gear ratios
12-08-2002, 02:14 AM
#1
Senior Member
Thread Starter
Join Date: May 2002
Posts: 1,093
Likes: 0
Received 0 Likes
on
0 Posts
gear ratios
1) i was reading about gear ratios on howstuffworks.com they said that the number of teeth on the gears determines the ratio. ex) one gear has 60 teeth, another has 20, so the ratio is 3:1. how is that if they have the same diameter? hsw.com said that since the number of teeth determine the ratio, slight imperfections in diameter can be ignored. maybe i'm just not getting the concept. i was always under the impression that diameter determines the ratio.
2) i was looking at the gear set that k-spec sells and comparing the ratios to that of my tranny. how do i read the ratios? i realize that if it says 4.12 (as in the final gear that k-spec sells), that it's 4.12:1, but how does that compare to 4.20 or whatever? i think i've heard that the higher the number, the shorter the gearing is for final gears. is this true for the other 6 (5 forward + reverse) gears? where as the higher the number, the shorther the gear.
2) i was looking at the gear set that k-spec sells and comparing the ratios to that of my tranny. how do i read the ratios? i realize that if it says 4.12 (as in the final gear that k-spec sells), that it's 4.12:1, but how does that compare to 4.20 or whatever? i think i've heard that the higher the number, the shorter the gearing is for final gears. is this true for the other 6 (5 forward + reverse) gears? where as the higher the number, the shorther the gear.
12-08-2002, 02:49 AM
#2
Senior Member
Join Date: May 2001
Posts: 1,153
Likes: 0
Received 0 Likes
on
0 Posts
I might be a little wrong on his but.
For the gears, the higher the number the shorter it is, the lower the number the taller it is.
shorter = quick jump to redline
longer = long jump to redline.
http://smokemup.com/auto_math/mph_range2.php
You can go here, enter in all your information and see what the outcome will be.
Final gear ratio affect all the gears. It a quick way to add or subtract 5/10mph from all the gears.
For the gears, the higher the number the shorter it is, the lower the number the taller it is.
shorter = quick jump to redline
longer = long jump to redline.
http://smokemup.com/auto_math/mph_range2.php
You can go here, enter in all your information and see what the outcome will be.
Final gear ratio affect all the gears. It a quick way to add or subtract 5/10mph from all the gears.
12-09-2002, 12:41 AM
#3
Member
Join Date: Apr 2002
Location: Harrisburg Pa
Posts: 54
Likes: 0
Received 0 Likes
on
0 Posts
Vehicle: 2000 Tiburon
2:1 is a taller gear ratio than 4:1.
The 2:1 ratio allows higher vehicle speeds at a given rpm, while 4:1 gives lower vehicle speeds at that same given rpm.
Turbulence: You're right about the 60 teeth:20 teeth being 3:1... but switch the two gears around and you get 1:3.
If you know the ratios of the gears in your car's transmission and you know the final drive ratio, just add the ratio from any gear (1st through 4th/5th/6th depending on how many gears your car has) and add it to the final drive ratio.
So if your car has a final drive of 3.5:1;
And 3rd gear (for example) is 2.5:1, then the final gear ratio for 3rd gear is 6:1, which means that the tranmission input shaft will turn six times for every one revolution of the output shaft. Shadohh's right... changing the final drive
in your car will affect performance in all gears. Many cars that share drivetrains will use a taller final drive in a sedan model, but a shorter final drive in a sports car. This way, you get better acceleration without having to make serious modifications to the engine, but at the expense of added engine noise and lower fuel economy on the highway.
As far as the number of teeth and gear diameter, it's basically the diameters of the two gears that determines the ratio. But because only a certain number of teeth can be cut onto a gear, and the teeth all have to be the same size, then the number of teeth is a factor as well, because you can't change one (diameter or number of teeth) without the other changing as well.
If the gear with fewer teeth is driving a gear with more teeth, then the ratio is shorter, meaning lower road speeds, such as first or second gear.
If the gear with more teeth is driving a gear with fewer teeth, then the the ratio is taller, meaning higher road speeds, such as an overdrive gear.
The same applies to motorcycle/bicycle chains and sprockets. On your bike, big sprocket up front and small sprocket in back is the gear for high speeds, going downhill etc.
Small sprocket up front and big sprocket in back is for biking up a steep hill.
Sorry for the long post... I hope that's helpful in some way. smile.gif
[ December 09, 2002, 07:43 AM: Message edited by: stickshift ]
The 2:1 ratio allows higher vehicle speeds at a given rpm, while 4:1 gives lower vehicle speeds at that same given rpm.
Turbulence: You're right about the 60 teeth:20 teeth being 3:1... but switch the two gears around and you get 1:3.
If you know the ratios of the gears in your car's transmission and you know the final drive ratio, just add the ratio from any gear (1st through 4th/5th/6th depending on how many gears your car has) and add it to the final drive ratio.
So if your car has a final drive of 3.5:1;
And 3rd gear (for example) is 2.5:1, then the final gear ratio for 3rd gear is 6:1, which means that the tranmission input shaft will turn six times for every one revolution of the output shaft. Shadohh's right... changing the final drive
in your car will affect performance in all gears. Many cars that share drivetrains will use a taller final drive in a sedan model, but a shorter final drive in a sports car. This way, you get better acceleration without having to make serious modifications to the engine, but at the expense of added engine noise and lower fuel economy on the highway.
As far as the number of teeth and gear diameter, it's basically the diameters of the two gears that determines the ratio. But because only a certain number of teeth can be cut onto a gear, and the teeth all have to be the same size, then the number of teeth is a factor as well, because you can't change one (diameter or number of teeth) without the other changing as well.
If the gear with fewer teeth is driving a gear with more teeth, then the ratio is shorter, meaning lower road speeds, such as first or second gear.
If the gear with more teeth is driving a gear with fewer teeth, then the the ratio is taller, meaning higher road speeds, such as an overdrive gear.
The same applies to motorcycle/bicycle chains and sprockets. On your bike, big sprocket up front and small sprocket in back is the gear for high speeds, going downhill etc.
Small sprocket up front and big sprocket in back is for biking up a steep hill.
Sorry for the long post... I hope that's helpful in some way. smile.gif
[ December 09, 2002, 07:43 AM: Message edited by: stickshift ]