Rear Spring Advice - drag racing

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Nov 24, 2009 | 11:40 AM

Highhat

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From: Philadelphia PA

Rear Spring Advice - drag racing

I need more traction. Cant hook anymore. I have a 7 leaf steel spring, and standard shocks. Will replace shocks with single adjsutable QA1s

Can anyone recommend whether to change the leaf spring, and if so to what (or to composite) and what rate? Thanks

Nov 24, 2009 | 11:58 AM

BKbroiler

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From: Lebanon Township New Jersey

How about a little more info? What trans, tires etc. What ET, mph and 60 ft are you running now?

Nov 24, 2009 | 12:03 PM

gkull

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From: Reno Nevada

2024 C3 of the Year Finalist- Modified

did you have anybody video your launches? Very valuable tool for seeing what the tires are doing (slicks) and how far does the rear end squat.

I was able to determine that 340 pound mono fiber spring had way to much squat. I went to 420# and that I needed VB&P smart struts to eliminate camber change with vertical wheel travel. As power rose I tried zero rear toe and things to prevent wheel hop.

Nov 24, 2009 | 12:27 PM

Van Steel

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From: Clearwater FL

Quote:

Originally Posted by BKbroiler

How about a little more info? What trans, tires etc. What ET, mph and 60 ft are you running now?

I've got guys on 500# spring rates. But we're talkin 8 and 1/2 9 second cars. A 420# spring is a good option as well if it's both a street and strip car.

Nov 24, 2009 | 12:36 PM

Highhat

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From: Philadelphia PA

Quote:

Originally Posted by BKbroiler

How about a little more info? What trans, tires etc. What ET, mph and 60 ft are you running now?

big small block, pump gas
TH400
ET drag radial 28" (275/60/15)
Has differential to trailing arm struts

10.5et/126 1.6 60ft
Then, dialed in my carb better, and it put more power to the ground, and spun for 100 ft.

here is one prior video:
http://www.youtube.com/watch?v=gqPNx...eature=channel

Last edited by Highhat; Nov 24, 2009 at 02:57 PM.

Nov 24, 2009 | 03:53 PM

gkull

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From: Reno Nevada

2024 C3 of the Year Finalist- Modified

If this is you also............. You need to use a shorter wider tire to induce weight x-fer.

Your body doesn't even come down on the rear. So stiffer springs are not what you need. Do you ever get daylight under both front tires? It looks like it is not launching hard enough because of no traction. Like you said spinning for the first 100 feet. I've always liked slicks

Nov 24, 2009 | 08:38 PM

C3 Stroker

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From: Youngstown Ohio

Quote:

Originally Posted by Highhat

Your car runs similar E.T.s to mine, and I've had success with QA-1s in the rear and a 380 lb. composite spring. (Though I really could a higher rate spring.) The QA-1s will tighten things up a bit and assist the spring. I use MT ET Street Radials, and generally hook without too much spin with 1.5 - 1.6 60 ft. times. Mine is also a TH400, so footbrake rpm is only around 2200 with immediate flash to about 4300 rpm.

Holeshot video for comparison:

Nov 29, 2009 | 11:06 AM

Highhat

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From: Philadelphia PA

Looks like I have a 5-leaf (with 2 spacers), 400lb+ by most accounts. Am installing QA1s in the rear. I'll report if there is an improvement

Any others running steel leafs?