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Author Topic:   Some setup issues and questions
fairlaniac
Dirt Maniac

Total posts: 110
posted September 09, 2005 05:50 AM  
We’re having a tough time getting a handle on a track we don’t run much at. They are having two 200 lappers the next two months and we want to get the car better. We ran there a few weeks ago to tune for the long races. We ran 5 laps and got in a tangle and bent the LH upper control arm. So we learned nothing. They are not running now until the 200 lappers. This is what we ran there last year and tried a few weeks ago.

The car has not been weighed in over a year. We lost access to some scales and with some changes the past year, I’m not relying on those old numbers. Hopefully we can get it running better without scales. Don’t blast us on the scale issue, we’ll be making some soon but not in time for the next race.

The car at this track with this set up has been loose in the middle and spinning the tires off. It’s a 4/10 mile track with tight moderately banked turns. We run 3.73’s but I keep telling the driver we need 3.90 or 4.10”s. Car is a ’82 Monte with stock control arms and spindles. Here is our tire set up. Should this be working or are there some positive changes to be made? The car weighed in at 3325 with driver, had about a 53/47 front to rear split and a 51/49 left to right split, a year ago.

RF 88” (235/70/15) 18 psi – 2” offset, 7” wheel – 1250# spring
LF 83” (225/70/14) 22 psi – 3-1/2” offset, 7” wheel – 1000# spring
RR 88” (235/70/15) 18 psi – 3” offset, 7” wheel – @175# spring
LR 86” (225/70/15) 18 psi - 2” offset, 7” wheel - @ 225# spring

Is there a chart anywhere that tells the following?

What does adding front stagger do?
What does adding rear stagger do?
What does running a smaller or larger offset (2” vs. 4”) do?


Thanks,

------------------
Doug
"Lift for a second, that's where you'll finish!"

CLBaker25
Dirt Maniac

Total posts: 193
posted September 09, 2005 07:47 AM  
So you are saying the car has 47% rear and weighs in at a hefty 3300 pounds. Move some of your weight back. Get your rear percent up to around 50%. With that high of a total weight this should not be a problem. Why are you running so much stagger? I would get that stagger down to an inch or less on a big track. Use this rule of thumb for stagger. On a smaller track you need more on a bigger track you need less.

Your springs look good but your air pressure look weird to me.

fairlaniac
Dirt Maniac

Total posts: 110
posted September 09, 2005 09:18 AM  
This is why I ask. Have you got any recommendations as that is what I'm looking for. How much front stagger? How much rear stagger? Give me some pressures, I'd really appreciate it.

Thanks,

------------------
Doug
"Lift for a second, that's where you'll finish!"

wetwolfone
Dirt Full Roller

Total posts: 51
posted September 09, 2005 10:42 AM  
quote:
Originally posted by fairlaniac:
Just run 88" tire on right side and 86" tires on left side. Try this for air;
LF 20
RF 26
LR 20
RR 22

Try to get as much weight off the front of the car as you can (You might have to add weight to left rear if still spinning tires off the corner.



CLBaker25
Dirt Maniac

Total posts: 193
posted September 09, 2005 11:07 AM  
On a 4/10th track I would run almost no stagger in my car. I would run an inch or less in the rear and an inch in the front. Normally if you run two tires that are the same type ie 255/70/r15 then just air the right rear up more and it will give you around a half inch of stagger. You can also air up a tire to say 40-50 pounds of air for a time to grow them a little then let them back down to the right pressure. For air pressures I would put your left side air pressures at 18 then run probably 22-24 pounds on the right side. You can use the air pressures in the front to adjust how your car handles. By going even up in the front at say 22 pounds it would tighten the car all the way around the corner. If the car is pushing in the middle you can lower your left front air pressure.

I am not sure if I am explaining my self very well but I hope this helps.

fairlaniac
Dirt Maniac

Total posts: 110
posted September 09, 2005 12:18 PM  
It helps alot!

Thanks!

------------------
Doug
"Lift for a second, that's where you'll finish!"

racer17j
Dirt Forum Champ
Total posts: 5390
posted September 09, 2005 03:17 PM  
Well front stagger helps you in and also helps leftside weight and cross weight.I am trying to just answer the ?s you ask. Rear stagger helps you through the corner if say you were tight you would want more stagger. I would think with a long race you will not need to worry about stagger your biggest worry should be running after 50 laps. Set the car up for a dry slick track and drive smart till you get to lap 150. On offsets i am going to leave that up to other people to answer. We know what offsets does for our car but with what they do on the scales still make no sense to me. Good luck and good racing

Eljojo
Dirt Forum Champ
Total posts: 968
posted September 09, 2005 07:29 PM  
As said before, get your weight back towards the rear of the car. A metric that heavy shouldn't be nearly that low on rear percentage.
Lets talk tires--by the looks of the post you made you are running on radial street tires. Air them up! 27+ right side 25+ left Street radials are steel belted and need proper inflation to keep them fromm rolling under.

Get out the tape measure and set your ride heights. start at the lf 7 rf 71/2 lr 8 rr 81/2
Since you don't have scales, set a jack under the pumpkin with a socket between the jack and the pumpkin. Raise the rear wheels up and notice which clears the shop floor first. You want the right rear off the floor 31/2 4 inches before the left clears. Think of your car as an X. You might have to shim the rf and cut the rr spring to get the bite you want. You might have to do the opposite. Let the car tell you what it needs.
Good luck!

[This message has been edited by Eljojo (edited September 09, 2005).]

CLBaker25
Dirt Maniac

Total posts: 193
posted September 11, 2005 03:00 PM  
Steve,

Running any size tire on any corner does not change the left or right side or rear percentages. The only way to change the amount of left side or rear in the car is to move weight (or wheel offsets which would give a minor change). Changing tire sizes will affect cross weight and corner weights.

[This message has been edited by CLBaker25 (edited September 12, 2005).]

Steve Dupree
Dirt Freak

Total posts: 316
posted September 13, 2005 03:52 AM  
tire size will effect left cross rear and right not a whole lot but it does change numbers and the amount of bite you have in the rear the same as wheel offsets do. So dont no what you mean by that statement CLBAKER. Air preasure alone changes weight so dont no what you are talking about.

CLBaker25
Dirt Maniac

Total posts: 193
posted September 13, 2005 08:19 AM  
Put your car on scales and right down your rear percentage. You can change the air pressures however you want and the rear will not change. If you take air out of the left rear it will take away weight from that corner but that weight will go to the right rear corner. Your rear percentage will not change. The same goes with the left side percentage. If you don't believe me check it yourself.

Steve Dupree
Dirt Freak

Total posts: 316
posted September 13, 2005 04:51 PM  
I have check it or wouldnt have wasted my time writing you back. Your weight transfer depends on what springs you are running front and rear and if you have a for excample 1200 rf and a 1050 lf and a 200 rr and a 250 lr and you change tire size you will change left % and rear bite and rear % depending on what you have. I do check it all the time and i know for a fact what the numbers are. I am not being a smart a-- but i think you might check it out before telling me what happens. I live,dye and eat this stuff everyday and i am learning more everyday on what happens...... On scales and off. Why even change tire sizes or crank in some wedge if it dont matter. Putting a bigger tire is just like cranking in wedge to a certain extent. So is air preasure!!!!!!!! Put your car on and do a few changes and then tell me that because ours is on scales onse again checking a few other things with different shocks. I changed the rear bite from 169 to 150 with changing a left front tire from a 84.5 to a 86.21 rollout. So if tire size dont move weight tell me why also gain 2% rear weight with the change so yes it does make a diffence.

MIKE S
Dirt Roller

Total posts: 5
posted September 14, 2005 08:22 AM  
Is it true you have to disconnect your shocks every time you put your car on scales? or can you wait awhile and let the car settle. Thanks

CLBaker25
Dirt Maniac

Total posts: 193
posted September 14, 2005 09:25 AM  
We usually bounce our car to get it to resettle. We bounce the front and then bounce the back. Now when I say bounce I don't mean put all of your weight on it and try to go through complete suspension travel I just mean push a little on each end to get the suspension to level out where it is supposed to be.

cd2
Dirt Maniac

Total posts: 161
posted September 21, 2005 08:40 PM  
Steve dupree
Maybe you can help me out.We have four dirt cars,one is a hobby car,one a super street,one a sportsman, one a limited late model.The hobby car is standard coil springs.The super street has leaf springs on the rear.The other two has coilovers.
Now let me explain the problem i'am haveing with these cars.I can put each car on the scales(I know they are right & my friend checks them once a year,he is a certified scale repairman)if i change a wheel spacer or use a diffrent offset wheel then i change the C.W. This change does not change the Left side weight or the rear weight.I can put 1# of air in the L.R.or take out 1#
of air & it will change each wheel weight about 7# & it does this on each car.If i change a spring i check the ride height change the spring reset the ride hight & if need be reset the wheel weights.The spring change does not change the left side or rear weight.I can put 1 turn into the R.F. take 1 turn out of the L.F. put 2 turns into the L.R.& take 2 turns out of the R.R.
this will change the C.W.50-60 # depending on which car but no left side change or rear change.Also have done some black top racing & it worked the same.Could you please explain what i have been doing wrong
for 41years? Sure would like to just turn a jack bolt or coilover adjuster & change left to right weight or front to rear weight.Or do the wheel & spacer deal.One other thing on the sportsman car we have 4 25# pieces of lead bolted on the left side one even with the driver & the rest between the driver & the axle.This is mounted just above the chassis rail,what will it change if i raise the weight up about 12-16" Need to know do not want to make a mistake.
Thanks cd2

Steve Dupree
Dirt Freak

Total posts: 316
posted September 22, 2005 03:58 AM  
Hey CD if you have been racing that long then you must know it all and i am sure we cannot help you at all. We have been running alot of different tire sizes and preasures this year and putting a bigger tire on say like the left front will change numbers and % if you dont go and reset ride heights and so will preasure. We have resently started running alot more preasure on are right side and it has changed alot of numbers on the car at first we were running like 14lf 16lr 19rf 16rr. Well we have now went to 20lf 20lr 28rf 27 rr with these changes the numbers are different on scales and the left% and left weight have changed. Maybe the ? ask or answered was in the wrong way by one of us so sorry if you took it wrong. If i put a bigger tire or more preasure on both right side tires i will up the right side weight which in return takes away from the left side weight so right there is a change in left % and rear bite. good luck to all and sorry if you took my answer wrong.

cd2
Dirt Maniac

Total posts: 161
posted September 22, 2005 06:40 PM  
Steve
Was not meaning to ruffle your feathers or anything like that. Just thought i might pick up on some new technology.I learn something every day some good some bad.
Was just trying to get up with the modern times.Sure wish you would give me the straight scoop on raising the weight up on the left side.
Thank's cd2

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