Article [13] ST1300 - Maintenance - Fitting Wheel Bearings - What the manuals don't tell.

Kevcules said:
Very confusing as to why the spacer isn't a few mm shorter, to prevent the problems you made us aware of.....
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I still have the same question, why is the spacer not shorter or equal as the hub shoulders distance?
Is the spacer acting as a seal, preventing dust and water to get from the hub to the bearings, or something else? This question is not answered yet and stand as a key point to understand the installation procedure.
Everything that have been said on this thread is very straight forward, but I keep wondering about the design of the spacer.
Thank you @jfheath for bringing clarity on the practical side of the installation, as always your work is very much appreciated!
 
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Sidekick said:
I still have the same question, why is the spacer not shorter or equal as the hub shoulders distance?
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It is a good question - one that I have pondered a number of times, and have not been able to find an official answer. Or any answer other than the one that I have come up with for myself.

The hub of the wheel is a cast alloy. I know next to nothing about the structural properties, but I have a few experiences.
  • For many years I rode a pushbike with a frame that was made of Reynolds 531 tubing. I never knew much about it but I knew it was supposed to be good - light, strong and had a certain amount of flex in it. I never appreciated how good this was until I replaced it with a more modern aluminium alloy frame. It is rigid. Absolutely no flex in it at all. It is a bone shaker.

  • At one time, I used to build and true my own wheels and used a cast alloy wheel truing frame. On one occasion, too lazy to turn the threaded rod the held the wheel axle in place the extra fraction I tried to 'spring' the two legs apart, as I would when trying to get the wheel hub between the bike's fork legs. The entire arm of the truing frame snapped off.

  • The rear ABS sensor on the ST1100 is a small cylinder which slips inside a hole in a short, cast alloy stalk - part of the rear final drive housing. It is a good, slide-in fit. Over the years the sensor rusts and the alloy corrodes, and it gets stuck. Faced with a failed sensor, it had to be removed, but would not budge. There was a slight gap at one point where the metal shim fits to adjust the air gap between the sensor and the pulsar ring. Enough for the tiny wedge shape blade of a modellers screwdriver. Armed with the experience years back of the snapped alloy truing frame, I knew that this had to be a very delicate procedure. I very gently gave my tiny wedge a tap into the gap, with nothing heavier than a toffee hammer, and a very light touch. I was being ultra cautious. Second tap, the bracket snapped off. Honest, it was a serious over-reaction to the slightest of taps. It was nothing.
So my thinking is that the cast alloy hub isn't really designed to take 78Nm or 108Nm force that is applied to the centre races of the wheel bearings when tightening the axle.

If that is the case then I reckon that some other things have to be true:

  1. The squeezing force has to be taken by the spacing tube. This means that the tube is clamped between the two bearings and is not free to rattle around.
  2. The length of the spacing tube must always be more than the distance between the hub shoulders to allow for temperature expansion / contraction of the alloy hub. (Heat / cold from tyres, brake discs, bearings, exhaust, sun, rain.... )
  3. As a result of #2, one bearing has to identified as the one to be driven in first, otherwise the wheel will be slightly off centre.
Years back, I used to wonder why there was a spacer at all on my previous bikes - it just seemed to be something that rattled around between the bearings when I went over bumps. But I never changed the bearings on any of those bikes.
 
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jfheath said:
I forgot to mention that pretty crucial point.

Here are some diagrams and more detailed explanation from me.

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Can the first bearing hub shoulder be considered as the reference alignment point for the front wheel on the axle?
I am in the process of replacing the front wheel bearing for the second time after having done it incorrectly recently. The first time, I heard a whining sound coming from the hub and the wheel was misaligned.
Thank you!
 
You drive in the first bearing to the shoulder.

The spacer goes in and then the second bearing goes in until the inner shell meets up with the spacer. Making contact is enough, you don't drive it beyond that if you want your bearing to last longer than your tyres. But they must meet up.

BUT

You do not choose which bearing is first. Which side you drive in first is specified in the workshop manual. I try not to write it down anywhere because I will think that I have remembered, and I know that the day will come when I remember incorrectly. Next Thursday.
It is the left hand side for one wheel and the right hand side for the other - and yes it matters. The difference could affect (say) the front disc rotor clearance through the brake caliper.

Probably not quite, but if you believe that, you will remember that it is important enough to get it right.

Or you could watch the video of me putting one in. I did that one correctly. The side of the wheel with the abs pulsar ring is the right hand side.

I'll look it up and post it here, but Ive just got off the pushbike and right now, standing up will be quite a challenge.

Rear wheel - drive in the left bearing first. (it doesn't help that the manual then says drive in the left bearing - but I have checked this out with the diagrams and left first is correct.
Front wheel - drive in the right bearing first, then the left.

But you should never trust information that you get from someone on the internet . Always check it out.
 
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jfheath said:
You do not choose which bearing is first. Which side you drive in first is specified in the workshop manual.
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yep...
Rear wheel - drive in the left bearing first. (it doesn't help that the manual then says drive in the left bearing - but I have checked this out with the diagrams and left first is correct.
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From a mechanical POV it might seem strange to have the narrow, LHS bearing going in first as alignment reference, and the heavier, double-row, load bearing RHS one to be brought home gently till inner race "touches" the spacer tube, but the brake/rotor side is in focus there...
 
jfheath said:
A PDF file to describe how to fit a pair of bearings into a wheel of the ST1300. It is straight forward, but if you don't know the correct procedure, there is a good chance of getting it wrong.
This pdf explains what things could go wrong, and how to avoid them.

A quick rundown and a few images - to remind of the content.
Insert first bearing - it matters which side goes in first.
Insert spacer
Insert second bearing driving inner and outer shell - until the inner shell touches the distance collar.

A few images of what could go wrong. Full diagrams and explanations in the attached pdf file.
(93 views of original file - updated 110221 to correct error P3 see post#17)

1586422773820.png 1586422797415.png 1586422621921.png

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Other related articles:

Article13.png ST1300 - Front & Rear Wheel Install and Front Axle Animation
Article13.png ST1300 - Front wheel bearing replacement [VIDEO]

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The attachment is VERY informative! Thank you!
 
jfheath said:
A thought popped into my head - something that I meant to try ages back, but never did.

Perhaps a much more certain way to install the bearings would be to install the first bearing in the usual way until it meets the shoulder, and then install the second bearing by using a long threaded draw bolt. Fit a bearing driver on each end and pull in the second bearing to meet the spacer.

Simple idea and I'm not the first to have considered this - but the thiught that popped into my head was to do with the mechanics of this.

When the axle is installed, it is tightened to quite a high torque, and it in doing so it is pulling the entire assembly on the inner race of both bearings. The axle distance spacer fixes how close together it can pull them. But if the outer bearings aren't driven in far enough, tightening the axle bolt could side load the bearing.

So if a threaded draw-bolt is used to pull them together, when do you stop pulling ? Do you apply the same torque as when tightening the axle, or is something much smaller adequate.

My feeling would be the latter. Once the bearing is tight against the spacer, it cannot get any closer, so stop tightening as soon as the bolt becomes tight. Any additional tightening cannot move the bearing further, and only serves to stretch the draw bolt, or strip the threads.

Is my thinking correct ?
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Just replaced the 4 bearings in the rear wheel with 3/8 rod and washers. Worked perfectly.
 
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