RC? from when the tractor was new

[olthumpa]

My L275 manual specifies 7-16 R1 front tires and 11.2-24 R1 rear tires.
It has alwayse had 12.4-24 R1 on the rear but has never had a binding problem in 4X4.

Currently has:
12.4-24 6ply R1 HI TRAC LUG TL on the rear
http://www.titanstore.com/info/48D614

7-16 6 ply R1 American Farmer tractor Lug on the front.
http://www.millertire.com/products/lawn-garden-tires/7-16/7-16-american-farmer-tractor-lug-6-ply/

1) Do you know why it would have came with 12.4-24 on the rear?
2) Shouldn't the RC be off?

 

[D2Cat]

Is your L275 4x4 or 2 wheel drive?

It makes a difference.

On the L305, for example, 2 wheel dr. has 5.50-16 on front and rears are 13.6-24. According to the specifications in the Operator's Manual it also came with 5.50-16 fronts and 12.4-24 rears.

Four Wheel drive had 8.3-16 front and 13.6-24 rears, or 7-16 front and 13.6-24 rears.

 

[olthumpa]

Is your L275 4x4 or 2 wheel drive?

It makes a difference.

Sorry I left that out. It is a 4x4.

 

[tiredguy]

I think what you're actually asking is what is the "ratio" front to rear.

RC is rolling circumference which is the distance the tire travels in inches to
make one complete revolution.
I went to the Titan-Goodyear company website and found the RC of your current tires there. Always use the tire brand manufactures specifications
NEVER assume that all sizes of tires are built to the same specifications.As
a general rule that major brands of farm tires made in the USA because they are OE ( original equipment ) suppliers they keep them pretty close so
back and forth whether new mfg or replacement market. So Firestone
Goodyear Titan if you compare them they're usually within the 2% rule below or closer. Tires made outside of the USA are usually not very close in size so it's buyer beware make sure of what you're getting.
The 7-16's have a rolling circumference of 89 inches.
The 12.4-24's have a rolling circumference of 137 inches.
To determine the ratio divide the RC of the front 89 by the rear RC 137
89 divided by 137=.6499 which rounds up to .65 or 65 that's the ratio.

If you change tire sizes for any reason such as R1 lugs to R4 industrial or R3
turf style treads you'll need to know the RC of each tire you're looking at and
do the math until you figure out which front and rear sizes that end up equal
to your 65 ratio. You must stay within 2% of the 65 in order for it not to cause you binding which can and will break parts usually starting with the front end gears which is a very costly repair. Now when I tell you 2% lets
get one thing clear from the start: 2% difference does not mean in the case
of using the 65 ratio of your tractor is NOT 63 or 67. You have to get the
answers from the calculations to figure it out but I'll show you now the proper
way to calculate it.
Example: 65 correct ratio and say you find tires that work out to 63 use this
formula 65 minus 63 equals 2 the divide 2 by 65 and the answer is .030 (3%)
and you need it to come out to .020 (2%)

It's that simple and if you use these formulas and stay within that 2% tolerance and your tractor and life will be good.
Al

 

[olthumpa]

Thank you for your response tiredguy.

I reread my original post and I see that I did not make it clear what information I was asking for.

My L275 manual and the info from TractorData both specifies the following tire sizes:
7-16 R1 front tires
11.2-24 R1 rear tires.

When the tractor was new in 1982 it came from the dealer with:
7-16 R1 4ply Bridgestone on the front
12.4-24 R1 6ply (Titan?) on the rear

This difference in tire size should have changed the factory determined RC ratio.

The tractor has never had a binding problem in 4X4 since it was new.
As long as the drive line in not under any stress or the tires are not slipping, the 4x4 can easily be engaged or disengaged, (while moving), in 1st through 6th gear. (I know that you are not supposed to do this)

I tore up the rear diff and locker about 4 years ago. Other than that, it has only been bearings, bushings, seals (in the front) and a clutch.

The tractor currently has:
7-16 6 ply R1 American Farmer tractor Lug on the front. (new in 2011)
12.4-24 6ply R1 HI TRAC LUG TL on the rear. (new in 2010 and new rims)
I got them from Central tire in Sanford Maine. http://centraltire.com/

As you stated, the ratio is 65 right now.
If it had the factory size of 11.2-24 with a RC of 130, (instead of the 12.4-24 with a RC of 137 that it came with), the ratio would be 68.46


Factory specs: 89 divided by 130= .6846 which rounds up to .69 or 69.
As delivered: 89 divided by 137= .6499 which rounds up to .65 or 65, if you round down it gets even worst.

According to the formula:
65 minus 69 equals -4
-4 divided by 65 equals -.0615 or a 6% difference. This is well outside of the 2% max yet I do not have a binding problem or a problem tearing up the drive line. (This is assuming I did the math correctly.)

My question should have been: does anyone know why, or have an explanation why I do not have a binding problems and destroying drive line parts with RC ratio that is so far out of specs?

Again,thanks for your time

Keith

 

[tiredguy]

Keith,
if it came from the factory with 7-16's and 12.4-24's and it's never had any
problems with binding then yes indeed you've figured it out correctly that the
ratio you need to maintain is the 69 ratio it was.
I've stated many times and you get the prize for observation that just because
the "book says X or Y or Z that it's not always the gospel. You did note and
did so in red that the sizes that were on it never cause any problems and all I
did was put the formulas out there which you used to verify where it's at with.

Now I will say the since you did figure it correctly just be sure and get the RC
of whatever brand you're looking at and do the math to confirm that they will
keep you withing that 2% window. Different brands are different sized and in
fact could be what that combination worked. I personally would be extremely
leery of some brands in particular the BKT brand as I've seen cases where the
sizes weren't even close to matching up with others, and I'm not so sure I'd
be willing to bet money ( losing costs big money plus then you still have to
buy another set of tires so it's double jeopardy) on what they show for RC.
As always "Buyer Beware" be sure if you do buy and install to immediately
do the measurements to verify rolling circumference.
Al

 

[olthumpa]

Thank you for the response tiredguy.

I do not need tires right now, front and rear are in good shape. This is just a question that I have wanted to ask for a very long time. The manuals say one thing and the tractor came equipped differently. I know that having different parts in older cars, truck and tractors did not always match the specs but I thought that they would have kept the final drive gear ratio and the RC ratio the same. Having not had a problem with binding or breakage, I just replaced the tires with the same RC ratio that it came with.

Again, thanks for your input.