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Swinging arm pins

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IanG View Drop Down
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    Posted: 29 Jul 2020 at 19:59
 Came to check my dogbone bearings expecting them to need some attention although they were good when I last checked them at the same time I replaced the bearings and pin in the swing arm a couple of years back??   ( I hardly use the bike so it only does about 500 miles a year)

Anyway,the bone bearings were well greased and sealed but the shocker was the new (ish) s/arm bearing,it was almost locked in place although well greased and sealed.

Bearings  directly after pulling the pin




Pin after wiping the grease off



These are the now more usual caged roller sets bought as a kit with new pin,my thoughts are inadequate heat treatment as the pin is pretty soft

Has anyone else noticed premature wear on these items?

Judging by the indentations the rollers seem to be shorter than full compliment and thus carrying more load

Thoughts..



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Post Options Post Options   Thanks (0) Thanks(0)   Quote wigginsjp Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jul 2020 at 20:21
Ian I’ve seen that all too regularly as it goes 

I only see it on the caged bearings even in a good regularly serviced condition. 

The small fiddly needle Aprilia ones I’ve dealt with, provided they were greased and serviced the same are never that bad. 

I may be wrong but more fine needle bearings will distribute the load better than less but twice the size ones. Of course caged is easier to maintain but I’ve seen it on every caged bearing set of greased over the years 

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IanG View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote IanG Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jul 2020 at 20:39
That was my thinking as well but as these have less than 1500 dry road miles and probably nearer 1000 and they are still well greased that seems almost not fit for purpose to my way of thinking.

Running a swiss file across the edge chamfer tells me the pin isn't hardened and tempered,in fact looking at the end machining marks it looks just like it's been drilled and parted off a length of silver steel.

I doubt that could be so but looks sure like it.  I'll have a chat with Griff when I order spares and see what his expectations are.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote 426hemi Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jul 2020 at 20:40
I think a problem with swingarm and linkage bearings is they only move in a very small arc, never a full rotation so once a small indentation happens it just starts to magnify it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wigginsjp Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jul 2020 at 20:59
I’ve a race torx dog bone and I’m sure they are titanium pins under caged bearings 

Will have a look at that as it’s not been on long and is most likely making its way onto the Tuono shortly. Will see how it’s wear is. 

But those pins are soft. I’ve done the same with a file and questioned its suitability 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Spoonz Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jul 2020 at 21:09
You might find in the tech specs that the load bearing capability of the bearings used is not sufficient. Simply because of load distribution on each needle. Lube will only reduce abrasion, that almost looks like the needles have pressed into the pin, the ends of the groove look burred over which doesn’t happen from normal surface wear Generally. 

I doubt any form or lube would have made the difference.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Stevex Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jul 2020 at 21:12
That is terrible Ian, that pin doesn't look as though it's made from the correct material or had any form of hardening. Where did you get them from?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote IanG Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jul 2020 at 21:23
Now there's the problem,that's why I wondered if mine was unusual because this was a bearing set I got from Griff.

If this was normal wear I doubt he'd sell them so I'm thinking perhaps this was a rogue pin somehow Confused

I'm due to put in an order shortly so I'll try and speak to him then

The pic off the bearings themselves looks odd probably due to the flash,but they were well lubricated with waterproof grease and you can see there's more than enough of it.

Couldn't believe it when the pin was reluctant to pull out


 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote IanG Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 2020 at 21:37
Having thought about this overnight I've decided to pull those caged bearings and replace with new genuine Aprilia spec full compliment loose rollers and a genuine pin which hopefully will be hardened and tempered.

While I have the bearings out I'll look into fitting a grease nipple as well

I do wonder if some sort of solid bush would be better in that location than a needle roller ?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tfcoulson Quote  Post ReplyReply Direct Link To This Post Posted: 02 Aug 2020 at 12:29
Looks exactly like mine, I'm sure I bought mine off AP a few years ago when the previous had snapped. I have probably put in 1000 miles or less in the last few years too as its spent most of its time in bits. Was thinking maybe the shock was a bit seized too but dont know.
Are the needle bearings not the oem ones then?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote IanG Quote  Post ReplyReply Direct Link To This Post Posted: 02 Aug 2020 at 12:55
Mine aren't certainly,the OE spec Aprilia parts are full complement loose needle rollers that fall out when you remove the pin if not held in place by grease.

These are an Aprilia only part,the more common replacements are caged rollers where there are probably half the number of rollers captive in the cage.

I'm guessing these caged units are up to the job but I question whether the pins supplied with them are. Certainly the spot loading from each of the fewer needles will have a higher surface loading and the pin that came with my bearings was nowhere near the hardness required to accept this.

In fact given my 50 years as a precision engineer working with all sorts of materials from plastics through exotic alloys I'd say there was no heat treatment at all and the pin was just a short length of untreated high carbon silver steel or similar, which quite patently wasn't able to take the surface loading and the needles just pressed themselves into the pin.

The sets in the dogbone which are probably original to the bike are still shiny and unmarked compared with hardly used s/arm unit that's completely knackered.

Perhaps an OEM pin would work fine with the caged rollers but I'm not prepared to try,while I have the arm out I'll fit a grease nipple and then a new OE spec bearing complete for peace of mind.

Sometimes perhaps the designers really did get things right first time round.


 


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