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Author Topic:   spring rate question to ponder...
3dracer
Dirt Full Roller

Total posts: 32
posted March 23, 2004 10:53 AM  
We are running a 79 monte that weighs 3100 with driver. 1200 spring in right front and 1100 in left front. On the scales the left front is heavier by 175 lbs. Right now going into the corner and through the apex, the car rolls hard on right front and causes it to be loose off the corner. Could I get the car to be more balanced with a 900 spring. Also we are having trouble with the bite in the rear. I think that if we change the left front it will be better. What do you think?

bigcityracer
Dirt Freak

Total posts: 431
posted March 23, 2004 01:48 PM  
What is cross weight and rear percentages?
Rasie rear roll center.

joetaylor
Dirt Forum Champ
Total posts: 640
posted March 23, 2004 04:26 PM  
sounds like the cross wight is off bad
we need more info like bigcity said

------------------
U LIFT U LOOSE

3dracer
Dirt Full Roller

Total posts: 32
posted March 24, 2004 10:44 AM  
Rear percent is around 53% and cross is about 48.6%. If we put lead on the left rear corner it almost puts more left front than left rear.? Puzzled by that too. We sent scales off to get recalibrated and tried again, same result. We are running a 250 spring in the left and 200 in the right also...with 13" tall. We have set cars up for years, but this is our first metric, and am really about disgusted by it. Keep on tryin'. B.J. Deal

Raz_900
Dirt Forum Champ
Total posts: 635
posted March 24, 2004 11:47 AM  
My car's close in weight to yours, but without the rear percentage. It's only around 48%. But, when I tried a 225 LR and 175 RR it felt like the car was standing on the RR coming out of the corners. It would point the front end to the infield and scrub a ton of speed in 2 & 4. Went back to a 200 RR and it help coming out quite a bit.

A RF shock with more compression dampening might help too.

Oh, for comparison, I run a 1000 LF and 1100 RF and a 1" swaybar and 11" rear springs (sometimes with spacers)

racer17j
Dirt Forum Champ
Total posts: 5390
posted March 24, 2004 05:48 PM  
do you run a sway bar? are you willing to try one?
my opinion is that your front is too stiff, but if your loose...
more cross is an option, how does the car enter the corner?
sway bar will mostly effect what you have described as your trouble area.
raise the rear roll center? on a metric car? when it is loose? i disagree.
is the rear suspension the stock chev 4 link? have you added "stiffer" bushings in the rear suspension?

racerman707
Dirt Freak

Total posts: 374
posted March 25, 2004 09:47 AM  
The front and rear suspensions are not working together.If too much weight transfers to the right rear it will load more on the right front.I would look at the rear springs and rear roll center.Just a thought.

3dracer
Dirt Full Roller

Total posts: 32
posted March 25, 2004 10:55 AM  
no weight jack... would be nice though.

Tried the offsets too. Not enough to make a difference.

Not really into running the sway bar, track is generally not smooth. But, brings up an interesting thought. If you guys are running the same rate of springs with a sway bar, shouldn't I run alot heavier springs without a sway bar? Going to put the car on the scales tonight to see what the 900 lbs. spring does to the cross and left front. Let you all know tomorrow. Keep the ideas coming.

Raz_900
Dirt Forum Champ
Total posts: 635
posted March 25, 2004 01:06 PM  
The 900 might make it a little mushy at speed in a relatively heavy car.

I've heard a 1" bar is about the same as 200# of spring. Seems pretty close since the guys at my track that don't run them run between 1100-1200 LF and 1200-1400 RF.

What shocks do you have? Heavy right front I hope?

ALCOHOL
Dirt Full Roller

Total posts: 46
posted March 25, 2004 08:44 PM  
I don't think a 4" offset wheel will let the tire clear the frame will it? Also the car has a medium stock mount shock on rf,,,really don't want to reveal brand right now,,,and it is a stock 4 link car,,so not much of a chance on changing rear roll center.The car enters turn real well and midway thru turn,,but problem starts on apex and thru the corner. We have a pair of 3" offset wheels on front,,,no tire stagger on front. When dry,,a 2" offset on rr and 4" on lr. I think I got everything,,,Thanks,,,,BJ"s dad

3dracer
Dirt Full Roller

Total posts: 32
posted March 26, 2004 06:52 PM  
My dad got the offsets backwards. There is a 4 in.on rr and 2 in. on left rearm but everything else he is right about. Got the spring in today but did not get it scaled yet. Will let you know about the numbers later. Any more ideas?

cd2
Dirt Maniac

Total posts: 161
posted March 26, 2004 07:57 PM  
3dracer It would help a lot if posted each wheel weight. sounds like you might be getting loose off because you are to tight in an through middle. How much stagger? The cross weight is not enough. Think about what the car is doing going in an around middle. If you are driving in hard an have to keep the wheel turned left until you pass the center then the rear gets loose an you come off hung out you are too tight getting in. Adding cross will help. You can change the L.F. to the 900 an that should help also.IF you can not use jack bolts you better get you some of those hidden adjusters that go up in the spring pocket so you can set your ride heights & cross weight or move over an let the guys that are running them blow on by you.Not telling you to cheat just saying get like the fast cars or follow them. Good handeling an being very smooth will be fast. cd2

iowa_dirt_track_girl
Dirt Freak

Total posts: 461
posted March 26, 2004 08:04 PM  
Well i may not have the answer for ya but we run a metric car same to what you are running and with them springs we wnet to texas this year and won sat night and got sec on fri
Try these offsets two inch on both fronts and stright up on the rear the car will be a little tight but you can live with that during the heat since that really dont matter but come feature time you should be about right
As far as the split in the front i have run up to 200 lbs in the fron and it works just fine try a little less spring on the left rear or swapping them when you get back on the gas in the muiddle of the corner the car wont roll back i would stay with a 13 inch spring it helps with forward bite in the rear also you can lower the left side trailing arm on the rear end that will help you out also on rear bite
hope this helps

3dracer
Dirt Full Roller

Total posts: 32
posted March 28, 2004 12:45 PM  
I will get you some wheel weights as soon as I can get the Mod off the scales. We tried the lowering of the control arm and got caught last year. They are measuring everyones this year. Also on the wieght jacks that are hidden, good idea untill one of my friends got caught last year, now they are looking for those. So really kind of stuck. Rules say that everything must be stock in stock location, other than springs and shocks, but they need to be stock mount. I will try to get the car on the scales by Wed. or so. We have another play day at the track on Tues. so I will let you know about that 900 lbs. spring. Thanks


B.J. Deal

droper23
Dirt Freak

Total posts: 233
posted March 28, 2004 11:12 PM  
I have a metric car (coils on all four corners with all stock mounts) that weighs 3200 lbs. I have
rf= 1150 spring ,75 shock and 3" offset
lf= 1000 spring ,75 shock and 3" offset
rr= 175 (13")spring ,95 shock and 4" offset
lr= 200 (13")spring ,95 shock and 3" offset
I run 50.2% cross, 53.1% left side and 53.1%rear percent. I have never had a car drive better. I was having a major pushing problem, until I scaled it and found I had 55% cross, 56% left and 57% rear. With my new percentages, it runs very good and very smooth. I also feel that with my current setup, it has a lot of forward off of the corner.

19J
Dirt Freak

Total posts: 370
posted March 28, 2004 11:36 PM  
This is off the subject but.. As CD2 was saying about driving the car in hard. I have a car that weighs 2500 and has all stock springs and HAS to remain all stock springs how can i get the car to turn better so i can drive it how i want. I like to drive to the apex then turn the car and get on the gas. I had one car that could do that in but ive never scaled a car. It was a cruiser throttle broke and i ended up driving and running the gas i ran full throttle to the apex burbed it and was on our way. We ran fast too. The car wasnt loose wasnt tight was perfect so how could i set my other car up to be like that? Thanks.

Raz_900
Dirt Forum Champ
Total posts: 635
posted March 29, 2004 09:28 AM  
quote:
Originally posted by ALCOHOL:
I Also the car has a medium stock mount shock on rf,,,really don't want to reveal brand right now,,,


A medium shock on the RF might be letting the RF compress all the way. So you go in the corner, it's ok. Get in deeper and it bottoms out and now it's really going to handle like %&**.

Might want to try a heavy or ex-heavy RF shock. With stock mounts, it's really difficult to get a RF shock that is too firm. They're almost always too soft even with the heaviest one available.

CLBaker25
Dirt Maniac

Total posts: 193
posted March 29, 2004 03:59 PM  
Try softening your left front spring. I would also think about lowering your rear springs to 200 lf/ 175 rr. That is what we run and it has worked pretty well. We have found that too heavy of a spring on the left rear can unload the left rear going into the corner. I would also atleast try and get your car to 50% cross. Lowering your left front spring rate should lower that corner and give you more cross.


3dracer
Dirt Full Roller

Total posts: 32
posted April 03, 2004 01:49 PM  
FINALLY, here are the scale numbers...

783 635
838 787

Rear % 53.4
X % 49.0
lside% 53.1
total weight 3195

spring rates:

900 1200
200 150

air pressure on street radials:

14 20
14 16

So now what? We ran last night and the car was great when it was wet. During the night it started to get dry and the car lost the momentum from the wheel spin. I know there is more forward bite to be had, because if I don't spin the wheels coming off the corner, other guys that are not spinning are driving away from me. ALTHOUGH, I did win the heat, the dash, and got 2nd in the feature by about 2 feet. So we are improving...

iowa_dirt_track_girl
Dirt Freak

Total posts: 461
posted April 03, 2004 05:36 PM  
my first question is why running so low of air pressure on the right side if after the feature you look at your right side tires and the dirt mark is all the way up the side of the tire it is doing you no good to run that low of air pressure on the right side of the car you get no grip on the flat side of the sidewall we run 35 lbs on the right side and that gives you more side bite cause you are running up on the tread and not the sidewall plus you have less blow outs i would bump that left front spring to a 1000 or 1100 also are you running a front sway bar
? also swap your rear springs around and see if that helps if you dont have any other ones that will atleast tell you if you need to get a softer left rear spring also remmember with a softer spring on the rear the more the car will squat comming out of the corner (to a point)
And yes fellas i know what iam talking about we have won 100 feature wins in 6 years so take our advice to hart we are trying to help you guys out!

cd2
Dirt Maniac

Total posts: 161
posted April 04, 2004 11:17 AM  
3dracer Give me a personal e-mail. dbroy@bellsouth.net cd2

juliaferrell
Dirt Freak

Total posts: 370
posted April 05, 2004 01:43 PM  
HINT HINT: IOWA DIRT TRACK GIRL!!!

Try this: If you want a combination that will dust your hind in with 100+ feature wins. Drop rear spring rates to 80 on the left rear and 85 on the right rear. Get a 350 dampening rate shock for the left and 330 dampening rate for the right. Talk about bite!!!! hehe

The stiffer shocks adds to the spring rate at a formula I will insert upon your request. Weaker springs are the way to go for forward bite off the corner. You just need this little combo to hold the car up until you start throttling.

Just say thanks!!


iowa_dirt_track_girl
Dirt Freak

Total posts: 461
posted April 05, 2004 07:05 PM  
ya but the only bad thing about going to soft in the rear is it tightens the car up and my cars are allready tight enough the work very very excellent on dry slick track but ya i know where you are comming from
Another bad thing is that we have to run stock shocks but i send mine to Bilstein to get revalved so they look stock

juliaferrell
Dirt Freak

Total posts: 370
posted April 06, 2004 09:28 AM  
What I'm getting at here is the use of an excessive dampening rate on the shock to create spring rate!! Softer won't tighten you up when you have the shock adding to the spring rate. For instance:

80# rear rate with 340 dampening rate is the same as a spring with 140# rate p/inch. The car still acts basically the same except during load through the corner as the shock compresses the spring rate changes (like a variable rate coil working backwards).

Ok.. Just figured I'd give you a tip.

iowa_dirt_track_girl
Dirt Freak

Total posts: 461
posted April 07, 2004 07:05 AM  
Ill call my Bilstein rep and see if i can get them rates you can e-mail me some more info on this i would be intere3sted in learing more about this
Bachs_racing_engines@yahoo.com
thanks for your help and ideas

factory58
Dirt Full Roller

Total posts: 41
posted April 07, 2004 08:08 AM  
what ride heights


juliaferrell
Dirt Freak

Total posts: 370
posted April 14, 2004 02:46 PM  
Maintain your normal 2x1x1 ride height settings. ie. example lf 6, rf 7, lr 7, rr 8
Remember**you don't spring for ride height. you spring and then adjust accordingly.

cd2
Dirt Maniac

Total posts: 161
posted April 14, 2004 08:44 PM  
3dracer Did you get your car going like you wanted it to? cd2

    

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