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 | hdpkwy
Join Date: Oct 2003 Posts: 3 virginia 
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2003-10-31 67687
I am sizing tires for my L2850GST with worn turfs. Called my local dealer to get front/rear gear ratios. This may be a help to others out there: L2850GST w/original ag tires 1.566:1 ratio L2850 w/original turfs 1.644:1. Found that goodyear makes a "Super Traction Radial" 12.7x20 with size the same as my turfs,although expensive ($383 per tire). Firestone makes a front tire with the right rolling diameter for an aproximate 2% slip on the front tire. Please give feedback if this is an appropriate calculation. Go to Goodyear Ag to see the calculation.
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley 
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2003-11-01 67703
We sure have thrashed that subject out a number of times here. I tried to find the old threads in the archives but I can't recall the subject titles and came up with nothing. I'm about out of time this morning and I couldn't find the right place in the Goodyear site. Maybe somebody will have more luck or has better memory.
From the comment, I guess that the tractors have different gearing--either the two models or depending on which tires they come with but the latter doesn't sound very likely. The basics from what I remember require knowing the front to back final drive ratios. Knowing that and the rolling circumference of one pair of tires gives the horizontal distance traveled for one rotation of the tire. The drive ratio and rolling circumference of the tires on the other axle gives the distance the other tires would travel. Axle lead can be calculated from the two distances, and 2% front lead is typical. Some tractors tolerate a fair difference from spec and a dealer could advise. ....
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| hdpkwy
Join Date: Oct 2003 Posts: 3 virginia
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2003-11-01 67708
Here's the calc
((front tire circumference x front/rear ratio)/(rear tire circumference))x 100 = slippage in percent of front tire
if the number>1 front tires pulling
if the number<1 front tires being pushed
Also, Firestone makes a an I-3 tration implement tire for the 11x20 rims with the right circumference. Anyone used these on the rear of a tractor? The load range seems Ok (3700 lbs.) Thanks. ....
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 | Art White
Join Date: Jan 2000 Posts: 6898 Waterville New York
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2003-11-01 67726
What happens when you get into soft dirt? What is the casing diameter comparisons? Both are needed. the casing diameter is often more important in soft soil as the bars or tread height will be in the ground. ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2003-11-02 67777
I believe that Art threw that wrinkle in before and I forgot it. It's a good one.
Some manufacturers publish rolling circumference or diameter as part of their tire data. I don't know if they're taken from the casing, lugs or something in between.
I wonder what the best strategy is for choosing a tire set that isn't a factory set? I imagine most tractors tolerate the difference between up on the lugs or down on the casings fairly well but whether it's better to pick a tire that would give lead on the high side on the lugs or minimum lead on the casings seems like a decent question. It'd be easy to think that the ratio isn't as important in soft soil since the tires can slip easier, but you'd still get a lot of traction with big weight in the loader. Exceeding the recommended lead when up on the lugs on hard surfaces also doesn't seem like a good idea. Guess my turfs save me from pondering the question. ....
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 | DRankin
Join Date: Jan 2000 Posts: 5116 Northern Nevada
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2003-11-04 67969
I had the impression that the rolling circumference on R-1's represented the casing diameter and that the rolling circumference on all others was the actually tread diameter under a load. ....
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| hdpkwy
Join Date: Oct 2003 Posts: 3 virginia
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2003-11-04 68006
Wouldn't the distance travelled per revolution of a tire be the same in soft soil as the distance traveled on top of hard clay? Imagine that the tire starts at 12 o'clock,then rotates 360' back to 12 o'clock. The same distance of rubber material should pass the 12 o'clock position regardless of diameter deflection at the bottom. I will grant that there may be a few thousanths of stretch at the front nip point,but that should contract at the outgoing nip and may be insignificant on a tire that is 141" in rolling circumference??????? ....
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| DRankin
Join Date: Jan 2000 Posts: 5116 Northern Nevada
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2003-11-04 68008
If the fronts and rears are the same size, it would not matter.
What does skew the equation is the fact that the smaller front tires generally have the same cleat depth as the rears, so they "grow" on hard surfaces and "shrink" on soft surfaces all out of proportion to the rear tires.
So the manufacturer has to pick a surface to regulate the size ratio and in the case of R-1's it makes sense to set them up for mud. ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2003-11-05 68031
I see the conceptual problem. My explanation would be that horizontal distance is lost when lugs sink into the soil because the lugs travel a vertical distance from the surface down and then back up. ....
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