Help with tire sizing

[Kernopelli]

My stock tires were 6.00-12 front, 8.3-24 rears. I mounted a set of 9.5-24's on the back and need to figure out the appropriate tire/rim size to keep the same F/R ratio.
The 6.00-12 has a circumference of 68.3". The 8.3-24 has a circumference of 115". I divide the rear circumference by front and come up with 1.68 so I assume that gives me a 1.68:1 ratio.

The new 9.5-24 has a circumference of 128", if I divide that by 1.68 I get 76" for my "new" front tire circumference, which would translate to what looks like a 7.00-12 tire ( 24" mounted dia.) like this 42D382,42D382GY,TITAN TIRE CORPORATION,712 7-12 7X12,GOODYEAR DYNA TORQUE II R1 TL,Tires 4 That

Am I figuring this correctly?

 

[ovrszd]

I cheat.

Google search is my friend.

tractor tire circumference comparison chart - Google Search

 

[Kernopelli]

Appreciate the response, I too subscribe to the GTS ( Google that stuff) philosophy. I had already checked out comparison charts, I just can't find anything on calculating front to rear drive ratios. If anyone could look at my original post and see if I am correct in my calculations, I'd sure appreciate it.

 

[rScotty]

My stock tires were 6.00-12 front, 8.3-24 rears. I mounted a set of 9.5-24's on the back and need to figure out the appropriate tire/rim size to keep the same F/R ratio.
The 6.00-12 has a circumference of 68.3". The 8.3-24 has a circumference of 115". I divide the rear circumference by front and come up with 1.68 so I assume that gives me a 1.68:1 ratio.

The new 9.5-24 has a circumference of 128", if I divide that by 1.68 I get 76" for my "new" front tire circumference, which would translate to what looks like a 7.00-12 tire ( 24" mounted dia.) like this 42D382,42D382GY,TITAN TIRE CORPORATION,712 7-12 7X12,GOODYEAR DYNA TORQUE II R1 TL,Tires 4 That

Am I figuring this correctly?

I can't tell from your descripition if you are figuring it out correctly or not. The number you want to match is called the "loaded rolling circumfernce". It is circumference measured on the ground as the distance covered in one tire revolution. It is different from from the arithmatic pi x diameter circumference.
rScotty

 

[pmsmechanic]

I can't tell from your descripition if you are figuring it out correctly or not. The number you want to match is called the "loaded rolling circumfernce". It is circumference measured on the ground as the distance covered in one tire revolution. It is different from from the arithmatic pi x diameter circumference.
rScotty

Just google "RCI chart" and look up which tires have the right circumference.

 

[Kernopelli]

Thanks for the help everyone. I think I already have the correct tire circumferences, my concerns are: Did I use the correct mathematical process to figure the stock front to rear ratio and consequently, did I use the correct process to find the new front tire circumference to keep the tractor's F/R drive ratio? I'll recap:

The stock tires had circumferences of F/68.3" , R/115". I divided 115 by 68.3 and come up with 1.68( F/R ratio of 1.68:1). What I need to know- Is this the correct way to figure my tractor's F/R drive ratio?

My new rear tire's circumference is 128". I divided 128" by the 1.68 ratio and come up with 76". To keep my correct F/R size ratio I figure I will need new front tires with a 76" circumference ( 7.00-12 tires). What I need to know-Is this the correct way to figure what size tires I need to buy to keep the tractor's F/R drive ratio?

 

[pmsmechanic]

The responses can be translated to mean "We don't know".

 

[ovrszd]

Sure. Go for it.