Suspension bolts

[TedS]

This would be a good style greasable bolt. Note the waisted reduced diameter where the cross hole is.

[Yoda]

. The knurled portions were worn flat on the other remaining bolts so they were spinning.

EDIT I didn't think to measure how far the bored hole went beyond the grease hole.

Do you know why they were spinning - everything looks greased? Was the suspension service before and did they possibly use an impact gun to improperly remove them. I have see several YouTube videos of them spinning the head with an impact gun to remove the nut. Also using the nut to seat the knurl home, again with an impact gun.. The spinning could have contributed to the bolt failure. Again just brainstorming.

Keith

[ajg617]

Do you know why they were spinning - everything looks greased? Was the suspension service before and did they possibly use an impact gun to improperly remove them. I have see several YouTube videos of them spinning the head with an impact gun to remove the nut. Also using the nut to seat the knurl home, again with an impact gun.. The spinning could have contributed to the bolt failure. Again just brainstorming.

Keith

I do not Keith. No maintenance done on the suspension unless the dealer performed some when it was delivered (highly doubt that). I greased the wet bolts after our first trip last year and the suspension was really making noise about half way through. The noise disappeared after greasing. I greased again this year before any trips. Last year it was difficult to get any grease in. This year the grease flowed in (and out of the opposite bushing end) with so much ease I had red & tacky all over the ground. That should have been a clue for me. As far as I know, all wet bolts were installed at the factory and all parts replaced by the GD Mobile Tech were brought to Elkhart.

The current wet bolts installed in MT were hammered in place before the nut was tightened with a standard ratchet and torque wrench - no power tools. Will be interesting when I grease them come April and what GD finds at Elkhart.

EDIT: I could understand a bolt/bushing set being considered a wear item, but that doesn't account for hanger damage due to wear or failure of either. My rear hangers were a mess - no way could they be re-used. So is the hanger also considered a wear item and which one (hanger or splined end of a bolt) gives first and much too soon?

[TedS]

Unless the new bolt knurl was aligned with the old spline in the hanger, the installation probably ruined the old as it created the new spline in the hanger.

[Scott'n'Wendy]

TedS
Why does the reduced diameter about the cross drilled hole make for a stronger/better bolt?

[TedS]

It places the edge of the crossdrilled hole in the lower bending stressed smaller diameter. The result is that the stress riser hole edge is less effective at starting a crack. The added benefit is the chance for 360 degree distribution of grease.

Shackle bolts are typically in little tension.

[d2reid]

[USER="6"]Recently Dallas reported the same thing. ...lol

Was that me?

Ok, if not; Last week I sheared a wet/hanger bolt on the left rear. FYI triple axle Momentum 376 at 20k. Noticed it at refuel becuase the space between the wheels was not correct. Investigated, found left rear most spring not bolted to hanger and just resting on frame. Ok, it had probably run that way for a while so I pulled into an RV dealership to see if they could help me. Nope. The receptionist was very nice and showed me where I could park the RV. Parts manager, service manager, technician; all kind of ignored me. They don't want to acknowldedge the broke down guy in their parking lot. I am not offended, I know they arlready have more work than they can do..

But there is still an empty hole where a bolt should be. Ace hardware to the rescue. No, they were sold out of the 9/16 x 3.5 grade 8 bolts, 1/2 inch or 5/8 inch. I bought both. Couldn't get the 5/8 in the hole, so went with the 1/2 inch. The hole in the hanger was already somewhat rounded out, no probablility of getting a new hanger installed in the next week to 6 months. Non-service is a thing. So I blocked up the level up system and adjusted the height so the LR spring aligned with the hanger. Dropped the 1/2 in grade 8 bolt in, applied a locking nut. I don't want to be the fella trying to get that off. Cinched it down, dropped weight on it, nothing went bang. Ok, good to roll on down the road.

Paranoid now, next rv site I crawl under the rv to look at the wet bolts. Grabbed a hold of the RF wet bolt and it wiggled. Huh? Took a better hold of it and the nut twisted off in my hand. Whew, that could have been ugly. Thought about a bunch of different fixes but had no resources. Had lots of grease on it. .So I got some gas and cleaned the bolt and nut as best I could, then grabbed my blue lock tight and dropped a couple of drops and retightened the nut. Not a fix, just a band-aid. Contacted my fovorite moble tech guy and scheduled an entire wet bolt shackle replacement. I am going to get involved with the replacement, I know, for techs, that's really annoying. Sorry, I am the guy that is going to drag this thing from Florida to Salt Lake City to Johnson City, TN over the next few months. I want to know what I am dealing with. I plan on marking the bolts to insure the orientation is correct. I have had issues of them revolving and then not taking grease. Next Tuesday I get to get grease on my hands.

Some other stuff;

Setting up tonight my right main slide would not fully extend. DW said she heard a bang while extending. You have to love RV's, it it's not one thing it's another. Tomorrows problem.

I have read other posts and seen pictures of suspension components rounded out and worn oblique from the action of the spring inside the hanger, also on the equalizers. The poor hangers don't stand a chance against the pressures and forces they must deal with. And then you bounce them in a pot hole. Poor things, no wonder they break. So now you have to think about how to make your suspension robust enough to handle Americas roads. Here is an opportunity for me to get on a soapbox, but I will refrain. You all can relax now.

Ok, you have three components that take a beating, the hanger, the spring, and the bolt. Ooops, I forgot the fourth, the shim, also called a bushing. In my experience I dont consider the bushing, they are just too weak to stand up to the stresses put on them and fail, quickly. Good idea, just doesn't work.

The hanger. I am no engineer and can't explain what I observe. But hangers are made of soft steel. Pretty strong, but maleable. Spring steel is super strong, very hard, and will not distort. It's somewhat brittle, in that you can break a spring, but you aren't going to get it to wear out. And then there is the bolt that holds them together. I don't know what wet bolts are made of, but they have to be preety hard and they have a hole in the middle to squirt grease through. That's excellent to keep heat friction away from the hanger/bold/spring connection. I think it's pretty cool.

Grade 8 hardened bolts. Again, I am no engineer, but in my experience grade 8 bolts don't break. They will tear the poopies out of everything around them, but they don't break. So you match a grade 8 bolt against a chinese hanger the hanger is going to get rounded out. Do wet bolt's do the same thing, I have not observed that.

Recently I have seen posts of adding a V tab to the inside of the hanger. It reinforces the hanger for side to side movement, but IMHO it adds more strength to the downward force of the hanger on the bolt. Instead of pressure on the two outside edges of the hanger bolt holes it adds a much wider pressure point on the top of the bolt. You can't just wear down the bolt holes, you must now wear down a 2' inch steel bump.

This adds credence to replacing the wet bolt system with a super hardened bolt system. The pressure is no longer on two skinn points, but distributed across the entire lenght of the bolt. Given that scenario, do really need lubricant?

Solution choices. As always there is a perfect solution, no matter how unpracticle. Then there is the practicle solution, no matter that it won'd work. Given that my 2019 wet bolt system lasted 4 years without fail I acknowledge it is not the best solution. I think, that it may be, a practical solution. Will the bolts fail, absolutely. But the time involved vs the expense makes it a viable option for me. I am going to take measures to mark the orientation of the bolts to insure that I can add grease to them. I had a couple shift and they locked up, not taking grease.

I will observe the hanger bolt holes. I am not planning on replacing them at this time, but I will make not of their individual wear. I am adding 2 hangers and 4 9/16 x 3.25 grade 8 bolts to my inventory for on the road repairs.

While apart, I will regrease and torque bearings.

12 years, hundreds of thousands of mile. 48 states, 8 provinces. DW has a lot of anxiety over each RV repair. We are looking for a landing zone. It's time for us to hand up our spurs. We aren't having fun anymore....

[Jlawles2]

In those instances where the holes have started to wear in the hangers, I wonder if shouldered bushings would be a repair option. They could easily be replaced with the bolts and help distribute the load over a wider area on the hanger.

Say something like https://www.grainger.com/product/46K...E&gclsrc=aw.ds it's probably the wrong size, but for graphical representation.

It might take a couple of days, but Fastenal could be your friend for 9/16 bolts.

[AlexPeterson]

I've mentioned this before, but I am again venturing an opinion that the real problem isn't crummy roads, but tight turns on sticky pavement. The lateral loads imparted on the suspension are very high in these maneuvers. It seems some sort of lateral stabilizers are needed, something along the lines of what some vehicles have. It is eye opening to watch the axles on a trailer being turned tightly.

Here is a depiction of what is called a track bar. It absorbs lateral forces, instead of these forces being resolved through a bending load of the leaf springs. It would also likely eliminate the frame cracking that many have seen, which I believe are also caused by lateral bending loads on the leaf springs when making tight turns.

[ajg617]

But there is still an empty hole where a bolt should be. Ace hardware to the rescue.

Old head bolts and large flat washers work well for a temporary fix also - that got the spring connected so I could at least drive from East Glacier to West Glacier where a mobile tech was willing to come out. Two days later the tech called me asking if I had any spare wet bolts - seems a 2022 376THS with under 10K miles broke down with the same issue (at the same railroad pull-off I got out to see if everything was still connected half way between the two) trying to make it back to the Bay Area and home. GD authorized repairs made and broke down again 100 miles from his home. GD is replacing his entire suspension.

Not sure how much the V-clips help - the weld on my RR V-clip snapped (as did the tack weld on the LR V-clip) and the hanger twisted so badly it took a mall to get the spring eye back into it to get any bolt through.

[ajg617]

Unless the new bolt knurl was aligned with the old spline in the hanger, the installation probably ruined the old as it created the new spline in the hanger.

If you are referring to my repair post, you may be correct but the splines are long enough on the bolt so that he should have been able to align with existing ones in the hangers. Tear down at Elkhart in April will confirm maybe.

[d2reid]

In those instances where the holes have started to wear in the hangers, I wonder if shouldered bushings would be a repair option. ...It might take a couple of days, but Fastenal could be your friend for 9/16 bolts.

They may be a help, but I think I would have to make the hole in the hanger larger. I am wondering if that would weaken the hanger too much. I am not familiar with Fastenal, google search says it's a large company with lots of products. Do you have a more specific reference?

.. I am again venturing an opinion that the real problem isn't crummy roads, but tight turns on sticky pavement.

Or both. Crossmember reinforcement is definitely a good idea. I think JerryH spent some buck to have a system put on his Momentum. Didn't quite fit, they had to move a sewer pipe. The equalizers take a lot of the strain during a tight turn. But I agree, the first time I made a tight turn with my triple axle I thought the wheel angle was pretty extreme. I try to avoid those tight turns when I can.

Not sure how much the V-clips help - the weld on my RR V-clip snapped (as did the tack weld on the LR V-clip) and the hanger twisted so badly it took a mall to get the spring eye back into it to get any bolt through.

There is definitely a difference in bolt strength. I was thinking that instead of V clips one could get steel tubes or steel bars to put in the area above the spring, inside the hanger. That would really beef up the hanger. If course if you take all the flex out of the hanger it would probably sheer the bolt.


There are no perfect answers, only decisions that will be tested by time and travel.


Safe Travels.

[Jlawles2]

At work we use Fastenal because of the number of locations nationwide. Just something to consider when you are in a bind looking for 9/16" bolts. Most stuff they can have in 24-48 hrs if not stocked at a location.

As for the bushing, there is more than enough material around the bolt to open the hole up some for a hardened bushing to help spread the load and minimize the wear. Might have to find a way to retain the bushing from rotating. I'd have to sit down and do a bit of math and searching to see if there is an off the shelf product available.

The Vee clips placed between the vertical hangers are intended to eliminate or reduce the flex in the hangers for cracking at the frame. I think Rob has more info on the whole arrangement and when / where it's beneficial.

[Jlawles2]

I've mentioned this before, but I am again venturing an opinion that the real problem isn't crummy roads, but tight turns on sticky pavement. The lateral loads imparted on the suspension are very high in these maneuvers. It seems some sort of lateral stabilizers are needed, something along the lines of what some vehicles have. It is eye opening to watch the axles on a trailer being turned tightly.

Here is a depiction of what is called a track bar. It absorbs lateral forces, instead of these forces being resolved through a bending load of the leaf springs. It would also likely eliminate the frame cracking that many have seen, which I believe are also caused by lateral bending loads on the leaf springs when making tight turns.

Track bar (pan hard bar) are intended for those suspension systems that do not have a method for preventing lateral motion of the differential. Most notable uses are trailing arm (Ford and Dodge SFA axles), race cars with straight bar supports and coil springs (non triangulated) and coil spring systems. Leaf spring systems are not by nature trailing arms (i.e. pushing the axle) but follower systems and the use of a track bar is not needed as it will induce lateral stress into the leaf springs. I cannot recall ever seeing a track bar on a leaf spring setup. In your picture, note the coil springs (grey) and trailing arms (orange), this is a very common setup in modern SFA vehicles. Any play in these components also leads to the dreaded DEATH WOBBLE as the axle naturally wants to FOLLOW the attachment point vs being pushed by it.

[Yoda]

They may be a help, but I think I would have to make the hole in the hanger larger. I am wondering if that would weaken the hanger too much. I am not familiar with Fastenal, google search says it's a large company with lots of products. Do you have a more specific reference?




Or both. Crossmember reinforcement is definitely a good idea. I think JerryH spent some buck to have a system put on his Momentum. Didn't quite fit, they had to move a sewer pipe. The equalizers take a lot of the strain during a tight turn. But I agree, the first time I made a tight turn with my triple axle I thought the wheel angle was pretty extreme. I try to avoid those tight turns when I can.




There is definitely a difference in bolt strength. I was thinking that instead of V clips one could get steel tubes or steel bars to put in the area above the spring, inside the hanger. That would really beef up the hanger. If course if you take all the flex out of the hanger it would probably sheer the bolt.


There are no perfect answers, only decisions that will be tested by time and travel.


Safe Travels.

Take a look at MorRydes X_Factor cross bracing they have several styles that drop down to clear sewer lines, AlexPeterson these operate similar to the track bar and limit axle movement at the hangers
https://www.etrailer.com/dept-pg-Acc...ossmember.aspx
https://www.morryde.com/products/x-factor-crossmember/

I know my trailer is dinky compared to yours, but they do make a major difference. I have them installed at the 3 hanger locations.
Keith