Lead/lag ??? on Grand L series

ttowne66 · Feb 3, 2006

Guys

With the knowledge gained by Tree Guy and AB4D, I have come up with the following solution
1) The Titan 12-16.5 NHS 49E3J7 fits right in the slot at 4.6% lead for the Grand L's with 17.5-24 firestone rear tires as they have a r.c. of 145. in fact, any tire that has a roling Circumfrence between 93 to 97 inches falls in the range.
2) The 3130 and 3430 are right at 4.6% with the stock set-up.
3) The scary part of this is that the stock set-up for 3830 thru 5030 tractors with industrials are all operating with almost a 2% lag condition. /forums/images/graemlins/confused.gif

CT_Tree_Guy · Feb 3, 2006

What practical (positive/negative/neutral) effect will there be in changing from 14.9 x 26 to 13.6 x 28 rear tires? (And just what do those numbers mean?) 

RFB -

The 14.9" and 13.6" are the width of the tire, measured, I think, at the widest part of the sidewall. The 26" and 28" are the diameter of the wheel/size of the "hole" in the tire. A 28" wheel vs. a 26" wheel would mean that the 28" tire would be "shorter" than the one on the 26" wheel, as measured from the ground to where the wheel starts. This would probably result in a harsher ride - not that we're talking about Lexus' here - but the tires are all the "suspension" you've got.

And of course, you'd also have to run the numbers on the rolling circumference of the 13.6 - 28 tire compared to the 14.9 - 26 to make sure it would still give you a "good" lead ratio - BUT - If it were me, that comparison would be for purely "academic" purposes. I'd insist on the wider, "stock" size of 14.9 - 26, and ask him some very pointed questions about why he's going against Kubota's recommendations. Sounds to me as if he's got an oddball set of wheels and tires that he's looking to get rid of, at your expense. Others might disagree, but they sound a little too skinny for my taste (and the dealer is starting to sound a little too "slippery", too).

Keep us posted, and again, don't hesitate to ask me any questions. A) You're not "bugging" me, and B) I'm sure I'm going to need your help before long. /forums/images/graemlins/smile.gif

Good luck, John

KennyV · Feb 3, 2006

Several years ago I was considering this same thing… Larger footprint while keeping the ratio right… I switched from factory Good Year R1 AG front 8.3-16 and rear R1 Firestone 14.9-24 To Titan R3 Torc Trac front 12-16.5 and rear 16.9-24. Had to get new wider rims for both front and rear, this gave me a 1.5 percent lead and it couldn’t have worked out better. The big front tires are great for loader work, they are perfect for mowing with no turf damage and larger tires gave a MUCH softer ride. These turf tires also have incredible traction in snow. KennyV.

CT_Tree_Guy · Feb 3, 2006

Tom -

Interesting stuff, thanks. I had never run the R4 numbers on the other Grand L's and never knew that the 3130 and 3430 had good ratios. I'm more than a little surprised at Kubota for not offering "properly" sized R4's on the larger L's. I was told by several very reputable sources that any amount of lag is "totally unacceptable", and it makes sense when you think about it. If the fronts are just being pushed along by the more "powerful" rears when in 4WD, how much good are they actually doing?

I was also appalled, and felt somewhat insulted even, when a Kubota rep suggested that I overinflate the fronts to try to compensate for the crummy lag ratio. Not very good advice in my opinion - but hey, we all say things we might later regret. Plus, tractor manufacturers have a lot of "real world" constraints to deal with when setting up contracts with suppliers, and I guess they did the best they could do. And they still build a better tractor than I ever could in my wildest dreams, so I certainly forgive them a little boo-boo or two.

Sounds like your homework is going to pay off though - good job.

John

ttowne66 · Feb 3, 2006

Tree Guy

I certainly couldn't have calculated this without the info you provided so thanks to you! Now the next question....as the Titan 12-16.5 NHS 49E3J7 recomends a 9.25 wide rim, will these wider Titans fit on the stock rim? To go along with your thoughts on the 2% lag condition on stock set-ups of 38-5030's here is an interesting quote form tractorsmart.com.

Proper tire sizing/matching on front wheel assist tractors is a function of insuring that the front axle 'lead" specification is kept within acceptable design and operational limits. Front axle lead (or slippage) is necessary on front wheel assist tractors in order to realize the benefits of front axle tractive assistance. Desired front axle lead is expressed as a positve increase in front axle speed over that of the rear axle, usually in terms of percentage (ideally +1%-+5% for most front wheel assist tractors). Lead percentages outside of this range will lead to problems such as accelerated tire wear, difficult steering, loss of tractive assistance from the front axle as well as increased drive train wear with premature failures. Negative lead (or slippage) will, from the outset, totally negate any potential advantages offered by front wheel assist.

/forums/images/graemlins/crazy.gif

CT_Tree_Guy · Feb 3, 2006

Negative lead (or slippage) will, from the outset, totally negate any potential advantages offered by front wheel assist. 

Now there's something you won't see in the Grand L brochure. /forums/images/graemlins/tongue.gif

Tom, as for whether or not the Titan 12-16.5's will fit on the stock rim, I'm reminded of one of Clint Eastwood's best lines ever, from "Magnum Force": "A man's gotta know his limitations". /forums/images/graemlins/smile.gif I'm really not sure if they will, and I'm not even sure what width the stock rim is. My gut feeling is that they should be fine, but I'd strongly recommend finding out the width of the Kubota rim and asking Titan for their opinion; they're sure going to know best.

Thanks for all the good info, and I must say, it's been reassuring to know that I'm not the only one who cares about this kind of thing. Sometimes I worry a little about myself. /forums/images/graemlins/laugh.gif

John

ttowne66 · Feb 3, 2006

Ok

I just went out and checked the rim size and it is actually 9.75 which is the exact reccomended width for the larger 12-16.5 NHS 49E3J7. So now the question of why kubota would intentionaly put on tires that are lagging?? You can't tell me they did not know! Everything is there except for the tire! I have no idea of why companies insist on doing the wrong things for extra profit. Just add the extra cost into the **** machine!

LRH · Feb 5, 2006

( What practical (positive/negative/neutral) effect will there be in changing from 14.9 x 26 to 13.6 x 28 rear tires? (And just what do those numbers mean?) 

RFB -

The 14.9" and 13.6" are the width of the tire, measured, I think, at the widest part of the sidewall. The 26" and 28" are the diameter of the wheel/size of the "hole" in the tire. A 28" wheel vs. a 26" wheel would mean that the 28" tire would be "shorter" than the one on the 26" wheel, as measured from the ground to where the wheel starts. This would probably result in a harsher ride - not that we're talking about Lexus' here - but the tires are all the "suspension" you've got.

And of course, you'd also have to run the numbers on the rolling circumference of the 13.6 - 28 tire compared to the 14.9 - 26 to make sure it would still give you a "good" lead ratio - BUT - If it were me, that comparison would be for purely "academic" purposes. I'd insist on the wider, "stock" size of 14.9 - 26, and ask him some very pointed questions about why he's going against Kubota's recommendations. Sounds to me as if he's got an oddball set of wheels and tires that he's looking to get rid of, at your expense. Others might disagree, but they sound a little too skinny for my taste (and the dealer is starting to sound a little too "slippery", too).

)

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Per the 2005 kubota retail price sheet; the tires included in the base price (5030) are 9.5-16 AG front with 14.9-26 Hi-Power Lug AG rear. A second ag choice is the same tires front with 13.6-28 R1 AG as a no cost option. Both rear tires are virtually the same rolling radius so front tire does not change. Then of course they offer R4's, turf, and Galaxy turf.

bugstruck · Feb 6, 2006

Hi John,

I can verify the 3130 has good lead on R-4's. I'm at 3.5% with Firestone 420 70-24 (136" R.C) and Titan 10-16.5 NHS #4123C8 (90" R.C). Assuming of course, I did the math right /forums/images/graemlins/tongue.gif You guys had me wondering though.. Take care John.

mojavedesert · Feb 7, 2006

Having read the above thread and being the owner of a new 3830 with r4's, I was concerned enough to call my dealer who then refered me to the Kubota rep in CA. The rep was forwarded a link to this thread along with links to the Tractorsmart calculation page. Bottom line is the rep was no help whatsoever and in fact somewhat curt in his response---
-(he said Kubota has done the engineering for correct lead and this tire setup is approved while any other setup( like the larger front tire suggested by ttown66) is not and would(presumably) affect the warranty of the tractor. He was not kind to "the self appointed experts on the forums". There was a thread a while back about the r4 fronts having a clearance issue with the front end loader on tight turns---I wonder if this could have led to the use of a smaller tire on the front? Since Kubota was so dismissive, I am wondering how to find out more about this. What do you other affected owners think?
K