Gear ratios and top speed relation? - TriStateTuners.com :: Home of Tristate Auto Enthusiast

pistoncup · 03-18-2012, 05:39 PM

Hey guys!,
I would like to know if somebody could help me in this one, I am playing with the nxgtr car performance simulator and trying to learn about gear ratios, so I added my RSX and see that the lowest the gear number (lets say 0.7 for 6th) the faster the car would run.

Then I change the Final Drive Ratio but I am not sure what gear is that and notice that if I go lower as in gears it actually reduce its top speed, seems the opposite I was expecting, and it even accelerates very slow, any input on this?

I have included a screenshot

rocknrace03 · 03-18-2012, 06:07 PM

think of your car as your bike from when you you were younger, your "final drive ratio" is like your front gear right at the pedals on your bike, the bigger the gear the harder you have to pedal to get going, but the faster you could go, imagine a 21 speed bike, if you were in 3 on the crank and 7 in the rear wheel it would be very hard to pedal, but you would reach your highest possible speed, but if you start in 1 up front and 1 in the rear you would be able to accelerate very quickly but not reach a very high over all speed. in your car you have your differential in the transmission. this would be your final drive ratio, this over all controls your overall speed in each gear, each gear is then geared to match the final drive so that you get good acceleration and high top speed while being economic, if your car was one speed it would just be like a single speed bike, hard to get going, and once you reach your top speed thats it. just like on your bike you can change the front gear (your differential) to make your same rear gears (transmission gears) into a shorter( more acceleration) or longer (top speed) gear ratio. or you can keep your same front gear on the bike (differential) and alter your transmission gears to make shorter or longer gear ratios, i don't know the mathematic equation but there is a formula for figuring out the transmission gear vs the differential gear for a final drive ratio.i hope this helps, and i hope it isn't confusing to you, just think about it the next time you ride your bike =]

pistoncup · 03-18-2012, 06:24 PM

I think I understand, however I have notice that there is a point that the car can not accelerate any more even if I change the gear ratio, it just gets a top speed when there is still plenty rpms to go, but you gave the idea.

By the way, funny thing but the car picture in your profile is the logo of that software, check at second 21 http://youtu.be/6UDeOs4Exj4?t=21s that headlights are unique.

rocknrace03 · 03-18-2012, 06:32 PM

thats funny, i guess thats cuz its a nissan NX, I'm not sure on the no more top speed, thing, maybe theres just no happy medium to have the car still accelerate while at a super high top speed, kinda like putting your car from 1st to 5th, you'll be able to drive, but it will barely accelerate, so there must be a point where its hard to make a ratio to allow you to keep accelerating even if the engine hasn't reached redline

03-18-2012, 05:39 PM	#1
pistoncup Noob-Jersey Join Date: Mar 2012 Member #22764 My Ride: It has 4 wheels iTrader: (0)	Gear ratios and top speed relation? Hey guys!, I would like to know if somebody could help me in this one, I am playing with the nxgtr car performance simulator and trying to learn about gear ratios, so I added my RSX and see that the lowest the gear number (lets say 0.7 for 6th) the faster the car would run. Then I change the Final Drive Ratio but I am not sure what gear is that and notice that if I go lower as in gears it actually reduce its top speed, seems the opposite I was expecting, and it even accelerates very slow, any input on this? I have included a screenshot

03-18-2012, 06:07 PM	#2
rocknrace03 Tri-State Post Whore Join Date: Sep 2010 Location: Schnecksville Pa Member #17593 My Ride: WRX iTrader: (2)	think of your car as your bike from when you you were younger, your "final drive ratio" is like your front gear right at the pedals on your bike, the bigger the gear the harder you have to pedal to get going, but the faster you could go, imagine a 21 speed bike, if you were in 3 on the crank and 7 in the rear wheel it would be very hard to pedal, but you would reach your highest possible speed, but if you start in 1 up front and 1 in the rear you would be able to accelerate very quickly but not reach a very high over all speed. in your car you have your differential in the transmission. this would be your final drive ratio, this over all controls your overall speed in each gear, each gear is then geared to match the final drive so that you get good acceleration and high top speed while being economic, if your car was one speed it would just be like a single speed bike, hard to get going, and once you reach your top speed thats it. just like on your bike you can change the front gear (your differential) to make your same rear gears (transmission gears) into a shorter( more acceleration) or longer (top speed) gear ratio. or you can keep your same front gear on the bike (differential) and alter your transmission gears to make shorter or longer gear ratios, i don't know the mathematic equation but there is a formula for figuring out the transmission gear vs the differential gear for a final drive ratio.i hope this helps, and i hope it isn't confusing to you, just think about it the next time you ride your bike =] Last edited by rocknrace03; 03-18-2012 at 06:10 PM.

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03-18-2012, 06:24 PM	#3
pistoncup Noob-Jersey Join Date: Mar 2012 Member #22764 My Ride: It has 4 wheels iTrader: (0)	I think I understand, however I have notice that there is a point that the car can not accelerate any more even if I change the gear ratio, it just gets a top speed when there is still plenty rpms to go, but you gave the idea. By the way, funny thing but the car picture in your profile is the logo of that software, check at second 21 http://youtu.be/6UDeOs4Exj4?t=21s that headlights are unique.

03-18-2012, 06:32 PM	#4
rocknrace03 Tri-State Post Whore Join Date: Sep 2010 Location: Schnecksville Pa Member #17593 My Ride: WRX iTrader: (2)	thats funny, i guess thats cuz its a nissan NX, I'm not sure on the no more top speed, thing, maybe theres just no happy medium to have the car still accelerate while at a super high top speed, kinda like putting your car from 1st to 5th, you'll be able to drive, but it will barely accelerate, so there must be a point where its hard to make a ratio to allow you to keep accelerating even if the engine hasn't reached redline