Counter Steering: Does Anybody Have An Explanation? - Demystification Required

[Bill Thomas]

I had a BIG Off at Oulton Park, "Sun Stroke " , Took to the Grass at silly speed , All My Fault ,
She shook her head and threw me off, Later found the lower bearing was loose in the frame,
She slapped so hard , Broke the lock stops I had made,
So packed the bearings out with feeler Gauge / Loctite.

And after a Proper Tank Slapper , Over the top job !, Mallory Park, I fitted Wider Handle Bars,
That made the Steering / Me Very Nervous, Too much input ?.

 

[greg brillus]

Yep.......on some bikes i've stripped the front end and found the bearing races either split, or a big chunk like a piece of pie broken away........Loads of bent lower links.......if the top link is bent then something pretty bad happened.......the links are not easy to straighten.......having 2 arms, it is like trying to straighten a set of bent handlebars.......not easy......I've only had one lower link bent too bad and i can't fix it.......the large eyes have become oval.......paperweight or bin job.

 

[timetraveller]

I have an idea to run past you chaps regarding the new steering heads. This comes about as several people have asked for them to be set up with taper roller bearing top and bottom. This meant making stainless steel top hat bushes for both top and bottom bearings to compensate for the Internal diameter of the bearings which are larger than the outer diameter of the steering column. It also meant taking the head lug off the oil tank and machining both the top and the bottom to take the outer diameter of the taper rollers. The chap who did the machining for me also obtained the bearings and assured me that getting them was a bit like obtaining rocking horse dung. However I discovered a few month ago that these bearings are actually now listed and are specifically for motorcycle head bearings. I have spoken to the firm which machined the new stems and it would be a trivial and zero cost option to machine a batch with a slightly increased diameter to take the new bearings. That would get rid of the top hat bushes but the washer FF36 would still be needed. The new lower motion blocks would be unchanged as would everything else. It would still be necessary to machine the inside top and bottom of the head lugs which means taking those off the oil tanks. I have refrained from putting this on the forum before as I have plenty of other things going on at the moment but this seems a good opportunity. I realise that this will only appeal to a limited number but if you have a head lug which has been damaged or has loose bearings then this would be a solution and a way of getting rid of all those loose ball bearings which head for the workshop floor when released.

 

[John Reynolds]

Hi Timetraveller,
Just a suggestion but, if there is sufficient 'meat', it might be possible to have the outer races machined to fit the existing bearing housings in the head lug. I have been supplied with taper roller bearings for a Velocette front hub where this has been done (because the original pattern bearings are no longer available) so it is possible and would be a much cheaper and more convenient option that having the housings machined.

 

[oexing]

Converting the steering head for taper rollers was on my list certainly, so went for available bearings for classic BMWs. These have 51 mm o.d. , just half a millimeter more than 2" standard, so super. Inner dia. is 34 mm , so easy to have a bush on the stem loctited. Total height is 12 mm, so acceptable. Critical matter is to get bearing seats in head lug concentric and parallel. When looking at a company for this job you better ask all details as to how they want to achieve this perfectly.
I had my Hunger manual valve seat recess boring head with vertical plus horizontal feeds on a double pilot for getting sizes right. I wonder how any company will go along for the same job.
As to low speed wallowing or shimmy as this is called: I do not believe in flawed bearings to cause this effect. Critical thing is often some weight at the rear end on soft luggage carriers that will effect the front end a lot for the low speed shimmy at speeds around 60 - 90 kph only. I had this shimmy long time ago with the Earles BMW when I came back from Munich with two new bench grinders, one at rear of dual seat and one on the luggage carrier. So this load was far from rigid on the bike. As soon as I went faster than 60 kph I got a massive wallow in the fork from this, hydraulic standard steering damper too weak to fight it. So with courage and concentration I accelerated to over 100 kph and it was allright again for the trip home 30 km .
A motorbike is a very dynamic contraption, not easily understood and fixed in case of troubles. Different speed ranges have different roots of the problem. A lot is down to tires on particular bikes and these got the job to do when road behaviour is less than desirable in times.

Vic
BMW taper roller 34/51/12 mm

 

[Keith Martin]

The loose balls vs tapered bearings has always puzzled me. When I first built a road racing Triumph 650 with the help of Jack Wilson I had installed a tapered bearing kit on the frame. Jack came in and told me to take them out as the tapered roller bearing kits were "to sell not to use".
We then installed loose balls and races but instead of putting in 20 balls top and bottom he installed 19 top and bottom. I raced the bike that way for years without any head shake or trouble. I was young but learned quickly not to question Jack when it came to fast race winning Triumph motorcycles.
I have seen photos of Yamaha Moto GP bikes using loose balls in their steering heads.
Are tapered bearing better for long term street riding? Less maintenance?

 

[Peter Holmes]

It has been discussed on this forum previously, but Ron Kemp only saw a benefit in converting the bottom headstock bearing to taper roller, on the basis that it is the bottom bearing that takes the battering, and the taper roller is more robust, the top bearing can stay as ball bearings, makes sense I suppose, maybe the best of both worlds.

 

[oexing]

My view is the taper rollers should be fine longer with good line contact. And the fit in head lug and steering stem is a lot wider so the press fit will be durable - unlike old type ball bearings. But due to the thin races of taper types the fit in head lugs has to be perfect. In cruel reality head lugs on many or most production bikes can be found less than perfect , meaning out of round from welding the frame up. So there are companies which got a sort of piloted reamer to get the oval bore oversize for outer race slip fit but no oval races. Then the races get Loctited in and you are good to go.
I do not think you find many ball bearings on modern serious bikes . Taper types are standard for decades so there should be a good reason.

Vic

 

[timetraveller]

Thank you John for your suggestion. I have been out in my man cave trying to find enough parts to measure. There is a taper roller bearing with a 30 mm ID. 51 mm OD and 15 mm deep. The problem is I can only find the cup apart of a cup and cone type original bearing so I do not know the over all size of the original bearings. Whether it would be sensible to reduce the OD of this bearing I do not know. The thin end of the tapered outer is about 0.5 mm so, even allowing for it to be a heated shrink fit in the head lug it is getting thin. As for the depth does anyone have the overall depth of a cup and cone plus ball bearings?
One thing where the taper rollers wins out over the originals is cost. Each of the taper roller bearings cost just over £20 while a cup and cone alone (i.e one of each) is about £120, then there are the ball bearing.

 

[Bill Thomas]

It has been discussed on this forum previously, but Ron Kemp only saw a benefit in converting the bottom headstock bearing to taper roller, on the basis that it is the bottom bearing that takes the battering, and the taper roller is more robust, the top bearing can stay as ball bearings, makes sense I suppose, maybe the best of both worlds.

I have been running the Ron Kemp idea for many years, Standard forks,
It's not easy to fit a taper in the top, I think that's why Ron says just the bottom,
For me it steadies up the steering a small bit, Not as loose as Balls.
Plus the cost of balls Cup and cones is huge.