TN75 questions on R4 tire sizes

   / TN75 questions on R4 tire sizes #1  

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Member
Joined
Jan 1, 2013
Messages
33
Location
albertlea, mn
Tractor
new holland tn75
does anybody else have a TN60,70 or 75 4x4 with the R4 tires? if so what are your front and back tires sizes.
the reason i ask is i bought my tractor with the tires that are on it (rear 16.9-28)(front15-19.5). and when in 4x4 you can tell there is a huge amount of drag. i did some measuring and it looks like it has an 8% lag.

Thanks in advance
 
   / TN75 questions on R4 tire sizes #2  
Not sure if there is a way to convert ag to R4, but here are the ag tires that came on it.

New Holland TN75 Tires:
Ag front: 7.50-16
Ag rear: 14.9-28
 
   / TN75 questions on R4 tire sizes #3  
Not sure if there is a way to convert ag to R4, but here are the ag tires that came on it.

New Holland TN75 Tires:
Ag front: 7.50-16
Ag rear: 14.9-28

That's one of many choices, not the only one and certainly not one at all for a 4WD tractor. A TN with 7.50x16 fronts is gonna be a 2WD tractor.
 
   / TN75 questions on R4 tire sizes #4  
I think the R-4 rears are 16.9x24 but not 100% sure.
 
   / TN75 questions on R4 tire sizes
  • Thread Starter
#5  
the 16.9-28 & 15-19.5 that are on my tractor are R4's and all the TN's i have come across have the ag tires on them. right now the front's are bald and the backs probably have 80% tread. is it possible that having bald tires on the front would give me 8% lag? i have checked and the tread depth on new front tires are .8, so new tires would give me an increased total height of 1.6". i don't think that is enough to get me out of a lag?
Rick, do you have any suggestions on how to determine how much bigger my front tires need to be or smaller back tires?

Thanks
 
   / TN75 questions on R4 tire sizes #6  
I have a tn75 4wd. The front tires are 10.5-20 and the rim is a W9-20. These are R4's. Currently I am using another set of galaxy turf tires....but these are the originals that I changed away from. Hope this helps.
 
   / TN75 questions on R4 tire sizes
  • Thread Starter
#7  
ironpen, what was the size of your rear tires?

Thanks
 
   / TN75 questions on R4 tire sizes #8  
16.9-24 with W14L-24 rims These are R4 as well. My tractor is a 2002 or 2003 TN 75S (with cab and Suspersteer) model. I don't know if they changed them in later years. What year is yours?? I go look in my operator's manual and see if there is any difference. I'll be back in a few minutes.
 
   / TN75 questions on R4 tire sizes #9  
My 2002 TN book calls for a -2% to -4% front rolling circumference lag for the supersteer and -1% to 4% lag for standard axles
 
   / TN75 questions on R4 tire sizes #10  
No difference in the tire sizes called for for supersteer and standard 4wd tractors. I have done some research based on a chart is my TN75 manual. As I understand it you have 16.9x28 (rather than 16.9x24 r4 tires on the rear. This gives a rolling circumference of 4508 millimeters (the chart is in millimeters). Based on that you would need front tires of 3350 to 3450 Millimeters circumference. Your current tires (apparently skid steer tires as best I can tell are 3112 millimeters.....so they are way to small. There are 25.4 millimeters/inch.....so that means you are around 12 inches too small on circumference. That's about 3.5 to 4 inches too small in diameter if you keep the current rear tires. If you go to 16.9x24 rear, then your current front tires would be ok. That's a much more expensive proposition of course. I hope this is not too confusing...let me know if it is.
 
 
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