tire school

[gerard]

Can someone explain what the front and rear tire #'s refer to? I'm familiar with car tires but the #'s don't seem to translate. Also when buying rims is it as simple as insuring the # of bolt holes are equal or do you have to measure the spacing from center. ie Is there any commonality between manufacturers? Tires 101 would be appreciated. (I missed out on buying 4 new turfs mounted on rims for $400 at auction due to lack of knowledge !! Not much of a bargain if they don't fit!!)

 

[MChalkley]

The numbers on my tractor tires are 12-16.5NHS (front) and 19.5LR24 (rear). Front first: the 12 means the section width of the tire in inches. Sometimes this is the same as the tread width, usually it's a little wider. The 16.5 means the rim size is 16.5 inches in diameter. You also need to have the correct rim width, but you'd need the manufacturer's data sheet for the tire to find that out. The NHS means Non Highway Service, which means low speed only and sometimes, depending on the manufacturer, means skid steer use only, meaning the tires don't have the sidewall strength to allow use on a turning axle. Now for the rear: The 19.5, again, is the section width of the tire in inches. The L means low profile, meaning the ratio of height to width is lower than would be the case on a typical ag tire. The R means radial, as opposed to bias ply. The 24, again, is the rim diameter in inches.

Does this help? There are several types of dimensions on tires - if the ones you're speaking of are different, give us an example.

Mark

 

[Anonymous Poster]

To clarify a bit further, the first number is the section width of the tire measured "cheek-to-cheek" across the outside of the tire at the Top of the tire when the tractor is parked. It will be wider at the bottom due to the tire bulge. The tread width across the tread bars is always less because the sidewall bulges beyond the tread bars. The several numbers in the tire size designation depend on whether it is an R1 or other tire, a bias-ply, or a radial. They are all different. When thinking about a given tire size, it is safest to refer to a catalog from a tire manufacturer or the tables of the Tire and Rim Association to find out the exact dimensions and required rim size. Radial tires on your car or truck and on large farm tractors follow this scheme---Example: Typical car tire size 185/70R14 means the width of the tire is 185 mm, the ratio of the sidewall height to the section width is 70 per cent, R means radial, and it is on a 14 inch diameter rim. I know it seems screwy to have the first number in millimeters and the last number in inches, but that is the world standard way to designate radial tire sizes be it for cars, trucks, or tractors. Go Figgar.

 

[gerard]

That helps some. I'll have to check my tires when I get home and I'll post what they are as they seem to be missing a third #. I have R1's on an L2500. I guess what I'd like to know is the easiest way to figure out if a turf for example should have the exact same #'s as the Ags or do I just have to insure the ratio for the circumference front to rear is the same? (4wd)

 

[Anonymous Poster]

Typical bias ply R-1 (ag), R-4 (Industrial), and SOME turf tires only use 2 numbers, the first being the tire section width and the second being the rim diameter. From this alone you cannot determine what the outside diameter of the tire or the rolling circumference is. You must go to a tire catalog to look them up. Turf tires sometimes use this same designation, but more often they use 3 numbers such as 36x13.50-15. Here the numbers are 36 inch nominal outside diameter, 13.5" wide tire section width, and 15 inch rim. The essential requirement when considering changing tire sizes is to have the rolling circumference ratio be as close to the original as possible. This is the same as the gear ratio of the front axle speed to the rear axle speed that is built into the gear train that drives the front axle. To insure that you get this right, it is necessary to refer to the detailed catalogs from the tire manufacturers (Goodyear, etc.) or to the tables printed by the Tire and Rim Association.

 

[MChalkley]

Or, if for some reason you're considering changing all 4 tires, you can just make sure the ratio of front tire rolling circumference to rear tire rolling circumference stays the same.

Or, even easier, if you can get the number for the mechanical ratio between the front and rear axles for your tractor (i.e. the number of times the front axle turns for each turn of the rear axle), you can then multiply the rolling circumference of the front tires by this number and the result should be 0% to 3% greater than the rolling circumference of the rear tires. It must never be less, or you risk killing yourself and/or your tractor.

Mark

P.S. Jack - do I pass or fail? /w3tcompact/icons/smile.gif

 

[gordon]

Hold on guys I need to enroll in this school. For something as important as tires my knowledge is very very shallow. That what always worried me about switching brands and types. Lack of knowledge and trust in the tire salesman. Sorry to all the salesman out there I don't trust any of you not just tire salesman. Anything that might be commission related that is---and sorry saleswomen too.

Gordon

 

[Anonymous Poster]

P

 

[richh]

LOOKS LIKE TIRES MOVED ON ME. Mark did you get the info on where to get those michelin from?? I also posted the sizes of the fronts on buying a kabota, I think?? to many headings on here.


Rich

 

[MChalkley]

RichH - Yes, I got it. I thought I replied to the email message, but maybe not. Anyway: Thanks! I'm going to call them Monday. I'll let you know.

Yeah, you're right: there are two tire threads (at least) going on here.

Mark