How are Leaf Springs Weight Capacities Determined?

[CL & EC]

Hello everyone. I am in the process of redoing my suspension. I have two 6K axles with 4 leaf springs. I assumed those leaf springs were rated for 3K lbs each. Makes sense right? 3X2=6? Well, in checking with a local supplier today, he informed me my springs were only 2,400 lbs. and if I bumped up to the Dexter 5 leaf he has, that would take me to 2,900 lbs. The guy has been around for many years but doesn't have the best communication skills if you know what I mean so I heard him out and figured I'd go online and see what I could find. Well, in searching online, I am still left uncertain on how this is determined. I thought by going to a 5 or 6 leaf spring I would be increasing my capacity from 3K upwards to 3.5K? Doesn't the springs have to support the minimum weight that your axles are rated for? Thank you in advance for any clarity you can offer.

Chris

[Hoopy Frood]

If you have 6,000 lb. axles I'd be very, very surprised if you didn't have 3,000 lb. springs, regardless of what the local supplier says. You can get springs in many configurations depending on what you need. The first thing you need to know is how much your trailer actually weighs. Grand Design seems to run close to the edge as far as weight handling, and axle springs. Moving to 3,500 lb. springs is not unheard of.

Why are you redoing your suspension? It's very likely in need of it, but why now, and what do you have, and what are you planning to do?

[CL & EC]

If you have 6,000 lb. axles I'd be very, very surprised if you didn't have 3,000 lb. springs, regardless of what the local supplier says. You can get springs in many configurations depending on what you need. The first thing you need to know is how much your trailer actually weighs. Grand Design seems to run close to the edge as far as weight handling, and axle springs. Moving to 3,500 lb. springs is not unheard of.

Why are you redoing your suspension? It's very likely in need of it, but why now, and what do you have, and what are you planning to do?

Yes, that’s what I was thinking as well. My family and I are traveling the lower 48 states. We started off in Early August and once we got into FL where we are now I saw that my springs were starting to wear out. So I’m replacing them and changing out my EquaFlex’ for most likely the MORRyde All Trek 4000. I have to still take some measurements to ensure it’s compatible but I’m pretty sure it will be. I’m also having those leaf spring hanger supports welded on.
Trying to find leaf springs has been a nightmare. I first tried e-trailer who sent me these 5 leaf springs but with 1/2” U-Bolts. Come to find out, they should have recommended and sold me the 9/16” U-Bolts but since they were out of stock they sold me the 1/2” U-Bolts. Well, at the time I didn’t know any better. I tried putting 9/16” U-Bolts on them springs but there was too much spacing where the U-Bolt bracket sits on the center bolt head of the springs. So I’m packaging it back up and shipping it back.
If I stuck with Lippert, I would have to bump up to there 6 leaf 3,500 lb springs since they don’t make a 5 leaf double eye. However, it would take them up to 5 days to retrieve from one of there warehouses 🤷**♂️ and then ship them to me. I get conflicting information though going to the 6 leaf from a 4 leaf. Lippert says it doesn’t matter the number of leafs but rather the weight. Meanwhile the local resident “expert” whose telling me I have 2,400 lb 4 leaf springs installed is telling me going to a 6 leaf will be too stiff.
So I am hoping today to locate what I need.

[Hoopy Frood]

There's nothing wrong with the 1/2" U-bolts, that's what I'm using on my 4,000 lb. springs. Did your local "expert" tell you otherwise? If I read the GVWR of your trailer, it's 14,000 lbs., but that may not be correct. That would put you at about 12,000 lbs. on the two axles. IMO, I would seriously consider the 3,500 lb. springs, but knowing your actual weight would be good. Personally I wouldn't be concerned that much with the number of springs as much as their rating.

Were your original springs only 4 leaf? What is your GVWR? That makes a huge difference in what rating you need for your springs.

[CL & EC]

There's nothing wrong with the 1/2" U-bolts, that's what I'm using on my 4,000 lb. springs. Did your local "expert" tell you otherwise? If I read the GVWR of your trailer, it's 14,000 lbs., but that may not be correct. That would put you at about 12,000 lbs. on the two axles. IMO, I would seriously consider the 3,500 lb. springs, but knowing your actual weight would be good. Personally I wouldn't be concerned that much with the number of springs as much as their rating.

Were your original springs only 4 leaf? What is your GVWR? That makes a huge difference in what rating you need for your springs.

You know, I used to work on F-18 fighter jets in the Navy. Everything we did was standardized. So approaching this suspension project, I had that same mindset. Boy, was that a mistake. Nothing about this is straight forward. So what happened was after I had installed the first leaf spring and u-bolts that E-Trailer sent me, I called Lippert to ask them a question regarding the torque. The torque assigned to the 1/2" u-bolts read a max of 70 ft. lbs. However, when I referenced the Lippert manual for installing leaf springs, it stated for the 3" round 6K axles, that the u-bolts should be torqued to 90 ft. lbs. The tech I spoke with confirmed this to be so and was concerned about the 1/2" u-bolts not supporting the axles properly and potentially rattling loose. The thought of breaking down on the highway due to a broken anything with the suspension is something I would really like to avoid so that conversation led me to put a hold on moving forward. Lippert overnighted me (free of charge) two 9/16" u-bolt kits which was really generous of them to do. So I took the leaf spring off and I installed the 9/16" u-bolts and plate. That's when I realized it would not work. Where the u-bolt plate sits on the leaf spring bolt head, there was too much space. I then called E-Trailer and found out there was also a 9/16" u-bolt that went with the springs they sold me but they were out of stock. So that's why (I'm assuming that is) they never mentioned that to me and just sold me the 1/2" ones. Now they do say those 1/2" u-bolts are rated for 5.2K to 7K axles and so I guess they should be fine.

To answer your other questions, yes my GVWR is 14,000 lbs. I have two 6,000 lb. axles with 4 leaf double eye springs rated at 3,000 lbs. The 5 leaf springs I ordered from E-Trailer are also rated at 3,000 lbs. which is another reason I'm seriously thinking about returning them and starting over. Like I said, this has been a major learning experience. When I placed the order with E-Trailer, I didn't think to increase the weight capacity but afterwards realized that would be the best way to go. Having that extra buffer would be invaluable seeing that I'm running at full weight. I would like to go with the 3,500 lb. leaf springs but I am having quite the time trying to find them. Like I said, I could order the Lippert ones but it would just take longer and cost quite a bit more ordering through them. Everywhere else I have seen is sold out those Lippert 6 leaf 3,500 lb. springs. So with all that said, I could either keep what I already have or return it and start over. I don't like that those springs I ordered from E-Trailer are only rated at 3,000 lbs. I would think with them being 1 size up from the 4 leaf that I had that they would hold more weight but I guess not. Thanks for your your feedback by the way. It is much appreciated.

Chris

[Hoopy Frood]

FWIW, Amazon actually has 3,500 lb. double eye springs that are the correct length for $83. But I have no idea what the quality of those springs would be. I do know that Lippert and Dexter both are priced a bit high IMO. I bought the 4,000 lb. springs from Lippert last summer for what they want for the 3,500 lb. springs now.

[CL & EC]

FWIW, Amazon actually has 3,500 lb. double eye springs that are the correct length for $83. But I have no idea what the quality of those springs would be. I do know that Lippert and Dexter both are priced a bit high IMO. I bought the 4,000 lb. springs from Lippert last summer for what they want for the 3,500 lb. springs now.

So do you have 7000 pound axles with 4000 pound leaf springs? Has it been any stiffer?

[Hoopy Frood]

So do you have 7000 pound axles with 4000 pound leaf springs? Has it been any stiffer?

That is exactly what I have. It seems to ride better, but that is probably more the result of getting rid of the EquaFlex and installing the EZ-Flex equalizer from Dexter. Generally speaking I've never really been able to tell much difference in the ride quality from new springs to old. I do know it rides much smoother at bridge transitions, frost heaves, and the like. That's the Ez-Flex in action. You really can't feel them any to speak of in the truck. I'm a fan. The ride itself is so subjective, I think it rides better, but honestly don't know.

[CL & EC]

That is exactly what I have. It seems to ride better, but that is probably more the result of getting rid of the EquaFlex and installing the EZ-Flex equalizer from Dexter. Generally speaking I've never really been able to tell much difference in the ride quality from new springs to old. I do know it rides much smoother at bridge transitions, frost heaves, and the like. That's the Ez-Flex in action. You really can't feel them any to speak of in the truck. I'm a fan. The ride itself is so subjective, I think it rides better, but honestly don't know.

Nice. I am surprised the momentumÂ’s do not have heavier rated axles. If I have 6K axles, I would think yours would have 8K.
I guess IÂ’m going to bite the bullet and order them through Lippert the six leaf 3500 pound springs that is.

[JKellerJr]

Hello everyone. I am in the process of redoing my suspension. I have two 6K axles with 4 leaf springs. I assumed those leaf springs were rated for 3K lbs each. Makes sense right? 3X2=6? Well, in checking with a local supplier today, he informed me my springs were only 2,400 lbs. and if I bumped up to the Dexter 5 leaf he has, that would take me to 2,900 lbs. The guy has been around for many years but doesn't have the best communication skills if you know what I mean so I heard him out and figured I'd go online and see what I could find. Well, in searching online, I am still left uncertain on how this is determined. I thought by going to a 5 or 6 leaf spring I would be increasing my capacity from 3K upwards to 3.5K? Doesn't the springs have to support the minimum weight that your axles are rated for? Thank you in advance for any clarity you can offer.

Chris

FWIW, If I was replacing my leaf springs I would find a local suspension shop and have them custom made. I was going to do that on my 2017 377 but ended buying a new unit before I had the chance.

I don't trust the steel or quality on the lippert/etrailer/amazon stuff.