A third type of common bearing cup is the lower cup used where you want to run with internal fork stops shown below. This particular set is from Paughco but several manufacturers offer similar set ups.
Note the small 'tab' machined into the cup. This tab fits into a corresponding 'slot' machined into the stop-plate that gets attached to your lower tree. The tab is normally positioned to the back of the steering neck so when installing these you have to make sure the cup doesn't twist as it's being pushed in to the neck. Ironically the most popular internal stops written up in all the bike rags Pro-One is the very same ones I've heard the most complaints about from riders so don't believe some of the sales hype you read.
The Paughco units have proven to be very reliable over the years. I personally don't care for internal stops and prefer old fashioned stops but that's just my opinion. Conventional external stops are fail-safe and you can protect your paint job by drilling and tapping the frame for chrome button head fasteners to be used as bump-stops or put a plastic or rubber sleeve over the stop pins in the lower tree.
For installing the new cups you've probably already seen videos of guys beating them into position with large hammers and backer boards but that usually just results in the bearing races being loosened. You can seat the cups this way but most builders prefer to use one of the cup and race seating tools sold at most cycle supply outfits.
They aren't to expensive. I've seen installers selling for between 39 and dollars depending upon the source. Homemade installers work just fine for most projects. The object of using a 'tool' rather than a hammer and a board is to insure that the cups get seated without going in cockeyed and that the cups and races don't get distorted out of round during the installation process.
Most cups are made from easy to machine steels, I suspect some are made from 12L14 as they're a lot softer than for sure. If you've ever had a cup roll off your bench and land on a concrete shop floor you're well aware that the race recess can be fairly easily distorted out of round. For this article were using the 'JIMS' installation tool but several suppliers offer similar products. This tool, or similar, can be used to install both bare cups and cups with the races factory installed or used to install new races in cups already in the steering stem.
For me the advantage of using a fancy store-bought tool compared to something I lashed together is that I can 'rent' it out to friends for more beer since it looks like something a 'professional' would use. Rental fees usually run around a six-pack per day. Optional tool 'instruction' justifies another six-pack.
The internal diameter of the cup recess in the steering neck should be around 1. Check this with a cheap Home Depot digital caliper to be sure.
The outside diameter of the cup 'sleeve' will be somewhere around 1. The cup fits into the steering neck with an interference fit of around. As a side note the exact dimensions of the two parts don't have to meet 'spec' so long as the cup sleeve is very slightly larger in diameter than the hole in the steering neck by a thousandths or so. I've found few necks and few cups that are within factory tolerances.
When working on old frames you may occasionally run into a situation where the bore in the steering neck is larger than any cups you end up buying. If this is the case just install the cups using a 'gap-filling' LocTite, assuming the fit is pretty good to begin with. If the fit is really sloppy you can have the sleeve on the cups knurled and in a worse case scenario weld a spacer sleeve inside the neck. This rarely occurs but you might see it every now and then. Before you try to install the cups in a neck where you have a proper interference fit it's a good idea to take a small piece of grit paper and make sure there aren't any burrs or rough edges on the parts to be joined.
You can polish the sleeve or outside surface of the cup neck slightly. The best way to approach getting the two parts mated is done by putting the cups into your freezer overnight and then heating the steering neck with a heat gun or hair-dryer without damaging the paint job. Alternatively you can leave the frame outside in he sun for about 6-hours on a hot day. Very lightly coat the inside of the steering neck recesses and the sleeve of the cup with oil and then position the cups on the steering neck so the installation tool can be set up.
Some oil on the threaded rod of the tool is a good idea. I've used STP as an assembly lube for decades and still use it today. The secret is to apply it so thin that it's hard to tell that the parts are actually coated. Most cups already have a slight taper in the sleeve so they can be fairly easily started into the neck by hand, maybe with light taps using a plastic mallet it they're tight.
It only takes about a sixteenth of an inch embedment to keep the cups started straight while the tool is installed. The snapshot above shows the cups started and the tool in place. The cup on the right is a little canted and needs to be straightened before the nuts are cinched down. Once everything looks straight start tightening the draw-nuts and the cups will be pulled into the neck.
Having this dummy neck makes the process look easy but I hope you have a frame attached to yours. A reader asked me if it was common to install the cups before welding the frame and it's definitely not. We use dummy necks like this when setting up the welding jig, minus the cups, so this photo is for illustrative purposes only.
When you're all finished you'll have a set of cups and races installed all ready for bearings. Place the bearing cone assembly, small end down, into the grease packer funnel. Plug the bore of the large end of the bearing cone assembly with the conical retainer. Firmly press down on the conical retainer. This forces the grease between the rollers, cage and cone. Smear excess grease on the outside of the bearing cone assembly.
Pack grease between the inner and outer cups in the hub cavity. Also, liberally coat the hub cap inner wall. This layer combats moisture and retains the grease in the inner and outer bearing cone assemblies.
Replace the grease seal when it leaks or when bearings are being repacked or replaced. Install the inner bearing cone assembly in the hub, then install the new seal. Use the proper seal installation tool. After following Step 4, pack the outer bearing cone assembly with grease. Install the outer bearing cone assembly, washer and adjusting nut on the spindle. Use a torque wrench to tighten the adjusting nut to 50 ft.
Back off the adjusting nut 1 full turn. Re-torque the nut to 10 ft. Lock the nut with a new cotter pin. Use a dial indicator to measure endplay. With the indicator tip against the end of the spindle, set the indicator at zero. Push the rotor in while oscillating and read the dial indicator.
Pull the rotor out while oscillating and read the dial indicator again. The bearing end-play is equal to the total indicator movement, which should be between 0. Reinstall all components as the vehicle manufacturer recommends. Proper maintenance and handling practices are critical. Always follow installation instructions and maintain proper lubrication.
Tensile stresses can be very high in tightly fitted bearing components. Attempting to remove such components by cutting the cone inner race may result in a sudden shattering of the component causing fragments of metal to be forcefully expelled. Always use properly guarded presses or bearing pullers to remove bearings from shafts, and always use suitable personal protective equipment, including safety glasses.
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