Any idea why my Rear Shock Bolt bends in the middle?

[RangerRick]

This is the second time I have replaced this bolt, any idea why it bends in the middle, maybe M2's shock is to stiff for it? Maybe I need a higher grade bolt than the stock one.

 

[EdMat]

Dang, you must have some big potholes up there in Oregon. For it to do that I would think it would have to completely bottom out so it would not be the stiffness of the shock.

 

[RangerRick]

Yes we do. But after looking at the parts list, and looking at the hardware on the stock shock, I believe Marcus's hardware of attaching his shock fell short of the stock hardware. His only uses steel spacers on either side of the shock instead of a thick collar (150) that the bolt passes through on the stock shock.

 

[Snowbelt Spyder]

Removed. No air suspension. Misread the parts diagram. Thanks Rick.

 

[RangerRick]

Yes a 2013 ST, no air suspension, just a rear shock that went from stock to an M2 Shock - I also have M2's on the front.

 

[CopperSpyder]

Do you use that as a jacking point?

 

[hogmemberisold]

If this has occurred a couple times now, and the bike doesn't have/use an air bladder, then it's probably under sprung.

 

[Mikey]

Are you physically bottoming the shock out? Does he have any kind of damping adjustment on that shock? Is it a rebuildable shock and how many miles do you think you have on it and how old is it? That part you called out 150 is that all the way through the shock head with that bolt going through the whole assembly. That tube is it alum or steel? it should be bending the bolt by itself; I would think that tube should be bending also. It sounds to me like ether that shock needs to be rebuilt and freshen up for your weight better or replaced! The spring or damping is all off it should not be bending that bolt like that, if that bolt's riding in a tight tube like that! I pound my sleds down the trail that are set up just like that one basically and never bent a bolt like that!

 

[hogmemberisold]

He said the tube is not used with that shock....

 

[safecracker]

I would upgrade bolt to a grade 8.

 

[RangerRick]

Thanks for all the inputs. I did not jack on that area as far as I can remember. If jacking on it, then it would be bent up in the center, not down. But hey, maybe jacking on it would straighten that bolt. I need to read the paperwork that Marcus sent with it to see how to adjust the damping. That shock only has around 2,000 miles on it.

 

[Yowzer]

Thanks for all the inputs. I did not jack on that area as far as I can remember. If jacking on it, then it would be bent up in the center, not down. But hey, maybe jacking on it would straighten that bolt. I need to read the paperwork that Marcus sent with it to see how to adjust the damping. That shock only has around 2,000 miles on it.

I'm thinking that, maybe more than damping or other adjustments, you may want to source some sleeves and collars that will replicate what parts #140 and #150 are supposed to do? There should be no play anywhere, yet the shock needs to be able to rotate slightly at its mounting points due to the arc the rear wheel travels in (from a side view) as the suspended wheel moves up and down through the stroke of the suspension... if that makes sense?!

In other words, you don't just want the shock eye clamped tightly from the sides, but free enough that it's able to rotate slightly around the bolt passing through it. So - rotating slightly around the bolt, but with no slop on either side-to-side or up and down movement (or anywhere else).

Hope my 2 cents help!

 

[BajaRon]

It is easy to check for bottoming out, which will tend to bend the shock mounting bolt if it is severe enough. There should be a rubber or poly bumper at the eye end of the rod. Bottoming will leave signs on that bumper. Frequent or severe bottoming can split or even remove this bumper altogether. All definite signs of bottoming. A higher grade bolt is probably not going to solve your problem if this is the case.

To get a very good idea of how much travel you are using, get a thin (small) zip tie and place it snugly around the shaft. Place it at least 1/2 way to the shock body. Clip the end so it does not hit or interfere with the spring. Then ride it as you normally would over the worse road portions that you typically ride. If the zip tie ends up at or very near the eye, then you need to make adjustments to the shock. But this will only solve your problem if the shock is still in good condition. If it is failing, then that will require a different approach.

A properly functioning and adjusted shock should leave your zip tie about 1/4" from the top of the bumper, unless you're running over craters at high speeds. Even a well functioning, high quality shock properly adjusted will bottom out given the right circumstances.

If the first bolt bent relatively early in its life, I would lean towards the first possibility. If both bolt bends have been at 30k or later, then a worn out shock may be the answer.

Jacking the bike using this bolt will bend it up. But the pressure of the shock will move it into the orientation shown in your picture in short order.

 

[RangerRick]

Thanks so much for the zip tie idea, Ron. I will admit I never tried to adjust the shock just put it on. So will be adjusting it after I do the zip tie check

 

[Snoking1127]

Thanks so much for the zip tie idea, Ron. I will admit I never tried to adjust the shock just put it on. So will be adjusting it after I do the zip tie check

Yep, it looks like the shock is not set to enough pre-load for the load you have on the trike, that is rider/passenger and things in the top and side cases.

 

[Mikey]

I would check to see what the torque spec is on that bolt! Myself if those two spacers only press to the sides of the shock bushing, I would call that a very crappy set up! It puts a lot of strain on that bolt. It should be setup like the factory shock was setup with a shaft all the way through with spacers on both sides and the bolt passing down the middle!

 

[KX5062]

The stock BRP shock bolt is known to be weak and is suspected to be made of material that is not quite up the advertised hardness. There were numerous threads in years gone by about it. At the time, many people just replaced it with an aftermarket bolt of superior quality.

 

[BajaRon]

Here is an example of the Zip Tie setup. This is a car shock. But the process is the same. As you can see, the bump stop can be on either the body or the mounting end. All the powersports shocks I've seen have the bumper on the mounting end. But I am not familiar with the M2 design.

I agree that the original design and materials used are marginally adequate. Beefing up the bolt and torquing to spec. is a good idea, in any case.

 

[Cobranut]

I'm thinking that, maybe more than damping or other adjustments, you may want to source some sleeves and collars that will replicate what parts #140 and #150 are supposed to do? There should be no play anywhere, yet the shock needs to be able to rotate slightly at its mounting points due to the arc the rear wheel travels in (from a side view) as the suspended wheel moves up and down through the stroke of the suspension... if that makes sense?!

In other words, you don't just want the shock eye clamped tightly from the sides, but free enough that it's able to rotate slightly around the bolt passing through it. So - rotating slightly around the bolt, but with no slop on either side-to-side or up and down movement (or anywhere else).

Hope my 2 cents help!

The center metal sleeve needs to be tight, and the bolt properly torqued to provide rigidity.
The rubber or poly bushing in the shock end will allow for sufficient rotation.