jwill
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I'm curious about tire options and determining just how much overrun I have. I've tried to get the number from my dealer with no luck. Thanks.
What is the front/rear gear ratio on an m7040?
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ovrszd
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I've not saw that data posted. On my M9540 there appears to be very little. It doesn't act like it binds up when driving in a straight line in 4wd. My previous tractor was an L4400. It had considerable overrun and bound up instantly. You'd have to back up to get it unlocked sometimes. I've saw several posts on here from guys that changed tire sizes on the 7040. If you don't get much response you might start another thread about "changing M7040 tire size" or something catchy like that to get involvement.
ovrszd
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I'll try to quote this and someone can correct me if wrong. The standard tire on an M8540 is 11.2-24 and 16.9-30. The standard tire on an M9540 is 12.4-24 and 18.4-30.
I don't think you would have any issues if changing all four. But, I'm guessing here, I think you are wanting to increase front tire size only?? For me, I wouldn't want to go more than one tire size. Even then you are probably going to creat overrun that will increase front tire scuff and wear. You'll probably also creat what I described about my L4400. It was very hard to get out of 4wd if on solid footing. Any more than one tire size and I think you'd create a driveline stress problem.
Maybe try Google searching for tire specifications. If you could find the running diameter of your 9.5-24s and compare that to the running diameter of the 11.2 or 12.4 for example, you could calculate how much overrun you are going to create. If you do a search and learn anything, please post the data as others will be interested.
I'd like to have the Canadian or European style fronts on mine, they are metric sized. They are considerable wider but I think the same diameter. Might also be something for you to Google search.
Yep, I've thought about the european style fronts.
I've done a ton of calculating on this and how the numbers work, EXCEPT, I don't know the gear ratio of the tractor.
Ex, rolling circumference wise, 11.2-24 will increase the overrun approximately 4% over 9.5-24. If with 9.5-24 it was at 0 or 1% it would be fine, but not if it was already at 3 or 4%. So, that's my dilemma.
I've done a ton of calculating on this and how the numbers work, EXCEPT, I don't know the gear ratio of the tractor.
Ex, rolling circumference wise, 11.2-24 will increase the overrun approximately 4% over 9.5-24. If with 9.5-24 it was at 0 or 1% it would be fine, but not if it was already at 3 or 4%. So, that's my dilemma.
If you new your transmission gear ratios you could use a gear calculator to get close. Punch in your tire diameter, rpm at a given speed and your transmission, and the transfer case ratio would be your High/ low ratio.
Planet 4x4 - Gear and 4x4 Calculators
Planet 4x4 - Gear and 4x4 Calculators
sixdogs
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I did the swap with an M8950 and got the info from a tractor tire dealer and I believe he got the info from a Firestone book. Not sure but the tire dealer had a book and looked up my info. As well, Firestone had a whole batch of computational info online and it really helped.
This info is out there and either a tire dealer or Kubota itself have the #'s. Your dealer likely won't know since it's something he wouldn't ever need to know. You can also just type in info needed in Google and see what pops up. I swapped tires on my JD 5520 and I fould the info there first and then double checked it elsewhere.
I can't recall but think Kubota liked a 3-5% front tire "pull" advantage.
This info is out there and either a tire dealer or Kubota itself have the #'s. Your dealer likely won't know since it's something he wouldn't ever need to know. You can also just type in info needed in Google and see what pops up. I swapped tires on my JD 5520 and I fould the info there first and then double checked it elsewhere.
I can't recall but think Kubota liked a 3-5% front tire "pull" advantage.
sixdogs
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It's an old thread but I just found where Deere keeps it's front-rear axle ratio.
This ratio is where all the tire size plans should start.
Doesn't sound right but on the back of the seat?
OMSU41643
Now the search is on for Kubota info.
This ratio is where all the tire size plans should start.
Doesn't sound right but on the back of the seat?
OMSU41643
Now the search is on for Kubota info.
KenBike
Silver Member
I think the front tires are geared stock to be a few percentage faster then the rear. If you drive on fresh groomed sand I noticed my front always are slipping when looking at the tire imprint.
I did change my fronts about 4 years ago and did not have any issues except it was hard for gage power steering to turn the tires in heavy dirt.
Just swapped my 7040 for a 2018 7060 with the metric radials.
The after market tires I purchased ended up the same size as the new tractor. You can order tires and rims from Kubota for $2000. I paid Miller tire in Oh about $1900 for custom rims and tires shipped to my home. Very nice rims but BKT tires. I would get a quote from your dealer.
I did change my fronts about 4 years ago and did not have any issues except it was hard for gage power steering to turn the tires in heavy dirt.
Just swapped my 7040 for a 2018 7060 with the metric radials.
The after market tires I purchased ended up the same size as the new tractor. You can order tires and rims from Kubota for $2000. I paid Miller tire in Oh about $1900 for custom rims and tires shipped to my home. Very nice rims but BKT tires. I would get a quote from your dealer.
KenBike
Silver Member
Look in the tire area, just reopened my old thread on wider front tires, good luck.
sixdogs
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Here's another way of using the "front axle gear ratio" to compute the acceptable range of rolling circumferences for the M7040/M7060. Using the supplied ratio of 1.4383 provided by lakeridge and using this site here
Mounting Tires on Four Wheel Drive Tractors
this is what I came up with. Using the OEM 16.9-30's with a rolling circumference of 173", the OEM 9.25-24 fronts and 123 rolling circumference provide around a 2% lead.
A 1% lead would equal a 121.48 front tire rolling circumference.
2% " 122.69
3% " 123.89
4% " 125.09
5% " 126.29
So, the 9.25-245 is perfect as is the 20" OEM metric option in Canada and Europe . The 11.2-24 tires some have used as a front tire option are too big with their rolling circumference of 127.9 exceed the desired range of 2 to 5% with it's more than 7% "lead". If guys are using 11.2-24's and haven't had troubles yet, it must be because they are in 2WD a lot or in very soft dirt that lessens the damage. Really, the only two choices for the M7040/M7060 are the OEM 9.25-24 and the metric 3.20-20's and bias 12.4-20's. The rolling circumference is very close to OEM in these.
Anyway, that's what we have so far. For me, I have Firestone 16.9-30 radials on the rear now and plan to order the radial equivalent of the 9.5-24's for the front and live with it. That is, unless someone finds a lower priced maker of 20" wheels for the front. Then I would use the Europe/Canada metric OEM 320-20's choice and be happy with it.
Mounting Tires on Four Wheel Drive Tractors
this is what I came up with. Using the OEM 16.9-30's with a rolling circumference of 173", the OEM 9.25-24 fronts and 123 rolling circumference provide around a 2% lead.
A 1% lead would equal a 121.48 front tire rolling circumference.
2% " 122.69
3% " 123.89
4% " 125.09
5% " 126.29
So, the 9.25-245 is perfect as is the 20" OEM metric option in Canada and Europe . The 11.2-24 tires some have used as a front tire option are too big with their rolling circumference of 127.9 exceed the desired range of 2 to 5% with it's more than 7% "lead". If guys are using 11.2-24's and haven't had troubles yet, it must be because they are in 2WD a lot or in very soft dirt that lessens the damage. Really, the only two choices for the M7040/M7060 are the OEM 9.25-24 and the metric 3.20-20's and bias 12.4-20's. The rolling circumference is very close to OEM in these.
Anyway, that's what we have so far. For me, I have Firestone 16.9-30 radials on the rear now and plan to order the radial equivalent of the 9.5-24's for the front and live with it. That is, unless someone finds a lower priced maker of 20" wheels for the front. Then I would use the Europe/Canada metric OEM 320-20's choice and be happy with it.
Dave M7040
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My hard earned lesson with a new M7040 is to no longer trust the tires meet the standards shown on the sidewalls.
This will be important when trying to select a different size of tire as it is when buying tire chains.
I wanted R4 tires on my new tractor. Never gave it a second thought.
Tires put on by Kubota Canada for dealer were 16.9-28 TG-01 by MITAS.
About two years later, I order TRYGG studded tire chains for the rear wheels. The advertisement from TRYGG said no cutting or fitting necessary with this design.
When the chains came in and I started to install them they were too long. There was no way to get them to fit.
I complained right to TRYGG's head office in northern Europe. I received a reply within a day!.
They asked me to measure the height of my rear tires which was 52.625.
TRYGG provided the Tire and Rim Association specification for my size of tire which is 57.17".
Using the simple formula for circumference C=pi xDia my tire chains were 14-1/4" too long for the tires I was given with my new tractor.
Kubota ignored me. Ignored the destroyed right step ripped up by a loose tire chain.
TRYGG to the contrary were beyond belief in their response. "Bring your chains to our distributor in Canada and we will, at no charge, alter them to fit the tires you actually have."
I just finished installing the modified chains and they fit like a dream. I was traveling on paved and gravel roads today at 20+ kph with no problem.
I feel badly let down by Kubota. On the other hand TRYGG came to my rescue.
Dave M7040
This will be important when trying to select a different size of tire as it is when buying tire chains.
I wanted R4 tires on my new tractor. Never gave it a second thought.
Tires put on by Kubota Canada for dealer were 16.9-28 TG-01 by MITAS.
About two years later, I order TRYGG studded tire chains for the rear wheels. The advertisement from TRYGG said no cutting or fitting necessary with this design.
When the chains came in and I started to install them they were too long. There was no way to get them to fit.
I complained right to TRYGG's head office in northern Europe. I received a reply within a day!.
They asked me to measure the height of my rear tires which was 52.625.
TRYGG provided the Tire and Rim Association specification for my size of tire which is 57.17".
Using the simple formula for circumference C=pi xDia my tire chains were 14-1/4" too long for the tires I was given with my new tractor.
Kubota ignored me. Ignored the destroyed right step ripped up by a loose tire chain.
TRYGG to the contrary were beyond belief in their response. "Bring your chains to our distributor in Canada and we will, at no charge, alter them to fit the tires you actually have."
I just finished installing the modified chains and they fit like a dream. I was traveling on paved and gravel roads today at 20+ kph with no problem.
I feel badly let down by Kubota. On the other hand TRYGG came to my rescue.
Dave M7040
