"Theoretically, you would get more power with smaller tires on, wouldnt you?"
With a smaller diameter tire, you'll accellerate faster, but limit your top end and RPM, as the smaller tire will make the gear ratio steeper geared. Heres a good example....
On my race car, I generally run a 30" radial slick. With the 3.73 gears, this makes an effective gear ratio of around 3.42. If I put a shorter tire on the back, for example, a 27" tire, it will make the gear ratio move up, for example, to a 3.60 or better. The car will accellerate and may in fact cross the 1000 ft mark faster with the 27" tire than the 30" tire,because the effective gearing is higher, but at the end of the track may actually be slower, because the gearing with the 27" tire has caused the car to hit the RPM limit, while the gearing with the 30" tire will still allow the car to accellerate without hitting the RPM limit.
heres another way to look at it....
at 55 mph, with a 30" tall tire, in 3rd gear, which would make for a 1: 1 gear ratio, and a 3.73 gear, we can find the cruise RPM would be 2,298 RPM
with the same combination, but with a 27" tall tire, the cruise RPM will be 2553 RPM, and will increase exponentially as the RPMs increase.
Lets try another one....a 185/75R14 ( stock baseline) compared to a 215/70R14 compared to a tire 2" shorter than a 185/75R14....1:1 transmission ratio in 3rd gear, and a constant of 3.23 for a final drive ratio....
at 55 mph, in 3rd gear (NOT overdrive)
2" shorter 23" tall 2595 RPM 207 RPM over stock
185/75R14 25" tall 2388 RPM
215/70R14 25.9" tall 2305 RPM 83 RPM under stock
at 75 mph, in 3rd gear
2" shorter 23" tall 3539 RPM 283 RPM over stock
185/75R14 25" tall 3256 RPM
215/70R14 25.9" tall 3143 RPM 113 RPM under stock
We can see by this that the RPM will increase or decrease exponentially with increases or decreases in speed.
So, by varying tire height, we can change final drive gearing without changing the gears themselves, and either gain low end response, or top end speed.
Will it make a huge difference on a FWD Olds? I imagine there will be a "seat of the pants" difference, but it will all depend on how much of a tire diameter change is made....
Oh, and for those wondering, switching from a 185/75R14 to a 215/70R14 will net the following results....
the speedometer will be 3.7% slower...at 60 mph you'll actually be going 62.2 mph..
Hope this helps clear some things up
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Shawn's Auto Repair and Performance, SW Wis.
www.shawnsautorepair.procarcarezone.com
69 Olds Cutlass S
70 Olds Vista Cruiser Wagon
72 Olds Cutlass S, 12:1 470 stroker, JM40 solid lifter cam, TH400, 3500 10" PTC stall, 4.11 posi
74 442 455/TH350
79 Cutlass 455/TH375 sleeper
'97 GMC Sierra Ext Cab 9" lift w/ 37's