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Author Topic:   Adding weaight to car
Raceman17
Dirt Maniac

Total posts: 165
posted April 16, 2005 03:15 PM  
I have a quick question. I know to get more rear weight percentage, I need to take weight off the front of the car or actually add weight to the rear of the car. I read the "placement tips" in the toolbox but it said nothing about how far back you mount the weight in relation to the rear wheels. Would you get more rear percentage if you added weight farther back in the car towards the fuel cell as compared to sticking it right over the rearend housing?

Steve Dupree
Dirt Freak

Total posts: 316
posted April 16, 2005 04:09 PM  
Yes the further back the weight the more % you will have. I have heard alot of talk on a pendulum effect if put it on the back but i am not sold on that yet. We have taking all the weight we can and the car acually has the same % as it did when it was 3720 with me in it. We use to add weight right over the left wheel and have added up to 150 lbs after we got the cars weight down. Well the car was way to tight and just didnt drive correct even if the % where correct or close to what they say to have. Last nite are track went really dry slick in the heat we started on the pole with no weight and finished 4th. We came in and changed one tire and added 40lbs. pretty much center but behind fuel cell and filled tank up with fuel so we added 75 lbs. before the main started. We started 8th and was in first in two laps and held the lead for 12 laps and ended up 3rd. In are car on the scales 40lbs moves the % double with the weight further back compared to right over wheel. So another words you can get the same % without as much weight. We would never add weight on a tacky track again after playing with everything but on a dry slick we sure know it helps.

Raceman17
Dirt Maniac

Total posts: 165
posted April 16, 2005 04:24 PM  
Thanks for the reply. I was talking to a guy who sets up late models and he said to put it back as far as I could also. I mentioned the pendilium effect deal and he said "yeah worry about it if your going 150 mph into the corner" he said it would cause the pendilium effect cause the speed was less. IM gald to hear about the the dry slick condition. Are track is ALWAYS dry slick so Im sure the extra weiught will help me.
Thanks

sideways
Dirt Forum Champ
Total posts: 715
posted April 16, 2005 06:51 PM  
Well I am not real sold on the idea of the pendalum effect no being in less than 150mph corner.I had my weight last year to the rear and I hated it.i moved it when on the scales over and around the rear axle,car much better now.jmho

Steve Dupree
Dirt Freak

Total posts: 316
posted April 17, 2005 05:42 AM  
Hey Raceman17 just so we are comparing apples to apples. We weigh 3300 with a full fuel cell 12 gl. and driver. Are % without weight L,52.9 Rear 45.3 cross 50.1 With weight behind fuel cell but a little left of center L 53.1 Rear 46.3 cross 49.9 We run a class with 9.5 compression,cast iron intake with 2 barrel 7" wheels, Tires no wider than a 255X60X15 When we ran friday we vidio all are races so we can check times and sometimes over turn verdicts on the track. Are times between the heat and the main are about the same but the thing is the other cars had slowed with it going so dry and we stayed the same all we did when we came in was add 5 gallons of fuel 40 lbs behind fuel cell we lowered air preasures on the rear from 18 on the RR to 16 and 16 on the LR to 14 and we had like a 3/4 stagger in the rear. Wish we could have been straight up but didnt have two tires tall enough to do that. You will hear alot about my % not having enough rear % but with the motors we have to run you do not need all that rear % to be fast we just dont have the power like a superstreet or a modified to break the tires loose when we want. When you play with your weight be sure to do it on scales with trying many diff. heights of tires and air preasure not to make your car fast but so you know what does make your car fast and then you have your baseline and know where to go from there. We were taught this by a friend that crew chiefs for a wing sprint and many other cars and he is a driver also. Oh just so you know we run two tracks one is a 3/8 mile little banking the other is a 5/16 15% banking and we run a ford that runs against 3000 lbs. metric cars. We are the only ford and it is a challenge and alot of work to race with giving them a 300 lb advantage. Well good luck and have fun and hope we helped. Steve Dupree

Raceman17
Dirt Maniac

Total posts: 165
posted April 17, 2005 07:16 AM  
[QUOTE]Originally posted by Steve Dupree:
[B]Hey Raceman17 just so we are comparing apples to apples. We weigh 3300 with a full fuel cell 12 gl. and driver. Are % without weight L,52.9 Rear 45.3 cross 50.1 With weight behind fuel cell but a little left of center L 53.1 Rear 46.3 cross 49.9 We run a class with 9.5 compression,cast iron intake with 2 barrel 7" wheels, Tires no wider than a 255X60X15

Your rules are pretty close to ours. Except we are limited to a tire no bigger than 235/75/15. I put the car on the scales (a metric car)a few nights ago and only had 40.5 % rear weight (only have 12 gal cell) The car weighed about 3150 with me in it. In the past I have built metric cars at had at least 50% rear weight and only weighing 3400 lbs. So I started looking for things on the front to lighten up. I remembered that a bumber off of a monte carlo was pretty light So i took the one off of mine and it weighted 78#. I will be replacing that on today with a monte bumper I hope. Hopefully that will give me alittle bit more rear%
Later

rocket36
Dirt Freak

Total posts: 209
posted April 17, 2005 07:35 AM  
i think you should check out www.jimmyjudd.com and read the article by scott bloomquist on ballast placement, which you can find in the tech section. it is very interesting, and is worthwhile reading several times.

one of the points in that article is to not worry about the percentage numbers everyone else is running (though it is a good place to start) and just concentrate on what YOUR car needs.

yes the pendulum effect is worth considering all the time. under some conditions it will work for you and other times against you. the big thing is to be prepared to change things on your car.

o5racer
Dirt Freak

Total posts: 402
posted April 17, 2005 08:50 AM  
Alot o it depends on the car and the track conditions. If you have a car that only caries in the mid 40s for rear weight then rear weight is more critical than pendulum. If you start going over 250# on the rear bumper though then there is a good chance its going to swing around in the courners. Been there done that. I ran 400# right infront of the rear bumper on night. Around the bottom it was great. Up high and in the middle it would start swinging and wouldnt stop. The car I have now I can get 54% with most the weight ontop of the rearend and 100# between the fuel cell and the rearend. I noticed a nig difference when it got dry out. The rearend seemed to stick a lot better in the middle and up high. At the same time if Im in an early heat race and its greasy yet the rearend doesent want to come around enough when I set it in the corner. For those I hang 50# as far back as i can to get it to swing. Rocket hit it right on the head when he said the pendulum can work for you and agianst you depending on the conditions.
Nick

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