What is the purpose of a tire, generally speaking?
The wheel has gone through numerous changes since it was first invented. I don't know if early man ever used solid stone wheels on a cart or not but if so, those would have been a huge problem. If you hit a bad rut hard enough, the wheel might have split in two and that would have been the very first truly "flat tire". :sidelaugh: Jumping ahead to the 1900's when pneumatic tires competed against solid rubber tires, the companies such as Goodyear and Firestone were struggling with developing more suitable tire carcasses. Canvas was one of the early choices but it did not work all that well. Flat tires were so common that many cars came with two spare tires. So, here we are today and technological advancements have produced tires that are absolutely light years ahead of anything found on cars 100 years ago.
A tire is supposed to do several things. First of all, it is supposed to support the vehicle it is mounted on. It should be resistant to the elements such as water, sunlight, gas, oil and other chemicals that it might encounter. It should try to provide a decent ride for the passenger/s while giving excellent tractive capabilities to start and stop the vehicle. It should not lose contact with the rim at the bead when subjected to high speed turning or heavy side loading. It should have wear characteristics that will justify its cost.
Tires come in all types of "ratings". Some car tires are "speed rated" to show that they can withstand constant vehicle rates up to 200 MPH, as an example. Almost all tires are "Load Rated" to show how many pounds they can safely support when inflated to a certain pressure. Other tires are rated for environmental conditions such as "Mud & Snow" or "All Season Radial". Truck tires are rated for location on the vehicle such as "Steering Service" or "Trailer Service".
One of the things that often comes up when owners of LT's and GT's talk about tires, is ply rating. In truth, it is AIR that supports the vehicle, not the tire. The tire is simply a vessel that contains the air so it can support the vehicle. We pressurize air inside this vessel and we measure that pressure by a unit known as Pounds per square inch. On the heavy trucks I own, the tires are inflated to 90 PSI minimum and as much as 110 PSI. We do that to minimize the flexing of the sidewall of the tire. Flexing causes heat. Heat causes deterioration to the tire carcass and so does the flexing. The two combined will cause tire failure in short order. High pressures in tires call for a strong tire carcass to contain the air. Therefore, it is common for such tires to have a PLY RATING of 10, 12 or 14.
Another tire problem comes from a brutal environment, such as the one found in mining and quarrying operations. The tires used on those huge machines can have ply ratings in the 40's to protect against sharp rocks impacting the sidewall and tread areas.
So what does all of this mean to those who own a 1000 LB garden tractor? Our top speed is less than 15 MPH. We are driving on grass or in dirt. Carcass temperature is not an issue as it is for a Ferrari owner. With only 1000 LBS to support by four tires, we are talking about an average loading of 250 LBS. You can put that much weight into a construction wheelbarrow that has a single tire on it. The manufacturer of the tractor states in the Operator's Manual that it is OK to run as little as 8 PSI and as much as 15 PSI in the tires. Your automobile probably calls for 28 to 32 PSI by comparison.
On all garden tractors and lawn tractors produced by Colt, Case and Ingersoll, 2 ply tires were spec'd. Only the front tires on the 600 series had a 4 ply rating due to the front end loader being present. When it comes to low speed vehicles such as these tractors, sidewall flex is important when it comes to "ride quality" because the tractor is unsprung. The only "suspension" you have is the flexing of the sidewall. You should want to retain that flexing for another reason besides the comfort factor for your fat ass. Flexing often aids in finding traction because it will allow the carcass to conform to the ground and increase the size of the "contact patch". The contact patch is the total area the vehicle is riding on. This contact patch is what keeps your car from sliding off the road while negotiating a curve at 60 MPH. In relation to the size of the tire, the contact patch is small. If you over-inflate a tire, the contact patch is often reduced in size. If you under-inflate a tire, that too can sometimes reduce the size of the contact patch. But, it is a well-known fact that letting air out of tires when you are off-road in sand or other similar conditions can increase the size of the contact patch and get you out of trouble.
So..... what's the point to all of this, you ask? Well......to me it's simple. Stick with 2 ply tires front and rear on your tractor UNLESS there is an overwhelming reason to do otherwise. What might that overwhelming reason be?
- you need new rubber but you absolutely cannot find 2 ply tires anywhere in the size you need.
- you own a property that has nasty things growing on it that routinely cause flat tires and a higher ply rating will resist puncturing.
- you have modified the tractor in some way that has upped the loading on the tires to the point where going to a 4 ply or even 6 ply carcass is essential.
When it comes to ease in mounting, dismounting and inflating tubeless tires, the 2 ply is the hands-down winner. Try slipping a pair of 6 ply tires onto 8" rims and you are in for a struggle. Try removing those 6 ply tires later on and thoughts of cutting them off will spring to mind. If you put 6 ply tires on the rear of a 400 Series, they will support the tractor with almost no air pressure due to sidewall stiffness. The main reason to put air into them is to keep the bead seated on both sides. Yes...... there are some advantages to a higher ply rating but there are also disadvantages because that stiff tire carcass won't conform to the ground like a 2 ply carcass will. You need to add a huge amount of weight to the tractor to make that happen. Choose your tires well. Do not assume that a 4 ply or 6 ply tire is automatically superior to your 2 ply OEM tire. Case engineers could have spec'd any tire. They chose the best overall tire for the application and that's what you should focus on. :thumbsup:
The wheel has gone through numerous changes since it was first invented. I don't know if early man ever used solid stone wheels on a cart or not but if so, those would have been a huge problem. If you hit a bad rut hard enough, the wheel might have split in two and that would have been the very first truly "flat tire". :sidelaugh: Jumping ahead to the 1900's when pneumatic tires competed against solid rubber tires, the companies such as Goodyear and Firestone were struggling with developing more suitable tire carcasses. Canvas was one of the early choices but it did not work all that well. Flat tires were so common that many cars came with two spare tires. So, here we are today and technological advancements have produced tires that are absolutely light years ahead of anything found on cars 100 years ago.
A tire is supposed to do several things. First of all, it is supposed to support the vehicle it is mounted on. It should be resistant to the elements such as water, sunlight, gas, oil and other chemicals that it might encounter. It should try to provide a decent ride for the passenger/s while giving excellent tractive capabilities to start and stop the vehicle. It should not lose contact with the rim at the bead when subjected to high speed turning or heavy side loading. It should have wear characteristics that will justify its cost.
Tires come in all types of "ratings". Some car tires are "speed rated" to show that they can withstand constant vehicle rates up to 200 MPH, as an example. Almost all tires are "Load Rated" to show how many pounds they can safely support when inflated to a certain pressure. Other tires are rated for environmental conditions such as "Mud & Snow" or "All Season Radial". Truck tires are rated for location on the vehicle such as "Steering Service" or "Trailer Service".
One of the things that often comes up when owners of LT's and GT's talk about tires, is ply rating. In truth, it is AIR that supports the vehicle, not the tire. The tire is simply a vessel that contains the air so it can support the vehicle. We pressurize air inside this vessel and we measure that pressure by a unit known as Pounds per square inch. On the heavy trucks I own, the tires are inflated to 90 PSI minimum and as much as 110 PSI. We do that to minimize the flexing of the sidewall of the tire. Flexing causes heat. Heat causes deterioration to the tire carcass and so does the flexing. The two combined will cause tire failure in short order. High pressures in tires call for a strong tire carcass to contain the air. Therefore, it is common for such tires to have a PLY RATING of 10, 12 or 14.
Another tire problem comes from a brutal environment, such as the one found in mining and quarrying operations. The tires used on those huge machines can have ply ratings in the 40's to protect against sharp rocks impacting the sidewall and tread areas.
So what does all of this mean to those who own a 1000 LB garden tractor? Our top speed is less than 15 MPH. We are driving on grass or in dirt. Carcass temperature is not an issue as it is for a Ferrari owner. With only 1000 LBS to support by four tires, we are talking about an average loading of 250 LBS. You can put that much weight into a construction wheelbarrow that has a single tire on it. The manufacturer of the tractor states in the Operator's Manual that it is OK to run as little as 8 PSI and as much as 15 PSI in the tires. Your automobile probably calls for 28 to 32 PSI by comparison.
On all garden tractors and lawn tractors produced by Colt, Case and Ingersoll, 2 ply tires were spec'd. Only the front tires on the 600 series had a 4 ply rating due to the front end loader being present. When it comes to low speed vehicles such as these tractors, sidewall flex is important when it comes to "ride quality" because the tractor is unsprung. The only "suspension" you have is the flexing of the sidewall. You should want to retain that flexing for another reason besides the comfort factor for your fat ass. Flexing often aids in finding traction because it will allow the carcass to conform to the ground and increase the size of the "contact patch". The contact patch is the total area the vehicle is riding on. This contact patch is what keeps your car from sliding off the road while negotiating a curve at 60 MPH. In relation to the size of the tire, the contact patch is small. If you over-inflate a tire, the contact patch is often reduced in size. If you under-inflate a tire, that too can sometimes reduce the size of the contact patch. But, it is a well-known fact that letting air out of tires when you are off-road in sand or other similar conditions can increase the size of the contact patch and get you out of trouble.
So..... what's the point to all of this, you ask? Well......to me it's simple. Stick with 2 ply tires front and rear on your tractor UNLESS there is an overwhelming reason to do otherwise. What might that overwhelming reason be?
- you need new rubber but you absolutely cannot find 2 ply tires anywhere in the size you need.
- you own a property that has nasty things growing on it that routinely cause flat tires and a higher ply rating will resist puncturing.
- you have modified the tractor in some way that has upped the loading on the tires to the point where going to a 4 ply or even 6 ply carcass is essential.
When it comes to ease in mounting, dismounting and inflating tubeless tires, the 2 ply is the hands-down winner. Try slipping a pair of 6 ply tires onto 8" rims and you are in for a struggle. Try removing those 6 ply tires later on and thoughts of cutting them off will spring to mind. If you put 6 ply tires on the rear of a 400 Series, they will support the tractor with almost no air pressure due to sidewall stiffness. The main reason to put air into them is to keep the bead seated on both sides. Yes...... there are some advantages to a higher ply rating but there are also disadvantages because that stiff tire carcass won't conform to the ground like a 2 ply carcass will. You need to add a huge amount of weight to the tractor to make that happen. Choose your tires well. Do not assume that a 4 ply or 6 ply tire is automatically superior to your 2 ply OEM tire. Case engineers could have spec'd any tire. They chose the best overall tire for the application and that's what you should focus on. :thumbsup: