bent shock mounts

Topic: bent shock mounts (Read 1300 times) previous topic - next topic

bent shock mounts

March 07, 2023, 10:06:48 am

I have a problem and I'm hoping some others can provide some insight. I'm in the process of changing out the airbags and shocks on my 02 U320 with tag. I was of the understanding that this coach would have come standard with Koni shocks but I discovered that mine was fitted with Gabriel shocks all around. The coach only had 43k miles when I bought it so I can't understand why anyone would have replaced the Koni shocks and particularly with low quality inexpensive shocks. The shocks are mounted with the upper eyelet in double shear (full bracket) and the bottom eyelet is in single shear (one sided bracket). Almost every bottom shock bracket is bent upward and the only explanation I can come up with is that the Gabriel shocks are slightly shorter at full extension. So my questions are, is the shock absorber itself designed to be the "limit strap" for the suspension, effectively limiting how far down the axle can travel? Is it likely that the airbags caused the shock mounts to bend by inflating to full height and overextending the shocks? I can't believe that the shock is strong enough to be the limiting device. When the "raise" function is enabled on the HWH panel (and mine locks in) what stops the raising of the coach? Even with the Koni's being slightly longer would they then act as the limiting device? Does it keep raising until maximum air pressure is in the airbags? Any ideas on how to straighten the bent brackets? I tried a few love taps with a sledge hammer but I get the sense that that is not going to work. I'm not sure if heating them up with a torch would be a good idea or not.

Re: bent shock mounts

Reply #1 – March 07, 2023, 10:21:07 am

I have a 24 inch adjustable crescent wrench I use for manipulating such tabs and brackets. Got me thinking I'll look at mine.wonder if the rebound is slower?

Re: bent shock mounts

Reply #2 – March 07, 2023, 10:39:01 am

Rebound definitely feels much slower (harder) on the Koni's however the Gabriel's are toast and you can see the oil all over the shock body (most likely from being overextended). I did try a 24" pipe wrench on the tab but there is interference with the fender and it also feels like I would need more like 4' of length to get enough leverage to get some movement.

Re: bent shock mounts

Reply #3 – March 07, 2023, 10:45:24 am

Wouldn't have the room to accommodate a 4'. What about using a come-a-long on the 24"? Another option would be a large ford wrench and a bottle jack. Guess what im say is mechanical advantage is your friend
Amazon.com: Crescent 18" Automotive Wrench - C718 : Everything Else

As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.

Re: bent shock mounts

Reply #4 – March 07, 2023, 10:49:01 am

Not seeing all of your undercarriage I can only say if possible buy a grade eight bolt the same diameter as the shock, as long as you can find and jam nut it to the bracket (one nut on one side and one on the other) then use a jack to push down on the end of the bolt finding something above with enough structure to bend the tab.

Re: bent shock mounts

Reply #5 – March 07, 2023, 10:52:55 am

George,

You have asked a number of excellent questions in your post. I don't know the answer to any of them. We have the Koni gold FSD shocks on our coach. When I raise our coach up to max height (to insert safety stands) I feel and hear a definite CLUNK, at which time all upward movement stops. What actually stops the upward movement? I don't know, but will be very interested in the answer...

I always assumed the upward movement was limited by the mechanical interaction of the frame/suspension members. We all know that when the coach is lowered (by completely deflating the air bags) the suspension hits the round welded steel "bump stops" on the lower member (see photo below). I would guess there is a similar upward travel limiting stop built into the suspension design, but where is it? I don't know.

Re: bent shock mounts

Reply #6 – March 07, 2023, 11:33:00 am

So just for reference. A fully inflated air bag loose inflates to 13". May go a little more
Retracted to about 6 inches

Re: bent shock mounts

Reply #7 – March 07, 2023, 02:35:59 pm

So I normally store my coach, with a nose raised as high as it will go, and then I actually over inflate the bags just to make it a little bit more stable. All four front lower shock mounts look good. Bag extended length 11" so yes against the shocks. I think I will reconsider overinflating in the future. Thank you.
Scott

Re: bent shock mounts

Reply #8 – March 07, 2023, 02:41:19 pm

Two potential issues:

Length of Gabriel shock collapsed/extended VS OE shock or correct replacement.

Is coach at correct ride height?

BTW, I have never seen a Gabriel shock on a Foretravel, so no first hand experience with them.

Re: bent shock mounts

Reply #9 – March 07, 2023, 02:44:22 pm

Scott, that's really interesting that your shock mounts have been able to restrain the force of the air bags but somehow mine have all bent. I really don't understand what happened to mine. My safety blocks are about 12 1/2" high and I'm going to measure the distance between the bag mounting plates when I get home. You and the others have given me some good ideas about how to straighten my brackets and I really like the wrench that you posted. I would like to know how mine bent because I don't want it to just happen again with the new shocks. BTW I noticed that you have the original (red) Koni's on yours? Have you considered replacing them?

Re: bent shock mounts

Reply #10 – March 07, 2023, 02:53:28 pm

There would be a considerably different load on the shock mounts STATIC (parked and gently loading using leveling system) vs bouncing down the road and the shock acting as the axle stop (on either compression or extension)!

BTW, I HAVE seen bent/broken shocks and shock mounts on U225 and U240's where ride height was way out of spec/ inches too low and the shocks were "crushed on compression".

Re: bent shock mounts

Reply #11 – March 07, 2023, 06:22:37 pm

Seems like Barry B and another (can't remember who) coach even broke off the shock mounts off of one axle. I can't find the thread as to the repair and cause. If the IT department head gets back soon she may be able to hunt it down and will link it.

Mike

Re: bent shock mounts

Reply #12 – March 07, 2023, 07:32:25 pm

BTW I noticed that you have the original (red) Koni's on yours? Have you considered replacing them?

No they have worked well the past couple of years and 30K miles. Last time I checked there were not leaking. I even considered adjusting the dampening up a little. Collapse the shock and rotate I think it was clockwise 1/4 turn each. On the list but not very hi.
Scott

Re: bent shock mounts

Reply #13 – March 07, 2023, 08:35:59 pm

Quote from: wolfe10 – March 07, 2023, 02:41:19 pm

Two potential issues:

Length of Gabriel shock collapsed/extended VS OE shock or correct replacement.

Is coach at correct ride height?

BTW, I have never seen a Gabriel shock on a Foretravel, so no first hand experience with them.

I've measured both the old and the new shocks and came back with the following, all measurements center to center of shock eyelets; Gabriel's; min. compressed length 12 7/8" vs. 13 9/16" for the new Koni's. Gabriel's max. extended length is 20 13/16" vs. 21 1/8" for the new Koni's. Conclusion is that the Gabriel's will compress more than the Koni's so no problem there, but the Koni's will extend 5/16" more than the Gabriel's so potentially a problem at full suspension drop. This weekend I will air up the coach and inflate to maximum "raise" with the shocks disconnected at the bottom. That should answer the question of whether the air bags could overextend the shocks.

Yes, the coach does ride at correct ride height (approximately half way between max and min suspension height.

Full disclosure, I first discovered this problem when I was pulling out of a camp site (off road) and I heard a loud bang. didn't discover the source of the sound until weeks later when I found that one of the front shocks had broke the eyelet off. Initially I attributed this to a low quality weld on the shock, but later I discovered the first bent shock bracket. I replaced the shock temporarily with a matching Gabriel that cost me about $35.

Re: bent shock mounts

Reply #14 – March 07, 2023, 08:37:54 pm

I broke a shock mount last year. I had/have koni gold shocks.
I was at the Cracker Barrel parked uphill with a slight lean to the left.
After the coach leveled it was obvious we were still slightly off so I adjusted manually. About 10-15 minutes later we heard a loud noise and thought someone had hit us but we never felt anything. Went outside and no one around. Quick look and didn't see any damage to the coach. Next morning I investigated further and found the left rear shock forward of the rear axle just hanging from the upper mount.
Had it welded and replaced rear shock.

Re: bent shock mounts

Reply #15 – March 07, 2023, 08:44:00 pm

Quote from: Chuck & Jeannie – March 07, 2023, 10:52:55 am

George,

You have asked a number of excellent questions in your post. I don't know the answer to any of them. We have the Koni gold FSD shocks on our coach. When I raise our coach up to max height (to insert safety stands) I feel and hear a definite CLUNK, at which time all upward movement stops. What actually stops the upward movement? I don't know, but will be very interested in the answer...

I always assumed the upward movement was limited by the mechanical interaction of the frame/suspension members. We all know that when the coach is lowered (by completely deflating the air bags) the suspension hits the round welded steel "bump stops" on the lower member (see photo below). I would guess there is a similar upward travel limiting stop built into the suspension design, but where is it? I don't know.

Agreed that upward movement is limited by the bump stops that you mention.'
Upon closer examination on the front suspension there is physical contact between the subframe and the front control arm bracket (arrow on photo) that limits downward travel of the suspension. There is no such contact in the rear (first photo) and as near as I can tell the only thing limiting droop of the rear suspension is in fact the shock absorbers.

Re: bent shock mounts

Reply #16 – March 07, 2023, 08:48:04 pm

Quote from: Lt403 – March 07, 2023, 08:37:54 pm

I broke a shock mount last year. I had/have koni gold shocks.
I was at the Cracker Barrel parked uphill with a slight lean to the left.
After the coach leveled it was obvious we were still slightly off so I adjusted manually. About 10-15 minutes later we heard a loud noise and thought someone had hit us but we never felt anything. Went outside and no one around. Quick look and didn't see any damage to the coach. Next morning I investigated further and found the left rear shock forward of the rear axle just hanging from the upper mount.
Had it welded and replaced rear shock.

you describe the exact same experience I had pulling out of my campsite. I'm amazed that the shock itself is stronger than the shock mounts welded to the subframe. Did your mounting bracket bend at all?

Re: bent shock mounts

Reply #17 – March 07, 2023, 08:54:15 pm

DSD has a triangulated shock bracket. Not just a straight single shear tab. Thats really poor engineering . Maybe bent it straight, add a gusset and the correct shock. Dont over lift it.
The down stops probably are the shocks . Thats most common.

Re: bent shock mounts

Reply #18 – March 07, 2023, 09:08:34 pm

that's a good observation. Mine is triangulated too but only on one side, the other side is open and that's the side it bent on. Agree with not over lifting but that's harder than it sounds if you use the HWH raise function to install the safety blocks at maximum height. Not all four corners come up at the same time and my raise button latches in. Adding a gusset is also a great idea but clearance is tight between the shock and the bulkhead wall, not sure I could get a welding gun in there. I'll examine this more closely this weekend and report back.

Thanks everyone for all of the helpful comments and observations.

Re: bent shock mounts

Reply #19 – March 08, 2023, 08:24:10 am

Quote from: Geodmann – March 07, 2023, 08:35:59 pm

Yes, the coach does ride at correct ride height (approximately half way between max and min suspension height).

Not sure I understand. Have you measured ride height the way the factory describes?

Re: bent shock mounts

Reply #20 – March 08, 2023, 09:02:17 am

Quote from: wolfe10 – March 08, 2023, 08:24:10 am

Have you measured ride height the way the factory describes?

For suggested measurement method, see "Ride Height Adjustment" in the ForeForums Wiki. Link below:

Ride Height Adjustment

Re: bent shock mounts

Reply #21 – March 08, 2023, 09:21:10 am

I would bite the bullet and find a welder to beef up the mount and or add more metal and strenthen the mounts,will be better in the long run,every time you bend metal it gets weaker,and please let us know where you got this coach if from a dealer so we can avoid them like the plauge,if your in an area of Mich. that has oilfield work you can find a "rig welder" that will come to your location .

Re: bent shock mounts

Reply #22 – March 08, 2023, 09:28:56 am

Quote from: wolfe10 – March 08, 2023, 08:24:10 am

Not sure I understand. Have you measured ride height the way the factory describes?

I should have been more clear. Ride height is 8" between plates. At max. height there is 12" between plates. At min. height there is 4" between plates. That's what I meant by "half way between max and min suspension height".
Yes my coach is at correct ride height. The question of what would cause my shock mounts to bend from overextension is still a mystery. If in fact by design the shocks are intended to be the limiting device, what could cause the suspension to max out with enough force to bend all of the lower shock mounts? It seems to me that only the force of the air bags could do this and that would be true regardless of if the shocks were the (slightly longer) Koni's or the shorter Gabriel's. In either case the shock would be the limiting device and when it reaches its maximum extended length it would transfer the force to the shock mounts (or break) which only one did.

Re: bent shock mounts

Reply #23 – March 08, 2023, 09:45:38 am

Good chance that a shock stud , with fixing nut to the mount , plus the shock retainer nut , would reduce the bending moment arm of the shock .
As it is with one bolt and nut through the shock, the bushing and bolt just want to sag .
I added a set of front shocks. . I welded the 3/4 in bolt to the bracket to avoid the load path issues that you are experiencing.

Re: bent shock mounts

Reply #24 – March 08, 2023, 09:51:35 am

Quote from: Geodmann – March 08, 2023, 09:28:56 am

The question of what would cause my shock mounts to bend from overextension is still a mystery.

I know we are talking about different year and model coaches in this thread, so what applies to my older coach may not apply to newer models.

We have owned our '93 U280 for 10+ years, and in that time I have raised it to max height (to insert safety stands) on innumerable occasions. As I mentioned up above, my standard procedure for "raising" is (engine running) to depress the RAISE button until I hear and feel the mechanical KLUNK noise indicating the suspension has topped out, and then I STILL hold the button down until my air dryer purges indicating the air system is at max pressure (130 psi on my coach). At that point my air bags should be exerting the maximum possible force against whatever it is that keeps the suspension from extending any farther.

I can only say that none of the bottom shock mount brackets on our coach are bent, and we have never had a shock absorber fail. Early in our ownership I replaced the 20+ year old original red Koni shocks with the gold Koni FSD's. I can see no signs of stress (in the gold shocks or in the shock mounts) that might have been caused by my "raising" technique. Other members may have had totally different experiences.

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