Rear Linkage Question(s)

[jb.junior]

Oi.  I recently removed my rear linkage for a rebuild and noticed something odd.  (Well, I sort of noticed this a while ago on the bike, but kind of let it ride, as it didn't seem to be bothering anything, and a I knew a full tear-down was impending.)  Namely, the rear-most hole on my linkage arm had a bearing that extended far out the sides of the linkage arm.  The front two bearings were smaller, the same size, and seem to fit more "flush" in the linkage arm. 

In order to fit this larger bearing, a larger clevis on the rear shock bottom connection was needed.  What resulted is, in my opinion, too much bearing sticking out of each side of the connection, potentially allowing for lateral movement of the shock on its pivot point.  Some details:

• This is a Robem Engineering after-market linkage kit.  I just realized today that this must be an earlier iteration, as it's designed to attached to a shock with a clevis, and not a shock with double eyelets.  If you look on the Robem website, they explain that their new linkage kit is designed for double eyelets. (Aside from this difference, I wonder if there any other differences, like changes in the dog bone length, etc...https://www.robemengineering.com/product-page/fz-07-linear-linkage-1)
• The width of the linkage arm is 23mm. 
• The width of the two forward bearings that are fit in the linkage are 25mm.  (This leaves 1mm sticking out of each side, which intuitively seems right to me.)
• The rear roller bearing is 30mm width.  Which leaves 2.5mm sticking out of each side, which does not seem right to me.
• The ID of the lower shock clevis is 30mm.
• On the OEM linkage arm, the bearings are indeed all the same width, per the parts ordering system.  But I'm not sure what width these OEM bearings are.  I'm assuming 25mm.  (It'd be great if anyone could please measure.)

Would there be any reason to have this longer bearing, and wider clevis installed on purpose?  I'd think not.  Perhaps whoever put this shock on there at one point maybe had a shock with a clevis that didn't quite fit, so they got the longer bearing to make it so.  Just to make it fit.  But wouldn't it just be easier to get another clevis?

My plan is to tell the shock rebuilder (Traxxion) to put a 25mm ID bottom clevis on the shock, and replace the bearing with a 25mm when I replace all the bearings.  Unless this was all done for purposes that I'm not understanding, and I should keep it like it is.

 

 

Edited February 6, 2023 by jb.junior

[cornerslider]

I have the OEM linkage. I tear it down every couple seasons to clean/lube it. I always wondered about that myself? It's been like that since day 1 (I'm the original owner). There must be a reason for it, but I have no idea why???? 

[jb.junior]

12 minutes ago, cornerslider said:

I have the OEM linkage. I tear it down every couple seasons to clean/lube it. I always wondered about that myself? It's been like that since day 1 (I'm the original owner). There must be a reason for it, but I have no idea why???? 

So the OEM linkage for sure looks like that?  Hmm, because it you look at the parts list  and diagram on Partzilla, the three bearings are the same part.  So they have to all be the same length.  (Part link: 

Just a moment...

)

[cornerslider]

I see what you mean on the parts list.... It certainly looks to all be the same? I took a pic of mine (just so we are talking about the same part). 

[jb.junior]

It's hard to say with just visual.  The bearing should stick out a little bit.  The only way to confirm would be the measure the width of the linkage and measure the width of the bearings.  

[jb.junior]

2 hours ago, cornerslider said:

I see what you mean on the parts list.... It certainly looks to all be the same? I took a pic of mine (just so we are talking about the same part). 

And that's also where the linkage arm connects to the linkage -- to the front of the bike.  The spacing issue I'm having is where the linkage arm connections to the rear shock - in the back of the bike.  But maybe there's a spacing difference up front on an OEM bike?  Hard to say without measuring.  Do the rear connections have the same amount of bearings sticking out?

[cornerslider]

Now I'm second guessing myself.... Based on the parts diagram, the spacing should be equal.... I see in your pic of the shock-to-linkage has a bigger gap than it seems like there should be . I took a pic of mine with a K-Tech Razor "R" shock mounted to the link, and it appears to be nearly flush? Yours has a visible gap

[jb.junior]

2 hours ago, cornerslider said:

Now I'm second guessing myself.... Based on the parts diagram, the spacing should be equal.... I see in your pic of the shock-to-linkage has a bigger gap than it seems like there should be . I took a pic of mine with a K-Tech Razor "R" shock mounted to the link, and it appears to be nearly flush? Yours has a visible gap

Ok, that's a good data point.  Thanks for taking the time to take those pics.  

The OEM bearings should be in this week.  I'll measure and share.

[sweetscience]

What model shock is that? 

The clevis may have been changed to a larger size to get the necessary clearance with the linkages.  Hence, a larger clevis needs longer bearing. 

Or, the shock was not designed for the 07, hence the mods.  In this case I would check also the dimension of the top eyelet bearing used is in conformity.

 

[jb.junior]

7 minutes ago, sweetscience said:

What model shock is that? 

The clevis may have been changed to a larger size to get the necessary clearance with the linkages.  Hence, a larger clevis needs longer bearing. 

Or, the shock was not designed for the 07, hence the mods.  In this case I would check also the dimension of the top eyelet bearing used is in conformity.

 

Penske 8987 triple.

The linkage is only 23mm wide -- a 25mm clevis should clear it easily?  The other end of the linkage arm connects to the linkage, and I'm pretty sure that the ID on that is 25mm, but I'll measure tomorrow.  It fits.

Good call on the eyelet bearing.  I remember everything fitting fine and not having play and remember it fitting in to the mounting spot on the engine just fine.  I don't have close up pictures, but the ones I see don't show any extra space, or anything that indicates a bad fit.  I've sent the shock off for rebuild already, but I'll make sure to double check when we try to mount it up.

[jb.junior]

And I should have mentioned this before, but a few people have seen this spacing on my linkage and asked about it and said it didn't seem right.  I had one suspension guy get close on it and move some things around, and he said it's probably ok, but to change the clevis on next rebuild.  So a few eyes have been on it and didn't notice anything obviously compelling about why it should be that way.  I guess I can have the suspension guy change to a 25 mm clevis, but just keep the old 30mm one, and keep the 30mm bearing, in case we notice that it was that way for a reason and need to put it back on.  Would be easy enough.  But I'm still just curious about what it is on there...

Edited February 7, 2023 by jb.junior

[M. Hausknecht]

Jeff, my guess is that was the clevis laying around and available when the shock was first installed, and the wider bearings were fit to take up the extra width. It probably worked without problems and any idea to change it at some point was soon forgotten. I have eyelets at both ends of my Ktech (AP version 2 knuckle), so I'm no help. 

[jb.junior]

40 minutes ago, M. Hausknecht said:

Jeff, my guess is that was the clevis laying around and available when the shock was first installed, and the wider bearings were fit to take up the extra width. It probably worked without problems and any idea to change it at some point was soon forgotten. I have eyelets at both ends of my Ktech (AP version 2 knuckle), so I'm no help. 

I'd say that's probably a good guess.