Dommie head bearings - taper or ball bearing?

You need the spacer that goes between top and bottom bearing, RGM part number 100006, cost  £5.90+VAT. This set up seems to work well.

I have one bike with the original  cup/cone setup and one with taper. They handle very differently. But there could be many other factors. Neither system has any worthwhile protection against damp and dirt so they regularly get sprayed with spray grease using a long thin tube. The sealed bearings appear to solve this issue. Not tried it myself. The taper bike handles perfectly but getting the bearings fitted with shims to give the right spacing for headlamp brackets has so far escaped me.Apparently angular contact bearings were fitted at Birmingham. Perhaps the cup/cone setup was a cheapskate AMC mod?.

... the sealed bearings are to convert to essentially the later Commando setup which I always thought was an excellent idea. But as Charles says you need the spacer between the inner races.

I've  never had any real problems with cup & cone apart from that awful moment when you get the steering column skew-whiff when fitting them and the balls all make a break for freedom.

If someone has got the sealed race /spacer job, I would be interested in feed back.

I used seal/ spacer combo back in the eighties . It’s fine, and taper rollers would make make only a marginal difference and more hassle to set up.

Don't squeeze the bearings if you go for taper rollers. My bike's steering was scary on sweeping bends and it was because I set the taper rollers fitted by PO too tight.

I have the sealed bearings on my Dommie. In fact it came with them and I assumed that was the way they were. I didn'teven know that cup and cones were an option! If I need to replace them  I would go with the same again as it is so much easier than cup and cones. 

Nb: Tony - Mine are as good as flush top and bottom in the headstock. 

George. 

I've used both tapered and sealed bearings.

The tapered bearings stick up above the headstock slightly and there's no easy way to keep to weather out.  They are also very difficult to get into that sweet spot of zero play and zero tightness.  I found that after seemingly getting them just right, 200 miles on I would get front brake chatter when stopping rapidly from speed and I would then have to re-adjust the bearings again.

After persevering for several years I bit the bullet and went for the RGM sealed bearings and spacer.  This mod has absolutely transformed the front end and handling of my Dommi.  I now have no braking vibrations, the steering is as light as a feather and none of that thrupenny bitting that can happen when things are tight.  The installation is dead easy (once you get the forks out of the headstock), the bearings are weather proof and dare I say it 'idiot proof' - once the spacer is in, you just tighten things up.

I would highly recommend the sealed bearing and spacer option to anyone who would like light, predictable steering and handling or if the headstock bearings needs attention.

Thanks ,Good reply Bob. I can tell you like the setup!!!. I will be doing that on the Atlas .As long as the bottom bearing sits properly full into the headstock and the spacer is not short the top bearing will probably not seat tight in the headstock and bearings will not be crushed . Sounds good to me. I am interested in how much axial load the bearings can take without damage.

 it's like wheel bearings in that the outer on one end is fully home in the recess whereas the one at the other end is deliberately not quite home when the assembly is tightened up. The wheel bearing setup is achieved by tightening the retaining ring, the steering head by the weight of the bike on the lower bearing.

In the Automotive setting the spacer would be designed to crush a little under a set Torque and both bearings could then fully seat and the correct axial load would be maintained. All a bit sophisticated for our old clunkers . If this thread gets you all exited(!)  and you rush out to adjust the bearings don't forget to undo the pinch bolts or things can get a bit twisted.

.. that needs tolerances unlikely to be met on what you call our old clunkers. I don't see anything wrong with allowing one bearing outer to find its own level as long as the one on the other end is constrained and the spacer is the right length.

Agree about the pinch bolts - easily overlooked when adjusting head bearings.

The only frame I've ever had with open bearings, like those of a bicycle headstock was my 650ss, not very nice and certainly no distance tube.                 In the frames of my 51, 56 and 57 f/beds the bearings were neither ball journal as such or taper roller.                   The head bearings on these frames had the appearance of a normal ball race from one side with the word thrust on the edge of the outer track.                  The reverse side was open while still retaining the fifteen balls, an angular surface ran down to the ball track.           The bearings were assembled into the frame open side out ,packed with grease followed by a heavy felt seal , again with no distance tube. With careful adjustment these bearings gave no trouble at all.  Special care was needed when removing these bearings as they would fly apart if you caught the centre track with the removal drift.

Hi Tony

I fitted the bearings into the frame with the spacer in-between, but before I did that I made sure that the bearing was a transition fit over the steering stem at the bottom.  (A transition fit for anyone that wants to know is a perfect sliding/push fit as opposed to a clearance fit or an interference fit).

It was necessary on my stem - where the bearing fits - to use a long, thin strip of emery paper in a sawing motion with the use of some engineers blue to keep checking the fit and roundness. I probably only had to take off about 1 thou.

I read somewhere that Norton Bracebridge St fitted Angular contact bearings up till the early 1960's . Which would be those that I scrapped. Did not notice that. I use that type of bearing in Bevel Ducati's and they are expensive.  As said above the ball races need to be a snug fit to the stem otherwise there will be chatter that will not adjust out. Think I would measure the stem before buying the bearings.

The reason my taper rollers were too tight was because I didn't know exactly how to fit them in that situation. But the reason I interfered with them in the first place was that I replaced them because  they had 'brinelled' slightly. That is because the angle you turn the head on the road is so small that they wear in the dead ahead direction. I believe this is more if an issue with taper rollers but don't have enough experience of trials.

After sleeping on this ,I have concluded that if Norton thought that this application really needed the more expensive angular contacts ,who am I to think I know better?.As these bearings were superceeded by cheaper cup and cone by AMC ,I will stick with tapers which are designed for both Radial and Axial loading . Those in my 99 have survived 30 years and are still perfect(despite having no seals) The sealed  ball races in the SV 650 failed after a much shorter life . The reference to Angular bearings came from Roy Bacons very usefull Norton Restoration Book.

Dresda, ( Dave Degans) in their builds, used Taper roller's and It was a common upgrade in the 80s, and the Endurance Racers used Taper rollers too, I upgraded my Z650 to Taper Rollers, this was especially important as bikes got heavier and heavier , if I remember rightly my BMW's used taper roller bearings also.

quote:

Re YamaHa R1 not using Taper rollers..........but we may have just been had: Our friend Brian Gillen, MV Agusta’s head engineer, tells us using ball bearings in the steering head does offer advantages regarding packaging, since they take up less space and also weigh less. But in most cases, he says, the choice is primarily cost; tapered roller bearings can cost over twice as much as ball bearings.The big advantage to tapered rollers is that they last much longer, thanks simply to the fact that the load is spread over much greater surface area"..

.SKF says: “Tapered roller bearings have tapered inner and outer ring raceways and tapered rollers. They are designed to accommodate combined loads, i.e. simultaneously acting radial and axial loads. The projection lines of the raceways meet at a common point on the bearing axis to provide true rolling and low friction. The axial load carrying capacity of tapered roller bearings increases with increasing contact angle α.”

PS: "No bike manufacturer makes its own bearings; they nearly all come from outside suppliers. If you have time to take your bike apart and get the old ones out, and if you’re lucky enough to have a bearing supply store in the neighborhood (they’re all over) with a nice person behind the counter armed with a micrometer, you can save substantial cash by going straight to the source."

Once when I checked it out, they were very few bearing suppliers in Britain ,,,,, Chorley Bearings ww.brt-bearings.com/location_chorley.html, my Sister worked here for a while!

As you engineer types would know casting are designed round bearing sizes and not the other way round!

John

That has the look of an angular contact bearing.    After checking ,it is.   I wonder if it was fitted from new. 2 of those fitted in opposition  would seem ideal apart from not being suitable for seals.

I'm curious about the use of the spacer sleeve with sealed ball bearings as in Commando.  The sleeve must be exactly the same length as the distance between the shoulders inside the head tube. Too short and the outer races will squeeze the balls  and too long and the inner races will do likewise. Presumably, Commandos had very tight machining tolerance on the length between the shoulders  but that would not have been critical with the Dommie. So are Dommie head tubes always a sufficiently accurate match to the spacer tube? 

David,

When you think about it, the lower bearing is held in place by the weight of the bike pushing down on it. As long as the inner spacer is always slightly longer than the outer bearing stops there is no need for extra fine tolerances (within reason).

The lower bearing, spacer, top bearing and top yoke are all clamped rigidly together and the upper bearing outer can freely move up or down a little bit during assembly.

In practise, it means that the preload/free play of the steering head bearings is no longer an issue.

OK, in a truly ideal world the lower bearing would be retained by a circlip to keep everything perfectly in place, but in reality it isn't required.

To me it is a great bit of engineering -  preload set without need for skilled fitter, cheap standardised parts, bearings sealed for life - whats not to like? The people going for tapered rollers " to make the handling great" or that "technically, they are the best choice" are forgetting that there are loads of rubber joints between the front and back wheels. Even the featherbed road bikes used simple, last forever rubber bushes for the swinging arm.

Keep it simple = less to go wrong!

Regards to all,

George

I am torn between taper rollers (I know they give great handling and last due to being designed for axial loads) and  Sealed ball races because they don't need adjusting or maintenance,but the downside is that they are not designed for the axial loads and could fail at any time (SV650!) with maybe a short life. If you could  get angular contacts with a retained sealed system and a crush  spacer that would seem to be the dog's doodah's.Don't think you can. COmmando's seem to last ok and handle (sort of!!).on ball races.

Thanks George. I'm afraid I confess to almost total confusion about front forks! Your reply makes perfect sense. At last! Ball bearings don't have as high an axial capacity as rollers, but they certainly have a good deal.

Just looked up SKF. The Norton Commando bearing is SKF 6205-2RSI. Static radial capacity is listed at 7.65kN or 770kg. Axial rating is 50% of radial  giving 386kg. Since the actual load is maybe anout half of 200kg bike plus 100kg rider...that's 150kg. So in theory it is a perfectly reasonable use of that bearing size and type. Whether that applies to a bearing that rotates through such a small angle might be another matter entirely. But that is the issue with all head bearings.

I tried taper rollers but they suffered badly from water ingress and corroded. I now use sealed balls Commando style and they are fine.

I had Taper rollers in both a  Dresda swing-arm and headstock on a Yamaha in the 1970s. Both locations suffered from water ingress and the restricted arc. Quite simply, grease is not carried round as it would be on a rotating component. The rollers never manage anywhere near 360° of rotation.

The sealed bearings are the most (only ?) reliable component on a Commando...simply fit and forget.

I'd be quite happy with original style cup and cones if they are of good quality (and preferably with grease nipples as per the earlier frames).

To work out the stress on a steering head bearing or indeed this part of a Motorcycle frame is not as simple as first thought.  Using Irving's formula, "if the weight on the front spindle is 150lbs  and the distance from the centre of the steering head to the Front Spindle is 10" the bending moment applied to the steering head will be 125 lb/ft, Radial loads of 250 lb will act forward on the bottom bearing and backwards on the top bearing under static conditions. The loads may be multiplied by 3 to 10 times under impact!"

When on the move, through road shocks the forces may vary widely and under heavy braking, the resultant forces may reverse! The variation and fluctuation of stress is more difficult for materials to cope with than a steady load and the most stressed part of the motorcycle frame/ Mechanism as a control point is the steering head.

As for lubrication there are lots of options, somewhere I saw a Taper Roller that was 15mm depth rather than the usual 16.5mm. My 650 SS steering head has holes for grease nipples and two were fitted. Water dispersant sprays exist too.

The heavier the machine and rider combination, the greater the consequences of the mechanical stresses also added to by poor road surfaces, plus the type of tyre fitted and it's frictional properties, old frames can be stressed by modern too grippy tyres, designed for super-sports machines putting out 100 bhp plus.

John

The static load on my 99 steering head when touring 2 up must be around  400lb . which mostly falls on one of the bearings unless preloaded.  So under heavy braking and shock loads  approx. 2 tons.The load is usually concentrated on a few balls in the straight ahead position . No wonder the races get indented .  I think rollers and a regular spray grease for me.

Hi Terry Blenheim, in your post of the 20th/May you say you were suprised to find an angular contact race in your headstock. Your photo clearly shows it to be a ball thrust race as fitted to my 51 Featherbed and exactly as I described in my post of the 15th, oddly enough Robert Tuck has confirmed the photo as being of an angular contact , am I seeing a different photo?

If you enter 7205B into a bearing  cat you will find it described..I have used Angular contacts in Ducati Bevel drive MotorsI have also read that Norton Bracebridge St fitted angular contacts ,but without further research I can't say with certainty these were or were not fitted..But they certainly would be more suitable for the load directions.The Information came Via John Hudson who for some years was  a service engineer and  Service Manager.  A roller thrust race bearing is used in my 99 clutch lifting gear. Helping to reduce drag.

Robert, the photo I'm speaking of was described as an angular contact bearing. It wasn't , it was a ball thrust bearing as I described in an earlier post as being fitted to my 51, 55 and 56 F/beds.                                                            I really can't understand what all the fuss is about fitting head stock bearings.          Members are asking " how far should my bearings protrude from the headstock"      The head stock has a bearing housing at either end, any outer track fitted into either housing must bottom out, whatever sticks out sticks out.                   Assemble the bottom and top bearings ,yokes and felt seals if necessary,  adjust bearings till satisfied, job done, what could be more simple.                        Distance/spacer tubes,  never yet seen one on an 88 or 99 or my 650 ss

Hi Ian,  Following from previous post I have found what looks like a suitable sealing gasket. It is a rubber seal originally for a car thermostat (Toyota Camry 4 Cyl). Sold in Australia under Tridon brand, part no. TTG34. It compresses nicely over the outer race and fills the gap as you will see from attached photos. The gaskets retails here for about A$8 each.

Cheers, Terry

My experience of fitting taper rollers is that they need some extra packing to allow the correct fit of headlamp brackets etc. effective seals may stiffen the steering and make it unresponsive.

Mine has this cover. I assumed when I first had the bike that it was standard, but then found taper rollers. I changed them after MOT advisory about slightly notchy steering. I now assume this was previous owner addition.

I am still pondering the differeces between my Nortons, The Atlas is going to get some Tapers and  a balance check. May have to do the Syd Lawton trick with the wheels offset to counteract the heavy Alternator and clutch.Also like to find out why the 99 has such quick steering,possible a shortened wheelbase

Hi Robert,  I take your point about possible stiffer steering with the seals in place. I am hoping that the application of light grease onto the seal surfaces will prevent this. I hope to give the bike a run in the next week or so.

Cheers, Terry