Steering head bearings (2013)

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MikeG

MikeG

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Does anyone know the trade or industry part numbers, not the Norton numbers, for the sealed ball bearings used in the steering head on my 71 roadster? I'm an SKF bearing warehouse, and I probably have them on hand, but I'd like to know before stripping them out. I can't seem to cross reference the Norton numbers.
Thanks
 
Any converts to tapered roller stem bearings? I know many other bikes will weave with loose head bearings, loose being defined in service manuals as "the fork falls to either stop when released from center", exactly what the ball type in the Cdo do.
Anyone report better stability with tapered rollers?
 
I put taper rollers in my 1970 Fastback years ago only from the point of view that they are a better engineering solution. I'd like to meet anybody who can tell the difference (if they're adjusted properly) While mine was supposed to have cup and cone and loose balls, it actually had sealed ball races fitted by the PO but unlike the later post 70 yolks (triple trees to you guys) there was no spacer holding the inner races apart. The sealed ball races were being used as sealed cup and cone. Struck me as being a bit dodgy.
 
I had my race bike converted to tapered rollers some years ago, and for the life of me I can't remember why I went to so much trouble! I really don't think you can tell the difference.
 
concours said:
Any converts to tapered roller stem bearings?
Click to expand...

TRB are generally a good idea - ACRB angular contact roller bearings - but are no direct replacement at least in post-71 Commando frames. In order to make both the bearings and the clamping nut work in this setup it needs a spacer with a tighly toleranced length. The inner races needs to be tightened against this spacer so that bearing pre-load and clamping force are partially de-coupled, actually the spacer acts like a very stiff spring and the clamping force os divided into a spring load and the pre-load. Therefore the spacer length needs to be correct within a few microns in the end. The tightening torque for the post-71 head stem nut is 40Nm which will lead to far to high pre-load on TRBs if you just replace the ball bearings - and if you don't tighten this one up the clamping force will not be sufficient.

No black art but it requires a bit of patience and tuning.


Tim
 
Microns ???. the cost of a part can be proportional to the tolerances. microns on length also require similar tolerances on squareness. usually a ground or polished finish also. half a thou approx 10 microns (metric).

has anyone got any idea of the factory tolerances including tolerance of bearing housing centres. maybe if the spacer length exceeds the bearing housing centre lenght by one or two thou, the bearings are clamped thus allowing application of realistic tolerances. After all it is only a bearing spacer and not the space shuttle.

Pommie John hit the nail right on the head. This is a storm in a teacup.
Bradley
 
My ( tapered) steering head bearings don't have a spacer, nor do most I've seen. You simply need to tighten the adjuster nut accurately. I take the bike off the stand, put a cable tie around the front brake lever and rock the bike back and forth while tightening the adjuster nut with a C- spanner. As you rock the bike you can feel the nut move and take up the slack.
My trailer wheel bearings have the same set up, no spacer and, from memory, the torque spec for the adjuster nut is around 5 lb feet. That's about "that tight" with a c spanner.
 
B.Rad said:
Microns ???. the cost of a part can be proportional to the tolerances.
Click to expand...

There's two ways of achieving this: Either you cut the spacer with a little bit of extra length and grind it down until the bearing pre-load appears correct - just like you do when you set the pre-load by a nut - and you end up with a correct spacer involving additional labour or you measure, calculate and manufacture to exact tolerances which will up the price considerably. IMHO the later approach will not work because of the inconsistency of a fourty year old headstock with huge tolerances. If I swap to ACRBs on my rebuild I will do the first version, a few hours of relaxed quality tinkering and it will be done.

If you chose to ignore accepted engineering standards and call that a storm in a cup that's your view, not mine.


Tim
 
pommie john said:
My ( tapered) steering head bearings don't have a spacer, nor do most I've seen. You simply need to tighten the adjuster nut accurately.
Click to expand...

There is an adjuster nut on the old style stems and yokes used until 1970. There is no adjuster nut on the post 71 stems, that is a clamping nut which has a thightening torque of eight times more than what you state for your trailer. If you tighten this with insufficient clamping force it will come lose - unless you use a counter nut which is the alternative to a spacer. There is counter nut on the old style stem which clamps the upper yoke to the adjuster nut. That is a correct setup and commonly used on all kinds of head sets, just look at tradional bicycle head sets. An unsecured and insufficiently tightened clamping nut abused as an adjuster nut is not a correct setup.



Tim
 
Tintin said:
pommie john said:
My ( tapered) steering head bearings don't have a spacer, nor do most I've seen. You simply need to tighten the adjuster nut accurately.
Click to expand...

There is an adjuster nut on the old style stems and yokes used until 1970. There is no adjuster nut on the post 71 stems, that is a clamping nut which has a thightening torque of eight times more than what you state for your trailer. If you tighten this with insufficient clamping force it will come lose - unless you use a counter nut which is the alternative to a spacer. There is counter nut on the old style stem which clamps the upper yoke to the adjuster nut. That is a correct setup and commonly used on all kinds of head sets, just look at tradional bicycle head sets. An unsecured and insufficiently tightened clamping nut abused as an adjuster nut is not a correct setup.



Tim
Click to expand...


Yes of course. I wasn't suggesting you take the ball bearings out and simply put taper rollers in and hope they work.
I had a new stem made complete with adjusters in the style of "normal" yokes with the stem fitted into the bottom yoke and the adjuster at the top, under the top yoke.
 
Tintin said:
There is no adjuster nut on the post 71 stems, that is a clamping nut which has a thightening torque of eight times more than what you state for your trailer. If you tighten this with insufficient clamping force it will come lose - unless you use a counter nut which is the alternative to a spacer.
Click to expand...


The steering stem nut should always be locked in place after tightening, using the 061912 'tab' washer - so it shouldn't loosen, regardless of the level of torque applied.
Item [42]
http://www.nortonmotors.de/ANIL/Norton% ... 17&Part=42
 
Two new 6205-2RSJ sealed ball bearings installed, just waiting for the paint to dry on the yokes before reinstall. I was surprised at how notchy the old lower bearing felt. I never noticed anything odd in the steering before, but if it's all you know then it must be normal right?? :shock:
 
L.A.B. said:
The steering stem nut should always be locked in place after tightening, using the 061912 'tab' washer - so it shouldn't loosen, regardless of the level of torque applied.
Click to expand...

So the tab washer renders this design which is flawed when used with TRBs into good engineering practise or what exactly is your point?


Tim
 
Tintin said:
L.A.B. said:
The steering stem nut should always be locked in place after tightening, using the 061912 'tab' washer - so it shouldn't loosen, regardless of the level of torque applied.
Click to expand...

So the tab washer renders this design which is flawed when used with TRBs into good engineering practise or what exactly is your point?
Click to expand...

My point was, that there is a tab washer to prevent the nut from loosening, what other point could there be?
 
L.A.B. said:
My point was, that there is a tab washer to prevent the nut from loosening, what other point could there be?
Click to expand...

Apart from the point that the manual states 40Nm for this nut plus the tab washer? None.... :roll:


Tim
 
Tintin said:
L.A.B. said:
My point was, that there is a tab washer to prevent the nut from loosening, what other point could there be?
Click to expand...

Apart from the point that the manual states 40Nm for this nut plus the tab washer? None....
Click to expand...

40 Nm or 4 Nm, the tab washer would prevent the nut from loosening....wouldn't it?

Tintin said:
If you tighten this with insufficient clamping force it will come lose
Click to expand...

Do you have any actual evidence the nut will come loose unless tightened to the listed torque figure?

Tintin said:
- unless you use a counter nut which is the alternative to a spacer.
Click to expand...


Apparently, a locknut (counter nut) according to you, would be a suitable 'engineering' solution, yet a tab washer is not?
 
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