just to add my into the equation, the engine is the muscle and speed to achieve that muscle. the transmission/rear end ratio is the Pulley and lever combo that determines at what point and how easily that force is applied. Hopefully im making sense here
You could possibly take that one step further and say: The engine is the muscle... The gears determine the speed that the muscle is used... I didn't think that one out very hard. It just popped into my head when I read your post. However, the gears do determine what rpm and how fast you get to the rpm that the power is used. I had 4.11s behind a built 302 and the car was always in power range. I put a stock 351 in place forward of the same wide ratio toploader and 4.11s. With the new engine it drove like a dumptruck! The engine could use each gear for 10' before needing to shift. (Not quite that bad, but almost!) Notice dumptrucks coming off a red light, sudden rpm, shift, sudden rpm, shift... etc All while you are moving forward still in first gear. That is how it was. I still like my first analogy, but this is food for thought. Dave
thats how my highboy was when i had the granny gear in it. again i think were saying the same thing in different ways. hopefully someone gains something from all this
The engine only makes torque available to the rear wheels. After that, the transmission and rear gear ratio multiplies the torque (but does not generate more HP) as a result. Why? the the gearing is non power productive unlike the engine. HP is a calculation number derived from the torque and rpm. HP = torque x rpm divided by 5252. What value is torque? The larger the motor displacment the more torque it is possible to make by passing more air thu the motor for conversion to torque. Any additional torque makes more pulling , speed and acceleration all possible. Excess torque is what makes it possible to accelerate at faster rates of time and distances. A small motor can run a car down the highway at 100 mph as well as a large motor but the place the two differ is under real loads of acceleration and loading etc. Bottom line is not to get only rapped up in HP numbers. HP may be usefull in certain applications such as running in a narrow rpm band at near peak hp but for overall street use, good torque numbers are the better consideration. Example: I just balooned a converter behind a little 280 cu /in motor but the application was the reason it happened. Pulling gross combined weights in the 11,500 lb range up steep hills quickly showed the converter could not take even the low torque of a small engine at those loadings. What this means is the gear muliplication is even important in how an application is used. The discussion about HP and torque must include application, motor size and many other parameters and be done with an open mind to the physics of the subject, then there becomes very little argument on the results when all understand. It's a science, not black art.
Not to resurrect a dead thread, but how does tire size play in this? Obviously everything needs to work together, but if you've got a decent performance gear for your engine (say 3.5ish for a 302) then how do you factor in the right tire size? *gets ready for a math lesson*
A taller tire takes longer to spin one revolution. If you like your gear ratio with one tire size, then go larger, it will be like you softenend the gear a bit. It will also make your speedo think you are going slower because the wheels are spinning less revolutions. If you go with a shorter tire, it will seem like you have a steeper gear. It will also show you are going faster on your speedo. The shorter tire won't get you a speeding ticket, but the taller tire can. There are several ratio calculators online that allow you to figure your tire size in. I am sure someone can point one out. Dave
a taller tire reduces the rear gear ratio. an example: (not mathematically accurate) you have a car running a 4.56 gear with a 9 x 28 in slick. you need a bigger tire due to spin, so you put 10 x 30 inch slicks on. to keep the same mechanical advantage in the car you might need to go to a 4.86 or 5.14 rear gear.
