Leaf spring fatigue
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Prolocutor
Joined: Jan 2009
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From: Western MA
Leaf spring fatigue
Anyone else have their rear springs "break in" after brief but heavy use? When we first picked up our 5th toyhauler wheel it had a pin weight over 3k with a full water tank in front of the axles and the garage empty. When I got it home, I was amazed and impressed to find the helper springs weren't even engaged with all that weight. Now, after two summers of heavy towing, I have a bit more squat in the rear end. With 2k in the garage, the tanks empty, and what I'm guessing is at least 1k less on the pin because of this, the trailer always puts the helpers on their stops. Then today, I put just one ATV in the bed (just under 1k) and the helpers were close to engaging. Anyone else have this much spring break in after hauling heavy? No problems and still rides and tows great. Just curious about something I noticed...
FTE Leadership Emeritus
Joined: May 2004
Posts: 18,787
Likes: 30
From: Melbourne, Aus
All springs do it. I just replaced the springs on my truck (admittedly, quite a bit older), and it now sits 2" higher in the rear unloaded with new springs, as opposed to the ones that were 190k old, and I don't think my truck has ever had anything more than a couple of motorbikes in it.
That said, yours sound like they are sagging quicker/more than normal. If you are still under warranty, I would get it checked out at the dealership.
That said, yours sound like they are sagging quicker/more than normal. If you are still under warranty, I would get it checked out at the dealership.
Postmaster
Joined: Sep 2006
Posts: 2,598
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From: Maryland
You have some interesting things going on there. With less than 2,000 lbs pin weight on my old camper, my F350 would engage the rear half of the overload leaf. By the time I got my current toyhauler that has over 3,100 lbs on the pin, the truck had 36,000 miles on it, but the toyhauler always puts the truck down to level with the overload fully engaged unless I have more than 40 psi in the airbags. Springs do fatigue over time, but it usually takes heavy loading and a lot of cycles for it to happen.
Most people would agree that any payload of over 3,000 lbs in a SRW F350 is going to require some help in the suspension department. Airbags and/or Timbrens are a quite popular topic of conversation on RV.net because people don't like the way their truck squats under the load of these large trailers.
Most people would agree that any payload of over 3,000 lbs in a SRW F350 is going to require some help in the suspension department. Airbags and/or Timbrens are a quite popular topic of conversation on RV.net because people don't like the way their truck squats under the load of these large trailers.
Fleet Owner
Joined: Mar 2012
Posts: 20,110
Likes: 15,788
From: Wisconsin
I had a very thorough and engineering based answer for you, but then the phone rang. I needed to check a different site and I deleted it before posting. Here is the short version...
it's steel fatigue. It's normal and impossible to get rid of it. The extent of the fatigue is directly related to the use and range of motion. I use airbags to compensate for the rear spring fatigue. Rather than replace springs often. Think how bad it would be if you were using under-designed springs? It would be a nightmare.
it's steel fatigue. It's normal and impossible to get rid of it. The extent of the fatigue is directly related to the use and range of motion. I use airbags to compensate for the rear spring fatigue. Rather than replace springs often. Think how bad it would be if you were using under-designed springs? It would be a nightmare.
Lead Driver
Joined: Apr 2011
Posts: 7,302
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From: Edmonton Alberta
I am actually very pleasantly suprised how my rear springs are not sagging...... Although not totally stock, I have the 2 main stock rear springs, overloads removed and 6 leaf add a packs. I haul 3,000 lb water tank quite often and sometimes leave it in there full for days on end.
I have been hauling it (the water tank) for the last 2 years and have 100,000 kM on the truck. Unloaded it still sits perfectly level. 11.5" between the tire and fender front and rear.
It used to sag 2.5" with the tank full, I have not checked it for a while but I will next time I fill it up (tomorrow LOL)
Thanks
I have been hauling it (the water tank) for the last 2 years and have 100,000 kM on the truck. Unloaded it still sits perfectly level. 11.5" between the tire and fender front and rear.
It used to sag 2.5" with the tank full, I have not checked it for a while but I will next time I fill it up (tomorrow LOL)
Thanks
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Prolocutor
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From: Western MA
Thanks for all the thoughts guys. I assumed it was normal fatigue, but was surprised so soon. I have run it hard. Over half my miles are towing with either 2200 or 3200 on the pin depending how we are loaded for the trip. I never thought of bags because even when loaded at the heavy weight, the truck sits level when hooked up. The overloads do a fine job of keeping me from actually sagging. It just doesn't pop back up to the raked look when empty like it did when new.
As for bags, I may add them at some point to some bounce I get on bad bridges, but 99% of the time, I'm really good as is. I had them on my 250 to carry the same weight which was more of a necessity. Although I'd never mention I had them on the RV forums. You mine as well say Tundra over there based on the reaction you get. Weight police go nuts. I'm on forums for everything I own. Boats, sleds, atvs, motorcycles, cars, RVs, guns, wine, tractors, plowing, and here and the only place I ever get in trouble is on the RV sites. They are the most scared group of people on the road or the net!
As for bags, I may add them at some point to some bounce I get on bad bridges, but 99% of the time, I'm really good as is. I had them on my 250 to carry the same weight which was more of a necessity. Although I'd never mention I had them on the RV forums. You mine as well say Tundra over there based on the reaction you get. Weight police go nuts. I'm on forums for everything I own. Boats, sleds, atvs, motorcycles, cars, RVs, guns, wine, tractors, plowing, and here and the only place I ever get in trouble is on the RV sites. They are the most scared group of people on the road or the net!
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Postmaster
Joined: Aug 2011
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From: Roll Tide, Roll
I can say mine are stock and even though they have sagged. The truck has seen incredible weights and twisting. Its the work horse, so I'm not dissapointed in a stock spring. But am leaning towards bags as I love the wonderful ride.
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Fleet Owner
Joined: Mar 2012
Posts: 20,110
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From: Wisconsin
Thanks for all the thoughts guys. I assumed it was normal fatigue, but was surprised so soon. I have run it hard. Over half my miles are towing with either 2200 or 3200 on the pin depending how we are loaded for the trip. I never thought of bags because even when loaded at the heavy weight, the truck sits level when hooked up. The overloads do a fine job of keeping me from actually sagging. It just doesn't pop back up to the raked look when empty like it did when new.
As for bags, I may add them at some point to some bounce I get on bad bridges, but 99% of the time, I'm really good as is. I had them on my 250 to carry the same weight which was more of a necessity. Although I'd never mention I had them on the RV forums. You mine as well say Tundra over there based on the reaction you get. Weight police go nuts. I'm on forums for everything I own. Boats, sleds, atvs, motorcycles, cars, RVs, guns, wine, tractors, plowing, and here and the only place I ever get in trouble is on the RV sites. They are the most scared group of people on the road or the net!
As for bags, I may add them at some point to some bounce I get on bad bridges, but 99% of the time, I'm really good as is. I had them on my 250 to carry the same weight which was more of a necessity. Although I'd never mention I had them on the RV forums. You mine as well say Tundra over there based on the reaction you get. Weight police go nuts. I'm on forums for everything I own. Boats, sleds, atvs, motorcycles, cars, RVs, guns, wine, tractors, plowing, and here and the only place I ever get in trouble is on the RV sites. They are the most scared group of people on the road or the net!
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Prolocutor
Joined: Jan 2009
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From: Western MA
Don't take this the wrong way because I agree with you 100%, but why listen to them? It's my truck and I run what I'm comfortable doing. I don't let a forum dictate anything. Those are the guys that are constantly "super busy" with their RV life to ever actually break bread together or have a beer when coming through their town...yet have all the time in the world to tell you what's wrong with your set-up. LOL at them.
Fleet Owner
Joined: Mar 2012
Posts: 20,110
Likes: 15,788
From: Wisconsin
Oh, I don't listen. LOL. I was kidding about not bring up what I do on those forums. I usually do what I want and try to explain my logic there. Right now I'm currently on a 30 day ban at irv2 for my take on the ST vs. LT tire debate. Let's just say, mods don't like being questioned when they chime in...
Postmaster
Joined: Jul 2009
Posts: 4,094
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From: Central Illinois
I had a very thorough and engineering based answer for you, but then the phone rang. I needed to check a different site and I deleted it before posting. Here is the short version...
it's steel fatigue. It's normal and impossible to get rid of it.*** The extent of the fatigue is directly related to the use and range of motion. I use airbags to compensate for the rear spring fatigue. Rather than replace springs often. Think how bad it would be if you were using under-designed springs? It would be a nightmare.
*** unless you are the owner of a Dodge. I that case your springs would never sag 'cus there better than Ford junk springs. Just ask any Dodge owner.
it's steel fatigue. It's normal and impossible to get rid of it.*** The extent of the fatigue is directly related to the use and range of motion. I use airbags to compensate for the rear spring fatigue. Rather than replace springs often. Think how bad it would be if you were using under-designed springs? It would be a nightmare.
*** unless you are the owner of a Dodge. I that case your springs would never sag 'cus there better than Ford junk springs. Just ask any Dodge owner.
Posting Guru
Joined: Sep 2009
Posts: 2,015
Likes: 4
From: Lakehills, TX
LT all the way. A good commercial version. I swear by Michelin XPS Rib and Kumho 857 for lighter trailers.
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Prolocutor
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From: Western MA
Absolutely! I went even heavier with load range G Goodyear G614's...
Posting Guru
Joined: Sep 2009
Posts: 2,015
Likes: 4
From: Lakehills, TX
Those are OK giant 5ers whose owners are willing to cruise nice and slow. They are a trailer-only tire with a modest max speed increase to 75mph, meaning 65 and you're golden. The Michelin Rib is a proper commercial truck tire with 100mph speed rating, which means I can actually keep up with highway traffic in Texas without fretting the whole time about heat build-up. Granted, the Rib is "only" rated for 3042 lbs in single applications, while the G614 RST is at 3750, but I'd be concerned if I were outweighing that anyway. For instance, on my 20k dual tandem gooseneck, I'm running 8 Ribs (at a max dual load of 2778 each) for a total of 22,224 lbs, already over the trailer capacity. I don't really need to trade speed rating and common availability to bump it up even further overweight to 27,320 lbs (at 3415 each in dual configuration), nor would I bet most people would need the overhead.
That said, as long as you're willing to take it easy on the highway, you can't ask for any more load capacity...
That said, as long as you're willing to take it easy on the highway, you can't ask for any more load capacity...