Looking for some relief from the heartburn that servicing wheels and rims can cause?
At the Technology and Maintenance Council (TMC) meeting in June, a new, updated version of the User's Guide to Wheels and Rims was introduced, and it promises to provide just the bromide you may need.
Many of you already have this guide, especially if you have been certified through the former International Tire & Rubber Association's Commercial Tire Service training program. The new guide is in color, has an updated format and offers a lot of new troubleshooting tips that have been added to it. It will be available for purchase at the end of this year.
A new section was added to the guide that deals with conditions that, though not out-of-service situations, will eventually cause wheel, hub, drum or stud failures. All of these conditions are found in the hub and drum area where most of us forget to check when servicing wheel assemblies.
But since these conditions can cause a great deal of heartburn for you down the road, it's good to know about them, how to prevent them and how to detect them before failures occur. This may drop the value of Maalox stock, but you don't own any anyway, do you?
Damaged stud head
The first condition is a damaged or bent stud head. You can see this condition if you inspect the studs on the back of the hub.
The edge of the stud head looks bent and prevents full contact with the hub. (You can probably see light under the stud head.) This is a very common condition. It results in improper seating of the stud in the hub stud hole. It is caused by using a hammer to install studs.
Since the stud is not in full contact with the hub face, full clamping force can never be attained. As a result, the wheel(s) will run loose. If you see this condition, scrap the damaged stud and the stud on each side of it. If two studs have bent heads, replace all of the studs.
When installing studs, use a press if available. And always use the recommended stud installation procedures provided by the stud or hub/drum manufacturer.
Some studs are made with burrs or raised edges on the underside of the stud head where the stud mates with the hub face. These raised edges will result in loss of clamping force for the same reason the bent stud head does. They prevent the stud from fully seating against the hub face. The cause of this condition is improperly manufactured studs.
When you see this condition in the hub, scrap the stud and replace it. Inspect other components of the assembly for damage and wear. Also, if the stud came from your stock, check your inventory to ensure that the rest of your studs don't have this condition. If you find that you have studs with this condition, return them to your vendor and make sure that you purchase fasteners that are made by reputable manufacturers and are clearly identified.
There are a lot of inexpensive, off-shore studs and lug nuts coming into the U.S. that are not made to the strict specifications to which American manufacturers adhere. Don't be tempted to ``buy cheap''-this can really cost you in the end.
Another condition associated with stud installation is the improperly installed stud. This condition occurs when the stud is not square with the hub and is actually installed crooked in the hub hole.
Again, since the stud is not in full contact with the hub, full clamping force is not attained and wheels can run loose. Also, since the stud is not straight in the hole, it can rub against the hub stud hole and wallow it out. When this occurs, you have to scrap and replace not only the stud but the hub as well. If you are really unlucky, you may have to replace the drum and wheels too, since their holes may be wallowed as well.
To avoid this condition, make certain you use the correct studs and install new studs using the recommended installation procedures provided by the stud or hub/drum maker.
Another condition that I'm sure you have seen is the worn or damaged hub pilot-often occurring when the hub pilot pads are worn, bent or missing. Loose wheels that did not have sufficient wheel nut torque usually cause this condition. When you have damaged pilot pads, the wheels run off-center and can come off the vehicle enroute. Before they do, the driver will probably complain about the ride.
When you find this condition, replace the hub assembly. Do not attempt to weld or repair hub pilots. Inspect the drum and wheels for damage and wear in the stud holes and bolt circle. Replace them if necessary. Also, check the lug nuts. They may have to be replaced as well.
To prevent this condition from occurring, be sure you install wheels properly using the right criss-cross pattern, torque level and maintenance procedures for cleaning the fasteners and mating faces of the drum and wheels.
Hub corrosion on the drum pilot also is a very common condition. You will see this as corrosion or debris buildup in the corner of the hub at the drum pilot when the drum is removed from the hub. This material will prevent the drum from being seated flush against the mounting face of the hub. If you are only doing a tire change, you will see the effect of this condition: a cocked, bent or cracked drum. Loose wheels will result and the brakes can drag as well when this condition is present.
The cause of this condition is galvanic corrosion and improper maintenance of the axle end. All rust and debris should be wire brushed away before wheel-end components are installed. To correct this condition, replace the drum if necessary.
Worn stud holes
The last condition is worn or damaged stud holes in the hub. As with wallowed wheel stud holes, the hub stud holes are enlarged or wallowed out, causing loose wheels and damage to the studs, drum and hub pilots.
Several things can cause this. The first is using improper studs for the hub. Insufficient wheel nut torque, rusty threads and the wrong drum for the hub also will cause this condition. If found, scrap the hub and replace it with the proper assembly including the right studs and drum. Inspect the wheels and lug nuts for damage and replace them if necessary.
If you find this condition on one axle end, the likelihood that it is present on the other wheel positions is good, so check them, too. To prevent this condition from occurring, always ensure that the proper replacement parts are installed and follow recommended wheel/hub/drum maintenance and installation procedures.
If you are installing wheel/rim assemblies on medium- duty vehicles, here are things you should do each time to ensure correct installation so they will perform as designed:
Clean everything using a wire brush to remove dirt, rust, debris and loose paint from nuts, studs, pilot pads, wheels and the drum face. This will lessen friction in the fasteners that reduces clamping force, ensure the parts mate tightly and allow you to see what's there.
Inspect and identify problems in all components of the assembly and replace non-serviceable parts. Here's what to look for:
* Damage in the center hole of hub pilot wheels; scrap the wheel if found.
* Bent rim flanges; scrap the wheel if found.
* Gouges in the tire bead seat area; sand out if they're minor flaws.
* Damage to ball seat stud hole chamfers; scrap the wheel if found.
* Bent demountable adaptors; scrap if found.
* Bent side and lock rings; scrap if found.
* Cracks in hand holes, bolt holes, disc face and valve hole of wheel; scrap wheel if found.
* Rim flange erosion; scrap wheel if it's significant.
* Burrs around a bolt hole; remove burrs with a file or grinder if found.
* Rust pitting in the tire bead seat area, mounting face, rings and ring groove; scrape out pitted parts.
* Rusty or stripped lug nut threads; scrap any nut that won't install smoothly.
* Worn radius on ball seat nuts; scrap nuts if found.
* Cracks in lug nuts; scrap if found.
* Broken, damaged (stripped threads), or severely corroded studs; replace if found.
* Gouges or wear on the pilot pads; replace the hub if the damage is serious.
* Embedded debris and wear along the outer edge of the drum face; replace the drum.
Remember to follow all proper installation procedures, including:
- Apply oil between the body and washer of two-piece flange nuts.
- Do not lubricate ball faces of ball seat nuts.
- Don't install studs with a hammer.
- Do fully seat studs into the hub.
Following these procedures and ensuring the components are healthy and happy will relieve your heartburn and ensure your customer's wheel systems live long and prosper.
Peggy Fisher is president of Fleet Tire Consulting, based in Rochester Hills, Mich.