How to Choose Correct Axle Placement for Tandem 7K Axles with Slipper Leaf Springs

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Question:

Hi, Im upgrading to 7k slipper spring tandems. Twin electric brakes. The hangers are larger than the 7k double eye springs. Would you have a placement diagram for the proper placement for the hangers? The trailer frame is of 1980s build, 2.5x2.5x.375 rails.The tongue is 3inch x .375 channel. The side rails are 2inch square tube, 18inch tall, with 2inch square tube top rail, all 3/16inch tubing. 2 5/16inch hitch, rough cut 2x8 oak flooring. The flooring cross supports are set on 12inch centers 1.5x1.5x.250 angle. The trailer from center ball to end rail of trailer is 196. The trailer is a tank, we found it in a field, purchased it an upgrading leds brakes 12k ctr landing leg, rear stabilizers. We are using it for maintenance in field during hay season. Thank you very much

asked by: Ron M

1

Helpful Expert Reply:

Slipper spring setups, like parts # e74SR and # APT6SE for 7K axles, do have different hanger sizes so what you'll want to do is cut off the older hangers and do some mock-ups of your new system before installing the hangers.

Start off by mocking up the center hanger setup about 2/3rds of the way back on your trailer. From there you need to measure your tongue weight and shoot for something in the range of 10 - 15% of the weight of the trailer. If you're outside of that range then you need to move things around until you get inside that range.

I wish there was a set "put the axle here for this weight and length of trailer" but each trailer is different (especially homemade trailers) so there is a bit of trail-and-error when it comes to getting the axle placement right. I've attached a helpful article on axle placement as well as a photo from that article for you to reference.

expert reply by: Jon G

1

Axle Placement Diagram
(click to enlarge)

Answer 1

In order to determine the torque rating for the lug nuts on your trailer you will need to know check out the chart I attached that shows all of the torque specs for all the trailer lugs available based on stud size, wheel material and wheel size.

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Answer 2

Thank you for providing the specs for the suspension components that you already have. Correct hanger spacing really depends on the components being used such as springs, hangers and equalizers. Most of the hanger spacing dimensions that we have are…

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Answer 3

I contacted MORryde and this does happen from time to time as the weight of the trailer can spread out the axles due to downward pressure on the springs/suspension. Odds are the 35" wheel base #MR27ZR will be the correct one for you, but they…

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Answer 4

Well shackle length is mainly based on the height difference between the front and rear hangers. The rear hanger normally doesn't hang as low as the front so that the shackle can offset the difference and add the ability to move. What is the…

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Answer 5

To correctly measure a leaf spring, you'll want to jack the trailer up on jack stands so the axle is hanging freely, then measure directly across from the center of one spring eye to the other, as shown in the provided diagram. The height of the…

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Answer 6

The spring hanger placement is going to be determined by your axle spacing. For example, if your axles are spaced 33 inches apart, as shown in the attached diagram, a 7K axle slipper spring, like #e74SR, requires a distance of 28-1/2 inches between…

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Answer 7

To find the load capacity for your axle you should look on the trailer VIN plate or sticker that lists the VIN number. The weight rating of the axle should be listed on that same plate or sticker. Also, the axle could have a tag or plate on it that…

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Answer 8

For a single axle trailer, you want the shackle strap to be able to move so that you have the spring deflection needed for your suspension. Angled like the photo or even almost vertical is fine you just don't want the shackle strap to bind and…

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Answer 9

The absolute best cushioned equalizer that fits the dimensions you mentioned having would be the MORryde ALLTREK 4000 part #MR89DR as this is only option to provide vertical and horizontal cushioning. This would make a big difference and you'd be…

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Answer 10

Yes, going from a 4 leaf to a 6 leaf spring would add slightly to your ride height. For example, if the current 4 leaf spring has 3/8" thick leaves, and you go to a 6 leaf spring with 3/8" thick leaves, you would be adding 3/4" of…

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Answer 11

Hey Patrick, so for your leaf spring upgrade I am going to need to know a couple of things before I can get you over to the right part. Specifically, the length from eye to eye, the spring width, leaf thickness, and the number of leaves. From here I…

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Answer 12

The hangers you currently have on your trailer are ones I have run into before. That being said, I spoke with MORryde and the #MR27ZR will still fit your trailer, but there is a modification that will need to be made. You’ll have to trim according to…

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How to Choose Correct Axle Placement for Tandem 7K Axles with Slipper Leaf Springs

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