18.4 x38 vs 18.4x42

DeltaRed · May 15, 2023

I have an oportunity to trade my 38 tires/rims for a set of 42. Both tires are about equal on tread. The 42s are radial. My 38 are plain bias.Would I be happy? Any real advantage?The 42 is comeing from a1586,going onto my 1456. One thing is certain,the taller rears will set the rear up so the tractor will set level.

Dieseltech · May 15, 2023

YES!! I'd take radials over bias for field work any day...

ADB-Ia · May 15, 2023

From a simple geometry perspective a 42 will put put more tire on the ground than a 38. And because of tire characteristics, the radial tire puts more tread on the ground than a bias ply tire. So you gain twice. Each gear will have a percentage speed gain that may have to be compensated for. Calculating - if tire profile is 12 inches for both tires it gives tire diameter of 62 inches for the 38's and 66 inches for the 42's. A smidge over 6% difference.

This post was edited by ADB-Ia on 05/15/2023 at 10:27 am.

Goose · May 15, 2023

Would that alter your ground speed to any degree? Just askin'.

sotxbill · May 15, 2023

On the internationals, that were know to shear the ring gear rivots?? We had to remove our duals to keep them running. Just wondering here.

BarnyardEngineering · May 15, 2023

(quoted from post at 08:18:48 05/15/23) Would that alter your ground speed to any degree? Just askin'.

Yes. Probably by around 5% just shootin' from the hip here.

18.4x42 is the same diameter as 20.8x38, so the tractor will be about as fast as it would be with 20.8's.

big tee · May 15, 2023

When I bought this 4630 from my Dad he had 24.5x32s and it was my planter tractor so I put on 18.4x38s--now my Son owns it and he put 18.4x 42s on it--Best it ever looked--finally sits level!!!---Tee

the tractor vet · May 15, 2023

Well taller tire will affect your power in every gear but it will also step up ground speed . when i went to 16.9x38's on my S/MTA plus along with upping the RPM Best make sure your hat is screwed on tight on the road , my road speed is around 28 MPH according to my one friend that was behind me in his pick up. . For ground speed while planting i am running less RPM or about 1/3 throttle in third gear for around 4.5 MPH. and this was clocked by a four wheeler , how accurate ?? it's what i have to work with .

18.4 x38 vs 18.4x42

DeltaRed

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Dieseltech

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ADB-Ia

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Goose

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sotxbill

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BarnyardEngineering

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big tee

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the tractor vet

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