Bearing Cup Installation

Bearing Cups

Before we talk about how to install new steering neck bearing cups and races we should take a minute to talk about how to remove the old cups, as it's likely you're going to be working on an existing frame. Keep in mind that we're talking about completely removing the cups and not just the races. The races are inside the cups.

You can google the process and come up with a dozen or so methods but the most popular one is to find a socket, mounted on a long extension of course, that barely clears the inside diameter of the neck cup. I used to have a foot long piece of 1-inch diameter brass rod specifically for this purpose but it's lost somewhere.

The obect is to 'wobble' the socket extension slightly moving it around the perimeter of the cup neck, or 'sleeve' as I'll call it so we don't get this neck confused with the steering neck itself. As you tap the rim of this sleeve from inside the steering neck, using a good sized hammer, it should start to move.

If you don't see a gap forming between the steering neck and the cup after a few good whacks try to spray a good penetrating oil down through the neck to soak the cup 'sleeve' from the inside. If this doesn't loosen it up try heating the neck with a propane torch until its to hot to touch. Keep the heat away from the cup. It the cup still doesn't budge there are a couple of things that might be holding it in place.

It's possible somebody in the past seated the cup using Loc-Tite in which case more heat and a bigger hammer will be needed. The other common problem is that somebody in the past actually drilled through the steering neck and doweled the cup in place. All you can do in this situation is to remove the paint and pray that you can find the dowel or dowels. If they were welded in place and then sanded down you might not be able to see the locations without more sanding. They tend to be at the 'sides' of the neck and not on the front. Sometimes you'll get lucky and find that the 'dowels' are threaded studs covered with putty and you can get them out with a screwdriver, or if hex head, with an Allen wrench.

If you find that the dowels or pins were driven in you won't have any option other than drilling them out. Hopefully this won't be the case and the cup will start to move after repeated hammering.

Once the cups are out inspect the bores and clean them up with some crocus cloth to remove any rust or burrs in the steel.

If you're lucky you'll be working on a new frame and all that's needed will be to install new cups. It's best to do this after painting but a lot of painters don't mind working on a frame where the cups are already installed..

Bearing cups come in several different 'styles' for want of a better term. By this I mean the outward visual appearance. Three common styles that we had laying around the shop are shown below.

 

 Note that the cup on the left has a very small radiused edge on the lower end and a small straight chamfer at the upper edge. The cup in the center has a small radius edge both top and bottom and no chamfers. It's also about an eighth-inch 'thicker'. The cup on the right has 1/8-inch machined chamfers both top and bottom. It's about a sixteenth of an inch thicker than the cup on the left.

 Each type of cup uses a slightly different set of dust shields so I recommend buying the cups, bearings, races and shields from the same supplier if at all possible regardless of style.

If you use what I call 'thick' cups it'll add to the 'stack-height' of your steering neck assembly by a full half-inch which might cause problems depending upon the length of you steering stem and type of fork trees you're using.

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.

The stop plate and it's special dust cover are seen below.

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.

 

Installation

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 57-dollars depending upon the source. A lot of people make their own version of these tools using 5/8" all-thread rod and stacks of washers. 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 1018 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' #1725 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 1.300-inches. Check this with a cheap Home Depot digital caliper to be sure. The outside diameter of the cup 'sleeve' will be somewhere around 1.303 depending upon the source. The cup fits into the steering neck with an interference fit of around .003-inch so the only way you're going to get the two parts to fit is to expand the hole in the neck and shrink the diameter of the sleeve.

(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). on the Paughco frame I'm working on now the neck bore is 1.310 and the cups are 1.313 which is good.

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 400-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.

While we're on the subject of bearings it's a good time to become aware that there are stem bearings being sold, almost everywhere, that are cheap imported copies of good Timken bearings. Even the packaging looks authentic but these products are out and out counterfeits of extremely poor quality. There are also bearings being sold clearly marked 'China' that are fairly good quality Timken replacements.

It's important to inspect your bearings closely regardless of what brand they are. Lightly moving the bearings around in the cage usually reveals 'tight spots', 'catches' and other abnormal behavior on bad units. Also check factory installed races. I've found more than a few where the races weren't fully seated and a few that were visibly way out of round.

If your bikes going to setting around the shop for any period of time before final assembly it's a good idea to oil down the races and bearings. Seal the bearings back into the packaging and keep oily rags stuffed inside the neck.

Also remember that the upper dust shield fits 'over' the upper cup and the lower dust shield fits up 'inside' the lower cup. Getting the shields mixed up will allow water and road crud to get inside the bearing recesses.

Read everything you can find since knowledge is power. Grab a service manual, visit and support discussion forums and talk things over with friends. The more information you have the better when it comes to bike building.

 

 

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