i just put a set of new tires on my car, i went from 26" tall to 28" tallI have 3.55 rear gears with the 26" tall tire, the rpm is a littlelower with the 28" tall tires at say 60 mph. I know the rear gear set is still 3.55 but by putting the taller tires on would that be the same as changing the reargears to say 3.42 or 3.23. Would the performance difference be the same goingto 3.55 from 3.42 as going from 28" down to 26' tires or are these two differentanimals altogether, just wondering Wayne
RPM = (168 x final gear ratio x mph) / tire radiusUse this formula to see how much of an rpm drop you'll get from the taller tires.In one scenario I had 28" tires w/o od and 4.10 gears. I gained 5mph at the same rpm when I went to a 31" tire.In another scenario I had 28" tires w/ od and 3.42 gears. I increased 100-200rpm at the same speed when I changed to 3.73 gears. At low speeds (35) it's 90rpm while at higher speeds (75) it's 195rpm difference.It really helps if you can plug this stuff into a spread sheet to see what changes do to the rpm & speed.
Yes I agree, it is the same as changing gear ratios when changing tire size. There is some advantage to the taller tire in relation to tire contact patch.That is why a tall slick has an advantage over a shorter one.
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Yeah as mentioned you will only drop to a 3:42:1. If you have a Posi unit,and tires with the 28" it will be almost impossible to determine the difference. The real and tested way is to use your Tach. I would use that way and set the speed at 60MPH. Then just compare the differences. If your engines cam is coming into it's power range you probably won't notice the difference. If you really made a big tire like to 30"-32" I would really be concerned aboutthe difference in the RPM drop.If you have an O/D trans sometime the O/D will make it's last O/D into the higher gear at about that speed. But when all else fails go out and have fun and enjoy your Ride.Bob