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Clyde
Member
Posts: 32

If all you have is one day a week to prepare your racecar for the upcoming season, that would be a total of 15 days before the first event! The reason I know that the alignment is the foremost item on the preparation schedule is a fact that the IndyCar teams agreed on and that is " an alignment that is off by 4 millimeters slows the racecar by 4 MPH at 200 Miles an hour" Our racecars do not get to 200 MPH but we sure get to over 100 MPH so how much free speed are you giving away?  You MUST use the center between the suspension pick-up points, not always the center of the chassis. Some designers allowed a slight offset for shifting purposes. The later suspension designs use rocker arms, the older outboard racecars used A-arms. Rockers came in different lenghts per chassis! You need to measure the lenght from the pivot to the Upright and to the shock mount. The older A-armed racecars need to also be measured to the center between the pivot points AS WELL as to check if the shock mounts also have the same as each other. This goes for ALL four corners. Do not center the steering rack by measuring to the rack housing, measure to the center of the racecar, again some designers have offset the rack therefore your slide-in steering locks may have two different lenghts. Now remove the Spring and Shock unit, you can use a drill press and a bathroom scale to check the spring tension, maximum difference from left to right may NOT exceed 10 pounds, the two rears are one reading while the two fronts will be another reading. Understand that a sticky tire wants a stiff rate while a hard tire wants a soft rate. The shocks should go to a test shop, but if your funds are tight you can close the shock and pull it open, if the left and right feel the same, you can take an educated chance on them being matched, not front to back but left to right. If you do not have a level spot to do your alignment you will need to use boards to level the area under the racecar. measure from pick-up pivot point to the level floor Adjust chassis to level now check the rear if those pick-up points are not level you have a bent frame and you cannot go fast with a frame that is different from one side to the other. You must get the frame straightened. A shop that has a level work table will be able to reset the frame and many times you do not need to strip the chassis. Once you have a level frame install ride height blocks, one can be different from the other, keep the frame level. This is a good time to check the trueness of the rims. Without the spring/shock units you can lift the wheel and place a block under the A-arm and spin the wheel, use a square with a vise-grip clamped to the square and place it very close to the rim, spin the wheel and check to see if the rim moves in/out or up/down, if the wheel is not true it will ruin the alignment; some shops use a square aluminum plate but I have never seen a racecar on track with these plates as wheels. The rims must be checked for trueness, do it now. While setting the ride height blocks understand that you  need the rear to be higher then the front, maybe 3/8 of an inch. If the back is too high the racecar will oversteer, you can lower the racecar a small amount to correct the oversteer. (Oversteer is when you hit the wall with the back of the racecar, understeer is when you hit the wall with the front of the racecar). This is a good time to check all the rod ends for wear, replace any with even a small amount of play as you are not as strong as the forces racing puts on them also never use a product with petro-dist, as that is what eats up the teflon in the rod-ends. Now you need to set the toe; Using the center marks you carefully marked on the chassis use a square to come straight up so you can measure out to another square you have outside each tire, make sure these squares are true and plum. Use any number you want, I use one meter as I like using metrics, I get crazy with 9/16 or 7/16 or 5/8, I like 16 or 17 or 18, just me. Once you have all four outter squares set, use a heavy item to tie a string from left front to left rear and right front to right rear. Next move the string evenly closer to the squares little at a time, when the string just barely touches the square, do the same to the other side, next you should check the overall measurement from left to right at the front and at the back, just to make sure you have to same numbers front and back. Now you are set to check and adjust the toe, measure from the string into the rim. The numbers need to show a small amount of toe-in BUT the numbers from one side Must be the same as the other side, including the steering links, each one must be the same as the other, I use slight toe-in both front and rear. Now is the time to checkand correct "Bump Steer" once you have the toecorreted lift the front tire, place a block under the tire and remeasure the toe numbers if they still show the front number larger then the rear nuber by the same amount as when the wheel was on the ground , you are set but if the number losses or gains you need to raise or lower the steering arm at the hub. The rear is just the reverse you need to remove Bumpsteer under braking when the rear of the racecar goes up, only this time all you need to do is lenghten or shorten the upper rod leading to the the hub. The force of the racecar going at speed causes the wheels to be forced outward (Zero Toe). The camber will be changed at the track according to track design or your style of driving, so set the camber at a number around one degree (4 mm per 13 inch). Caster is a help in turning the racecar to the apex but too much caster will wear you out (fast start/ slow at the end). After putting the spring/shock units back in place, adjust the spring platform until the racecar just clears the ride height blocks, this needs to be done with your weight in the seat as if you were in the racecar, yes alignments are better done with two people, next you need to set the the corner weights, the anti-roll bars must be disconnected, after the corner weights are set the Anti-roll bar links must be adjust so they can slip onto the anti-roll bar without bending or forcing. Time it takes? The first time about eight hours, longer if done by yourself, but what a difference in how fast you will go!

January 3, 2018 at 12:38 PM Flag Quote & Reply

Andrew graham
Member
Posts: 405
Great info as always Clyde keep it coming now I just have to find 1day a week to do it all
January 9, 2018 at 8:35 AM Flag Quote & Reply

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