Steering head check. (2018)

Guys.Can someone tell me if this fitment order is correct? My bike is a 1970 Roadster.Hence the part diagrams from Andover can be conflicting.My main concern is the bottom "cup" the bearing sits in it prefectly.However,the hole is slighter larger diameter than steering rod which travels through it.A difference of 3mm.Im using sealed bearings.
I realise the "top" bearing isnt shown.

You are aware that you have late model sealed bearing and a '69-'70 triple tree that uses loose bearings and races? Not to say it can't be done, but it will take a little engineering to make it work. The far left item looks like the upper dust cover, but I don't recognize the part you are calling the bottom "cup".

Most popular upgrade for this type triple tree is a set of tapered roller bearings.

coomo said:

Can someone tell me if this fitment order is correct? My bike is a 1970 Roadster. Hence the part diagrams from Andover can be conflicting.

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A 1970 model would normally have had adjustable 'cup and cone' bearings. (Ron L posted as I was typing)
https://andover-norton.co.uk/en/sho...t-incl-balls-dommi-early-commando-2-per-bike-

coomo said:

My main concern is the bottom "cup" the bearing sits in it prefectly.However,the hole is slighter larger diameter than steering rod which travels through it. A difference of 3mm.

Click to expand...

Looks like it might be an Isolastic end cap that's been used as a spacer?

coomo said:

Im using sealed bearings.

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If they are two standard '71-on non-adjustable 6205 sealed ball bearings (and not a pair of 'angular contact' bearings) then it should have the 06.7742 bearing spacer tube (39).

https://andover-norton.co.uk/en/sho...nt-forks-steering-lock-steering-head-bearings

Ron L said:

You are aware that you have late model sealed bearing and a '69-'70 triple tree that uses loose bearings and races? Not to say it can't be done, but it will take a little engineering to make it work. The far left item looks like the upper dust cover, but I don't recognize the part you are calling the bottom "cup".

Most popular upgrade for this type triple tree is a set of tapered roller bearings.

Click to expand...

Thanks Ron.Ok so I get the tapered bearings.I presume I use the same dust cover, on both ends I presume.
The sealed bearing that was fitted is 25mm deep.The depth to the ridge in steering head is also 25mm.Surely sealed bearings, washer and dust cover would work?

L.A.B. said:

A 1970 model would normally have had adjustable 'cup and cone' bearings. (Ron L posted as I was typing)
https://andover-norton.co.uk/en/sho...t-incl-balls-dommi-early-commando-2-per-bike-




Looks like it might be an Isolastic end cap that's been used as a spacer?



If they are two standard '71-on non-adjustable 6205 sealed ball bearings (and not a pair of 'angular contact' bearings) then it should have the 06.7742 bearing spacer tube (39).

https://andover-norton.co.uk/en/sho...nt-forks-steering-lock-steering-head-bearings

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Those are not my forks.These are.https://andover-norton.co.uk/en/shop-drawing/267/roadholder-front-forks the yoke has different fitting.Mine use the steering stem shoulder nut, that comes up from bottom yoke, not down to bottom yoke.

coomo said:

Those are not my forks.These are.https://andover-norton.co.uk/en/shop-drawing/267/roadholder-front-forks the yoke has different fitting.Mine use the steering stem shoulder nut, that comes up from bottom yoke, not down to bottom yoke.

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Yes, as I said, your 1970 model would normally have had two cup and cone bearings.

The sealed 6205 bearings were fitted from '71 when the yokes also changed (the stem then being attached to the upper yoke) so those sealed bearings if 6205 (and the 'cup') are not likely to be original.

L.A.B. said:

Yes, as I said, your 1970 model would normally have had two cup and cone bearings.

The sealed 6205 bearings were fitted from '71 when the yokes were also changed (the stem then being attached to the upper yoke) so those sealed bearings if 6205 (and the 'cup') are not likely to be original.

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Ah ok.Sorry getting confused.However, the sealed bearings fit flush with top of steering head stem.So can you forsee any issue with using them?

coomo said:

Ah ok.Sorry getting confused.However, the sealed bearings fit flush with top of steering head stem.So can you forsee any issue with using them?

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Not if you fit the spacer tube.

The 'sealed' bearing assembly was used from '71 until the end of Commando production and although unconventional it generally causes no problems.

Ok thanks.I ll order spacer tube.

I have changed out ball bearings to tapered roller bearings on steering necks in the past and it does affect the feel of the steering.
Many contemporary motorcycles still use ball bearings in the steering neck and it might be because of how it dampens the feel of the front wheel.

coomo said:

Ok thanks.I ll order spacer tube.

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I suggest you check the length of spacer tube required, as I'm not absolutely certain the standard tube is the correct length when used with the earlier frame, yokes and later sealed bearings?

Edit: Incorrect tube length info deleted

thanks.I can always cut down or use spacer,if its short,

Some things I learned from 40 years in the machine shop building race bikes after hours. Most old steel frames were fabricated with a steering head tube fresh off the lathe with accurate bearing bores each end. It got welded to several frame tubes all on one side of the steering head tube. Now the accurate bores are a little out of round but worse the head tube is shorter at the rear from shrinkage after welding. I've measured many but not a commando yet and its usually .005" to .03" shorter. In bicycle racing they have a tool to trim both ends of the head tube parallel before they press the bearing cups in for a ridged assembly with good feel for the road. You and I are familiar with putting triple clamps on a bike and screwing the nut on till it stops then put a wrench on and tighten a ways, on some it tightens to a stop, all slack out and steering left right gets tight you find the sweet spot and done. On others you screw the nut on then a wrench and before the nuts tight the steering left right is already too tight. Its clamping bearing balls on one side while all the others float loose. Taper roller bearings are better in this situation as they have way more contact area and the rollers at an angle conform to the distortion better. In big money racing you will try several frames to find a good one or set up the frame you've got on the mill and recut bearing bore bottoms in one setup to get them parallel or bores and bottoms for sleeves. Your rider will say man this bike feels good! Big job and no honey I wont be home tonight.

Keep in mind that commando triple clamps need to be spaced apart correct so tubes don't bind as tubes and stem aren't parallel.

Math and motorcycles Alan

Luke

Makes me wonder how they came up with a tube length for between bearing inner races when they didn't have a clue what the head tube length would be after welding.

If you look at the 2 seats on the later ball bearing frames the top seat depth is sized for the bearing length/thickness but the bottom one is oversize so the bottom bearing position can only be set by the length of the tube and not by the seat depth.

kommando said:

If you look at the 2 seats on the later ball bearing frames the top seat depth is sized for the bearing length/thickness but the bottom one is oversize so the bottom bearing position can only be set by the length of the tube and not by the seat depth.

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Thanks, I should have thought of that. But with the load coming from below shouldn't the bottom bearing seat up and the top float?

Does not happen, mines untouched since I powder coated the yokes 30 odd years ago and no movement.

coomo said:

Thanks Ron.Ok so I get the tapered bearings.I presume I use the same dust cover, on both ends I presume.
The sealed bearing that was fitted is 25mm deep.The depth to the ridge in steering head is also 25mm.Surely sealed bearings, washer and dust cover would work?

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I find the depth and thickness data quoted not thrustworthy. A 25 mm thick sealed bearing would be considerably thicker than the cup-and-cone bearing NV fitted originally prior to 1071.
Norvil and others list 6205 as a substitute for the cup-and-cone bearing, and I think the OP meant 15mm rather than 25mm. The ID of bearing 6205 is 25mm.

kommando said:

If you look at the 2 seats on the later ball bearing frames the top seat depth is sized for the bearing length/thickness but the bottom one is oversize so the bottom bearing position can only be set by the length of the tube and not by the seat depth.

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Sorry Kommando, but I don't believe your recollection of fitting. I am convinced NV designed the headstock such that both bearings are supposed to rest on respective bearing seats. Otherwise the upper bearing will lift off the seat when yokes are subjected to an upward action.
As there would be no means to transfer axial upward loads, bearings will wear off the bearing bore as they start to move laterally within the headstock.

So, the only arangement able to absorb fork actions is one in which the (sealed) bearings rest firmly on their resepective seats, clamped by the inner races, the force of which is transmitted by the stem and the bottom yoke. The upper yoke transmits the counteracting force by means of a collar which compresses the inner (upper) race. The only purpose of the bearing spacer tube is to limit the cllamping force , which would crush the bearings ballls or bearing cages otherwise by pressing the inner races out of track.

- Knut