pro/con: lower weight or better weight percentage in IMCA sportmod?

[regor]

My car with me weighs about 120 lb over the minimum. I have taken all the ballast off the car to achieve that level. However, I don't have the greatest rear (53.6%) or left (54.7%) weight percentages.

So the question is: is it more important to get good rear and left percentages (by adding ballast), or more important to have a lower overall weight (but not optimal percentages)?

[Flyin Iowan]

Have the %'s right

[7uptruckracer]

You can get better left with wheel offsets and add minimal back to the rear but the right percents are way more important

[clbaker25x]

Why so much left? Most folks I know are running around 52%. We are running a few points higher on our sportmod stuff than what you are for rear percentage. Maybe move your battery further back or do stuff like that.

[7uptruckracer]

Depends if its with or without driver. we are 55 with driver and 57 rear on our mods without its way different

[regor]

These numbers are with me in the car. I'd like to get more rear and less left %. I already have the battery in the RR. The fuel cell is centered in the back.

[regor]

what can I do with the wheels/spacers to help the percentages? If I push the left sides in, and push the right sides out, would that drop the left %?

[MM90]

Put a 4" on the RR, it changed 0.5% of left side on my car.

[mod88s]

what can I do with the wheels/spacers to help the percentages? If I push the left sides in, and push the right sides out, would that drop the left %?

That's the opposite of what you would do. Can sportmods run different offsets or spacers??
If so, run 2" offsets on left, 4" offsets on right and see what the %'s look like.

[7uptruckracer]

No you would NOT run 2" on the left and 4" on the right they were right 4" on left 2" on right it essentially move the the chassis in relationship to your contact patches 2" backspace is from the back of the rim plate to the rim edge the shorter distance the farther it sticks it out. It's worth around 2% left side or so

[regor]

Ok so pushing the left side out will help lower the left %? Just wanting to make sure I got it straight. And to increase the rear %, is there any tips besides adding ballast?

[MM90]

I know of some A-mods with crates running around 53% rear. So I would work more with the left side weight and get it down around or below 54% with you in the car. I put a 4" beadlock on my RR for the first time from a 3" and it took 0.5% LS weight out.

[regor]

Ok so I got it backwards. Push out the right side and push in the left side wil decrease left side percentage?

[Renegade Cust Susp]

A simple way to look at it to avoid confusion. The close the tire is to the spring the heavier it will become. Make sense now?

[BlackMagic]

If you want to reduce left side % you will need to push the left side wheels further from the frame, and bring the right side wheels closer to the frame I have no idea what your current offsets are so here is just a scenario For example lets say you have 3" offsets on all 4 conners for a starting point the left sides would now need to be 2" offsets The right sides would now need to be 4" offsets if I had to guess that would be probably upwards of a 2% reduction in left side percentage, if it were me I would put a 4" on the rr and a 2" on the LR and that should drop you into a safe left side zone, put your car on the scales and mess with the offsets and see how much it effects your car getting your correct percentage numbers and having to run over weight to do so is far more important than being right on target with weight but having jacked up scale numbers.... The only way you will be able to gain rear percent is if you take weight off the front end or add it to the back.... Look for even the smallest brackets or excess length bolts or bumper bars.... Any little bit you can trim off helps, does your radiator fan have a spacer on it? Remove the spacer and move the radiator closer to the motor.... Look for little things like that.... Pounds are made out of ounces!

[setup479point2]

I guess my question would be , why do you want less left and more rear ? Those numbers aren't that bad .

[regor]

I race at a semi banked quarter mile and talking with other drivers, I had more left and less rear percentages than them. So that's what got me looking into tweaking the scaling.

[let-r-eat]

What's your handling issue?

[regor]

The car is usually a little loose in, then it pushes in the middle. I end up having to get off the gas a lot so I lose a lot of time in the corners

[regor]

Thats part of the prob. I have almost 150 lb LR bite.

[7uptruckracer]

I think sport mods are in the 50-100lbs range, last time I looked at a setup baseline for the ones I help

[regor]

7uptruckracer, thats what I understand too. So to get down to that level, I didnt know if there was anything I could do besides adding ballast to the RR to get down to that range.

[regor]

what do I do to get the LR bite down to the 20-80 range?

[let-r-eat]

You braking the car?What does it do if you enter without brake?

[regor]

stock car driver: I have played with the weight jacks in the back a little, but I have not sat on a scale to see what it does. Do you turn the weight jack in or out on the RR and/or LR to get the LR bite down?

let-r-eat: I do brake going in, but I do it pretty late. If I just try to let off the gas, it pushes going in.

[clbaker25x]

regor,I would recommend jumping on the dirt forum. I have put quite a bit of our setup informaiton on there. We normally run quite a bit more bite as a baseline than what these guys are recommending. Key is your entire setup has to work together. I am a big believer in freeing up the car on entry and then making plenty of forward bite off. Just need to have the motor to pull it, and it also depends on whether or not you are running a crate or open motor. Shouldn't need as much bite with a crate motor because they generally run quite a bit less gear than an open motor. PM me or give me and we can exchange information and I can give you more help if you want it.Where do you race? Good luck!BBR (Baker Brothers Racing) Motorsports

[killer bee]

stock car driver is giving you some good advice. my question is: how do you know you have 150lbs of lr bite if you haven't had the car on the scales and you have been adjusting the rear weight jack bolts? Get the car on the scales and record how it is now. then adjust like stock car driver told you.

[regor]

killer bee: I had the car on the scales. Thats how I knew my weight percentages and LR bite. But I did not adjust anything while it was on the scales - just put it on the scales, recorded the numbers, and left. My bad. Next time I will do some adjustments while on the scales to see how the numbers change.

[killer bee]

sorry, I misread your post. here is a link to an adjustment sheet that might give you a little help also. good luck.

http://www.larryshaw.com/printablesetupsheet.pdf

[clbaker25x]

sorry, I misread your post. here is a link to an adjustment sheet that might give you a little help also. good luck.http://www.larryshaw.com/printablesetupsheet.pdfI am a huge believer in this sheet. The big thing we have found that is different is that with only 2 bars instead of 4 things are more of a balancing act. Your right side bar basically acts like the right side lower bar. Your left side bar generally acts like the left side upper bar. If you use this as a basic guide your car is going to be fast most nights.

[mod88s]

No you would NOT run 2" on the left and 4" on the right they were right 4" on left 2" on right it essentially move the the chassis in relationship to your contact patches 2" backspace is from the back of the rim plate to the rim edge the shorter distance the farther it sticks it out. It's worth around 2% left side or so

7up, Im very confused about what you are saying here. How does putting 2" wheels on the left and 4" wheels on the right NOT lower his left side %?? Not sure how you figure things where your at but Im glad I disagree with you on this.

[7uptruckracer]

2" Rights and 4" lefts will raise his Left Percentage, which is what he wants, He suggested sucking in the lefts and Shoving outs the rights to LOWER left side which you told him is the opposite of what it would do, which is correct you then told him to run 2" on left and 4" on right...4" lefts and 2" rights is MAX left side 2" and 4" rights is MIN left side agree?

[7uptruckracer]

I apologize he wanted less left. I thought he wanted more!!! Less left with tighten your entry but also tighten the rest of your corner. Post all your setup and we can all get you straight.

[regor]

Back in the spring, these were my corner weights: LF 613 RF 528 LR 734 RR 587. That was with no ballast on the car. Springs were 700 across the front and LR 175 RR 150. I run the Bilstein sportmod shock package. My ride heights were about one inch higher from the front to the back, and about one and a half inch higher from the left to the right. Unfortunately, I made the mistake of not writing down what wheel offsets, spacers, or air pressure I had when I did it.

I'm going to go back to the scales and make sure I have all of that documented too, so I can test changing the offsets, spacers, tire pressures, and see how it changes it.

I'm also trying to figure out what is a good starting point for ride heights. I've heard everything from LF 5 RF 5.5 LR 5.5 RR 6, to numbers at least 2-3 inches higher than that. I measure ride height on the flat part of the frame rails.

[7uptruckracer]

Nothing seems to off the wall except maybe your RR spring being a little soft it will free you entry but tighten your exit on throttle. I'd say your bite might be a good place to start It will take some LR weight off the car which puts less on the LR on Decel which is what turns you into the corner along with the LF but being your on a stuff LF spring already that seems ok.. One thing to pay attention to is your bar angles and your Jbar/straight bar mounting as well. If your weights are in the ballpark I wouldn't worry to much. Depending on your chassis make and chassis manufacturer those could be ok heights if you know your manufacturer post it. Sorry for the confusion!

[7uptruckracer]

I don't like that setup sheet either AFCOS is one of the more accurate or complete rather, best thing I ever did was go to the RACEWISE school the other year! It explains from the ground up as if you are completely inexperienced and want to learn how and why it works the way it does.

[oldtrackchamp4x]

I measure my ride heights for the front at the center of the lower a arm bolts. Measure off the front part of the bolts. .
8in lf 7 3/4 rf is what i use. When you get into the car the front "should" be level doing it this way.If track is really dry slick i will set front with the rf 5/16- 3/8 lower to help car get over on rf. JMO

[killer bee]

http://www.afabcorp.com/exp/files/resourcesmodule/@random440610d5778ca/1168265974_circle_tuning.pdf

[clbaker25x]

Cool guide. We do the same as stock car driver is saying for ride heights (get lower control arms level). I measure my amount of shock extended and normally use that as my base measurement as it is easier for me to be consistent with it.