Gear Ratios

[fjxt3]

I'm still struggling with tire sizes for the 1510D. Does anyone know the actual gear ratios (final drive ratios) in the front and rear differentials of the 1510D? I've read through the discussions and I've read through the manuals that came with the tractor and I can't come up with the numbers.

 

[turnerbend]

Please enlighten me on why the gear ratios is so important when buying tires??

 

[dieselfuelonly]

Well, since his tractor is 4WD, I'm guessing it may be important because when in 4WD, the tractors are geared so that the smaller front tires turn faster than the larger rear tires so that both sets of tires (front and rear) pull along at the same speed, since the front tires would have to turn more times to keep up with the larger rear tires, right?

Sorry I can't be of much help, maybe ask Hoye Tractor?

 

[oliver28472]

Gear ratios and tire sizes come into play when the 4WD is engaged. Tires have to be sized properly so that when 4WD is engaged, the front and back tires pull at close to the same rate. Otherwise there would be more wear/binding on the gears. This really becomes obvious when you have your tractor in 4WD and make a sharp turn on dry pavement. The front tires travel a longer distance in a turn than the back tires.

 

[Mickey_Fx]

I'm sure I read somewhere the front tires actually turn a little faster (ground speed) than the rears.

 

[blackd]

IIRC, the difference should be within +-3% front to back. They almost never match up perfectly due to wear and replacement schedules.

 

[dieselfuelonly]

Yeah, when I say the same speed, I mean "close" to the same speed.

Sorry if I confused someone.

 

[fjxt3]

It's true. Everything that is said about 4WD and tire sizes, etc. Some in the industry have used 0% to 5% positive slip, some have used + or - 5%, some have used 3%. Regardless of which number you use, the actual final ratios are part of the slippage calculation. I have found a number of ways to estimate the ratios in the discussion groups along with a lot of discussion on the topic in general but I have yet to figure out what the real ratios are and I haven't yet been able to find anyone who knows. I really appreciate the responses and I'll post the answer if I find it.

 

[turnerbend]

Could you just put the manufacturer original spec sizes tires back on?

 

[fjxt3]

Came with "rice tires" 8-18 on the rear, 5-12 on the front. I want to replace them with something a little friendlier. Put 275/70R18 truck tires on the rear and 5.30-12 on the front. Seems OK as far as the ratios go. The 5.30-12 tires are still pretty narrow. I would like a bit more flotation. 8-18 and 5-12 ag tires are not an option. I think I will likely look for wider wheels. I had hoped to find tires without replacing the wheels. Local Les Schwab store can have wheels made but then the gear ratio becomes even more important.

 

[MJPetersen]

Maybe try this idea that I have. If you get the rolling circumference of the rice tires (front and rear) and put that in the form of a ratio that is your constant. Then whatever tires you choose for the rear you should be able to figure out the size that you need for the front. Or at least the rolling circumference.

For example Let's say that the rolling cir of the rear tires is 100 inches (I am guessing as my tractor is at church and I am home) and the front is 70 inches. Then our ratio of 100 to 70 or 10:7 that is the front would need to turn 10 times for 7 revolutions of the rear. Say you find a tire for the front that is 75 inches then you would need a rear tire of about 107 inches to keep the same ratio.

To my way of thinking then the most important ration is not the gears (although that would be sufficient), but rather the proper rolling circum ratio front to rear and that is what you need to maintain.

Of course all this may be moot as I know that Hoye and LMTC (and probably others too) have tires and I think conversion kits for these tractors to change to turf tires.

I am thinking out loud for my own use in the future.

What do you think of this idea.

Mike

 

[California]

What do you think of this idea.

I think you are on the right track, but doing this right will require some very careful work.

I looked in the parts manual for my tractor (not that same model) and there were four different transfer case gearsets for four different tire size combinations. Standard Rice Tires, Oversize Rears, Turf, and something else I think.

Given that these units might possibly be cobbled together out of dissimilar parts, I think it is necessary to start by counting the ratio of front revolutions to back revolutions. Maybe jack up one side of the tractor and revolve the front tire in 4x4 while counting revolutions at the rear.

Then calculate the tire circumferences needed to overdrive the front by about 3%, and try to find suitable tires to do this.

In this case theory may be irrelevant, due to an unexpected combination of parts. Maybe that's not even the same front axle that should be on that tractor. You don't want to destroy the front axle discovering this.

 

[irwin]

I went through this a while back with my Deere 770. see this..http://www.tractorbynet.com/forums/...0-770-mfwd-ratio-r4.html?highlight=mfwd+ratio

I was able to get the ratio from Deere, but before that I measured the tires on the tractor.

I marked the tire and the ground on very flat ground. Drove til rear wheel did three complete revolutions, measured and divided by three, did the same with front wheels. Divide front rolling diameter into rear and got the difference of the tires on the tractor, then i tried to find tires that would fit with the same ratio. I got close, actually the tires I found were the ones that worked properly after I got the proper ratio from Deere.