Tires The last word on flipping tires.

[dcyrilc]

I have to agree with you on the Foam filled tires. The ground is supporting the tires, the weight of the tires is a non issue. The only concern I have heard was that the tires have a lot less give in them, so you get a rougher ride. I am willing to risk it.

To some degree this is true, however it also is affected by which foam is used and how fast you drive. I have 8 forward speeds and almost never have any reason to go above third gear (8-10 MPH if even that fast).

 

[davygp38]

As some one pointed out, you need to adjust your wheels to fit the rows so the fronts match the back. If they dont allow you to move the fronts, then I guess the tractor was only meant for FEL work or mowing and you need another tractor for gardening. Better hang on to the old D17 or 8N. I have been running my Yanmar 4220D with the wheels turned out for nearly 3 years and no problems. It does steer differently with them turned out, but I challenge anyone including manufacturer to prove that it causes more stress on the axle. The force on the axle acts like a simple lever, pushing one way and pulling the other. It cant put any more force on the axle than the amount of dish in the rim. If you added spacers to the axles like some folks have to do with the SCUTs for chain clearance etc. then you would put more stresses on the axle. A tractor with no adjustment to wheel base has very limited uses as a tractor. Just my H.O.

I sold the D17 two years ago. I was always fixing something on it. The power steering on it was starting to go, and that was far beyond my skill. As far as another tractor for planting Who knows, you can't have too many.

 

[crazyal]

Doesn't the front axle pivot in the center? I'm not sure you'll get much out of making it wider.

 

[Reg]

There are several threads of thought going through here...

For use as a field tractor, row spacing matters.
For use as a loader you might want R4s on the front.
Some manuals warn that the front hubs/axles warn against the outside position.
(whatever we may think about the manufacturer's stress analysis)

I'm thinking Swiss Army Knife again (-:
CUTS are compromises, SAKs have limitations; when using any tool, fold all other tools away.

When cultivating row crops remove the loader, use R1s and either set the spacing to match your rows - or your rows to match your tires (NOT generally recommended).

Yes, the front axle typically pivots - at some point it runs out and the wider the stance the better chance you have of returning to the upright position.
Whether or not a couple of inches makes a critical difference in a particular case is debatable.

 

[davygp38]

Doesn't the front axle pivot in the center? I'm not sure you'll get much out of making it wider.

My thinking on the front Axel pivot, is that it is all relative. For example,if the distance between the outside of the tires was 72 inches before flipping, and it is 76 inches after flipping, that increase is still going to add stability regardless of the Axel pivot. The front Axel does not pivot all that much, and at some point it stops. It is at that point that you get the benefit of the wider stance. Your point about "not getting much out of making it wider," is the problem. Is the benefits of a wider stance worth the chance of damaging the machine, and costing me money. If I were following my normal practice of getting a new machine every five years, I would do it. In the case of this tractor, I was going to keep it for a long while. I am thinking I will put the tires on dish in, and see how it goes.

 

[slowzuki]

Not opinion but fact, increasing the offset increases the load on the wheel bearings. So dishing out is harder on wheel bearings. I won't teach you static load analysis but as an example, take a 5 lb weight in each hand, and hold them by your chest, then stretch your arms out as wide as you can.

Which one stresses your muscles more? The wider one.

OK, I am going to toss out a speculative theory that by flipping the tire on a dished rim that you dont put any extra stress on the axle.

 

[V1Rotate]

Rearding stabilty
Just to make a point, let's suppose that you could widen your front end to make it 10 feet wider on each side. If the left front wheel dropped into a deep hole the axle would pivot until it reached its limit of travel. If the other tire were located directly under the centerline of the tractor (which it wouldn't be) there would be little or no force to make the tractor want to roll over. But because the front axle is now so long, the leverage from the right front tire will exert a large amount of force that would try to roll the tractor over.
So widening the front end may not increase stability if a tire drops into a hole. However, if a rear tire drops into a hole, a wider front end would definitely offer more lateral support and help keep the machine upright.

 

[davygp38]

Regarding stability
Just to make a point, let's suppose that you could widen your front end to make it 10 feet wider on each side. If the left front wheel dropped into a deep hole the axle would pivot until it reached its limit of travel. If the other tire were located directly under the centerline of the tractor (which it wouldn't be) there would be little or no force to make the tractor want to roll over. But because the front axle is now so long, the leverage from the right front tire will exert a large amount of force that would try to roll the tractor over.
So widening the front end may not increase stability if a tire drops into a hole. However, if a rear tire drops into a hole, a wider front end would definitely offer more lateral support and help keep the machine upright.

I disagree. A longer axle will not cause the tractor to flip, if it is centered on the pivot point. Using your theory, any size Axel would cause a flip, if the other side went into a hole. as far as balance goes, it is all relative. If you have a ten foot Axel, or a 100 foot Axel, as long as you are located at dead center, you are balanced. In point of fact, if your tire was located under the direct centerline of the tractor,as you stated it would make it much more likely to flip over.

 

[Soundguy]

not to mention that the longer the axle is from center, thathe less drop seen at center when the tire falls into a hole. that parallel line thing vs hypotenuse.. etc.

soundguy

 

[slowzuki]

Wider front axle increases stability when you use your tractor on very steep side hills, and going over bumps at speed, but its not nearly as important as the rear. If you start to roll, the oscillation stop on the front axle will only catch you if you were barely going to roll. It won't stop a good bump induced roll or if the hill is just too steep for the rear tire spacing.

 

[Mace Canute]

Wider front axle increases stability when you use your tractor on very steep side hills,

No it doesn't. The tractor's stability is totally dependent on the rear fixed axle. The front axle is at the same relative angle to the tractor as it is on level ground. The front axle oscillation stop doesn't come into play until the tractor has gone a considerable distance over. If you are on a smooth but steep side hill and the rear uphill tire lifts off the ground, you are going over...the rear track width is as wide as or wider than the front and since it wasn't enough to prevent the back from going over, the front definitely won't prevent the roll over, especially seeings as how the tractor has gone over a considerable extra distance.

and going over bumps at speed, but its not nearly as important as the rear. If you start to roll, the oscillation stop on the front axle will only catch you if you were barely going to roll. It won't stop a good bump induced roll or if the hill is just too steep for the rear tire spacing.

Exactly right! There may exist a certain set of circumstances where the oscillation stop on the front axle will prevent a roll over, but those circumstances would be very rare and if the stop prevented a roll over, you are definitely operating with a zero safety factor and well into the danger zone. Hitting a bump with the uphill rear tire or dropping the downhill rear tire into a hole introduces a set of unknown factors into the circumstances and the tractor may or may not go over...but whatever it does, I would bet my own money that the front track width would have nothing to do with it. Relying on an increase of a handful of inches in front wheel track width to save you from a roll over is just plain foolhardy and thinking that it increases the tractors stability is just wishful thinking.

Safety does NOT depend on wishful thinking!

 

[slowzuki]

Yes it does. The wider front axle causes the bumps on the uphill side to exert a smaller side thrust on the front end and can withstand a harder fetch up from a sideways slide before tucking under and rotating on the pivot.

This is wide highway row mowers have duals on front or very wide spacing. Just parking on a tilt table, no it doesn't matter much, but when moving it does.

No it doesn't. The tractor's stability is totally dependent on the rear fixed axle. The front axle is at the same relative angle to the tractor as it is on level ground. The front axle oscillation stop doesn't come into play until the tractor has gone a considerable distance over. If you are on a smooth but steep side hill and the rear uphill tire lifts off the ground, you are going over...the rear track width is as wide as or wider than the front and since it wasn't enough to prevent the back from going over, the front definitely won't prevent the roll over, especially seeings as how the tractor has gone over a considerable extra distance.

Exactly right! There may exist a certain set of circumstances where the oscillation stop on the front axle will prevent a roll over, but those circumstances would be very rare and if the stop prevented a roll over, you are definitely operating with a zero safety factor and well into the danger zone. Hitting a bump with the uphill rear tire or dropping the downhill rear tire into a hole introduces a set of unknown factors into the circumstances and the tractor may or may not go over...but whatever it does, I would bet my own money that the front track width would have nothing to do with it. Relying on an increase of a handful of inches in front wheel track width to save you from a roll over is just plain foolhardy and thinking that it increases the tractors stability is just wishful thinking.

Safety does NOT depend on wishful thinking!

 

[Reg]

Yeah, I think that "tuck under" might be where a wide front axle could save you.

ONE of the reflexes that I most fear on side/downhills is to try and turn up the slope if/when things get out of hand - the "tuck under" roll over.

Tricycle front ends went out for some other reasons too, but I don't think stability was one of their strong points.

 

[davygp38]

Yeah, I think that "tuck under" might be where a wide front axle could save you.

ONE of the reflexes that I most fear on side/downhills is to try and turn up the slope if/when things get out of hand - the "tuck under" roll over.

Tricycle front ends went out for some other reasons too, but I don't think stability was one of their strong points.

Since I don't have much in the way of a formal education, I tend to use other means to make some decisions, and one of the simplest is to take a look at different set ups, and how other people do things. I think you are dead on about the highway mowers. I figure, that whoever is in charge at the highway department, didn't just wake up one day, and decide to just go with a wider wheel track. I'm guessing that at some point, some egg head with a slide rule got a call about whether a wider track would be more stable. Obviously I can't throw out the old (x to the y squared= this that or the other,) but I feel that since most mower operations use a very wide track, there might be something to it. Now in this thread, almost everybody who has chimed in agrees that a wider rear tire set up is the best way to go. Now at the risk of sounding like a simpleton, why wouldn't a wider front end be just as big of a help? Remember the whole point of the thread, was to answer weather a wider front would help stability. My point is this. If my front wheels are a certain distance apart, and whether the Axel pivots or not, won't adding width make the machine more stable?

 

[Arky217]

OK, I am going to toss out a speculative theory that by flipping the tire on a dished rim that you dont put any extra stress on the axle. You simple transfer the stress in opposite directions. The rim centerline location is still bolted at the same spot. So when the dish is set to inside direction (narrowest)the stress on the axle is wanting to push the axle end down whereas when dished to the outside (widest) the stress would want to push the axle tip up. The same amount of force is on the axle and bearings, just pushing it in the opposite direction. The amount of steering load increases due to the longer leverage distance between the tires so you would get harder steering and likely a bit more wear on the steering knuckles. As for not worth it on the front due to pivot, folks claiming that have likely not noticed that the axle hits the frame way before the tractor would reach a roll over point, so widening the front stance helps to prevent tip over just as much as widening the back.
Please one of you engineering folks prove me wrong with some actual computations or CAD model not opinions.

I don't know how the front wheel bearings on a Kubota L4400 are set up, but on a vehicle that has a bearing setup typical of many past vehicles (a large inboard bearing and a smaller outboard bearing), changing the plane of the wheel thrust on the bearings from it's design point to further outboard can have undesirable consequences.

Real life case in point:

Years ago, I was traveling in a typical 2 ton truck (8.25x20 dual tires on the rear), when I had a blowout on one of the rear tires.
I didn't have a spare, but I decided to continue on my journey anyway after removing the wheel with the blown tire.

Before continuing, I considered whether to mount the remaining one wheel inboard or outboard. Well, I thought outboard would give me more stability (I didn't give a thought about the wheel bearings).

Turns out this was a BIG mistake. Within a couple of hundred miles, the smaller outboard bearing seized up to the point that it also ruined the axle.

Although the attachment plane of the wheel was in the same position, the thrust plane (from having only the outboard wheel mounted) moved further outboard and caused most of the weight to be transmitted to the smaller outboard bearing and comparatively very little to the larger inboard bearing, thus the outboard bearing quickly became overstressed and failed.

 

[dcyrilc]

Now at the risk of sounding like a simpleton, why wouldn't a wider front end be just as big of a help? Remember the whole point of the thread, was to answer weather a wider front would help stability. My point is this. If my front wheels are a certain distance apart, and whether the Axel pivots or not, won't adding width make the machine more stable?

The technical answer would be yes it adds stability. In a real world situation though, the answer in no. Here's the reason. The amount of stability is negligable, and on a side slope (or sometimes in a turn) where tipping is an issue, the amount of added stability is not enough to stop the tractor from rolling once it has started to tip and the momentum of the weight is already shifted past the edge of the rear tire (solid axle).

Picture the tractor sitting on a tilt table. Begin tilting the tractor to the side. Once the Center of Gravity of the tractor gets past the edge of the rear tire the tractor will begin to tip (roll). At this point, the COG is also already past the edge of the front tire as well. By the time the tractor has tipped far enough to hit the stop on the front axle, the COG will be so far past the edge of the tire that there is no way it is going to stop the tractor from tipping over. If the front axle was extended to a wide enough position, there is a point where it may have a chance of stopping the roll, but that point is way past where rotating a dished rim is going to have any effect.

Does this help at all?

 

[slowzuki]

No actually is does help in real life. Unlike the tilt table, in real life, tractors slide sideways and fetch up when operating on slopes. If the front tires aren't wide enough, they tuck under, lifting the front end, making the load (moment is the correct term) the rear tires have to resist much greater leading to roll over.

 

[dennis52]

No actually is does help in real life. Unlike the tilt table, in real life, tractors slide sideways and fetch up when operating on slopes. If the front tires aren't wide enough, they tuck under, lifting the front end, making the load (moment is the correct term) the rear tires have to resist much greater leading to roll over.

You guys both sound like you know your business!

With regard to impending side rollovers and fetch up, can you advise the effect of
1. Fully loading tyres (above and below centre of gravity)
2. Only loading tyres to axle height (below centre of gravity)
3. Not loading tyres but carrying equivalent weight very low with loader and bucket on front and 700lb brush hog on rear.

 

[slowzuki]

1. Loaded tires usually help, they are generally loaded to the top of the rim, and would slightly lower the COG.
2. Less loading of the tires could lead to more sloshing, and up here calcium is used so it is always over the rim. I don't have experience.
3. Always carry loads low when on a hill, in my experience, loads in the front loader are tough to get low enough to help, once the centre of a loaded bucket is level with the axle pivot, its isn't helping. Higher makes it worse.
Rear ballast helps, if is low and isn't swinging.

 

[RoyJackson]

So far, we're up to 40 or so "Last Words..." in this thread.

I flipped mine on my old 790. Can't say with certainty it helped much (only gained a couple inches in track) but it did feel better, even with that pivoting axle.
If you're already on a slope, the axle has (likely) already pivoted as far as it's going to go, once it's hit it's stops (taking that out of the equation). That wider stance may give you a bit more stability.
As far as the wheel bearings wearing faster...probably...and more so if your front wheel are deeply dished (meaning a much wider track when reversed), the wear would be quicker. Then one has to determine if that relatively slight increase in stability is worth the potentially early replacement of those bearings.

However, I've not reversed the fronts on my 4400 and I don't intend to. I've got more weight in the rears (much larger tires) and just don't see much need for it.