Does the B8200 4WD have a lagging Front/Rear setup or negative slippage?

[superquiet]

I am a new owner of a used B8200. I have been reading online about tires and front to rear gear ratios. I read on page 14 in the goodyear handbook
http://www.goodyear.ca/tires/farm/pdf/GoodyearFarmHandbook_1.pdf that there should be a positive slippage of up to 5%, that the front tires should lead the rear tires. Mainly that the front tires should slightly pull relative to the rear tires.

Using the tire specs in the B8200 manual and calculating the front/rear gear ratio, I determined that the B8200 has a negative slippage. The rear tires are pushing instead of the front tires pulling. Is this correct and proper? My info is below.

I jacked up the right side and rotated the rear tire 20 turns.
The front tire rotated 31.75 turns
Front/Rear gear ratio = 31.75/20 = 1.588

I happen to have turf tires that match what is specified in the B8200 manual.
Front tire Turf = 24x8.5-12
Rear tire Turf =13.6-16

According to firestoneag.com the rolling circumference for the 24x8.5-12 is 70 inches and the 13.6-16 is 115 inches.

Firestone Agricultural Tire Division : Tire Details

Firestone Agricultural Tire Division : Tire Details

From what I've read the calculation is:
1.588 x (70/115) = 0.9667
(0.9667-1) x 100 = -3.3%
and supposedly a negative is bad (the rear tires are pushing).

My question is;
What is going on here? What am I missing in my understanding of this stuff?
Does all of this not apply to my tractor? If so is there another method for determine tire sizes when changing to a size other than what is specified in the owners manual?

Thanks for any input.
Perry

 

[Mike058]

Rather than take the rolling circumference from the book, try measuring it on the tractor. Mark the tires and see how far you travel in so many turns of the tire. Other than that, I'd say you're right. The front wheels aren't pulling you forward, the rear wheels are just shoving them across the turf.

 

[dodge man]

Wow you did a lot of work to figure that one out. Without checking your numbers, it looks like the math is sound. Usually the front should pull a little bit, but with your numbers, I'm not sure you'd notice the difference. The question I have is, how does the tractor handle? If it seems O.K., I wouldn't worry about it.

 

[KennyV]

My question is;
is there another method for determine tire sizes when changing to a size other than what is specified in the owners manual?


Perry

Well Perry it is a big deal if you do not have lead... as for how to determine the proper size see the attached .doc... This is from a rather lengthy discussion some years back.
BTW, I see this is your first post... Welcome to TBN. this can be a fun place. come back often. KennyV

 

[art]

From what I've seen the up to five percent max lead is right! Some manufacturers when they finally caught up with the rest with a gear drive front end actually tried 7 percent and of coarse wore out fronts like crazy.

Now about the -3.3, I don't perfer that but some manufacturers are lagging up to 6%!!!!

My favorite is about 3% lead! If you can drive the tractor on pavement and engage and disengage without trouble don't worry! If you do have trouble try changing your air pressure some to facilitate easy shifting and run with it. It's to late to redesign that tractor.

 

[pdowling1]

I'm with Art on this. Run the rears on the hard side & check on pavement for binding. It IS too late to adjust the gear ratio. You can also check the actual lead/lag by running straight on pavement in 2wd and again in 4wd. count wheel rotation front & rear both ways. This eliminates tire circumference as an uncertain variable.