Tandam Axle Leaf Spring Mount Spacing

[Nobby]

Is there such a thing as a generic guide to the spacing of spring mounts based on axle spacing and spring length.

Or more specifically for 33" axle centers and 25 1/4" double eye springs what should be the mount spacing?

Cheers
Nobby

[cowboywildbill]

If your mounting tandem axles and you have decided how far back to place them so that your tongue weight and balance is correct.
Then I have always used a trunnion between the two sets of springs.
I always mounted my trunnion checking for square on the frame first and then made sure it was level. Then mounted the forward and rear springs onto the trunnion and welded on my front and rear hangers.
Sometimes using shackles if needed.
The trunnion is a triangular looking piece that bolts onto a frame hanger between the front and rear springs and keeps the springs equalized. Hope I didn't confuse you. I hope that was what you were asking.
If you see a factory built tandem trailer take a look at how they set up the suspension.

[Nobby]

It's on a factory built equipment trailer that is set up with low clearance and is pretty much pushing it with regards to its set up. Now that springs and equalisers are worn the axle hits the frame. I am planning on lengthening it and hence moving the mounts and am trying to figure out if I should stick with their spacing. I like the low clearance but am planning to install the more triangular 4" deep equaliser to sneak up the height a wee bit.

cheers
Nobby

[cowboywildbill]

Maybe getting the springs re arched or installing new springs will get your clearance back.
Or adding a block or shim between the axle and springs if the springs are mounted over the axles.
Let us know how it goes.

[DmaxMaverick]

Look at the axles. How are they sprung? If the axle tubes are above the springs, they can be mounted below them. This will increase height: the diameter of the axle tube + leaf spring stack. If this is the case, and you do that, rotate the brakes 180° on the hub (the axle will be rotated 180°, and brake orientation must be retained).

If the axles are already sprung below the leafs, you can extend hangers and shackles to gain height. I don't recommend axle blocks. I've seen this done a couple times, and in each, severe chatter during braking resulted.

[Nobby]

Springs are underslung and to be honest overhanging them will raise it up to much and start to defeat the low ride nature of the trailer.

I definitely concur that new/re-arched springs and all new bushings etc will no doubt stop the axles from hitting so at this point I'll try a freshen up and take it from there.

Also I guess when moving the mounts I can perhaps narrow the spacing a tad as well be carefull of course not to bring the wheels to close together, they are around 32.5 right now on axle spacing.

Cheers
Nobby

[arveetek]

Look at the axles. How are they sprung? If the axle tubes are above the springs, they can be mounted below them. This will increase height: the diameter of the axle tube + leaf spring stack. If this is the case, and you do that, rotate the brakes 180° on the hub (the axle will be rotated 180°, and brake orientation must be retained).



I just want to point out that the proper way to relocate axles to where they are mounted under the springs (sometimes referred to as 'flipping axles') is to purchase new spring mounts (perches), bolt the axles under the springs, and then weld the spring mounts in place. This keeps the axle in proper orientation, and does not rotate the axles 180*.

Most trailer axles are arched from the factory, especially RV axles. This is done to compensate for the weight of the trailer, so that the wheels and tires will remain straight up and down. If you rotate the axles and flip them upside down, the arch is now upside down. This will cause extreme and fast tire wire.

I have seen several cases where an owner flipped his axles and turned them upside down. You can actually look at the trailer and see that the wheels and tires are splayed out at the bottom.

I typically recommend relocating the springs on top of the axles one side of the trailer at a time, leaving one side of the axles bolted in place. This keeps the axles correctly aligned while performing the work. Simply unbolt the u-bolts, remove the springs, place new spring mounts on top of the axle, place the springs on top of the mounts, and bolt the springs on with new u-bolts and nuts. Measure the distance between the old and new spring mounts making sure the space is equal, and then weld the mounts to the axle tube. Bolt the springs back to the shackles, and then move on to the other side of the trailer.

http://www.etrailer.com/Merchant2/graphics/00000001/pics/q/u/qu30768_800.jpg

Casey