,or move the rear offsets to the rt 1 inch.


leapinlizard
Dirt Freak

Total posts: 402
posted September 21, 2004 06:57 AM  
I can probably borrow a spring for the night. I'll try that depending how well raising the panhard works out.

dirtywrench13
Dirt Freak

Total posts: 324
posted September 21, 2004 11:27 AM  
YOU SHOULD BE ABLE TO CHANGE THE RR SPRING ONLY AND SCALE IT OUT TO YOUR SATISFACTION. THEN TRY THE PANHARD BAR ADJUSTMENT. GO UP ON THE LEFT SIDE A COUPLE OF INCHES. EVERYONE ELSE SEEMS TO LIKE 3-4 INCHES ON HERE, BUT ITS NOT THEM DRIVIN IT! YOU MAY WANT TO DIAL OUT SOME LR BITE TO GET THE THROTTLE PUSH TO CALM DOWN,MORE STAGGER MAY HELP ALSO.

cd2
Dirt Maniac

Total posts: 161
posted September 21, 2004 06:01 PM  
leapinlizard,if you want to loosen center only add rear stagger & reset the wheel weights.Then if it is still a little tight raise the panhard bar straight up for the heavy track.If need be you can move the R.R. out 1" on the heavy & as the track looses bite move it back in. cd2

leapinlizard
Dirt Freak

Total posts: 402
posted September 22, 2004 09:25 AM  
We run a spec G-60 tire so we are limited to stagger. I decided to raise bar up 1 hole on left side during heat and depending on the inprovment we up the air pressure for the feature. The track doesn't change very much between the our heat and the feature be cause they get run back to back with intermission in between. I should think air pressure up to 16 on RR and 12 on LR will be enough. That leaves the RF at 16 and the LF at 10. Air adjustment's will probably add a small amount of cross as well if we were to add 2 pound to the RF.

FlyNLoIMCA17
Dirt Forum Champ
Total posts: 753
posted September 23, 2004 06:08 PM  
As far as air pressure affecting cross weight goes: More air in the LR or RF equals more cross weight. Raise air pressure to increase WEIGHT on that corner and of course the opposite is true.

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