tire size vs. final gear ratio
- Thread starter gregz
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SSdoxie
Elite Member
Affects it on both styles transmission.
The tire size will not effect the gear ratio on gear drove tractors. It is a fixed ratio determined by the number of teeth on the gears.
It will however affect the final ratio through the effective ratio which determines torque, and the dynamic ratio which comes from the size of the tires.
I would assume the same for a hydro drive tractor.
If you want to calculate the effective ratio and dynamic ratio Google the formulers for it and they will come up.
It will however affect the final ratio through the effective ratio which determines torque, and the dynamic ratio which comes from the size of the tires.
I would assume the same for a hydro drive tractor.
If you want to calculate the effective ratio and dynamic ratio Google the formulers for it and they will come up.
Not sure what you are asking but the tire size affects your ground speed at a given engine rpm and gear. As for a hydro it will affect it the same way except you have infinitely variable speeds so your peddle position will vary to achieve the same speed.
greg_g
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The most important factor to consider when changing wheel/tire size on tractors with front drive assist - is rolling ratio. Lets say the factory fronts rotate 3 times for each single rotation of the rears. In 2WD the fronts are passive (not driven) so rolling ratio isn't critical. But when the front drive is engaged, there's now a mechanical front/rear coupling. You don't want one rotating faster than the other, or the coupling will suffer. Hence any chane in rolling diameter at one end must be matched proportionately at the other end
My concern is I am looking to buy another tractor with a loader. I found a 855 with mismatched tires
turf rear and r4 front. however both correct size. Is this any gearing issue causing wear and tear on the drive train
Owner been using it this way for years in 2 and 4wd
turf rear and r4 front. however both correct size. Is this any gearing issue causing wear and tear on the drive train
Owner been using it this way for years in 2 and 4wd
greg_g
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Both correct - IF they matched on all four corners. I personally wouldn't buy one like that. But if you're a gambler, which tire type would you outfit it with: R3 (turf) or R4 (industrial)? That way you'd only have to buy one set. If you want R1s however, you'll have to replace both sets. When making your decision, understand that making all four corners compatible could likely involve at least one set of new rims too
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greg_g
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Both correct - IF they matched on all four corners. I personally wouldn't buy one like that. But if you're a gambler, which tire type would you outfit it with: R3 (turf) or R4 (industrial)? That way you'd only have to buy one set. If you want R1s however, you'll have to replace both sets. When making your decision, understand that making all four corners compatible could likely involve at least one set of new rims too
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PCABE5
Platinum Member
My question is are the sizes appropriate for R3 or R4? What size front tire was used if it had R3's on the front when it was stock. I have seen some JD models have different size tires when you choose R3 vs R4 (example 25-14 vs 23-12).
Also not sure about your specific model but the mechanical 4wd usually spins faster at the front axle and it has a certain ratio it needs to be in for everything to be happy.
Wyobuckaroo
Platinum Member
Go to tractordata.com to look up info on the JD855.
On my JD855, the "33 inch rear turfs" and "23 inch front turfs" indeed do measure those diameters.
If the tires on the prospect you are looking at do measure those diameters, you should be OK.
I would think anyway....... Good luck
On my JD855, the "33 inch rear turfs" and "23 inch front turfs" indeed do measure those diameters.
If the tires on the prospect you are looking at do measure those diameters, you should be OK.
I would think anyway....... Good luck