# 16.9-38 vs 18.4-34 tires



## FarmerCline (Oct 12, 2011)

I'm looking at buying JD 6420 4wd with loader. My only concern with the tractor is that it has 16.9-38 rear tires instead of the 18.4-34s that you see on most 6420s. The neighbors 6420 which I have been using for the past year has 18.4-34s which seem to be a nice size for that tractor. I'm worried that I might not like the slightly taller but narrower 16.9-38s.....especially for loader work. Moving bandit bundles out of the field will be the main job for this tractor but will also likely mow and/or rake. When it's not in the hayfield the tractor will likely be used to pull a notill drill some and do odd and end jobs. Will the 16.9-38s okay for these uses? Will I have less traction?


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## Nate926 (Apr 6, 2014)

I have a inline baler so I like the 38"s over 34"s for extra windrow height. You may have to adjust you rake hitch height, but besides that I don't think you will notice a difference as far as traction. 16.9 make me think it might have been used in veggies in the past?


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## swmnhay (Jun 13, 2008)

The taller the tire the longer the foot print so my guess you would get about the same traction and floatation from the 16.9 tire.

Ditto on the extra clearance under the drawbar.I went from a tractor with 38's to 42's and a lot less issues with hay dragging under the draw bar.


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## Gearclash (Nov 25, 2010)

For your use I would rather have the 16.9-38. My #1 baler tractor has 14.9-46s. Get along fine other than the rougher ride.


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## glasswrongsize (Sep 15, 2015)

Comparing apples and apples; I have to assume, for ease of calculation, that the 16.9s and 18.4s are same brand, mounted on recommended width rim, and are of same style- as manufacturers vary on specs.

18.4x34 is 18.8" wide 65.4" diameter and has 279 square inches of ground contact

16.9x38 is 17.1" wide 66.6" diameter and has 235 square inches of ground contact

The 38 inch tire will move hitch up .6" from the 34 in tire's height...which is a fairly small amount; treadwear will move the hitch-to-ground relationship farther than that over the life of the tire.

The width of the tire and footprint can effect traction either way depending on soil condition/type. On harder/more compact soil, a smaller footprint tire will get more traction (as a general rule); on looser/softer soil, a wider tire will pull better. Ground compaction would be less with the 34s.

73, Mark


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## FarmerCline (Oct 12, 2011)

Okay, it sounds like I will be okay with the 16.9-38s then. I won't gain much in clearance under the tractor though since the two tires are almost the same height......I won't be baling with this tractor so that isn't a major concern. I was just worried that the narrower tire would be worse for compaction and flotation using the loader to move hay. This tractor has rack and pinion axles with the heavy cast centers which I like over the steel flanged wheel like the neighbors 6420 has......even with fluid in the tires it seems too light in the rear when using the loader.

Forgot to mention that it has 13.6-28 front tires matched with the 16.9-38s. The neighbors has 14.9-24 fronts with the 18.4-34s.


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## Orchard6 (Apr 30, 2014)

We have 2 6420's one 2wd with 18.4-34's and the other is mfwd with I think 18.4-38's. The taller tire on 4wd makes it a real dog in my opinion, I prefer the 34's myself.


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## FarmerCline (Oct 12, 2011)

Orchard6 said:


> We have 2 6420's one 2wd with 18.4-34's and the other is mfwd with I think 18.4-38's. The taller tire on 4wd makes it a real dog in my opinion, I prefer the 34's myself.


 I test drove a 6420 a while back with 18.4-38s and didn't like it.....I thought it was too much tire for that size of tractor. Now on my 7510 18.4-38s seem like a perfect size.


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## slowzuki (Mar 8, 2011)

I think if you live in a dry area the narrow tires will have better traction than wide. Here I prefer as wide as possible because its so wet.

Wide tires are not great if you don't have the weight to plant them for the soil conditions, they will just spin on top.


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