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Open Roads Forum  >  Travel Trailers

 > Leaf spring selection for replacement

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Eric45653

Clearwater, Florida

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Posted: 08/29/07 07:05pm Link  |  Print  |  Notify Moderator

I cant seem to figure this out. I found the tag off my axles and they are made by "Al-Ko", and they are 3500 lb axles......so.....what size springs should i use to replace the old ones? Is that 3500lbs per axle, or is it each side which would make it 7000 lb axles???? Do i put 3500lb springs on each side..or 1700lb springs?????

Im confused!!!

Bennypup

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Posted: 08/29/07 07:13pm Link  |  Print  |  Notify Moderator

Not sure if you have looked here but they seem to have some knowledge about all things under the trailer.

http://www.etrailerpart.com/traileraxles.htm


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Loopy

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Posted: 08/29/07 07:35pm Link  |  Print  |  Notify Moderator

You can also check Al-ko's website. They have info on all their springs.


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dbbls

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Posted: 08/29/07 08:47pm Link  |  Print  |  Notify Moderator

Measure the thickness of the old springs and get new ones that are the same. I have found that some springs used by Al Ko are only available from them.


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spike99

North America

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Posted: 08/29/07 09:52pm Link  |  Print  |  Notify Moderator

> What springs size to replace the old ones????

From a white board perspective, many replace "like for like" leaf spring rating. If you know your trailer has 3,500 lbs springs on your axle, then replace with same 3,500 lbs springs. Yes. They are listed as 2 x 3,500 lbs leaf spring sets but in mechanical reality, each leaf set is only rated at 3,500 / 2. Or, 1750 lbs rated (if only one leaf set is used).

And when buying replacement leaf sets, always buy the same model, same size and same "batch number". Just like batches of bathroom tiles, no 2 tiles from different assembly line batches are the same. Always get 2 x replacement leaf spring sets from the the same "batch / lot number" bin. Thus, why I never order replacement leaf spring sets over the Net. Visit a store and pick the leaf spring sets out yourself. Thus, ensuring same size rating and from the same lot size - for both sets.


Here's come "reality" influences....

If it were me and i had to replace my trailer's leaf spring sets, I would weigh my "average loaded" TT. This would include onboard battery, onboard full LP, all internal items and your water tanks being near full. Load up as if you were dry land camping for a few days. Your trailer's "real weight" could be 2,400 lbs and it could be 3,400 lbs. Or, it could be even much more. Do remember this "total average weight of Trailer" number.

Unknown to many, leaf springs above 80% load of their max load rating "can" snap. Think of a car accident and the driver's window is up and its glass is under full stress. A cop or fireman walks up to window, hits its corner with a sharp object and the entire window shatters. Leaf springs are like that as well. A leaf spring "set" can handle more then its own weight (if under smooth and constant load) but if above 80% load and you drive over double railway tracks (or even a big bump at the end of your driveway), the leaf spring "leaf" can snap. Especially when one is loaded in the their 90%-PLUS range of its MAX capacity.

With the above in mind, you may want to increase the rating of your replacement leaf springs. If your trailer's "average load" weight is 3,400 lbs, I'd replace its leaf springs with 3,800 or 4,200 lbs sets. Probably go with a 4,200 lbs rated set. This is assuming a single axle. If double axle trailer, divide the trailer's average load weight by 2 and do your math as if a single axle trailer. If your trailer's average weight is 2,600 lbs and you have 3,500 lbs leaf springs, then by all means, replace with 3,500 lbs leaf spring sets. 2,600 over 3,500 is well under the 80% load formula.

Hope this helps as well...

.

spike99

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Posted: 08/29/07 10:36pm Link  |  Print  |  Notify Moderator

.

I also wanted to mention that using the "rating tag" on the trailer's axle is risky. Risky that you could obtain the incorrect rated leaf spring replacements. Some folks install lighter rated springs on their original axle (to obtain a smoother ride for their trailer's lighter loads) and others use a stronger rated spring - to stay under the 80% rule (to reduce future leaf spring snapping). Or, they have a much larger rated axle under their trailer to obtain stronger trailer brakes. For example, 6,000 lbs axle that has 3,500 lbs leaf springs on it. Thus, they obtain a 3,500 lbs ride comfort (sort of speaking) but their trailer has 6,000 lbs strength of breaking power. For me, I don't use the axle weight "rating tag" to buy replacement leaf springs. I use the trailer's "average loaded" weight and its replacement leaf springs are larger weight size - to stay under the trailer's "average dry land camping" total weight load.

Hope this helps as well...

.

JIMNLIN

Oklahoma

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Posted: 08/30/07 05:28am Link  |  Print  |  Notify Moderator

Eric
your profile shows a 35' TT. Are those little 3500 lb axle for that trailer ?? As other poster says use the springs rated for the axle which means you look for a set of 3500 springs for those 3500 lb axles.
Chech out etrailerpart.com web for springs and axles and accessories.
JIM


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Eric45653

Clearwater, Florida

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Posted: 08/30/07 07:25am Link  |  Print  |  Notify Moderator

JIMNLIN wrote:

Eric
your profile shows a 35' TT. Are those little 3500 lb axle for that trailer ?? As other poster says use the springs rated for the axle which means you look for a set of 3500 springs for those 3500 lb axles.
Chech out etrailerpart.com web for springs and axles and accessories.
JIM


Yep.. (2) 3500 lb axles for that big trailer. etrailerparts.com says each side gets a 1750lb spring. It doesnt really make sense to me thats why im trying to understand it! Whould it hurt to put just a little bigger spring on it..say a 2000lb?


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spike99

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Posted: 08/30/07 07:43am Link  |  Print  |  Notify Moderator

.

For an overview, surf: http://www.truckspring.com/trailer-springs_562.html

For their sizing chart, surf: http://www.truckspring.com/double-eye_563.html


Installing too strong of a leaf spring set replacement will create too rough of ride comfort. For example, vibrate its internal cupboard and dishes apart. Installing too light of a spring replacment makes its ride too soft. And, creates a higher risk of a leaf spring snapping.

As mentioned above, take your trailer's "average loaded weight" (also need this number for WD bar sizing and other towing needs) and times by 1.2. This 20% buffer is often used to eliminate leaf spring snapping. Especially if you pull your trailer across rough roads / camp grounds. Then, take that total number and divide by 4 (4 wheels under your trailer). Each leaf spring set (on a 2 axle system) would be this number.

Take for example, 7,700 lbs (assume your trailer's average weight when "average loaded" is 7.5K). 7.5K x 1.2 = 9K 9/4 = 2.25. Therefore, I would recommend a leaf set size of 2,500 lbs range. For example, 2,480 or 2,500 within the above table. Lower 2,250 lbs rated leaf set if you only travel down smooth roads.

For validation, do call their free 1-800-358-4751 number. They will confirm what exact leaf set replacement and "their" part number you will need.

Hope this helps as well...

.

Eric45653

Clearwater, Florida

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Posted: 08/30/07 08:35am Link  |  Print  |  Notify Moderator

spike99 wrote:

.

For an overview, surf: http://www.truckspring.com/trailer-springs_562.html

For their sizing chart, surf: http://www.truckspring.com/double-eye_563.html


Installing too strong of a leaf spring set replacement will create too rough of ride comfort. For example, vibrate its internal cupboard and dishes apart. Installing too light of a spring replacment makes its ride too soft. And, creates a higher risk of a leaf spring snapping.

As mentioned above, take your trailer's "average loaded weight" (also need this number for WD bar sizing and other towing needs) and times by 1.2. This 20% buffer is often used to eliminate leaf spring snapping. Especially if you pull your trailer across rough roads / camp grounds. Then, take that total number and divide by 4 (4 wheels under your trailer). Each leaf spring set (on a 2 axle system) would be this number.

Take for example, 7,700 lbs (assume your trailer's average weight when "average loaded" is 7.5K). 7.5K x 1.2 = 9K 9/4 = 2.25. Therefore, I would recommend a leaf set size of 2,500 lbs range. For example, 2,480 or 2,500 within the above table. Lower 2,250 lbs rated leaf set if you only travel down smooth roads.

For validation, do call their free 1-800-358-4751 number. They will confirm what exact leaf set replacement and "their" part number you will need.

Hope this helps as well...

.


Spike....do you work for truckspring.com??? I just got off the phone with them and i can sware that i was talking to you!!

They said my 12k GVW is distributed throughout the frame of the TT and some into the TV suspension as well. Springs are rated at their exact downward/upward force. Unless i have 12k exactly over the axles, there is no reason to put (4) 3k springs under there due to ride stiffness.

Explained this way: if you take a 2x4 and place it over two cinder blocks and stand on it, it will support your weight. But if you start jumping up and down on it it will eventually break. Do the same with a 4x4 and it will never break, but the 4x4 will never move either. Need to find a balance between the two.

Heres the scary part Spike: They recommended a spring between 2k and 2.5k depending on what kind of ride im looking for.

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