Headstem Bearings - Kawasaki ZX-10R.net
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post #1 of 15 Old 03-30-2008, 01:51 AM Thread Starter
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Headstem Bearings

After all these years they are still using a ball race head stem bearing..... Does anyone have the bearing part numbers for tapered thrust bearings. 2004 10r as I can't locate an after market supplier that handle them. Thanks
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post #2 of 15 Old 03-30-2008, 07:44 AM
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Nothing worng with ball race Thrill, a lot of the time they have less surface contact than taper rollers and you dont have to preload them as much.
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post #3 of 15 Old 04-01-2008, 03:42 PM Thread Starter
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Personally I believe there is. Ball races are really not suited to a static type situation, ie cruising down the highway where the balls are hardly rolling. The vibrations cause the balls and the race to become bruised resulting in a notchy feel in the headstem. I realise that tapered thrust bearings are not perfect either, however you at least have a fighting chance. Technically the pressure at each ball is through the roof given only a single point of support at each ball, (pressure = total load/area this is a divide by 0 situation as there really is no area of contact)
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post #4 of 15 Old 04-01-2008, 07:04 PM
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The problem is the preload with tapered bearings like I said , you would have to have an inner spacer accurately machined to get the required amount of torque, the ball bearings and seat arrangement allow the top and bottom bearings to share the load.

You are also relying on a bigger and larger diameter outer/top race so to speak, with a tapered roller you would have all the load on the inner race allowing too much mechanical advantage to try and offset the bearing under braking, to counter this you would have to tighten the bearing and then you wouldnt be able to turn it so easily.

The ball race headsteam takes the loadings vertically and shares it with the 4 bearing surfaces, the taper relies on 2 mating surfaces and relies on thrust to keep it together.
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post #5 of 15 Old 04-02-2008, 02:48 AM Thread Starter
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The frametube itself is machined and spaces the outer races (exactly the same as a car wheel bearing setup ... the hub spaces the outer races). This setup works extremely well and definitely does not affect your turn in. Have been doing it for years, on track and road bikes. Under most riding situations load is taken on the lower race, and lateral movement controlled by both. These bearings are capable of significantly higher loads and I can honestly say outlast open ball races about 3 to 1. If they were a problem as you suggest, they would not be used as wheel bearings in cars. With open headstem ball races the load is taken along the fork line as you say, however the bearings do not share the load ... the lower races are forced toward each other while the upper races are forced apart, except of course during wheelies
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post #6 of 15 Old 04-02-2008, 09:06 AM
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I see what you are saying, but wheel bearings are used to take huge rotational loads and a lot of friction.

Ideally you would want 2 standard ball race bearings on the spindle for rotation and stability and then torrington bearings top and bottom (flat needle roller bearings).
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post #7 of 15 Old 04-02-2008, 09:11 AM
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2 ball races to centralise the inner spindle.

And 2 of these for thrust.

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post #8 of 15 Old 04-02-2008, 03:44 PM Thread Starter
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not a bad idea. of course the tapered thrust bearings are not a perfect answer to the problem, but they are a good compromise. What I have found in the past though, is that normally no bearing company make a standard tap' thrust race that match the headstems inner & outer diameter requirements, and all the performance bike part shops around used to import special kit bearings for them which are made up from 2 different bearings (inner from one set outer from the other) or they would supply a bush if they couldn't match the inner to the stem. None of these performance shops seem to carry that sort of thing anymore, propably because there are so many models now they cant keep up. Don't get me wrong though, I only started using the thrust bearings because they were easier than the ball type to install, and quite a bit cheaper, because in the days of my Mach 4 & Z900 riding, you had to go genuine for the standard race, but I quickly found (especially on the track, with the Mach 4) that the tap' thrust sets cut out near all of the front end chatter
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post #9 of 15 Old 04-02-2008, 09:12 PM
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I tell you one thing that occured frequently years back,more by accident than intentionally, you would reassemble the headstock and lose a bearing or two and from that day on the chatter went away and the bikes turned easier, I guess the balls had more room to move and wouldnt stay in the same position for too long , relieving the bearing of having dents worn in it.

They have applied that to modern free running ball races and now there is a larger gap between each ball.

The thing that bothered me about the taper bearings is getting the preload just right and once they had bedded in the only way to adjust them was to machine or shim the spacer tube , if you are 0.001" out of tolerance they are as loose as hell or too tight.

If you get them just right then they will do a good job, its getting them just right which is a pain.
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post #10 of 15 Old 04-03-2008, 05:30 AM Thread Starter
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This is not how they are set up. There is no spacer. The outer race of each bearing are fitted into the top and bottom of the frame neck exactly the same as the open ball race part (into a factory machined recess. You then fit one of the inner races to the base of the stem (at the bottom triple clamp) exactly as you do with the ball race. you slide the headtem up into the frame and your lower bearing is done. Next step you slide the other inner race over the stem from the top... fit the top clamp and tension it down. All exactly as you would a stock ball set. Its a piece of cake to do and you never lose any bearings. When I do mine I will post the pics. The tensioning is the same as a front stub axle type car bearing ... the outers are spaced by the hub, or in the bike case they are spaced by the frame head. This really does work a treat... never fails and no problems.
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