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Author Topic:   Minimum rear percentages on 3lnk
ukandesperate
Dirt Full Roller

Total posts: 45
posted May 07, 2005 04:42 AM  
What would the minimum rear percentage be that you guys would suggest on a three link,our car only weighs 1800lbs with the driver and rear percentage is only 47%,as you can guess this isnt running to your weight rules,over here in the uk we can run as light as we want.
the problem were having is traction down the straights and corner entry being very tight,im sure we can fix the tight in but overall traction seems low.were using a three link rear end,and having read all the three link posts regarding angles and with help from zero on here (top man!),weve used all the info but with no real gain yet,when setting the rear for really good traction it just picks the rear up rather than making the tire bite harder???
So in your wisdom what would be the minimum weight over the rear,want to keep overall weight down but will add if need be,also what spring rate would be a good start,both clamped infront,100lbs at the mo but feels too soft? any input on this would be great,dont want to harrass just zero!

dirtzone
Dirt Maniac

Total posts: 102
posted May 07, 2005 06:21 AM  
I'd try around 54% and a pair of 200's in the rear and take it from there. You definitely need more rear %, JMO

ukandesperate
Dirt Full Roller

Total posts: 45
posted May 07, 2005 06:43 AM  
200????thought that would be way high for the weight of car,would that be after adding rear weight to get the percentage up?

xhubby
Dirt Freak

Total posts: 376
posted May 07, 2005 08:03 AM  
We are running around 61% rear on our short bar 2-link, with an x-factor pullbar(red biscuit), & we have good forward bite. I wouldn't worry so much about overall weight as much as I would worry about the forward bite. Add some weight ,up your rear% & make her fly. A really light car is no advantage if it won't go forward. JMO. Good luck.
PS. as dirtzone stated, you will probably have to go up in spring weight to hold up the added weight.

[This message has been edited by xhubby (edited May 07, 2005).]

ukandesperate
Dirt Full Roller

Total posts: 45
posted May 07, 2005 08:22 AM  
ok so i need to add weight,can you give me a rough rear weight that you run along with a spring rate,so i can get some sort of spring to weight ratio?,im thinking my rear springs are too soft at the minute but how do i check,can i set the car on the springs and measure drop to get a start point? dont want to change too much at once so trying to figure out if its weight or spring or both??!!

HERNDON
Dirt Full Roller

Total posts: 73
posted May 07, 2005 08:36 AM  
I don't see any other way to get rear% but to add lead. 1800 pounds??? The car doesn't way enough on it's own to get that rear % up...

chapa73
Dirt Maniac

Total posts: 169
posted May 07, 2005 08:50 AM  
My old mod,On sclaes I noticed about 1% more rear % with sitting a battery on the back.(AN extra battery on the decking,just seeing how much wight it would take)

Prolly about 350 pound is what you need to add I think.

ukandesperate
Dirt Full Roller

Total posts: 45
posted May 07, 2005 08:52 AM  
yes theres no way of reducing front weight to gain rear percentage so will be adding rear if needs be. just not sure if to address the spring rates first or to drop some lead in,what weights do you guys run,overall or rear?that will help me with our rates and setup if i know if im way soft or hard? im guessing you guys are 3000 plus lbs say 55% rear so spring rates of around 1/4 the corner weight,am i way off? i know spring placement/motion ratio all comes in but trying to get a good start point to work from,cheers guys

racer17j
Dirt Forum Champ
Total posts: 5390
posted May 07, 2005 01:36 PM  
yes ,understand the idea,more behind axle will lose front weight in theory,so what rear axle weights are you guys running???

mavrik82
Dirt Forum Racer

Total posts: 93
posted May 08, 2005 04:37 AM  
I spent a few years tuning on an imca mod that was a good car but nothing reaaly trick, but with an absolutely incredible driver.Thru testing we found that while everyone is gundrilling bolts and sneaking in aluminum parts to shave wieght, our fastest runs were when we ran 250lbs heavy!!!We even tried it lite and heavy in one night and it held true.If you have good horsepower and run a limited tire I think traction is paremount to acceleration, more so than weight.Do a scale session, put weight in the car so your percentages are correct,mark locations and pull it out. Go to the track, run it lite in warmups, add weight at marked area and run it.I think you'll be suprised!

ukandesperate
Dirt Full Roller

Total posts: 45
posted May 08, 2005 08:44 AM  
we only run 200 lb foot torque 250hp so yes limited hp,we do rev to 9000 tho so can use small gears,prob we have is spinning the tires hard

bigphillb
Dirt Roller

Total posts: 19
posted May 09, 2005 04:24 PM  
Is this a 4cy. car?

boas51
Dirt Maniac

Total posts: 190
posted May 10, 2005 07:10 AM  
add weight until your lap times quit improving. keeping in mind that where you add it will effect handling differently. make it easily moved or removed.

ukandesperate
Dirt Full Roller

Total posts: 45
posted May 10, 2005 11:21 AM  
yes its a four cyl,we can go bigger on power and have in the pastbut find it useless in wet slippy conditions and no quicker in the dry due to more wheel spin,if weight improves grip tho we will maybe go up in power.cheers for the input
would 130 springs be close on the rears?

trasrat89
Dirt Full Roller

Total posts: 46
posted May 10, 2005 11:34 AM  
We have around 250lbs. of lead on our rearend to make weight,(2550lbs). We had to go from 200 LR spring to a 225, & from a 175 RR spring to a 200lb. We run a 12-1 comp 355cid. engine with a 500cfm carb & stock 10.5" clutch in a limited class, & run 60.7% rear. The car is very good on a dry track.

racnfool
Dirt Forum Racer

Total posts: 89
posted May 10, 2005 12:21 PM  
trasrat,
Where do add your extra weight?
Thanks,
Racnfool

ukandesperate
Dirt Full Roller

Total posts: 45
posted May 10, 2005 12:48 PM  
so what should i be looking for to decide on rear spring rates,looking roughly at your springs its saying roughly corner weight divide 3.6 =spring weight,would this be right,if so then im way too low on rear springs would need more like 140lbs?

trasrat89
Dirt Full Roller

Total posts: 46
posted May 10, 2005 01:34 PM  
racnfool, We have a 50lb chunk on each side of the front corners of the fuel cell,(valve cover size mounted vertically, right behind the rearend), a 25lb. chunk directly beside each side of the fuel cell, about 50lbs. on a cross bar even with the top & right in front of the fuel cell, & a 50lb. chunk on a cross bar directly below the bottom front side of the fuel cell. As you can see, we pretty much have even amounts on both sides, with a single chunk low & centered. We needed this much lead to make weight,(2550lbs.), as my kid,(the driver), only weighs about a buck twenty. Hope this helps. P.S.I guess it only comes up to 200lbs. total.

racnfool
Dirt Forum Racer

Total posts: 89
posted May 10, 2005 01:57 PM  
Thanks trasrat,
I have similar problem to make minimum weight and appreciate the info. I overloaded the left side last year and fought a push on the dryslick. You seem to be getting good results by what your posting here so I'll give it a go.
Thanks again,
Racnfool

trasrat89
Dirt Full Roller

Total posts: 46
posted May 10, 2005 02:53 PM  
Good Luck! I hope it works for you. If it doesn't, I'll deny ever being on this web site. LOL.

bigphillb
Dirt Roller

Total posts: 19
posted May 10, 2005 10:47 PM  
just got a 4-mod and looking foward to setting it up. It's a 3 link and we have to weigh 2350lbs. Would one of these be more like a regular mod or like a pony stock as far as % go. Only my 2nd year and got good at setting up our last car but this is new to us.

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