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Thread: Any wheel alignment issues?

  1. #1
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    Any wheel alignment issues?

    I am using Dr. Ruth's string alignment procedure outlined on the '33 HR Forum, to rough align my early chassis (#15) '35 Pickup. I think his procedure should work on the pickup. I have installed the rear axle per the manual, centered the panhard rod, measured axle to cabin bulkhead, and everything seems OK.

    When I stretch the string from the rear wheels up to the front wheels (for setting toe) I would expect the distance from string to wheel edge to be similar on each side of the car. But, I am getting 3 7/8" on left side and 5 3/8" on the right side (string to tire side). In my simple mind, that would imply my rear axle is cocked to one side, or am I missing something.

    Would you guys that have done a home alignment like to comment?

    Thanks, Ralph

  2. #2
    Seasoned Citizen NAZ's Avatar
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    If you have the conventional rear axle there are two common things that would cause that: the rear axle is offset to one side and or the axle is skewed. On a three-link axle there is a panhard bar (or track bar depending where you live) that locates the rear axle and makes the axle swing in an arc. That means that even if the axle is centered in the chassis when the panhard bar is level with the world, when the axle goes over a bump in the road it travels in an arc as viewed from the back. And of course that moves the axle laterally.

    If the axle is skewed that means that the longitudinal center line is not square in the chassis. If you were to draw a line down the center of the chassis and a line through the pinion shaft they would not be parallel so stretching a string along the sidewall of the rear tires would be skewed or not parallel to the chassis center line.

    But there is a much easier way to adjust toe -- use toe plates and two tape measures. Do a web search for Longacre toe plates to learn more: http://www.longacreracing.com/produc...Magnets-(pair)
    Dart Little M 406" SBC 800 HP N/A & 1,100 HP on nitrous, 2-spd Powerglide with trans brake, 6,000 RPM stall converter, narrowed Moser 88 3.90:1 spool with 35-spline gun-drilled axles & Torino bearings, custom parallel four-link, custom tube chassis & roll cage NHRA certified for 8.5-sec (only two FFR Hot Rods have this cert).

    33 Hot Rod Super Pro Drag Racer Build: 33 HR NHRA Cert Roll Cage Build

  3. #3
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    Thanks NAZ. I am not having trouble adjusting the toe, just concerned about what is causing difference in readings from rear wheels. Followed all manual attachment dimensions, and not sure where to turn next.

    Let the journey continue.

    Ralph

  4. #4
    Seasoned Citizen NAZ's Avatar
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    When I build a new chassis, or in your case, assemble a new chassis, the first thing I do to the bare chassis is mark the center line in several places with witness marks. That's the datum I use to set the engine, trans, rear axle, and suspension components to. I also establish a perpendicular line at or near the rear where the control arms attach. This is the datum used for ensuring the rear axle is square in the chassis. Between these two datum lines I can get the drive train, axles, and suspension parts squared to the chassis. Without these reference points you are just hoping that everything is aligned correctly in relation to each other.

    The other thing this does is make it easier to determine how much damage a chassis has sustained in a crash and gives a reference to facilitate repair work.

    Hope this helps.
    Dart Little M 406" SBC 800 HP N/A & 1,100 HP on nitrous, 2-spd Powerglide with trans brake, 6,000 RPM stall converter, narrowed Moser 88 3.90:1 spool with 35-spline gun-drilled axles & Torino bearings, custom parallel four-link, custom tube chassis & roll cage NHRA certified for 8.5-sec (only two FFR Hot Rods have this cert).

    33 Hot Rod Super Pro Drag Racer Build: 33 HR NHRA Cert Roll Cage Build

  5. #5
    Senior Member DamnYankee's Avatar
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    The problem may be at the front - when the lower control arm sleeves are turned (for caster adj) they basically move the front wheel forward or back.

  6. #6
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    I have not touched the lower front control arm sleeves yet (caster). They are still set at the 15 1/2", bolt center to bolt center, setting recommended by Dr. Ruth. I see the assembly manual uses 15.625", but don't think the extra 1/8" can make that much difference.

  7. #7
    Seasoned Citizen NAZ's Avatar
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    Ralph, I'll give you something to ponder. No mater what you hear, there is nothing "perfect" in manufacturing -- everything has a variance around a target. When engineers design things they provide a dimension and a tolerance, usually stated on a drawing as a +/- value. When you look at all these tolerances stacked on top of each other the total variance can start to become significant. The axle shafts, hubs, brake rotor nested on the hub, the wheels, and the tires (tires have the most variance of all). Then you stretch a string across the sidewall of a tire and try your best to set the string where it just touches the sidewall. Extend that string out 16' or so and any error is multiplied significantly.

    If you want to accurately measure toe use toe plates.
    Dart Little M 406" SBC 800 HP N/A & 1,100 HP on nitrous, 2-spd Powerglide with trans brake, 6,000 RPM stall converter, narrowed Moser 88 3.90:1 spool with 35-spline gun-drilled axles & Torino bearings, custom parallel four-link, custom tube chassis & roll cage NHRA certified for 8.5-sec (only two FFR Hot Rods have this cert).

    33 Hot Rod Super Pro Drag Racer Build: 33 HR NHRA Cert Roll Cage Build

  8. #8
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    NAZ, completely agree on tolerances in manufacturing. I am just confused by 1 1/2" difference between the string to tire distance between the two sides of the car, regardless of the length of the string.
    Like your tag, I am a seasoned citizen also.

    Thanks, Ralph

  9. #9
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    I think I have discovered my problem. I had not driven the truck before attempting alignment. After driving around the block a few times, the distance from front tire to the alignment string seemed to get pretty close on both sides. So, lesson learned, drive the car a bit to let the suspension components normalize.
    Thanks for the help.
    Ralph

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