Loose Lugs on Bobcat 371

I recently rebuilt a Bobcat 371 skid steer and have found the rims were very loose after minimal use.

Originally the rims were held on to hubs using wheel bolts, but the threaded holes in hubs were worn enough that I went with bolts through the hubs and lug nuts. However, it appears that the rims don't have a deep enough "dimple" around the lug holes to let the cone of the lug nut center and hold the rims tightly.

The rims were new with the rebuild, and now one has had the lug holes reamed bad enough to need replacement. I'm thinking of welding the bolt heads on the back side of hubs enough to hold tight (and prevent backing out) and going with lock washers and nuts (and Loctite) to get more clamping power around rim hole.

Sorry for the long post. Any thoughts or similar experience?

Just guessing here based on what I've seen happen before, but I think what you'll find is that the lug nuts you've got have the wrong taper on them, or are the wrong diameter. As a result they are tightening through the rim and onto the hub instead, at least that sounds to me like what's happening. I know from past experience there are a variety of tapers available on lug nuts, as well as a variety of hex sizes available for the same thread. If it were me I'd get your local parts house to get in their wheel hardward book and find some nuts with the largest hex available for the bolts your using, as well as with the smallest taper available (for example, 60 degree vs 90 degree) that will all match up with the holes in the rim such that the small part of the taper is just setting in the top of the holes taper. If you can find a set like that it ought to eleminate your problems.


Thinking further, if you simply went with a bolt that would fit through the existing hole in the hub and said bolt doesn't fit tight in that hole, then your gonna have problems regardless of what you do. The bolt needs to be tight in the hole, with no movement, or the rim will have the room there to rotate back and forth every time you go from fwd to rev. Even with the rim tight initially, the constant torquing action from the movement of the machine can, and usually will, cause them to loosen up.

Don't know which particuar scenerio suits your problem best, but I have seen one, or both in combination, happen other over the years, so those are my best two guesses.

You are probably right on with the lug nut taper suggestion. The lug taper matched the original wheel bolt taper and that is why I went with those nuts. Thanks for the help.

Does the center of your rims match the center hole on your hubs??? If it is not a good fit there that can also cause your problems. The service manual clearly shows the hub having a raised area that fits the center of the rim. Cute little toys them 371s are and handy in tight places but also easy to do a nose dive BTDT on one a friend has and I do all the work to it and even rebuilt the engine and have the service manual here

The rims do have a center hole that matches what's on the hub, but the raised area on the hub does not extend far enough to contact the rim.

Wish it was easy for me to look at this one my friend has but it is 20 miles from me other wise I would look so see how it is. But I seem to remember having a problem getting the rim off to fix a tire due to being rusted to that center area but that was 2 or 3 years ago so can not be 100% sure it was on that or something else

Had the same problem with my 371 yeaers ago when I bought it. Mine has a combination of lug bolts and nuts...all had egg shaped holes and constantly worked loose. To solve the problem I used 1/2" dia washers and flared the center hole using a tapered pin on the shop press. I then mounted the wheel with a washer (flare out) under each lug, snugged them down (for correct spacing) and tacked them. Took the wheels back off and finished welding the washer to the rim. I haven't had a wheel work loose in the eleven years since. In fact, I made washers for the neighbor's loader tractor tire over 8 years ago and they're still holding as well.

Double nut the bolts. Rim holes need to be perfect circle- worn ones will never stay tight for any length of time.