Rim width 18.5R38 tires

16" is recommended rim with for that tire. I'll be watching this because I'm planning on running 18.4 - 34 on my 70 for tractor pulling they too need 16" rims.
 
I ran some 18.4x38 tires with 18.4" wide wheels with the theory I could run more air pressure and have less squatting under a load, hence loosing hitch height. The width was to get them to lay flatter and the air to hold it up AND stop any give at the center of the track surface. Seemed to work out. gm
 
Personally, I have had good luck with 18 inch wide rims and Firestone 18.4R38 tires with low air pressure. The footprint gets wider and longer - although the hitch height drops under load at the end of the track. This is all under 4 mph. However, I still want to hear from someone who uses 20 inch rims under the same conditions. Thanks.
 
18.4 - 38 on 16" rims are 68.9 inches in diameter. Our speed limit is 3.5 mph. My 70 in first gear with 15.5 - 38 are 61.8 inches in diameter. That extra 8 inches in diameter I'm afraid would make me go over the speed limit. The 18.4 - 34 on 16" rims are 65.1 inches in diameter which I believe would work out just fine. Of course I'm assuming it would at least any input is welcomed.
 
To finish my 70 in first gear with the 15.5 - 38 runs at 2.9 mph so tire diameter is a very important consideration.
 
Have you got enough HP to start it out at what ever throttle it takes to get 2.9 mph and as you get down the track and you can open it up to maintain 2.9 mph ?
 
You guys below are right about taking more air pressure to keep center of tire down with wider rim. Which also shortens your foot print.Bad. Also no matter how wide rim is you can't change how wide tread is. Tire company's spent a lot of time and money figuring out rim widths.
 
Plenty of power with new engine, start the pull just off idle then to full throttle out till the tires start to spin. Then start throttling back finishing the pull almost back at idle with frontend in the air.
 
I pull a farmstock IH 450 with 15.5 x38s (max for club rules) in 7,500-10,000 lb class. and have tractor balanced so that at the end of pull front end might get about 4" of air under tires the last 3 feet of pull.
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