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Thread: Tuning a Rigid Framed Altered

  1. #1
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    Tuning a Rigid Framed Altered

    I bought an older Rigid Frame Altered. I just completed the car with a .030 over 700 HP 454. The car weighs approximately 1800 lbs. The chassis is a tube chassis with rigid (unsprung) suspension (Front and back). I launch at 3200 RPM for tuning purposes instead of 4200+. Front is a king pin set up. 116 inch wheel base. The car weighs approximately 1800 lbs. I have Good Year Front Runners (23x5-15) and 33x16-15 rears. When launched, the car wants to go right. Subsequently, it never gets good traction going down the track. The rear end is all over the place. Rear air pressure is set at 8.5 lbs. I am currently checking rollout and front end alignment. I have heard the car should be launching off the wheelie bars? Is this correct? Can anybody help me with any other tuning tips that will correct the launch and traction problem? Thank you in advance.

  2. #2
    Senior Member RACING JUNKIE curtisreed's Avatar
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    One thing I think is 8.5lbs is too much for a 1800 lb car. We run 5.5 in our dragster at that weight and I only run 7.0 in my roadster. If you have no traction problems then go with the 8.5. You are on the right track checking the roll out and front end alignment. See what you find there first then look elsewhere.

    You might want to check the chassis really good for any broken welds that could move under power also. If the chassis doesn't have enough caster built into it they can be a handful. I've seen it before. Wouldn't affect the launch though.

    Curtis

  3. #3
    Senior Member RACING JUNKIE TheYellaBrick's Avatar
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    Might want to check the chassis for square as well.
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  4. #4
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    Thanks to all. I am definately going to check the chassis for square. I talked to S&W. They also recommended I check for "preload." Not exactly sure what that means. However, I was told to raise the car by the center of the front crossmember. If the right front tire rises by 1/4 inch preload is correct. If not, I obviously have more work to do. Just not sure how to correct it? Ballast, drive train movement? Any idea?

  5. #5
    Senior Member RACING JUNKIE
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    Quote Originally Posted by doorracer
    One thing I think is 8.5lbs is too much for a 1800 lb car. We run 5.5 in our dragster at that weight and I only run 7.0 in my roadster. If you have no traction problems then go with the 8.5. You are on the right track checking the roll out and front end alignment. See what you find there first then look elsewhere.

    You might want to check the chassis really good for any broken welds that could move under power also. If the chassis doesn't have enough caster built into it they can be a handful. I've seen it before. Wouldn't affect the launch though.

    Curtis
    I have a ladder bar car. 150" altered. I run 9 lbs in the slicks at the last event with no problems. We upped the pressure in our door car also after seeing pics from the track photographer. We were folding the sidewalls way too much.

  6. #6
    Senior Member RACING JUNKIE
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    Launch it harder not softer, them cars normally like to hit the tire harder to help them. I also agree less tire pressure.
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  7. #7
    Junior Member SHOW GUEST
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    I have a 125" rigid car and i understand your frustration.After you get the left and right problem figured out the traction issue will change from track to track. Tire selection will make a change. Stiff / soft sidewall, rubber compound choice. Also if you run a torque converter, using a low rpm chip will flash the converter harder.Without a chip the engine will get up on the stall. The object is to get the car up on the tire. My problem was an issue with the wheelie bar flexing.My car would try to steer out of the groove at the launch. If you can get someone to video the launch from behind it helps. I would contact your tire company to see what tire they would have you use.


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