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20.8-38, 18.4 42, or 20.8-42???

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farmerboy

09-21-2006 17:38:00

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Looking to get new tires on dad's 4840. It currently has 20.8-38s but we're hoping to upsize. Nows the time to switch sizes as we are also gonna buy duals so the only extra cost will be changing the original rims. I was wondering what people here think about these sizes.

The tractor will be hauling a 3500 gallon manure tanker up and down steep hills in SW Wisconsin. We have two farms about 5 miles apart so it will be pulling loads of manure between the two often.

The 4640 will be doing the same but it has a good set of 18.4-42s on it. They seem to be a good size but we supposedly could get better flotation and a slightly faster road speed with the 20.8s.

Thanks.

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farmerboy

09-23-2006 04:35:58

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Re: 20.8-38, 18.4 42, or 20.8-42??? in reply to farmerboy, 09-21-2006 17:38:00

Thanks for all the advice guys. I'll let you know what way we go.

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billyiron

09-22-2006 10:26:17

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Re: 20.8-38, 18.4 42, or 20.8-42??? in reply to farmerboy, 09-21-2006 17:38:00

we had 20-42s, and duals, on our 4840,we blew one axle housing,when we did it again the next year we went back to 20-38s didnt have any more trouble,,maybe just a fluke,,but something to consider,,,Id stay with the 38s,,,,my 2-cents,,,,billy

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Cliff Neubauer

09-22-2006 06:29:30

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Re: 20.8-38, 18.4 42, or 20.8-42??? in reply to farmerboy, 09-21-2006 17:38:00

Something to consider is that a 20.8 tire is not very good for row crop work because you can't get the inside tires in narrow enough for 60" centers (they will hit the cab first) and around here at least the 18.4x42's are going to increase the tractor's resale value over either of the other two sizes.

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evielboweviel

09-22-2006 03:19:10

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Re: 20.8-38, 18.4 42, or 20.8-42??? in reply to farmerboy, 09-21-2006 17:38:00

One place to look is here
Link
shows tire dimensions

20.8x42 are 76.2
18.4x42 are 73.1
20.8x38 are 72.2

you should decide what tire manufactor then look up his chart
Ron

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jddriver

09-21-2006 19:22:11

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Re: 20.8-38, 18.4 42, or 20.8-42??? in reply to farmerboy, 09-21-2006 17:38:00

In our experence The taller the tire the less compaction and better traction you get,you also get more lugs on the ground at one time.The extra width would be nice also.What brand are you going to go with?Steve

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Duke Denning

09-21-2006 19:15:48

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Re: 20.8-38, 18.4 42, or 20.8-42??? in reply to farmerboy, 09-21-2006 17:38:00

Well, if cost is of minor consideration, I'd certainly opt for 20.8-42's with the new rims they would require...especially on this pretty high-powered 2 wheel drive tractor. This will bring improved traction, higher speed and floatation. You will notice a little loss of power in each speed, but with power shift that's no serious problem.....bumping up or down 1 speed is no trouble.

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Jonfarmer

09-21-2006 18:16:18

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Re: 20.8-38, 18.4 42, or 20.8-42??? in reply to farmerboy, 09-21-2006 17:38:00

You would get a faster road speed out of taller tires, not from the width, in other words the 42" would be faster than the 38". You will also gain 2" of drawbar clearance with the 42's over the 38's. The wider the tire, the better the floatation, which is better for soft conditions. I guess I would stick with the 20.8 width since a 4840 has alot of power, and it would be nice to have tires wide enough to be able to get the power to the ground effectivly.

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farmerboy

09-21-2006 19:09:13

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Re: 20.8-38, 18.4 42, or 20.8-42??? in reply to Jonfarmer, 09-21-2006 18:16:18

I thought that too but the tire guy says a 20.8 38 and a 18.4 42 has the same total height. I don't know so who am I to doubt him? Must be in the sidewall. He says the same as you about width and power to the ground.

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Old Pokey

09-21-2006 20:15:32

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They are.... in reply to farmerboy, 09-21-2006 19:09:13

If I knew how to post a picture onhere, I'd go take one of our tractors. I have a 4840 with 18.4x42s, and a 5488 with 20.8x38. They are excactly the same height. That is, the 20.8s are firestone 23 degees, and the 18.4s are Titans.

Personally, I have ran 4840s with all three sizes you mention. For a work tractor, the smaller ones go a lot better for the powershift between 4th and 5th. The 20.8x42 arejust too tall to pull 5th, but too short to work the implements in 4th. But for road travel, you'd be amazed mow much speed you increase. The back of the tractor will sit quite a bit higher with the bigger tires. Also, it will tire scrub more in gravel and want to push the front end if its slick with the 20.8x42s.

My 3.5 censt anyway.

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iowa_tire_guy

09-21-2006 20:11:50

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Re: 20.8-38, 18.4 42, or 20.8-42??? in reply to farmerboy, 09-21-2006 19:09:13

It is true that the 20.8-38 and 18.4-42 are the same diameter because the width of the tire affects the diameter. Which means that a 20.8-42 has a larger diameter than a 20.8-38. If you don't mind spending a little extra green and you want the most traction I would go for the 20.8-42.

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