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SportTrac Discussion
Engine & Drivetrain
Tuning Help Pt. 2
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<blockquote data-quote="Dan Long" data-source="post: 731341" data-attributes="member: 65387"><p>The overall diameter of your tire will vary depending on how wide of a rim its on, how much tread is left and what tire it is. Even though the size calculations seem like they should be right, if you look at different tire specs for the same size, they can vary almost 1/2" between tires. </p><p></p><p></p><p></p><p>The best way is to do a rolling chalk test. On a flat, hard surface make a chalk mark on the tire tread. Roll the vehicle until the chalk leaves two marks on the ground, then measure between them. This will give you your actual rolling diameter of the tire with all the variables taken out, convert that to RPM's and your set. The only thing this doesn't account for is tire deflection from the centrifugal force, but its as close as you're gonna get.<img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite6" alt=":cool:" title="Cool :cool:" loading="lazy" data-shortname=":cool:" /></p></blockquote><p></p>
[QUOTE="Dan Long, post: 731341, member: 65387"] The overall diameter of your tire will vary depending on how wide of a rim its on, how much tread is left and what tire it is. Even though the size calculations seem like they should be right, if you look at different tire specs for the same size, they can vary almost 1/2" between tires. The best way is to do a rolling chalk test. On a flat, hard surface make a chalk mark on the tire tread. Roll the vehicle until the chalk leaves two marks on the ground, then measure between them. This will give you your actual rolling diameter of the tire with all the variables taken out, convert that to RPM's and your set. The only thing this doesn't account for is tire deflection from the centrifugal force, but its as close as you're gonna get.:cool: [/QUOTE]
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SportTrac Discussion
Engine & Drivetrain
Tuning Help Pt. 2
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