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Old 05-16-2021, 08:05 AM   #8
Bored&Stroked
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Join Date: Jan 2011
Location: Central Ohio
Posts: 5,009
Default Re: Columbia rear ratios

It is important to consider the final overdrive ratio - given your tire sizes. I'm building a Columbia for my 32 with a 4.44 (because I have a very big cam in it and I'd like more low-speed acceleration). The OD ratio is 28%, so my final gear ratio will be 3.2. With this gear ratio and my tire size of 29.5" in the rear, it will be running about 2550 RPM at 70 MPH - which is just fine by me. If I started with 4.11 gears, the final ratio would be 2.96 - or 2360 RPM at 70 mph. Both of these RPM ranges are just fine for me and my style of driving.

Now - if I was going across the United States at 70 mph, then I might consider the 3.78 gears as my starting point - they'd drop the RPMs to 2177 . . . which would be about perfect for long distance driving - yet still give the car have enough acceleration from a standing stop to please the driver. It all comes down to what you want out of the car, where you plan to drive (and how much), etc..

Also, consider the whole package (like your brakes, suspension, steering, tire type, etc). I'm not sure I'd like to be traveling in my 32 Cabriolet at 70 mph for many hours at a time . . . even with all new suspension, Lincoln brakes, etc.. It could use some sway bars, it could use some seat belts, it could use a lot of things to make a long trip at 70 mph a more pleasant ride.
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