New L5740, bigger tires, please check my math

[jc7]

I currently have a l5740, I am about to get a new one. I want bigger wider r4's.
proposed: r4' from m9540,(19.5-24) rear.
R4's from b2320 rear, for front,12-16.5

1. Will the wheels fit hubs

2. My math shows that aspect ratio is within 1.5%. With that margin going to bigger fronts, therefore I will error on the side of fronts pulling a little more vs. being pushed.

There is a huge $ difference if you have to order wheels and tires outside of Kubota, therefore trying to use what is in the system.
The tire set up is what I would prefer and will provide more ballast and width.

Please check my numbers,
Thanks
Jc

 

[jc7]

I currently have a l5740, I am about to get a new one. I want bigger wider r4's.
proposed: r4' from m9540,(19.5-24) rear.
R4's from b2320 rear, for front,12-16.5

1. Will the wheels fit hubs

2. My math shows that aspect ratio is within 1.5%. With that margin going to bigger fronts, therefore I will error on the side of fronts pulling a little more vs. being pushed.

There is a huge $ difference if you have to order wheels and tires outside of Kubota, therefore trying to use what is in the system.
The tire set up is what I would prefer and will provide more ballast and width.

Please check my numbers,
Thanks
Jc

Some more info for calculations and opinions, Thanks in advance.
factory wheel circumference:
L5740 Front r4- 92" Proposed tires circumference: Front r4-99"
Rear r4-145" Rear r4-154"

 

[greenrider1]

I tried doing the same thing when I ordered my L5740. Unfortunately, I could never get an answer on whether the 19.5-24 rears from a M9540 would fit, so I finally gave up and ordered my tractor with the factory tires. I have since learned that the rear rims off a M9540 will fit the L5740. I called a company that makes wheel spacers for tractors and was advised that the lug pattern and center hole are the same. I also found one to measure, and confirmed this. The MX5100 uses 12-16.5 on the front, and these will also swap over to an L5740.

Now for the math. The drive ratio for the L5740 (and several other L series) is 1.564, with 0-5% lead, which means you want the front tires turning slightly faster than the rears, or trying to pull the tractor when in 4 wheel drive. Here are the figures I found frolling circumferences for Titan tires. It seems the numbers vary slightly between different brands and models.

Tire size Rolling Circumference (Titan)

10-16.5 91" (L5740 front)
12-16.5 99" (MX5100 front)
17.5-24 145" (L5740 rear)
19.5-24 154" (M9540 rear)

145/1.564=92.71+5%=97.35 So the stock setup on the L5740 actually has a LAG condition with the factory R4's, since the 91" front tire is too small for the rear. Not good. 154/1.564=98.47+5%=103.39. The 99" front tire falls within this range. According to my math, the larger sizes you proposed would actually have a more favorable lead ratio as compared to the factory R4's.

I guess another way to calculate it would be 145/91=1.593, and 154/99=1.556. Hopefully someone else can chime in and check my math, and correct me if I'm wrong.

 

[jc7]

I tried doing the same thing when I ordered my L5740. Unfortunately, I could never get an answer on whether the 19.5-24 rears from a M9540 would fit, so I finally gave up and ordered my tractor with the factory tires. I have since learned that the rear rims off a M9540 will fit the L5740. I called a company that makes wheel spacers for tractors and was advised that the lug pattern and center hole are the same. I also found one to measure, and confirmed this. The MX5100 uses 12-16.5 on the front, and these will also swap over to an L5740.

Now for the math. The drive ratio for the L5740 (and several other L series) is 1.564, with 0-5% lead, which means you want the front tires turning slightly faster than the rears, or trying to pull the tractor when in 4 wheel drive. Here are the figures I found frolling circumferences for Titan tires. It seems the numbers vary slightly between different brands and models.

Tire size Rolling Circumference (Titan)

10-16.5 91" (L5740 front)
12-16.5 99" (MX5100 front)
17.5-24 145" (L5740 rear)
19.5-24 154" (M9540 rear)

145/1.564=92.71+5%=97.35 So the stock setup on the L5740 actually has a LAG condition with the factory R4's, since the 91" front tire is too small for the rear. Not good. 154/1.564=98.47+5%=103.39. The 99" front tire falls within this range. According to my math, the larger sizes you proposed would actually have a more favorable lead ratio as compared to the factory R4's.

I guess another way to calculate it would be 145/91=1.593, and 154/99=1.556. Hopefully someone else can chime in and check my math, and correct me if I'm wrong.

Thanks for the info. I was unable to find the gear ratio for a L5740. If it is 1.564, i found a formula in a tire site that lets you calculate the lead.
I, like you howeve,r have figured that the new tires would give the fronts marginally more speed, about 1.5% increase over stock. I really appreciate the info on the hubs fitting.
I am sure you probably encountered what i did when you tell the sales guy who is nice but definately not an engineer what you are proposing, Yu can see in his head he's thinking (Oh Boy).
I really believe this combo of tires makes more sense on the tractor for traction, ballast, and flotation, compared to stock, Don't forget how it looks.

Thanks again, if anyone else has any info or opinions, please fire away.
Jeff

 

[curtisfarmer]

I was told the M7040 was the biggest Kubota one could get with R4s. Check out the pics of my new machine I posted on the Buying forum.

 

[TripleR]

I was told the M7040 was the biggest Kubota one could get with R4s. Check out the pics of my new machine I posted on the Buying forum.

rjkobbeman has R4's on his M8540, but he hasn't posted in quite some time.

 

[greenrider1]

Already saw the pics. Those big R4's do look mean. My dealer originally offered to swap out the stockers for larger sizes, for minimal extra cost, however he couldn't guarantee the rears would fit the bolt circle/hubs. If I had known what I know now, I would have upgraded to the larger size. Are the rears on your M7040 19.5-24? Can't remember where I found the info, but that's the size listed for the M9540.

 

[greenrider1]

I definitely think the front tires (R4's) on the L series are way too small, and I'm not sure why Kubota would set these tractors up with a lag condition. I recall a post on here where someone upgraded just the front tires to 12-16.5's, and claimed the shifting in and out of 4 wheel drive was much easier and smoother. I might have to start driving on the roads so I can wear the stock tires out quicker, and then upgrade. Otherwise, I'll never be able to convince the wife I need bigger tires!:laughing: All I really need is a little wider front tire, so it doesn't sink into soft ground quite so bad while mowing.