mfwd tires/ratios

[rp1555]

I need a list of recomended tire sizes that go with certain gear ratios on mfwd tractors.I thought I had one ,but can't find it.I have one for molines,but I need one mainly for 50/55 series.
Can you guys help ?

 

[oliver fan]

Oliver's list of sales notes shows 433-565 to be the number covering the ratios up to 1967. I'm sure there is a newer one that also lists the 55 series.

If B.A. Starr doesn't have the later version, you might call Mary Ann at the Floyd County Museum and see if she has a copy of the later one. I don't have the numbers of the later sale notes to tell you what to ask for.

 

[Anonymous-0]

RP1555:


    I do not have a sales bulletin on the later tractors, however there is a letter explaining ratios and setup that was not published for dealers.

    Tell us what model tractor you need the info for.  The front axle ratio is stamped on the top of the front axle differential.  There is a possibility that the ratio has been changed and the housing has not been restamped.  To determine the front axle ratio: place the transmission in "N", disengage the transfer gears, raise one wheel off the ground.  Now rotate the wheel two revolutions and count the driveshaft revolutions, give us the results of either the stamping or your rotation check. Give us the rear tire size and brand and we should be able to help you.

 

[rp1555]

I know the ratio is 24.6-1 or a 6.83. The 6.83 was used on the big cradle 2150/2255.they have 26 inch rims.Here is the story. Have a 2255 carcass ,frame, axles ,rims. It has 18-38 rear rims and 12-26 front ,which makes for 20.8-38 rear tires and 14.9-26 fronts.Ok,the problem is that all the others that have 20.8 rears have 16.9-26 fronts. The only time I see a 14.9 -26 used ,is with 18.4-38 rears. I think all the rims are original, but being a parts tractor,who knows

 

[Stu]

With a front axle ratio of 6.83:1 that is correct for a 2255. You are correct that from the factory, 18.4x38 were matched with 14.9x26, & 20.8x38 were matched with 16.9x26. The overall rear ratio should 32.26. The front should be 23.72. If you measure the loaded radius of the rear tire, then divide that amount by the front loaded radius you can figure the lead/lag ratio. For a 2255 a 0% lead condition would be 1.360. This can be found by dividing the rear ratio by the front ratio. If the number is larger than 1.36 your front axle will be in a lag condition. Oliver listed a 3% lead at 1.319. On my 2255 I have a 5% lead don't have any problems with the front bouncing ir trying to paw at the ground. My rear tires are 20.8x38 and the fronts are 18.4x26(origionally 16.9x26) New tires were going to cost about $1300 for the front so I bought a pair of 18.4x26 wheels & tires for $200. Tis size can be found pretty cheap as they were used on combines. I cut the centers out of the wheels & welded in a 1/2" plate with my bolt pattern. The loaded radius can be manipulated by air pressure. I have a link to the firestone site where they discuss lead/lag. I hope this helps, Stu.

Firestone lead/lag

 

[Anonymous-0]

    The post by Stu is very good information.  As he stated the match ratio is 1.360, 1% lead is 1.346, 2% lead is 1.334.  A properly inflated Goodyear 20.8x38" tire has a 32.3" Loaded Radius.  The goodyear 16.9x26" properly inflated loaded radius is 23.9".  That will give your 2255 a ratio of 1.351 or about a .5% lead.  If you match a Firestone 20.8x38" to the goodyear 16.x26" front tire you go into a lag.  If you are a level land farmer with straight rows closer to match is good, however if contour farming is your game go for more lead.


    You can work at matching the tire sizes and that is certainly important, however the load on the tractor and tire inflation is probably more important.  when heavy three point hitch loads are applied you now have increased the lead should the rear tire pressure not be corrected.  Likewise front loads are applied like fertilizer tanks or a front loader without adjusting tire pressure it is a lag condition.  As an observer it don't take you long to see the operators that have not taken the time to adjust tire pressure.


    Agribusiness people are doing a lot more road travel with their operations spread out.  Like the Firestone post stated, road travel with the front axle engaged is murder on front tires should the operator not disengage it, the little guy is fighting the big guy and the little always looses.  Modern tractors with all the electronics will disengage and engage the front axle automatically at approximately 12 MPH.

 

[rp1555]

Thank you guys for the info,very very helpful
and Merry Christmas