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  1. #21
    Veteran Member rScotty's Avatar
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    Rural mountains - Colorado
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    Kubota M59, JD530, JD310SG. Restoring Yanmar YM165D

    Default Re: 336d tire size and other questions

    Quote Originally Posted by yanmars View Post
    I was at the farm today so I checked. They are 12.4 11-28. Bridgestones as I recall but did not check that.
    Hey, that's nice. Thanks for looking. And that size does match one of Yanmar's published specs - although as Aaron pointed out, there are a lot of YM336D tire & rim options that can be used with what is presumably the same internal F/R mechanical ratio.
    And it does make sense that the Rolling Circumference of a Bridgestone 12.4 11-28 would be very close to the rolling circumference of the other tire we know that Yanmar used: The Goodyear Field and Road 13.6/12 12-26. So it all adds up right.

    BTW, the titan Tire site has an easy to use automatic calculator for what we have been discussing as the front to rear 4wd ratio. Titan calls it the "lead-lag ratio", but it's just a different expression for the same thing. I checked their automatic calculator math against my own calculations and it is sufficiently correct.
    To use it go to: Lead Lag Calculator

    good luck beats good planning,
    rScotty
    Attached Thumbnails Attached Thumbnails 336d tire size and other questions-ym336-yanmars_back-jpg  

  2. #22
    Veteran Member Kernopelli's Avatar
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    Mitsubishi MTE2000D, Dig It 258 Backhoe Deere Z930A ZTR

    Default Re: 336d tire size and other questions

    I originally posted this in Parts and Repair but never got a real answer to my questions.

    My stock tires were 6.00-12 front, 8.3-24 rears. I mounted a set of 9.5-24's on the back and need to figure out the appropriate tire/rim size to keep the same F/R ratio.
    The 6.00-12 has a circumference of 68.3". The 8.3-24 has a circumference of 115". I divide the rear circumference by front and come up with 1.68 so I assume that gives me a 1.68:1 ratio.

    The new 9.5-24 has a circumference of 128", if I divide that by 1.68 I get 76" circumference for my "new" front tires I need to buy, which would translate to what looks like a 7.00-12 tire ( 24" mounted dia.) like this 42D382,42D382GY,titan TIRE CORPORATION,712 7-12 7X12,GOODYEAR DYNA TORQUE II R1 TL,Tires 4 That

    Am I figuring this correctly?
    Darryl

  3. #23
    Elite Member
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    gilmer tx
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    Bobcat CT235

    Default Re: 336d tire size and other questions

    I think you are figuring correctly.

  4. #24
    Super Star Member California's Avatar
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    Sonoma County
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    Yanmar YM240, and now just one YM186D

    Default Re: 336d tire size and other questions

    Quote Originally Posted by Kernopelli View Post
    I originally posted this in Parts and Repair but never got a real answer to my questions.

    My stock tires were 6.00-12 front, 8.3-24 rears. I mounted a set of 9.5-24's on the back and need to figure out the appropriate tire/rim size to keep the same F/R ratio.
    The 6.00-12 has a circumference of 68.3". The 8.3-24 has a circumference of 115". I divide the rear circumference by front and come up with 1.68 so I assume that gives me a 1.68:1 ratio.

    The new 9.5-24 has a circumference of 128", if I divide that by 1.68 I get 76" circumference for my "new" front tires I need to buy, which would translate to what looks like a 7.00-12 tire ( 24" mounted dia.) like this 42D382,42D382GY,titan TIRE CORPORATION,712 7-12 7X12,GOODYEAR DYNA TORQUE II R1 TL,Tires 4 That

    Am I figuring this correctly?
    A couple of minor points. I haven't read the preceding posts so I hope this is relevant:

    * My neighbor advised that for front tires with a loader that is used often, trailer tires with a lot of plies last much longer than ag tires. Looking in the world of trailer tires might give you a wider range of diameters to find a closer ratio match, assuming you have 2wd and don't need the ag tire's better traction.

    * You mentioned 6.00-12 front tires. Beware the difference between 6.00 x 12 and 6-12, respectively the left and right tires in the photo below that I posted in an old thread when someone asked if they are different. They obviously have very different rolling circumferences.


  5. #25
    Veteran Member rScotty's Avatar
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    Default Re: 336d tire size and other questions

    Quote Originally Posted by Kernopelli View Post
    I originally posted this in Parts and Repair but never got a real answer to my questions.

    My stock tires were 6.00-12 front, 8.3-24 rears. I mounted a set of 9.5-24's on the back and need to figure out the appropriate tire/rim size to keep the same F/R ratio.
    The 6.00-12 has a circumference of 68.3". The 8.3-24 has a circumference of 115". I divide the rear circumference by front and come up with 1.68 so I assume that gives me a 1.68:1 ratio.

    The new 9.5-24 has a circumference of 128", if I divide that by 1.68 I get 76" circumference for my "new" front tires I need to buy, which would translate to what looks like a 7.00-12 tire ( 24" mounted dia.) like this 42D382,42D382GY,titan TIRE CORPORATION,712 7-12 7X12,GOODYEAR DYNA TORQUE II R1 TL,Tires 4 That

    Am I figuring this correctly?
    You may be figuring it correctly or not. It sort of sounds like it is NOT correct. To tell for sure, we need to know how you measured the rolling circumference of the tire? I'm assuming that you know the difference between measuring the circumference of a circle and measuring the rolling circumference of a tire. They are not the same. However, most tire technical data sheets do list the rolling circumference. That is the circumfrential measurement that you need to be using. However, unless your tractor is very heavy or very light, the manufacturer's data for rolling circumference will be close enough for you to use.
    DO NOT USE ARITHMATIC CIRCULAR CIRCUMFERENCE. YOU NEED ROLLING CIRCUMFERENCE.
    rScotty

  6. #26
    Veteran Member Kernopelli's Avatar
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    Default Re: 336d tire size and other questions

    Thanks for the replies.

    California, thanks for mentioning the difference on 6.00x12 and 6-12 tires. The R1 thread is a must, I use my loader and am in muddy conditions quite a bit.

    RScotty, I used manufacturer listed RCI numbers for calculations.That being the case, does it look like I got it in the ballpark.
    Darryl

  7. #27
    Veteran Member rScotty's Avatar
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    Default Re: 336d tire size and other questions

    Quote Originally Posted by Kernopelli View Post
    Thanks for the replies.

    California, thanks for mentioning the difference on 6.00x12 and 6-12 tires. The R1 thread is a must, I use my loader and am in muddy conditions quite a bit.

    RScotty, I used manufacturer listed RCI numbers for calculations.That being the case, does it look like I got it in the ballpark.
    Darryl, I just don't know what to say. If you did use the manufacturers numbers for Rolling Circumference - which is abbreviated RC or sometimes RCI for Rolling Circumference Index, then your calculations are correct.

    But what makes me unsure is that in all your previous posts - including the one in Parts and Repair - you didn't mention RC at all. You said that you were using "circumference". Used alone that way, the word "circumference" typically means arithmatic circumference (pi times diameter).

    If you are confident that all your numbers are indeed rolling circumference throughout, then yes, the calculations are correct.

    Lets delve a littlle deeper into the "why" of ratio matching. You should think this through, because with lugged tires matching the front to rear ratio becomes more difficult. Think about it this way: with turf or industrial tires, the rolling circumference is about the same regardless of the soil type because the tires don't sink in. But with big lugs in mud, tires can sink in so far that using them in muddy versus hard soil affects the rolling circumference and therefore the ratio match.... a lot.

    Large construction machines and some offroad vehicles can have lug tires and work ok in sloppy soils with dry stretches inbetween because they are using a different additional way to protect the drivetrain from windup. Their designers know that a single ratio match doesn't cover all the bases,
    so those machines either have a fluid coupling in the driveshaft(s) or an additional center differential between the front and rear axles.

    But compact tractors don't have that extra layer of drivetrain protection. That's because they are simpler, and are derived from farm tractors which were nott originally built to carry loads in the first place. Compacts were built to PULL loads through sloppy soils with a 3pt hitch, not to carry weight out in front in a loader. PULLING loads allows for easy tire slippage, carrying loads does the opposite. When you put a loader on a tractor, you have to not only get the F/R ratio right, you have to pay attention to some other clues... It can work, but needs more operator input to use 4wd intelligently when the only protection for the entire drivetrain is in making the tires slip.

    So with lugged tires and a loader used in both muddy and hard surfaces, the important thing is not the ratio match so much as why you are trying to match the ratio in the first place. You are matching so that you can avoid windup in the drive train.

    Are you? Are you getting windup? If not, or if you are dealing with it, then you may already be OK. After all, you've had the new rears on for a few weeks now. How does it steer and how difficult is it to shift into and out of 4wd? Those are the clues to whether the ratio is close enough for use - especially in slippery conditions.
    If you suspect that the ratio is way out of whack, only use 4wd sparingly at low speed and just to get through the tough spots and then immediately shift back to 2wd when you get traction. If you do that religiously then tire slippage will protect the drive train no matter how far out the ratio is.
    rScotty
    Last edited by rScotty; 05-04-2018 at 08:57 AM.

  8. #28
    Veteran Member Kernopelli's Avatar
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    Default Re: 336d tire size and other questions

    Thanks rScotty. I'll give a little back story, I have had the larger 9.5-24's on for some time. Before I bought them, I knew it would cause me to go to a larger front tire eventually. The 6.00-12's that are still on the tractor were like new then and initially "worked" well enough that I could use 4wd all the time but they were obviously not ideal. They have worn quickly and the more they wear, the more evident the symptoms have become. The wind up and shift bind has now become unacceptable. It's forced me to start doing exactly what you describe: shifting in and out of 4wd to unload the drive train and using 2wd most of the time.....it's a pain to constantly shift in and out and more importantly, I don't want to break any hardparts!

    In my original post as well as here, I should have been more clear and wrongly used the terms circumference and rolling circumference interchangeably. My real question in all of this was since I didn't trust that I was using a correct mathematical process, I needed to know if it was correct or not? You have put my mind at ease, I REALLY appreciate your help!
    Darryl

  9. #29
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    Default Re: 336d tire size and other questions

    Quote Originally Posted by Kernopelli View Post
    I originally posted this in Parts and Repair but never got a real answer to my questions.

    My stock tires were 6.00-12 front, 8.3-24 rears. I mounted a set of 9.5-24's on the back and need to figure out the appropriate tire/rim size to keep the same F/R ratio.
    The 6.00-12 has a circumference of 68.3". The 8.3-24 has a circumference of 115". I divide the rear circumference by front and come up with 1.68 so I assume that gives me a 1.68:1 ratio.

    The new 9.5-24 has a circumference of 128", if I divide that by 1.68 I get 76" circumference for my "new" front tires I need to buy, which would translate to what looks like a 7.00-12 tire ( 24" mounted dia.) like this 42D382,42D382GY,titan TIRE CORPORATION,712 7-12 7X12,GOODYEAR DYNA TORQUE II R1 TL,Tires 4 That

    Am I figuring this correctly?
    Yep...

  10. #30
    New Member
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    Northville, NY
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    336D

    Default Re: 336d tire size and other questions

    Quote Originally Posted by normde2001 View Post
    Did you see post #6?
    yes that what I got.

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