Rear wheel bearing failure

[Steve Case 943]

Thank you Honda-san,

 

for you are the purveyor of fine motorcycles with some of the dumbest faults known to man...

 

I put my NC750X 17 reg thru its first MoT today and the rear wheel bearings have failed, I knew this was a possibilty as a friend of mine had the same issue on his (Adventurescot are you out there) NC750X which is also a 17 reg.

 

The reason for the post is the cause is known as the distance piece between the rear wheel bearings is too short and does not support the bearing inner races correctly, my friend had this shown to him by an Italian Honda shop who had a fix by using a longer distance piece.

 

The Mot/repair shop I use were aware of bearing failure on the Hondas but not the cause. I asked when they replace the bearings if they can get a measurement of the gap.

 

There is an Italian fix out there, but we need a fix here in Blighty and its probably as simple as a longer piece of steel tube or some shims to take up the slack. If anyone is aware of the Italian bike shop or of the dimensions of the distance piece or has used their own method to remove the slack let us know.

 

For everyone else please check your rear wheel to be on the safe side and remember that there should be a remedy shortly - in the meantime get the bearings changed (not that expensive 6204 bearings I was charged £24 for a pair of SKF sealed type) as they will last long enough for any remedial work to be carried out.

 

Most of all, keep riding if your not all snowed in....

[Steve Case 943]

Right update, Raceways in Stevenage Old Town replaced the bearings and had a look at the 'gap' for me.

 

They described the gap as not substantial but there is a gap, and this means the inner race is not supported.

[Tex 36,816]

Quote

They described the gap as not substantial but there is a gap, and this means the inner race is not supported.

 

Really tricky one, this. Too short and the bearings will be ‘loaded’ as the axle is tightened - too long and the bearings will be loaded as the outer is pushed home. Shimming would probably provide the answer but that would require a lot of time and error and all too much bearing removal and refitting. 

[Steveg 1,022]

Seems a real mixed bag re life on nc750 , but a lot of reports of 20-30k fails not good , may be a bad batch ? Never jet wash my bikes and never got less than 60k miles from any other bike wheel bearings , 80k+ on triumph sprint original bearings

My nc750x seems fine at 17k will keep a eye on them 

Cheers Steveg

 

Edited January 6, 2021 by Steveg

[shiggsy 529]

I do jet wash my bike and got 60k out of the originals.

[outrunner 4,457]

The sprocket carrier bearing went on my 2016 X at 24000 mies but I just replaced the lot as a matter of course as they are not really expensive although I do my own maintenance, now at 57000 and all good so far.

 

 

Andy.

[Grumpy old man 4,670]

Not sure I quite understand the issue with the spacer between the 2 bearings, as I remember one of the bearings is tapped up to the stop in the hub then the spacer is put in from the other side and the second bearings inserted untill it meets the spacer the danger is you'd tap the the bearing in too far  and distort the race by pushing it to hard against the spacer, no gap.

Edited January 6, 2021 by Grumpy old man

[Tonyj 6,907]

Mine went at 24 k done three on back wheel .

[Steveg 1,022]

Looks to be a bit of a lottery ..

[davebike 943]

I lay money on tyre fitters and doing the rear wheel spindlu=e up with power tool   should go up to about 60Ft/lb    air go=un 1/2" dose 250 /500 

I seen inner spaces rippled !

 

Grease the bearings and spindle each time it is out!  don't over tighten! replace nut if /when it no longer is tight to wind in ! 

[Slowboy 20,357]

19 minutes ago, davebike said:

I lay money on tyre fitters and doing the rear wheel spindlu=e up with power tool   should go up to about 60Ft/lb    air go=un 1/2" dose 250 /500 

I seen inner spaces rippled !

 

Grease the bearings and spindle each time it is out!  don't over tighten! replace nut if /when it no longer is tight to wind in ! 

I’d agree with that Dave. That’s one of the reasons why I do my own tyres, including balancing. I seem to have had fewer bearing problems since I did. The windy hammer is a useful tool but in the wrong hands can be quite damaging.

[davebike 943]

I have a realy good Windy hammer 

It is great for undoing

I use it in very limited places for doing up  and with great care

Wheel nuts on anything 2, 3, 4, 6, or more wheels should not be  Just banged up EVER!

 

Every week I we see bikes with over tightened wheel nuts 

Last year I had real issues with a new belt on an F800 BMW  phones the local independant as I could not move the belt adjuster

"You will not whth the wheel on"  "I have got one stud that will not move"  "Bet Watlings catford did the Tyre"  having drilled the bolt head off  and undone the thread with my fingers  Yes the tyre was fitted by Watlings who whindy spanner the bolts !

The BMW expert  says they see 4/6 a year  the taper seat steel bolts bite into the soft alloy wheels and have to be drilled

 

[Slowboy 20,357]

I’ve also got a windy hammer, in fact I’ve got two now because once the 250ft/lb one was not enough 😳. Like you they are for undoing, not doing up.

 

And that nut I couldn’t shift without a 500ft/lb windy? The front sprocket nut on my Daytona 1000 when I fitted a new chain and sprockets. And no, I hadn’t fitted them previously. Luckily the output shaft was not damaged.😁

Edited January 7, 2021 by slowboy

[Steve Case 943]

I use a torque wrench and tighten to 100Nm as the book (98Nm but my torque wrench is not that accurate).

 

The problem as I see it is that the inner race is being moved inwards as the wheel is tightened just enough that it's putting a side load on the bearing (or the load is no longer radially outwards more truthfully).

 

I am going to look at shimming as there will be a tolerance on a 6204 bearing and I just need to reduce the displacement below that, not sure how to measure the gap at the mo. But I'm sure there will be lots of suggestions.

[Steve Case 943]

My Daytona had the front sprocket done up with a Windy gun and i had a powerbar with the leg of a towercrane on the end of it and I couldn't crack it.

 

I hired an 18Vdc impact driver and put this on the nut, thinking "this may take a while if it works", BRAAAAP and off she dropped in less than 30 secs....

 

Since I have the name of the bike shop that did the work on the bike I was tempted to pop past and tighten their nuts with a windy gun!

[Steve Case 943]

Oh and finally, no part of my anatomy will be used in measuring the width of the gap before anyone makes the suggestion...

[Grumpy old man 4,670]

44 minutes ago, Steve Case said:

I use a torque wrench and tighten to 100Nm as the book (98Nm but my torque wrench is not that accurate).

 

The problem as I see it is that the inner race is being moved inwards as the wheel is tightened just enough that it's putting a side load on the bearing (or the load is no longer radially outwards more truthfully).

 

I am going to look at shimming as there will be a tolerance on a 6204 bearing and I just need to reduce the displacement below that, not sure how to measure the gap at the mo. But I'm sure there will be lots of suggestions.

If you can tap the bearing in far enough to trap/bind the spacer then surely that would be fine as then there would be very little/no gap between the bearings and spacer and any tolerances at all would be taken from both bearings. Adding shims between the bearings and spacer would just put you in exactly the same position just adding another piece of metal that might be even softer. Or am I missing something?

[MatBin 5,080]

2 hours ago, Steve Case said:

I use a torque wrench and tighten to 100Nm as the book (98Nm but my torque wrench is not that accurate).

I also read it depends on friction of nut/bolt thread as to what torque is actually being applied?

[kayz1 2,928]

Go here, as it will depend upon the bearing you buy/bought.

https://www.skf.com/uk/products/rolling-bearings/principles-of-rolling-bearing-selection/general-bearing-knowledge/tolerances

[Slowboy 20,357]

18 hours ago, MatBin said:

I also read it depends on friction of nut/bolt thread as to what torque is actually being applied?

The science of thread strength and torque settings is very complex. Having worked in the nuclear industry for 32 years you might not be surprised that this was important to us. We used to have specialists who could do the out of spec assessments for special circumstances. It was not straightforward. The torque figure is really an easy, rough and ready way of giving you the right fastener stretch and hence clamping force. The designed in factor of safety will mean there’s a tolerance between which it will be ok. The manufacturer will never give you this margin because the daft beggars will want to tighten it up to the top of the tolerance “just to be on the safe side” (spoiler alert, it isn’t on the safe side).

it also depends whether you are stretching the fastener into the yield zone (single use fastener, replace every time on disassembly) or whether you are within the elastic zone where the fastener fully returns to its original length. 
Then there’s the friction between the surfaces of the threads, lubed and not lubed, the thread angle, the properties of the fastener material and those of the material being fastened.

 

Thats why replacing all your fasteners with stainless or titanium ones is often not such a good idea, especially in strength critical areas, as the torque loads are specified for the OEM zinc plated fasteners with different material properties.

 

Dead hard sums, especially when you are working at the limits of the materials.

Edited January 8, 2021 by slowboy

[djsb 491]

https://en.wikipedia.org/wiki/Young's_modulus

[Defender 3,834]

On 1/8/2021 at 09:29, slowboy said:

The science of thread strength and torque settings is very complex. Having worked in the nuclear industry for 32 years you might not be surprised that this was important to us. We used to have specialists who could do the out of spec assessments for special circumstances. It was not straightforward. The torque figure is really an easy, rough and ready way of giving you the right fastener stretch and hence clamping force. The designed in factor of safety will mean there’s a tolerance between which it will be ok. The manufacturer will never give you this margin because the daft beggars will want to tighten it up to the top of the tolerance “just to be on the safe side” (spoiler alert, it isn’t on the safe side).

it also depends whether you are stretching the fastener into the yield zone (single use fastener, replace every time on disassembly) or whether you are within the elastic zone where the fastener fully returns to its original length. 
Then there’s the friction between the surfaces of the threads, lubed and not lubed, the thread angle, the properties of the fastener material and those of the material being fastened.

Thats why replacing all your fasteners with stainless or titanium ones is often not such a good idea, especially in strength critical areas, as the torque loads are specified for the OEM zinc plated fasteners with different material properties.

Dead hard sums, especially when you are working at the limits of the materials.

We have our torque wrenches calibrated every year and use aircraft type Nord Lock washers which are replaced every time of the rotating disc/drum/gantry items.

When you have something weighing almost 2 tons spinning at 150/180/210 rpm anything coming off can cause a lot of damage, we have on machine with a dent in an access door where a counterbalance weight came off it at speed, fortunately it was still under the project teams care when that happened.

[Steve Case 943]

Just to make the point 95N, 100N, 102N is close enough as its a grubby wheel nut done up with a halfords torque wrench. But i'm riding a Honda commuter not a eurofighter so I may be ok.

On the other question the bearings cannot be tapped in snug to the spacer/distance piece as it is too short.

However this made me think maybe the distance spacer thing was the correct length before the wheels were coated. So if i remove the coating in this area it could fit.

[Johnnie Mototrans 2,742]

Perhaps we all overthunk this.

Bigly. 

[Steve Case 943]

Probably.

I'll just knock the bearings out and shim it in the summer, then it'll be fixed and the bearings will not fail again.