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FarmallTom

18.4-38's vs 20.8-38's

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I know there’s been a number of tire discussions here in the past but, although I tried to search, I didn’t see one that specifically addressed my question.

I’ve been looking at a few different machines as a possible replacement for my 1466. (Hoping to upgrade a bit)

Most that I have looked at so far have 20.8-38 rears...

Now - I don’t mind the look of the 20.8’s but, being a wider tire, I’m not altogether sure that they would actually “hook up” or put power to the ground any better than a good set of 18.4 Firestone radials..

Anyone have any real-life practical experience in comparing results between 18.4-38’s  &  20.8-38’s?

Opinions..?

 

TIA

 

FT

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If you're comparing 18.4 radials to bias 20.8, then you're probably right.

The benefit there is if the tractor already has 16" rims you won't need to buy new rims for the larger tires.

If the tractor already has 20.8's on it and needs tires, I would just upgrade to 20.8 radials. I wouldn't screw around trying to downsize.

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3 minutes ago, Matt Kirsch said:

If you're comparing 18.4 radials to bias 20.8, then you're probably right.

The benefit there is if the tractor already has 16" rims you won't need to buy new rims for the larger tires.

If the tractor already has 20.8's on it and needs tires, I would just upgrade to 20.8 radials. I wouldn't screw around trying to downsize.

Well, there are a few reasons I've been kicking this around..

* This tractor will have to serve year-round duty and will need to wear chains in the Winter for blowing snow. Since both my sets of chains are for 18.4-38's, changing to larger tires would necessitate buying different chains or trying to lengthen my old ones.

* Both my sets of duals are 18.4's so if the eventual new machine doesn't come with a set, I'd have to buy those too.

* A quick Google search of tire prices appears to indicate that a person could probably buy new rims and 18.4 tires for the price of the 20.8's.

 

It's just speculation at this point since I haven't found or decided on any specific machine.

The tire issue is something I have kind'a wondered about for a while but now have a more vested interest in.

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Since going to no-till years ago, we've made the switch from 18.4-38's to 20.8-38's on three of our tractors.  The first was Dad's 1066.  We changed those because we needed more ground clearance when lifting the 15' 5400 soybean special drill at the ends of the rows.  On 18.4's, the packer wheels & arms would drag when turning.  20.8's lifted the tractor up enough to eliminate the dragging.

My 1256 was upgraded about two years ago.  It pulls the corn planter in the spring.  Really had no reason to, other than Dad thought it would look good.  He was right, we like how it looks & performs.

The 1456 was done last fall, simply because a 1456 on 18.4's looks silly next to a 1256 on 20.8's.

 

Since we don't do tillage, we don't need duals, so all the 18.4 duals are rolled up n the shed.  Haven't acquired any 20.8 duals, since we don't have a need.  Everything seems to perform just like it did with 18.4's.

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You get a lot of Road speed out of 20.8's.  I have used them mainly for that reason, and to gain draw bar height when pulling a manure spreader through snow.  Other than that, I'd never buy a set.  18.4 radials, are great.  20.8 radials, like you are seeing, are Expensive. The wider rims are expensive, and the larger front tires you should have to equal out the package, those cost more too. As do the tubes.   They look cool though.   I've noticed no difference in traction when running duals, 18.4 -20.8.  We do the same tillage jobs with one of each. Tire condition and weight seems to have more to do with it. Imo. 

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I would think this would mostly have to do with your soil type.   Here in IL heavy black...no way a 20.8 is any better.  If you have sandy or powdery stuff like those guys on here with the big tires and 20+ rear weights on a 1256 apparently have --  then maybe the 20.8s would help.   

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We  have three 1486's, two with 20.8s and one with 18.4s. The older one with 18.4s just seems to have a lot more guts and go than the other two, and the only difference is tire size.

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Matching 1486's one with 20.8 Firestones and one with 18.4 Firestones. The 20.8's will flat blow the doors off the 18.4's in every field application where traction is needed. The road speed is a major plus as well. 18.4 x 38's are only enough traction for an 18 foot field cultivator and 15 foot disk IMO. Sure see your point in being all set up for the 18.4's though.

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1 hour ago, INTERNATIONAL 1466 said:

Matching 1486's one with 20.8 Firestones and one with 18.4 Firestones. The 20.8's will flat blow the doors off the 18.4's in every field application where traction is needed. The road speed is a major plus as well. 18.4 x 38's are only enough traction for an 18 foot field cultivator and 15 foot disk IMO. Sure see your point in being all set up for the 18.4's though.

I have the same experience. My former 1466 with 20.8x38 radials would outpull my 5288 with 18.4x42 radials on a pull type implement. Not so much on a mounted one. But the 1466 had a lot more weight on the wheels. The 5488 I have now with 20.8x38 bias tires spins pretty bad on the pull type disc chisel. But I had a 5 shank DMI inline ripper on it a few days ago and it went pretty well. 

Depends on what horsepower tractor you are looking at. 

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We had a 4568 with 20.8s, much more traction than the Steiger with 18.4s that replaced it.  The versatile 835 also had 18.4s and lacked the traction.  All 3 weighed close, similar power.

john

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1 hour ago, FarmerFixEmUp said:

I have the same experience. My former 1466 with 20.8x38 radials would outpull my 5288 with 18.4x42 radials on a pull type implement. Not so much on a mounted one. But the 1466 had a lot more weight on the wheels. The 5488 I have now with 20.8x38 bias tires spins pretty bad on the pull type disc chisel. But I had a 5 shank DMI inline ripper on it a few days ago and it went pretty well. 

Depends on what horsepower tractor you are looking at. 

Some good points, especially on the horsepower, I think.

I’m mainly looking at 5288’s at this point.

 

FT

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What will you be pulling behind it for tillage equipment?

IMO a tractor over 170 HP needs bigger tires than 18.4x38's if it pulling something heavy. In our soil type here anyway. Or add some weight to the existing tires. My 1066 has 18.4x38 Firestone bias tires  and I have 4 sets of split weights on it. I pull a 21' Krause disc with it and a 24" 4800 field cultivator. 

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I got 18.4x38's on my 5288, they work but left a lot to be desired in the traction department.  We thought about 20.8's, but at the time it was the NH3 side dress tractor so that was out(20.8's on 30" rows on hills is a disaster) and it was quite the expense to go to 18.4x42's on both the main tires and duals, so just put new tires on and kept what was there.  I personally think 18.4x42's would have worked well here.  1456 has 20.8's on it........IMO I can see how IH had rear troubles on the 1466's, you slap on a set of those plus duals and some weights and you could do a lot more with the tractor than should be done.

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20.8x38 tires have a BIG footprint.  If you need tire on the ground they are a very good option.  They are high priced and I feel as they become less common will get even higher.  I switched my 5488 to 18.4x42.

bill

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20.8x38 are taller and wider than the 18.4x38.  Both the width and height add ground contact.  The difference is substantial.  I would run whatever is on the tractor before I replaced it.  A neighbor has 18.4x38 duals on a 4630 with 20.8x38 on the inside.  The duals don't touch when on hard ground but work in soft ground.

IMHO a 1066/1086/5088  should pull fine with 18.4x38 duals but anything bigger should run 20.8x38. 

Thx-Ace

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20.8 will pull a lot more than 18.4. Twenty five years experience with both sizes on like tractors.

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