Indexed head bearings

[Dragonrider]

Finally, I have a picture that illustrates this problem.

Essentially, the bike is always making micro-corrections to your track, even when going straight. You can't really feel them, but they are there.

These corrections are very small, and the majority of wear in your front lower head bearing is all in the same spots. This results in small wear areas that Þrúðr on the VRCC tech board accurately calls "Indexed head bearings"

When the head bearings get worn, it takes the bike being further "off" track before there is sufficient force to overcome the wear in the bearing and make its correction. Then, it tends to "snap" out of the index and overcorrect.

Keep in mind, we are not talking corrections you make, we are talking the micro-corrections the bike is constantly making due to steering geometry and road surfaces (and lots of other stuff). You cannot feel these at the handlebars.

The indexed head bearings result in "hunting". The bike seems to wander a bit. It also results in unstable feelings in turns, particularly on wet/slick surfaces.

The Valk is VERY picky about this, but the XS feels it too, despite the frame flex. You cannot feel these by turning the wheel, even jacked up. It will feel smooth to you...but they are there.

If they've been loose, replace them. If you've never checked them, replace them. OEM's didn't lube them particularly well, and they are subject to gathering dust as well. They ARE a wear item.

If you are experiencing wandering, and think you've checked your head bearings by feeling the smooth action of your steering, think again.

So, when I harp on about replacing your head bearings, now you can see why. This is my lower race...still felt perfectly smooth to MY hand, but the bike was hunting. Retensioning the bearings did not help. They must be replaced.

I'll write the entire thing up as a tech tip in the future.

[John]

This is a very common ailiment with most any bike. It results from the constant jarring the steering head is absorbing. With the front wheel being in the striaght forward position most of the time, all of that force is transferred to the bearigs, and will result in this condition. A friend of mine had an XS650 Special, and his races were so bad that you had to force the bars one way or the other to initiate a turn. A very hazardous condition. When we replaced the bearings and races, the wear pattern could be easily felt with your fingers. The races can be a pain to remove, but using a Dremmel or a die grinder with a de-burring bit, you can cut through the race and then they can be driven out. Once they are out, use the de-burring bit to grind a notch in the shoulder (land) that the race bottoms out against, so you can get to it with a tapered punch, and drive them out easily the next time they have to be replaced. Remember to pack the bearings thoroughly before installing them. Dry bearings will wear very quickly.

[fredintoon]

Crowded races

Hi Daniel,
however far had those head races gone?
I've seen lotsa ball head races indent so they clicked but never a Timken show that amount of wear. As you say, it's the micro-movements that do it, if the beggars went round & round they'd not wear in that fashion.
John,
the XS650 has ball head races just like an 1880's bicycle. Those bastards Brinell for a pastime. SOP upgrade is tapered rollers, compared to the ball races, those last for ever, so long as you grease 'em.
Fred Hill, S'toon.

[Dragonrider]

Re: Crowded races

Originally posted by fredintoon
Hi Daniel,
however far had those head races gone?
I've seen lotsa ball head races indent so they clicked but never a Timken show that amount of wear. As you say, it's the micro-movements that do it, if the beggars went round & round they'd not wear in that fashion.
John,
the XS650 has ball head races just like an 1880's bicycle. Those bastards Brinell for a pastime. SOP upgrade is tapered rollers, compared to the ball races, those last for ever, so long as you grease 'em.
Fred Hill, S'toon.

Only 100,000 miles!



I've seen them go considerably sooner, particualrly if they've been run loose.

[mason79]

mine had a few stripes when i took it apart, 50,000 mile on them,

maybe if you position the rollers in a non worn area, you take 50 percent of the looseness out, that's my rationalization, since i didn't replace them and,


i felt them with my fingers and felt nothing
after cleaning and regreasing,and retightening, i do feel more confident riding, wonder how long that is going to last.














by the way i broke a tire iron trying to take my old front off, you guys who do it yourselves are nuts...

[prometheus578]

"Interesting thread..."

...on an often neglected subject.
A real pain to replace, but these are machines, and machines need maintenance.

[tommystinson]

The damage noted would be considered brinelling, an argument could be made for "false" or "true" brinelling. False brinelling occurs when a bearing is rarely or slightly rotated and the lubricant is no longer distributed through the bearing, causing wear. True brinelling is metal "compaction", so to speak. As fellow XSsives have pointed out, the axial loading is significant due to the impacts the bearings are subject to. A thrust bearing used with cylindrical roller bearings would be nice, but cost becomes an issue. FWIW: It's not possible to check any roller bearings for damage by feel, etc. A ball bearing race has a tolerance of 3 microns. A micron is 1/1000 of a millimeter. But hey, $40 isn't so bad. I replaced a double angular contact bearing in a Mazak mill a decade ago. The bearing, about the size of the XS's front tire, cost $18,000. A set of P7 grade spindle bearings would typically run $5 k.

[eroellig]

My steering head bearings were bad enough that it felt like there was a detent in the straight ahead posision when the front was off the ground.

When i replaced them, I could most definitely see the marks and feel them as well on the lower race. The upper one "looked" ok, but I replaced them both.

Eric