A little disappointed with Kubota

[RickB]

Any time I have ever seen wheels that looked like that they had been run loose. I do not expect this to be different, although it is possible the wheel or hardware are incorrect for the application. If it were not any of the aforementioned scenarios, this forum would be flooded with similar text and photos from other Kubota owners, as well as the dealership shop I run. BTW both that wheel and all the hardware is scrap metal. If the photo is of the better of the two, the other set is junk as well.

 

[the old grind]

I'm seeing a situation where making (radial) spacers/rings (think sleeve adapters to install grinding wheels on smaller arbors) to hub-center the wheels in the first place could allow using existing nuts vs repairing their holes precisely and/or using typical tapered nuts.

Agree with Rick that most pictured is bagged and worthy of replacement. What I suggest will sound shad-tree to many. I've had holes elongated from running loose, but only one wheel ever, and with center hole intact proper torque held in place as long as I still owned the tractor.

Start with OD of hub, ID of wheel, and`wheel thickness minus say .040-.060" (1-1.5mm). Once 'centering adapters' are installed, lugs would see rotational forces then but no longer enlarge radially from load. Hub would carry the weight as usually intended. If the wheels' center-holes are still undamaged, this could be < an hour to make, ~ the same to install, and wheel holes might only need deburred..

Kind of a band-aid option, but IMO entirely workable. Easier to do than say making wheel spacers that require hole pattern etc. I make/ship small one-off tractor stuff for free, but not many ask. Got steel. Got dimensions?

 

[rScotty]

AGAIN THIS DIDN'T HAPPEN BECAUSE THEY LOOSENED UP. I have removed the left wheel, the worst of the two so I could see how bad it was. The right wheel has never come off and I've only removed one of the bolts on the right wheel just to make sure that the shoulder wasn't bottomed out on the axle. To get that bolt off I had to put a cheater bar on my breaker bar because it was that tight from the factory.

If I had made the mistake of letting them get loose I would just buy the replacement parts and accept it. In fact if I had missed the bolts loosening I would feel better as I could point blame at myself and know that replacing the bad disk with a new one would fix the problem. However buying a new center disk could very well mean 8 to 10 years from now I'll be replacing them again. Also the holes in the left wheel are not egg shaped yet so I would like to prevent it from happening. However if it keeps moving they will be.

You keep saying that the nuts didn't loosen up, and I believe you. But I don't think that the nut loosening or not is the problem here. And it doesn't look like the diameter of the hole is either.

From a mechanical engineering point of view, conical nuts and tight-fitting wheel stud holes are nice, but those features are backups. In this type of joint, It should be the simple clamping pressure from the nut that does the work of keeping the wheel tight enough to the axle face so that it doesn't move.

From what you say, it simply looks like the clamping pressure is insufficient to keep the wheel from moving. And that is such a simple calculation that I can't believe that Kubota got it wrong. Al, when I look at that picture you posted of the stud, lock washer, and nut stack back at the beginning of this thread it just looks wrong to me. I seriously doubt that is a stock setup. Have you checked against an exploded parts diagram? It would be downright weird and unique if any joint like that was originally designed with a lock washer carrying the compressive force between the nut and wheel face.

So to me it seems like the nut and washer stack were assembled wrong when the tractor was new. Maybe by the dealer, or the tire shop, or some other place. At the least there should be a large hard flat washer between the wheel face and the nut.

rScotty

 

[JWR]

AGAIN THIS DIDN'T HAPPEN BECAUSE THEY LOOSENED UP. ....

What you just described is a contradiction. If they were never loose and if the holes were not originally oval shaped then how does one think they got oval shaped ? Something does not add up here. This whole thread seems to make a very strong case for hub centric wheel mounting. All the Kubotas I've worked on (granted older machines...) have protruding hubs that force the wheels to be centered and holds them centered. Some of not most of the wheel spacer companies make use of that feature and carefully mate up with the protruding hubs as well as providing a small protruding hub center out where the wheels mount on the spacers.

 

[JWR]

You keep saying that the nuts didn't loosen up, and I believe you. But I don't think that the nut loosening or not is the problem here. And it doesn't look like the diameter of the hole is either.

From a mechanical engineering point of view, conical nuts and tight-fitting wheel stud holes are nice, but those features are backups. In this type of joint, It should be the simple clamping pressure from the nut that does the work of keeping the wheel tight enough to the axle face so that it doesn't move.

From what you say, it simply looks like the clamping pressure is insufficient to keep the wheel from moving. And that is such a simple calculation that I can't believe that Kubota got it wrong. Al, when I look at that picture you posted of the stud, lock washer, and nut stack back at the beginning of this thread it just looks wrong to me. I seriously doubt that is a stock setup. Have you checked against an exploded parts diagram? It would be downright weird and unique if any joint like that was originally designed with a lock washer carrying the compressive force between the nut and wheel face.

So to me it seems like the nut and washer stack were assembled wrong when the tractor was new. Maybe by the dealer, or the tire shop, or some other place. At the least there should be a large hard flat washer between the wheel face and the nut.

rScotty

Scotty I agree. Certainly raises the question (if this was bought 'new') then why was someone dorking with the wheels? No idea how long ago the purchase was but I'd sure put some pressure on the dealer to explain this one.

 

[SPYDERLK]

You keep saying that the nuts didn't loosen up, and I believe you. But I don't think that the nut loosening or not is the problem here. And it doesn't look like the diameter of the hole is either.

From a mechanical engineering point of view, conical nuts and tight-fitting wheel stud holes are nice, but those features are backups. In this type of joint, It should be the simple clamping pressure from the nut that does the work of keeping the wheel tight enough to the axle face so that it doesn't move.

From what you say, it simply looks like the clamping pressure is insufficient to keep the wheel from moving. And that is such a simple calculation that I can't believe that Kubota got it wrong. Al, when I look at that picture you posted of the stud, lock washer, and nut stack back at the beginning of this thread it just looks wrong to me. I seriously doubt that is a stock setup. Have you checked against an exploded parts diagram? It would be downright weird and unique if any joint like that was originally designed with a lock washer carrying the compressive force between the nut and wheel face.

So to me it seems like the nut and washer stack were assembled wrong when the tractor was new. Maybe by the dealer, or the tire shop, or some other place. At the least there should be a large hard flat washer between the wheel face and the nut.

rScotty

The OP pic shows how all my Kubot rears are mounted. I agree with the high strength flatwasher but have never had trouble with the stock setup over many years experience. ... My Mahindra 7520 was mounted similar, but using flange nuts and no washer. I added washers on that one because the forces generated in use are huge by comparison.

OP situation is mysterious.​

 

[ovrszd]

Those are stud piloted not hub piloted wheels, a pia. Too late now to do anything as the wheels are pooched, you won't be able to keep them tight. Thinking out loud, wondering if you had used conventional wheel nuts, tapered seat which would have kept the wheel centered on the stud.
Lockwashers are crap IMHO, only time they come into play is if the nut comes loose that is if they don't break first. The Jinma that I had used them everywhere, I changed the bolts and nuts out to 10.9, used 10.9 flats and Loctite..............Mike

Good points Mike. If the wheel fits the hub tight it' call "hub centric". If it relies on the bolt it's "lug bolt centric".

In regards to bolt/nut type. Are the lug bolt holes in the wheel chafered? Taper hole like a car wheel? If not, that might be a solution. Shop for tapered nuts. Then buy a tapered bit and taper the wheel holes.

I don't recall ever seeing a lug bolt centric setup that didn't use tapered wheel holes and nuts.

 

[rScotty]

Well, I got to thinking, "Am I missing something here?". So I went out and checked out a few (4) tractors. Sure enough, some use wheel studs and some use nuts, but all have heavy flat washers under them. Most have a similar heavy flat washers on the fronts as well. None have lock washers anywhere. Interestingly, the only one that has beveled nuts has those just on the fronts - and it's an older 2wd farm tractor...

Agree that hub spacers might be a workable solution. Depends on the hub & wheel. Worth looking into.
rScotty

 

[ovrszd]

To me it looks like the rear wheels loosed up at some point and started the "elongating" issue that now continues. Once that starts you either have to replace the wheel center or do a weld and drill repair. Welding and drilling is difficult because the bolt holes are very precisely located and drilled only a whisker larger than the studs. It's hard to do that. From what I see, I'd buy new wheel centers and use the correct OEM parts. Then keep them tight.

I agree with this theory.

For clarity though, Six isn't saying the nut turned. He's saying the prescribed torque of the nut doesn't provide enough force to hold the wheel in place. I too call this "loosening".

 

[ovrszd]

Here's a pic of a rear wheel. It's hub centric. The bolts/nuts prevent spinning and hold the wheel tightly on the hub. They do not keep the wheel centered. The nuts are flat on the backside and use a flat washer.