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Saturday Night Racer >> RACE TECH >> Dirt Mod Lft Rear weight
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Message started by slick vic on 04/05/13 at 8:16pm

Title: Dirt Mod Lft Rear weight
Post by slick vic on 04/05/13 at 8:16pm

Question about adding weight on the left rear,.or taking some away.

What would be the scenario or reason for needing to add weight to the left rear,...????

4 link rear set up, shock in front.

thanks in advance

Vic

Title: Re: Dirt Mod Lft Rear weight
Post by CaliforniaPickle14B on 04/05/13 at 10:13pm

this comes from the harris racing chassis book give alittle insight on adding weight

8) Add weight if needed. Some tracks have a minimum weight rule, if that is the case you will probably have to add weight to your car. Most tracks include the driver in the total car weight, so keep that important point in mind when figuring the amount you will need to add. Adding weight to the chassis is an important key in the quest for additional froward bite. Remember that you are only dealing with an 8” tire! On extreme dry-slick conditions, you may want to have up to 60% rear weight percentage. Before you add weight on the car at the track, you need to make sure that you know how it will affect your weight balance on the car. In other words, you need to scale your car before you get to the track with the additional weights on the car in their proper positions. Adding weight without knowing how it will affect your percentages will probably cause more problems than it will help you. The optimum goal here is to add rear percentage while not changing diagonal percentage or left side percentage.
If you normally run a 4” offset wheel on the right rear when it gets dry, put that on your car with the stagger you normally run (when you scale the car in this scenario). Fill the car with fuel. See where your percentages are at this point. Now you can add weight as needed to obtain desired rear percentages.
For example, if you normally burn 15 gallons of fuel during a feature race, you should put 100# on to offset this. (Alcohol weighs 6.58#/gallon x 15 gallons = 98.7#.) If you put 40# on the right rear rail, you may only need to put 25# on the left rear rail to keep the diagonal and left side percentage the same. (Or as close to 50 ½% as you can get.) The other 35# you may want to put on the 1 ½” round tubing in front of the fuel cell or on the 2” x 2” behind the fuel cell. Keep in mind that weight transfers better the higher it is placed.
Remember that with more weight on the tail at this point, you will want to make sure that you keep the car as tight as possible going into the corner. This will allow you to come off the corner faster. You may need to slow down upon corner entry to achieve this – sometimes SLOWER is FASTER!

Title: Re: Dirt Mod Lft Rear weight
Post by slick vic on 04/06/13 at 9:40am

Thanks for that reply, but I was referring more to a tunning scenario as oppse to making the min weight across the scales or a scalling balance of my cars percentages,..

What type of conditions/scenario, or why would it require for one to add more Left rear weight,..grip.?? side bite..very slick track,..tacky..etc.....

Thanks
Vic

Title: Re: Dirt Mod Lft Rear weight
Post by 4QChris on 04/06/13 at 1:47pm

We add bite (left rear weight over right rear weight) as the track dries out. Slicker track more left rear weight. We sometimes do this by putting a turn in tye left rear and right front and removing a turn from the oppisite corners. This for us is about 30lbs.

Title: Re: Dirt Mod Lft Rear weight
Post by slick vic on 04/06/13 at 6:17pm

Thanks Chris,. That was the answer I was looking for, I appreciate your response.
I bought a car out of the mid west and it had like 90lbs more on the left rear than the right, so I can only assume he was running on really slick track conditions...??? ride heights were good.

thanks again

Vic

http://www.vicmillerracing.com/

Title: Re: Dirt Mod Lft Rear weight
Post by 4QChris on 04/06/13 at 7:44pm

I would consider that more of a starting point. Really dry will be around 120-160. Maybe more. Depends on the rest of the setup and drive ability

Title: Re: Dirt Mod Lft Rear weight
Post by slick vic on 04/06/13 at 8:57pm

Car is a 05 Shaw,.
Set up says 20-30lbs more on lft rear than right.
What might be my new result with that much less weight on the lft rear,..????

Here is a link to my very first and only race ever so far on the dirt let alone a dirt modified,..the camara will follow on me after lap 7 when the 57 car falls off,..I am #19 red car starting at the back,.again one race only under my belt (newby)

http://www.youtube.com/watch?v=L5h8bbQFyp8

Vic

Title: Re: Dirt Mod Lft Rear weight
Post by childressJr.16 on 04/06/13 at 11:00pm

Just remember these all are THEORIES an advice every person is different!! Some people tighten there cars up a ton on a DRY surface an go no where cause they wont rotate the center! I no from driving the 4bar car we ran a tighter setup for tacky an LOOSEN up car when it dries out so u can roll through the corner kinda like asphalt! We start with about 15 lbs Lr bite without driver init for BASE POINT! AN every adjustment u gotta "GIVE A LITTLE TO GAIN A LITTLE" "

Title: Re: Dirt Mod Lft Rear weight
Post by slick vic on 04/07/13 at 9:14am

Thanks Jr....as mentioned my set up calls for 20-30 to start, I based lined it at 28lbs,.....now if we could just get a weekend up here without rain ,...lol

Thanks again

Vic

Title: Re: Dirt Mod Lft Rear weight
Post by 4QChris on 04/07/13 at 9:28am

There you go. Virtually anything will work to begin. Theres so much more than just bite that goes into setup to be able to know just what you need. One thing that we believe as well is a loose car is better than a tight car. The biggest thing to learn in the mod class is throttle control. No matter the bite you have if you're not smooth on the throttle you're not going anywhere.