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Author Topic:   42% rear !!
timcsim7
Dirt Roller

Total posts: 18
posted July 15, 2002 03:25 PM
Car pushes bad from center out. I finally got it scaled. How do I get the rear % up??

54% Left
52% Cross
58% Front
42% Rear

72 monte, already 100lb over minimum. NO Ballast. Do have larger tires in rear. Will changing to smaller or same as front make any difference?? That would change ride height, but could I get 8% change?? Do I go ahead and add weight? I've cut everything my rules allow. Any ideas??

2nd2none
Dirt Freak

Total posts: 368
posted July 15, 2002 04:54 PM
if car pushes bad middle-out with 42% rear then increasing rear will make it push even more, there has to be something setup wise wrong. Give spring rates and shocks and what stagger/tire press. your runnin

timcsim7
Dirt Roller

Total posts: 18
posted July 15, 2002 05:11 PM
2" stagger front, 0" rear (would have had 2" but we had to throw our only spare on).

Springs 1000 lf, 1200 rf, stock rears

Have since installed 250 lr, 200rr

Tire pressure 20 left side, 22 right.

Pro Shocks, stock location

No weight jacks.

o5racer
Dirt Maniac

Total posts: 115
posted July 16, 2002 10:47 PM
Your springs shocks and air pressures all sound pretty close. I really dont see any reason you are pushing with 42% rear. It should be lighting the tires. Have you had it on an alignment rack? if the front end isnt workin as well as it could then its goint to push. on the left front run as much positive (top of the tire leaning out) camber as you can and still keep .5-1 deg positive caster. on the right front around 3-3.5 deg negative(top of the tire leaning in) camber seems to be a good starting point. caster on the right front should be between 2.5 and 5 positive for starters. set the toe out 1/4 inch. make sure the front end isnt binding also.

What is the competition running for cars? If they are running metrics then, Im sorry to say, you are pretty much ******* . Double check your rules (look into gray areas)and see if there is ANYTHING you can remove or replace with somethig lighter on the front or middle of the car. Gut the hood and doors if you can. gut the hood out. make sure to get rid of all hinges and latches. they dont weigh much by themself but it all ads up. get rid of any brackets that arent being used, maybe try to find an aluminum front bumper. the stock front bumper weighs way to much for the front of a circle track car. great for derbys, bad for circles. get rid of the stock bumper shocks too. if i remember right i think they weigh about 10-15# each. Get rid of the stock radiator support. run a piece of 1 1/4x1/8 round tubing between the front frame horns and mount the bottom of the radiator to it. Just getting rid of the heavy core support and getting a lighter bumper will help your overall and rearweight.
without seeing the car i dont know what else to reccomend for the diet.
get it back on scales. see how much weight you have to put right on the rear bumper to get 45%. that should be the absolute minimum for a dirt track. I run 210# right in front of the rear bumper with no problems. 300# seems to be the limit at my track before the pendulum effect starts to kick in. your track may be different. depending on how much you can strip off of the front end it may not take much to get 45%. 100# of of the front end will make alot of difference on the scales.

timcsim7
Dirt Roller

Total posts: 18
posted July 17, 2002 09:28 AM
05racer

I'll have the alignment checked.

There are a few metrics. The points leader drives an early 80's Impala (2 door), but 2nd is a mid 60's chevelle (and people still give me **** for ruining an early monte..). We still have a lot of early to mid 70's cars.

The only thing left I haven't skinned is the passenger door. I've cut everything on the front that the rules allow (hinges, fenders, supports, latches, etc).

How much would ride heights affect my percentages? The car sits high in the rear. I thought maybe the new springs would change it, like they did on the front (they lowered it), but there's no change. Would it be worthwhile to lower the rear or raise the nose?? Some of the guys here run with with the nose a little higher.

I'll also try adding weight. A couple hundred pounds could put me around 45%.

Thanks for your help!

WesternAuto17
Dirt Freak

Total posts: 248
posted July 17, 2002 11:45 AM
Sounds like you really need to lower the back end. Bigger tires aren't helping either.

However, something isn't right if you're not busting the tires loose every lap with 42% rear.

timcsim7
Dirt Roller

Total posts: 18
posted July 17, 2002 12:23 PM
Westernauto17

Lowering the rear makes sense. That would shift weight to the rear. What's the best way to do that? Would you heat the street stock springs I have now?? They're 250L, 200R. I'd be increasing the rates.

OR should I put the stock springs back in and heat them? It wouldn't hurt them to be stiffer, but would it add enough rate??

What about some type of spacer up front?? Between the spring and the a-arm. Anybody ever done it?

I'm going to change to larger tires on front and smaller in the rear. I just don't have the exact sizes worked out yet.

Thanks!

ryan
Dirt Freak

Total posts: 430
posted July 17, 2002 01:32 PM
Are you sure the scales are correct????

timcsim7
Dirt Roller

Total posts: 18
posted July 17, 2002 02:08 PM
No. You think I should find some different scales?

2nd2none
Dirt Freak

Total posts: 368
posted July 17, 2002 06:49 PM
are they electronic scales or grain scales? if they are electronic they should be real accurate. grain scales are usually pretty close too.

couldnt you use lowering blocks to lower the rearend? i dont drive streetstocks but i'd think lowering blocks and adjustable shackles would help changing ride heights. I know guys here use shims on the fronts to get car to scale out, IE: shim RF spring to help gain LR bite.

o5racer
Dirt Maniac

Total posts: 115
posted July 17, 2002 10:09 PM
Nah, hes got coils and a stock four link. dont bother with heating the stock springs they will just be short and you sill wont know the rate. did you get the full length rear springs or the short ones? on mine I used the short pigtail springs with no spacers. normal ride heights for montes and chevelles(pre '77 models) is 8 1/2 left, 9 1/2 right. on mine its 6 1/2 left and 8. when you lower the rear it puts more angle in the upper arms making the rear end lift up on the chassis when it twists back. BUT, you have to drop the rear mounts for the lower arms on the housing to make it work. if you dont the rear end will be pushing ahead and down on the chassis unloading the tires. lengthen the lower mounts on the rearend untill the arms are angled up about 5 deg with the front end higher.

moving the bigger tires to the front cant hurt. more tire to help it turn.

another idea i had. how well do the the brakes turn the car going into the corner? if the car isnt turning enough on entry it will throw off the whole rest of the corner. do you run a right front brake? if your rules allow it i would get rid of it. it might take a night or two to get used to it but it does help the car get into the corner.

I was just wondering about your competition. at my track its about 75% metrics. the two cars above me in points are metrics and the next five below me are metrics. its a pretty big disadvantage to run against them with an older car. the only thing saving me is the 3500# weight limit.

ryan
Dirt Freak

Total posts: 430
posted July 18, 2002 12:23 AM
Go to a truck stop with scales or a local grain elevator/co-op and weigh it there if the totals come out reasonably close you should be fine. I was just givin you another thing to consider.

timcsim7
Dirt Roller

Total posts: 18
posted July 18, 2002 09:52 AM
Ryan

I use the grain scales at the local co-op. The ground is level. I think they're pretty accurate. Even if they're not, the percentage they're off would be the same from wheel to wheel. Right?

timcsim7
Dirt Roller

Total posts: 18
posted July 18, 2002 10:57 AM
o5racer

My springs are same height as stock. Thanks for the advice on lowering it.

It's ok going in. I have to run all four brakes. Although I've never heard of them checking, I do know I'm dq'd if a brake doesn't work.

The class above me has more metrics, but they also can run unibodys (nova, camaro). In my class if we're under a certain wheelbase we have to be full framed. I probably should have used a metric, but this monte was free.

They dropped our weight two years ago from 3400 to 3200. When it was 3400, the champ was driving a 80's oldsmobile (not a cutlass, but their big two door boat).

Thanks for the help!

timcsim7
Dirt Roller

Total posts: 18
posted July 18, 2002 02:34 PM
Been thinking of ways to lighten the front. What about losing the sway bar? That should be worth some lbs. Think I'd need to change my spring package after??? AND if it's adjusted wrong now (I have no clue) would that help make it push??

AC156
Dirt Freak

Total posts: 295
posted July 18, 2002 03:00 PM
i may be wrong, but i believe that a front sway bar would make a car push.

[This message has been edited by AC156 (edited July 18, 2002).]

tilley88
Dirt Freak

Total posts: 353
posted July 18, 2002 09:00 PM
With that much spring combined with a sway bar it WILL push!

FirstLight7
Dirt Full Roller

Total posts: 30
posted July 19, 2002 12:02 AM
I'm not familiar with the Monte Carlo suspension but these are 3 general setup ideas to think about

1) Rear percentage - can you move the motor back any? Every inch helps.

2) What is your wheel base on the left vs right side? Increasing the right side length greater than the left side should help bring the car around when you are in the throttle (might try 1/4 inch to start).

3) You will need more stagger on the right rear than on the left rear to loosen the car. You might have to move your right front tire to the right rear. Currently there is more left in the car. The smaller tire on the right front will decrease cross%. If the track stays wet or tacky less cross will help. If it is dry you may need to add the spacer you mentioned under the right front spring to get your cross% back after rotating the right side tires.

WesternAuto17
Dirt Freak

Total posts: 248
posted July 19, 2002 09:28 AM
Loose the sway bar!!!! It will help weight a little, but more importantly, it will allow the car to roll and transfer weight to the right side tires.

o5racer
Dirt Maniac

Total posts: 115
posted July 20, 2002 12:10 AM
with a 1200 RF and a 1000 LF you shouldnt need a swaybar. definatley ditch it.

are you allowed to shorten the wheelbase to the minimum? cutting it down to 108" will gain you a couple of percent.

another benefit of montes is the engine location. Stock V8 montes have the #1 plug even with the upper balljoint. thats almost 4 inches back from a metric.


timcsim7
Dirt Roller

Total posts: 18
posted July 24, 2002 09:00 AM
I ditched the sway bar and some misc brackets from the front bumper on fri.

I also changed tires. I've got 29' on front, 27' rr, 26'lr. These are rough tire heights. I know that changed by ride height all the way around but I don't have the exact numbers with me right now. It raised the nose about an inch and dropped the rear 3/4 to 1 inch. I haven't been able to scale it yet (been out of town for 5 days).

Don't know my wheelbase from side to side. I'll check it.

Can't move the engine. Rules say no setbacks.

How much stagger do you think I should start with??

Thanks for the help!

motorhead77
Dirt Newbie

Total posts: 2
posted July 25, 2002 02:35 PM
try 225 lr spring instead of 250. that will loosen you up a little. also try around 2" rear stagger. you could also decrease the front stagger which would take some of the cross out.

stockcar5
Dirt Full Roller

Total posts: 63
posted July 25, 2002 08:29 PM
you WILL handle better without the sway car.i was running about the same ad ihad a swaybad and it pushed almost all the time (i can believe i won a feature with that setup) i ditched the sway bar....100% better. sway cars can work but you need alot softer springs up front.

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