GEAR RATIO?

[john_bud]

Rear tire diameter divided by the front tire diameter=front to rear ratio.

Hey BX1860, check your last thread you started. I just explained it all there.

Not true. Close, but off a bit.

The gear ratio of the front is higher (smaller number) that the rear as the front MUST spin the tires faster or drivetrain bind will occur. You want the tractor to be pulling with the front tires a weeee bit faster than the rear. About 5% is the target with an acceptable range of 3-7%. Some are out as far as 10%.

The generally accepted way is to put white shoe polish marks on the front and rear tires. Then in 2wd, go forward 10 rear tire revolutions dead straight. Repeat going the opposite direction. Write the number of front tire revolutions that were needed to equal the 10 rear tire revolutions.

Repeat that, but with the tractor in 4wd. You will get a number larger in 4wd than in 2wd. So, if it took 20 when in 2wd it would probably take 21 when in 4wd. That ratio of 21/20 is 105% or 5% over.

You can then use your math skills to determine the correct front tire size if you increase the rear so that you will maintain that 5% target over.

jb

 

[Sherweld]

One more resource.
TractorSmart home page > info > tire size matching

 

[Matt_Jr]

Not true. Close, but off a bit.

The gear ratio of the front is higher (smaller number) that the rear as the front MUST spin the tires faster or drivetrain bind will occur. You want the tractor to be pulling with the front tires a weeee bit faster than the rear. About 5% is the target with an acceptable range of 3-7%. Some are out as far as 10%.

The generally accepted way is to put white shoe polish marks on the front and rear tires. Then in 2wd, go forward 10 rear tire revolutions dead straight. Repeat going the opposite direction. Write the number of front tire revolutions that were needed to equal the 10 rear tire revolutions.

Repeat that, but with the tractor in 4wd. You will get a number larger in 4wd than in 2wd. So, if it took 20 when in 2wd it would probably take 21 when in 4wd. That ratio of 21/20 is 105% or 5% over.

You can then use your math skills to determine the correct front tire size if you increase the rear so that you will maintain that 5% target over.

jb

I understand that won't get you exact gear ratio's. You're completely correct and I agree with you. However if the only reason you want to know the gear ratio differences because you want to get a different tire size and keep them the same ratio this is the easiest and fastest way to make sure the tire size ratio is correct.