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Author Topic:   Rear Weight % (stock metric)
Deak-Jr
Dirt Forum Racer

Total posts: 81
posted April 20, 2005 11:39 AM  
Scaled car last night. Came to about 3180 total. 8-gal cell, 150# of weight sitting back there.

- ride heights look pretty nice
- 53% left (happy w/that)
- only 46% rear

I'm looking at it like the 8-gal cell + the 100-lb weight equals a full 22-gal cell, so I'm not really counting that 100-pounder as additional ballast -- just as a chunk that puts me on the same page as folks with bigger cells.

Looking at it that way, we have 55# added to the back left (just behind the LR wheel, in the trunk) and are at 46% rear.

At this point, we'd be happy with the 50% ballpark in the back -- which would mean adding about 150# more on top of what's already there.

High-banked 1/4-mile dirt, stock metric car, 60-series DOTs, around 6.30 final drive. Track usually smooth, and usually slick or getting to slick by the time we run our feature.

What kind of rear %s has anyone gotten to -- and been happy with -- on a metric car, while not being way loose?

Thanks much. Any ideas appreciated.

racer17j
Dirt Forum Champ
Total posts: 5390
posted April 20, 2005 03:54 PM  
51.5% rear 200 lbs, 22 gal tank & 220 driver 3375 total. If your down on power the weight won't help but if your spinnin add it or take it off the front.

racerss10
Dirt Full Roller

Total posts: 31
posted April 20, 2005 09:33 PM  
55% with 150lb lead and 300lb driver 3400 total

340duster
Dirt Maniac

Total posts: 195
posted April 21, 2005 12:27 PM  
Put the ballast as far back as possible, this will take weight off the front and add more to the back to get you close to 50%. People will argue that that is a bad thing as it causes the back end to act like a pendulum, but until you get to 50 or 51% rear you won't even notice it. The benefits it forward bite greatly outweigh the handling effects it causes. The true test will be lap times

bcarter3477
Dirt Roller

Total posts: 13
posted April 22, 2005 07:37 AM  
All this learning is sure a lot of fun!

Well I have been to the track twice now. This is my 1st race car ever and I decided to jump into an IMCA stock car.

When I first scaled the car (before the season) I came out ok:

Left: 52.6%
Cross: 49.6%
Rear: 49.0%

Total weight: 3110

Then I started playing with the car with the LR weight jack by putting in a couple rounds of wedge and moved my 50# of lead from the right to the left and my cross weight went down??? Go figure. I called it a fluke...I put everything back to baseline and went racing.

The good news.... Plenty of power (overheating problem resolved)...the car is still in one piece (the wall jumped in my way only once) and I pulled out an 11th and 21st finish.

Bad news: good luck getting the thing to turn or to stop turning....the car was all over the track.

I figured that something is still wrong. I measured everything again (mic'ed the springs).... it turns out that in re-assembling the car I put the big spring on the RR and the little spring in the LR.

I switched the springs and reset the ride heights and moved a few things back in the car. Now I get the following at baseline:

Left: 53.5%
Rear: 50.6%
Cross: 49.9%
Total car (fully loaded): 3,140 (within 20# of the track scales).

I figure this is my 'early night' setting.

Now I put in a couple rounds of wedge in the LR (along with dropping the rear pressures 1/2#)and the cross goes up to 52.1% for my 'slick' setting.

This sounds close to what everyone here says is good. I can't wait to see if the car behaves better this weekend.

Track is 3/10 medium banked.

Give me your guidance. Minimum weight required is 3,100. Should I add some weight to bring up the rear %? I am getting a lot of tire spin but I attribute a lot of that to inexperience in my 'applicator' within my right shoe. Will the extra weight offset this problem until I can control my right foot or should I leave the weight off the car?

Thanks for your continued help and support,

Brian

340duster
Dirt Maniac

Total posts: 195
posted April 22, 2005 10:34 AM  
That's tough to answer and only you can determine that by measuring lap times, but I would try the weight first especially if the feature is very slick.

    

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