Switching drive tires on John Deere 7720 combine

Elky01 · Jan 17, 2017

I recently bought a John Deere 7720 prwd, it's set up with 18.4 42 duals in front, the rears are 16.9-26's. I need to switch to singles in the front but I'm not sure what size I need to run so that I don't hurt the prwd

JD Seller · Jan 17, 2017

The most common front tires would be a 30.5 x 32 tire. You also do not have to worry about gear ratios on the power rear axle as it is hydraulic driven. It just puts so much pressure/torque on the rear tires. It does not care about what the front tires are doing.

coonie minnie · Jan 17, 2017

Why are you looking to switch to singles?

We purchased a 9500 with 18.4 42 duals- it had some aftermarket setup called Kurcher, with big heavy centers. We wanted narrow tires because we harvest corn stalks, and wanted to eliminate the tires stepping
on the rows. And the duals were too wide to use with a 6 row head. So we just took the duals off, and run with an 18.4 42 single. We keep them aired up pretty good, and have no issues whatsoever. You would
think it would cut in pretty bad, but I think it leaves less of a footprint with the narrow tire! That might because it has radials instead of bias, too.

Elky01 · Jan 17, 2017

I'm looking to switch over because the 6 row head is about 4 inches too narrow for the combine and I run extremely wet ground so I need the flotation.

Mike N Mo · Jan 17, 2017

According to the Firestone website, a 480/80R42 radial All Traction 23* (replacement for 18.4R42) is 73" diameter, and the same tire in a
30.5R32 size is 71.6" diameter. Not exactly the same, but close. Just passing along some info for you.

Mike
Firestone 23 radial

Bob · Jan 17, 2017

Exactly.

4520BW · Jan 18, 2017

Not sure about the 7720 but we bought a 9600(cheap) with duals and could not use with a 6 row so we had to buy special rims because the final drives were different for duals.The new rims had to have a deeper offset. A tip on changing tires is go buy to long bolts the same thread as your lug bolts and make dowel bolt. The 9500 era combines came with a dowel from the factory.

coonie minnie · Jan 18, 2017

I have seen some duals that use a 15.5 tire on the outside to narrow the width.

I also think you would be surprised how little impact the 18.4 tires will have.

big tee · Jan 18, 2017

I did just the opposite 6-7 yrs. ago. I took 30.5s off and at the time all I could find were 18.4 straddle duals. It worked. We could have made a GOOD deal----Tee

Switching drive tires on John Deere 7720 combine

Elky01

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JD Seller

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coonie minnie

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Elky01

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Mike N Mo

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Bob

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4520BW

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coonie minnie

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big tee

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