Front/Rear 4WD Gear Ratio - Ford 1620

[Reg]

With Ag tires;
Front tire: 5.00-15
Rear tire: 9.5-24
O.E.

Hmmm, tough finding rolling circumference for something this small.
Even Firestoneag.com compact tractors doesn't have anything.
Firestone Agricultural Tire Division | Compact Tractor Tires
Firestone Agricultural Tire Division | Compact Tractor Tires
Doesn't include "Ford", only NH and goes back to TC models.

My previous mention of Goodyearag.com, goes off to the Titan site.
I havn't found their compact tractor tire area (yet).


Anyway, I was going to try and "back into" the front/rear ratio with the assumption that the rolling circumference of a 5.00-15 is 1.05 times that of a 9.5-24.
That would be "desirable" and Ag tires were probably the "design center".
Looking to each side of this... I doubt that it would be higher than 7% or lower than 3%.

FWIW, etc.

EDIT:
Titan info
http://www.titanstore.com/info/4T1335
http://www.titanstore.com/info/48D694

So it looks like 75:126 tire ratio ?

Ummmm, someone check my arithmetic;
IF there is a 5% lead (the unknown IF)
75/1.05 = 71.43

126/71.43 = 1.764

ANOTHER EDIT:
IF you can lay hands on a shop manual you MIGHT be able to find the number of teeth on the final drives.
I don't know where this is done on this particular tractor, i.e. you might have to take a ratio of transfer case output shaft speeds and multiply that by the ratio of differential ratios (yeah, THAT punctuation kinda makes it work).

 

[jdfire]

Let me know if the answer turns out to be 1.6:1

I ended up with a ratio of about 1.5875:1

 

[Reg]

I ended up with a ratio of about 1.5875:1

As we were told in lo skool; "Show your work, how you got the answer matters more than the answer"
(I showed you mine).
(-:
Seriously, how did you get to 1.5875 ?

 

[jdfire]

Seriously, how did you get to 1.5875 ?

I jacked up the right side of the tractor, put it in 4WD, marked the front and rear tires and counted revolutions. After 100 revolutions of the rear the front had rotated 158 7/8 times. Sorry for the typo, the number would actually be 1.58875.

 

[jdfire]

Further information:

Current turf tires:
Front 25x8.50-14 with a rolling circumference of 74 (per Titan and actual
measurement)
Rear 13.6-16 with a rolling circumference of 113 (per Titan)

The tire I contemplated using on the front was an R-4 that was 25x8.50-14 with a rolling circumference of 77.

Using the formula I referenced earlier the lead with the turf tires is about 4%
(74 x 1.58875) / 113 = 1.04

With a 77 inch rolling circumference the lead would be about 8.3%

(77 x 1.58875) / 113 = 1.0825

From what I've read a normal range for acceptable lead is 2-6% (or 3-5% depending on the source).

Based on this I decided to just replace the fronts with the same size tires for now.

 

[Reg]

Here is an irrelevant snippet;
I was talking to a guy today about his tractor's front tires.
He does ball fields, resurfacing & refinishing mostly, so it is just about all flat work.
They spread and level clay, do mower work, etc.
So BALD tires on the front make a lot of sense... I guess ???
They are racing slicks, he gets them at the track for FREE !
For him the more worn the better, better still if the sharp edges are gone and they usually are.

15 inch rims, but I don't know the width or section.
They looked to be about the same profile/proportions as turfs.

 

[Reg]

Further information:

Current turf tires:
Front 25x8.50-14 with a rolling circumference of 74 (per Titan and actual
measurement)
Rear 13.6-16 with a rolling circumference of 113 (per Titan)

The tire I contemplated using on the front was an R-4 that was 25x8.50-14 with a rolling circumference of 77.

Using the formula I referenced earlier the lead with the turf tires is about 4%
(74 x 1.58875) / 113 = 1.04

With a 77 inch rolling circumference the lead would be about 8.3%

(77 x 1.58875) / 113 = 1.0825

From what I've read a normal range for acceptable lead is 2-6% (or 3-5% depending on the source).

Based on this I decided to just replace the fronts with the same size tires for now.

For TURFS ???

WHY use 4WD ? (front assist, whatever its called).
R4 fronts with turf rears......
I think we discussed it the other way around in another thread recently.

 

[dqdave1]

I wanted to put r4s on my tc29 because the turfs are 4 ply and wanted 6 ply and could not find 6 ply turfs . I use the FEL alot. I finally just put 30psi in fronts and they work pretty good.

 

[irwin]

Below is an exerpt from my correspondence with the John Deere help site.

Response (Jo Ann) 05/04/2007 11:55 AM
Dear Mr. "irwin":
The MFWD axle ratio for the 770 and the 790 is 1.571.


Thank you,
Jo Ann

The rolling circumference I got from the Titan site.

23x8.50-14 frt tire rolling diam. is 71"...12.4-16 rears are 110" . ratio is 1.549 ..

this equals 1.4% lead on frts

Using that vital information I was able to replace my turf tires with R4's.
turf = 13.6-16 and 25x8.50-14, R4's = 12.4-16 and 23x8.50-14.
So I ended up with a positive front wheel lead of 1.4%. This worked out great at the time. I was able to use my existing rims.

 

[art]

Below is an exerpt from my correspondence with the John Deere help site.



The rolling circumference I got from the Titan site.
this equals 1.4% lead on frts

Using that vital information I was able to replace my turf tires with R4's.
turf = 13.6-16 and 25x8.50-14, R4's = 12.4-16 and 23x8.50-14.
So I ended up with a positive front wheel lead of 1.4%. This worked out great at the time. I was able to use my existing rims.

This would not be true on soft or tilled soils where the industrial would be able to sink in enough to get to the tire carcuss.