Broken Penske Clevis.

[Cav47]

WOW Tom. So that is what you just pulled out today?? Mine also has one side that seems still securely attached. Given the amount of dirt showing in between my parts where it was fractured, I would guess mine was broken for a while as well.

Fred, no apology needed.

One of my best attributes as a teacher that can translate to fixing things is reading the directions. I am just smart enough to know that I do not know what I am doing......so I read the directions and YouTube is my friend. I often times take my kids I pad into the garage and watch a technical video on installation or some other maintenance item. Laying on my back in the garage under the bike is common.

Thanks again to all who responded and offered suggestions both here, via PM, or text.

Now go check and make sure your clevis is not cracked from putting the wrong bolt in there!!!~~~~~~~~~~~~~Wouldn't Don have had some fun with this statement!! He would certainly volunteer to be a clevis checker!

 

[TomInPA]

Josh, we have the right bolt...Fred gave it his blessing in post #36.

Still, it sucks you broke my shock.

How did you get that center bolt out? My wrenches are too fat to fit the double nut.

 

[Cav47]

My shock must be a different model or updated. I have a nut on the shock that stays stationary while I could get a thin crescent wrench on the nut attached to the clevis. I then was able to unscrew the actual clevis. I did have to detach the top of the shock to clear the lower rear attachment point. Compare my first picture with your shock.

.

 

[Fred W]

Yup, you guys have the right bolt. It was the other guys that had the wrong one.

Sorry for the confusion.

(edit) Or, after the latest post... maybe not?

 

[Cav47]

Yes Fred. The spacer is the bearing race. It would not fit between the OEM clevis when I first tried, so it would take some persuasion. Just a tight fit. It appears the shock should work with OEM attachment hardware.
BTW, my bike is still ridable (seems to be). Since I broke the other side, there is still a strong attachment between the relay arm and shock. I didn't know until I pulled it apart.

On the shock you have pictured which is the OEM (if I am not mistaken) how do you get the clevis out??

 

[Cav47]

SO, after all this correct/not correct bolt questions. I must not have done anything too wrong if (and that is a big if) I used the wrong bolt. And as I admitted to them at Penske, I did not use a torque wrench but did read somewhere about tightening excessively could damage it. Now Pants wants me to go borrow one and torque spec it. Dang, more reading about how to do stuff. >>>>>JEEZE

What caused this? I know I am going to lube all the points and set the suspension up with Sag measurements and all kinds of other stuff I have been reading about!

I am just happy that they are going to help me out. They clearly could have stuck me for a lot of money. Without that clevis, the shock is not worth much more than a paperweight.

Props to the people at Penske for standing behind their product.

 

[Fred W]

I do not think the problem would be caused by incorrect torque of that bolt. Either incorrect bolt or spacers could cause it, or else it's just a weak part. I was going under wrong assumption that people were using the wrong bolts, which may not be a shoulder type bolt, and that was exerting side force on the sides of the yoke creating the break, since that was what happened with the guys with the Wibers bolts.

When you install the parts correctly all of the bolt's compression will be applied against only the one side with the smaller hole. The other side of the yoke with the larger hole just floats on the shouldered shaft of the shoulder bolt.

To remove the shock you would just pull out the bolt and the yoke should slip off of its bearing in the relay arm. The inner race / spacer should be a tight fit in the yoke, as Tom mentioned his was, but it should be slightly shorter than the yoke is wide.

 

[TomInPA]

One possible failure mode I saw would be if the shoulder of the bolt did not properly seat in the clevis, and instead the shoulder seated outside the hole, then the clevis could be bent during tightening. The tolerances are close, so you must be sure the bolt is fully inserted in the large side before tightening.

Josh, I used a grinder to make a thinner wrench and it worked. Same setup as yours, my cheap wrenches were just too fat. This is the part loosely assembled.

 

[Fred W]

Yeah, I can see that. Probably push the bolt through all the way before even putting the nut on would prevent that.

 

[08FJR4ME]

What I don't get is it is breaking in the thicker section. Why is that? Now you would think it would break in the corner in the side where it is thinner. It may not be the bolts fault. Something else is going on.

Dave

 

[wheatonFJR]

One-way beam shear at the face of the support.

Or tension across that section more likely...who knows.

 

[Fred W]

So, Mark... From a structural engineering standpoint, could it be that because one side is well clamped and totally fixed, and the other end is a looser fit and "floats" a small amount, that the constant hammering and relatively small amount of flex that results within that tolerance, levered across the structure of the clevis because of those tolerances on the loose side, that the metal fatigues and results in the shear?

Or am I just throwing blunt darts?

(hopefully that made some sense)

Reason I pose the Q is that I know alloy bicycle frames are more prone to cracking at the joints due to the stiffness of the alloy tubes vs. the relative flexibility of a steel bike frame.

 

[0Face]

ANSWER: Me Josh... me no like Penske...

 

[TomInPA]

I think it's really interesting that the two shocks in this thread failed in the same way, but on opposite sides.

Nice one Marty!

 

[08FJR4ME]

I would more suspect to think the force of the constant up and down motion of the shock is what is causing this failure. They need to redesign this clevis part. I don't think the bolt has anything to do with it. Having both crack on opposite side would tend to support this theory. Then again I am just a machinist and backyard designer not an engineer.

Dave

 

[wheatonFJR]

So, Mark... From a structural engineering standpoint, could it be that because one side is well clamped and totally fixed, and the other end is a looser fit and "floats" a small amount, that the constant hammering and relatively small amount of flex that results within that tolerance, levered across the structure of the clevis because of those tolerances on the loose side, that the metal fatigues and results in the shear?
Or am I just throwing blunt darts?

(hopefully that made some sense)

Reason I pose the Q is that I know alloy bicycle frames are more prone to cracking at the joints due to the stiffness of the alloy tubes vs. the relative flexibility of a steel bike frame.

That crack occurred at the point of maximum moment/flexure and maximum shear...but obviously the crack/fracture should not have happened. Don't know enough by looking at it to know why these failed.

 

[majicmaker]

The radius between the last thread just before it becomes the top of the Clevis is the culprit. That's the weakest point. If it's going to crack, that's where it'll happen on either side. That spot is under both shear and tension.

 

[boyitgobob]

Just for the record, traxxion replaced my clevis when rebuilding the shock this summer. I was shocked when I removed it and the clevis came apart in my hands, looking the same as pictured above.

Now I've got to go back in and see if i installed it is correctly.

 

[redneckj]

Fontanna man Jim's part broke the exact same way earlier this year

 

[Cav47]

All the aforementioned hardware.