Tires Tire size question for dealers

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I am about to pull the trigger on a 2615. w/ag tires. My dealer is hesitant or doesn't know about my request to increase the tire size all around the machine. I told him I would gladly pay for the tires. It comes standard w/11.2 out back and I have requested 12.4's along with the increase in front tire size. Is this a feasible swap?

 

[LAWALLSTRACTOR]

I doubt it. I think you already know that you have to keep the front to rear tire circumference ratio the same, and it is hard to jump sizes and find proper sized tires to keep the ratio the same. I would keep the originals, that way there is no question about it being correct.

 

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Thank you very much for your response. I am trying to duplicate the size on the 3015 HST. It looks like the same body as on the 26. I realize that an hst gear ratio may be different than a regular geared tractor but if I can with keeping the 4wd balance, I'd still like to explore putting the 3015 tires on the 2615 as long as they clear the body of course.

 

[SPYDERLK]

I am about to pull the trigger on a 2615. w/ag tires. My dealer is hesitant or doesn't know about my request to increase the tire size all around the machine. I told him I would gladly pay for the tires. It comes standard w/11.2 out back and I have requested 12.4's along with the increase in front tire size. Is this a feasible swap?

I have done this on a smaller tractor with good results. It increased my lead ratio and made the tractor steer very nicely. However, that tractor did not have a loader so the fronts were more free to slip a little to keep the stresses down. I really would like to increase the lead % a little on my 7520. It seems to be about 0% now judging from the way the fr tires push when turning in 4wd, but I am afraid that stresses may go too hi when the tractor is heavily laden. You will need to do homework to make sure your lead is less than the allowed spec for the tractor. 5% is a max in the industry. Usual range is 1 to 3%. 0% is not good.
larry

 

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Thanks Spyder I know how to figure gear ratios for cars. Would you be so kind as to explain how to figure lead percentages?.

 

[Wombat125]

I could be very wrong here, but I don't think the front/rear ratio tolerances are nearly so tight as on a 4wd truck.

The JD 5103 4x4 comes standard with 13.6 x 28" R1's and you can up size to either 14.9 x 28 or 16.9 x 28. Each upsize is slightly taller in height as well as width. Regardless of the rear you select, the front tire stays at 9.5 x 24".

Deere uses Dana or Carraro MFWD axles in this application and I very much doubt they run different front axle gears based on tire size. When I speak to my dealer I will try to verify this theory.

I think spyderlk has some good advice about having the fronts override the rears just a scoash.

 

[SPYDERLK]

I could be very wrong here, but I don't think the front/rear ratio tolerances are nearly so tight as on a 4wd truck.

The JD 5103 4x4 comes standard with 13.6 x 28" R1's and you can up size to either 14.9 x 28 or 16.9 x 28. Each upsize is slightly taller in height as well as width. Regardless of the rear you select, the front tire stays at 9.5 x 24".

Deere uses Dana or Carraro MFWD axles in this application and I very much doubt they run different front axle gears based on tire size. When I speak to my dealer I will try to verify this theory.

I think spyderlk has some good advice about having the fronts override the rears just a scoash.

Is that an upsize done by JD? - if so maybe they change the front/back gearing ratio as part of it. No way I can see such a large bias to the rear without speeding up those little fronts, or else putting 11.2 width fronts on.
Please let us know what your dealer says.
larry

 

[Wombat125]

Is that an upsize done by JD?

Yup. It's a factory option right on the 'Build Your Own' link at deere.com/ag.

It's entirely possible that my theory is wrong; I'm pretty used to that. I guess they could might just use a different planetary gearset on the front hub. That would be a lot more fun than different ring & pinions.

I don't think they are changing the rear final drive ratio because the bigger tires give the tractor a higher published top speed.

Please let us know what your dealer says.

Definitely. Now I'm really curious. Even if the dealer doesn't know, I should have a factory service manual sometime next week.

 

[SPYDERLK]

Thanks Spyder I know how to figure gear ratios for cars. Would you be so kind as to explain how to figure lead percentages?.

Search on key words "lead/lag". In particular the thread Lead/lag ??? on Grand L series. There are some good links in there with info to prompt you in the right direction. There is really a lot to explain. One way to do it experimentally if you have the tractor. [Not a luxury you have I think.] Another way based on published tractor and tire spec. Tire specs, rolling circumference, are usually easy, but tractor gearing specs....? Getting info from Mahindra? - - I just dont know.
Check out the info on the forum and get back to us.
larry