Best Suspension for Off Road Boat Trailer?

[Mike2000]

I need to build a trailer that will haul my 14' fishing boat on bottom and a RTT on top. My favorite fishing spots are down long distances of washboard roads and I need a trailer that won't rattle my equipment apart along the way.

Can anyone recommend a good suspension setup for this build?

Thanks,
Mike

 

[ottsville]

Whatever style you go with, the important thing will be having it tuned to the load you are carrying. More important than the style of suspension.

 

[honda250xtitan]

I'd say Timbren axle-less setup.

http://timbren.com/axle-less/

set goes for less then a grand depending on the setup you choose. E-trailer has them.

 

[CampStewart]

If you go with something with trailing arms or links or leafs go with the longest you can get. I will add that you should carefully consider your tires as part of your suspension. For trailer tires for what you are describing I would look for a balance between weight, diameter, and durability. If cutting sidewalls on rocks and roots is not a concern than go for a lighter load range. Big tire, light, and low air pressure will help quite a bit. I would look at LT rather than trailer tires. Good shocks also.

 

[Jmanscotch]

As CampStewart said, light truck tires over trailer tires, aired down some when offroad, will help a lot no matter which suspension route you go.

I don't have experience with the Timbren axle-less suspension, heard good and bad, but for the price I just never ventured that direction. Trailing arm setups are nice, but also pricey. The rest of my response will be tuned towards classic leaf spring suspension as that's what I know a little about and can offer information on.

The general consensus is stock trailer springs suck for anything other than smooth highway/city towing. This should be obvious, since that's their intended use. Why do they suck? They're rated for the maximum rated weight the trailer will see (boat springs should be slightly better than say a cargo trailer), they're short and there's no dampening happening. So what can you do to improve it for some washboard road use? Easy. Run longer (36" or longer), softer leaf springs (that still meet load rating expectations) and add shocks to the setup.

The setup I bought for my offroad trailer, which is a semi-common choice for off road trailer builds, is all Jeep CJ-7 rear suspension stuff. The longer leaf springs offer a smoother and more flexible ride while still meeting weight ratings (the GVWR for a entry level -or light duty suspension- CJ-7 is roughly 4150 lbs with ~2,100 of that being for the rear suspension, so I choose them with the idea that they're appropriate for my 1,200 lb trailer and not too over rated). I'm adding shocks to the setup to help dampen the suspension (I'm using the CJ-7 leaf springs perches with a built in lower shock mount to attach the shock at the bottom and running a custom top mount that'll weld to the trailer frame).

To complete the conversion from my stock crap suspension to the CJ-7 suspension, I bought:

- 3 used leaf springs from local recycling yard (2 to use and one for spare) $100
- leaf spring hangers, shackles, bolts, bushings from 4 wheel parts $230
- custom 1/4" top shock mount $10
- my old Tacoma factory rear shocks $0

Here's the link for the CJ-7 suspension diagram to help see what all you need if you choose this route: https://www.4wheelparts.com/hardparts/HP_PartList.aspx?hpDID=134

From that diagram, I bought:

2 - #44 Front leaf spring hangers
2 - #37 Front hanger bushings
2 - #39 Spring perches w/ lower shock mounts (they is specific drivers/passenger side part numbers)
2 - #51 Bump stops
2 - #38 Rear shackle kits (includes bushings and bolts needed)
2 - #46 Rear lead spring hangers
2 - ???? U-bolts that fit my 2.38" diameter trailer axle and yet fit the CJ-7 spring perches (forget the part numbers I found, but for you it depends on your axle diameter)

You'll need to be able to weld, or know someone who can, but it's a good route to go on a semi-budget and get great results for your use. Hope that helps.

Jake

 

[elnip]

I'd say Timbren axle-less setup.

http://timbren.com/axle-less/

set goes for less then a grand depending on the setup you choose. E-trailer has them.

X2
Best mod I have done.

 

[elnip]

I'd say Timbren axle-less setup.

http://timbren.com/axle-less/

set goes for less then a grand depending on the setup you choose. E-trailer has them.

X2
Best mod I have done.

 

[Mike2000]

Thanks everyone. I'll let you know what i end up with.

 

[calicamper]

Sailboat racing yr around trailering the trailering is the most damaging to the boats. Wide supportive bunks located under key hull structural points will prevent hull weight / bouncing and constant flex on the hull. Aluminum hulls do better than glass but both can suffer hull damage being bounced hard on narrow unsupportive trailer bunks. Roller style bunks will just dimple the hell out of your hull and allow for movement as you rattle down rough roads.

The comment about the trailer being sprung perfectly for the weight goes a long long long way to having a smooth ride for the boat. As such dont put 3500lb springs on a trailer hauling a 1500lb boat etc.

 

[honda250xtitan]

As CampStewart said, light truck tires over trailer tires, aired down some when offroad, will help a lot no matter which suspension route you go.

I don't have experience with the Timbren axle-less suspension, heard good and bad, but for the price I just never ventured that direction. Trailing arm setups are nice, but also pricey. The rest of my response will be tuned towards classic leaf spring suspension as that's what I know a little about and can offer information on.

The general consensus is stock trailer springs suck for anything other than smooth highway/city towing. This should be obvious, since that's their intended use. Why do they suck? They're rated for the maximum rated weight the trailer will see (boat springs should be slightly better than say a cargo trailer), they're short and there's no dampening happening. So what can you do to improve it for some washboard road use? Easy. Run longer (36" or longer), softer leaf springs (that still meet load rating expectations) and add shocks to the setup.

The setup I bought for my offroad trailer, which is a semi-common choice for off road trailer builds, is all Jeep CJ-7 rear suspension stuff. The longer leaf springs offer a smoother and more flexible ride while still meeting weight ratings (the GVWR for a entry level -or light duty suspension- CJ-7 is roughly 4150 lbs with ~2,100 of that being for the rear suspension, so I choose them with the idea that they're appropriate for my 1,200 lb trailer and not too over rated). I'm adding shocks to the setup to help dampen the suspension (I'm using the CJ-7 leaf springs perches with a built in lower shock mount to attach the shock at the bottom and running a custom top mount that'll weld to the trailer frame).

To complete the conversion from my stock crap suspension to the CJ-7 suspension, I bought:

- 3 used leaf springs from local recycling yard (2 to use and one for spare) $100
- leaf spring hangers, shackles, bolts, bushings from 4 wheel parts $230
- custom 1/4" top shock mount $10
- my old Tacoma factory rear shocks $0

Here's the link for the CJ-7 suspension diagram to help see what all you need if you choose this route: https://www.4wheelparts.com/hardparts/HP_PartList.aspx?hpDID=134

From that diagram, I bought:

2 - #44 Front leaf spring hangers
2 - #37 Front hanger bushings
2 - #39 Spring perches w/ lower shock mounts (they is specific drivers/passenger side part numbers)
2 - #51 Bump stops
2 - #38 Rear shackle kits (includes bushings and bolts needed)
2 - #46 Rear lead spring hangers
2 - ???? U-bolts that fit my 2.38" diameter trailer axle and yet fit the CJ-7 spring perches (forget the part numbers I found, but for you it depends on your axle diameter)

You'll need to be able to weld, or know someone who can, but it's a good route to go on a semi-budget and get great results for your use. Hope that helps.

Jake

Sailboat racing yr around trailering the trailering is the most damaging to the boats. Wide supportive bunks located under key hull structural points will prevent hull weight / bouncing and constant flex on the hull. Aluminum hulls do better than glass but both can suffer hull damage being bounced hard on narrow unsupportive trailer bunks. Roller style bunks will just dimple the hell out of your hull and allow for movement as you rattle down rough roads.

The comment about the trailer being sprung perfectly for the weight goes a long long long way to having a smooth ride for the boat. As such dont put 3500lb springs on a trailer hauling a 1500lb boat etc.

****, you guys are making me really doubt my leaf spring setup i'm about to use. its setup for the axle, which is a 3500 lb axle. Trailer is gonna be 2k 2.5k max...Might start with taking one leaf out and see how it does. in addition to low tire pressure. I'd love to swap to the Timbrens. but 800 is about half my entire trailer budget lol.

 

[ottsville]

Timbren's are nice and maybe the best way to go without building arms if you are doing serious off-roading, but the cost is prohibitive for most people. Springs are fine for forest service and washboard roads, just get them set up correctly. Adding shocks to the axle may be a cheap way to help smooth the ride also, but others here would be more knowledgeable than me on that.

 

[bluejeep]

So the challenge is tuning the suspension based on the carried load, which of course varies significantly.

I have experience with airbags on a trailer I built to haul my jeep. The carried load varied from 5300 lbs (loaded jeep plus trailer weight) to 800 lbs (trailer weight only).

The air bag solution worked perfect. Increase air pressure when loaded, decrease when not loaded.

By far the smoothest riding trailer I have ever pulled, whether loaded or unloaded.

Worth the cost and effort involved, which I did not consider to be excessive compared to leaf, but truth be told I never did a direct $ to $ comparison.

Sounds like folks who have experience carrying boats warn about damage to the craft if not properly supported / cushioned. May have to factor that into final design and cost comparisons.

 

[Jmanscotch]

****, you guys are making me really doubt my leaf spring setup i'm about to use. its setup for the axle, which is a 3500 lb axle. Trailer is gonna be 2k 2.5k max...Might start with taking one leaf out and see how it does. in addition to low tire pressure. I'd love to swap to the Timbrens. but 800 is about half my entire trailer budget lol.

Try it out first and see if you're actually disappointed with the ride and tune from there. The biggest issue with trailer designed leaf springs, in off road applications, is their SPRING RATE, specifically it's too high. Removing a leaf will help soften the rate up, but could be bad for the springs LOAD RATE. Quick break down if needed; Spring rate is how much weight it takes to deflect the springs 1 inch. Load rate is how much weight the springs are designed to support safely.

2.5K is pretty close to the 3.5K so you should be decent to start, unlike many who end up with a 1-1.5K trailer on 3.5K springs, their spring rate is just never going to reach it's potential for the off road conditions and the springs won't deflect much to conform to rough terrain. On my last trailer, that weighed in at 1K pounds, I switch to 1,350 lb springs that were the same length as the stock ones, so kinda short at like 27" eye-to-eye. They rode great though, combined with the tires at low 20 PSI. No shocks, no fanciness, just derated springs and a little better spring rate.

Is your leaf pack a 3 leaf, 4, 6, etc? If it's a 3 leak pack, I'd be weary of removing one leaf...that might put you under a safe load rate. If it's 4 or more leafs...I'd think you'd be closer to safe by removing one but it depends on the pack setup and how the load is dispersed on the additional springs.

So the challenge is tuning the suspension based on the carried load, which of course varies significantly.

I have experience with airbags on a trailer I built to haul my jeep. The carried load varied from 5300 lbs (loaded jeep plus trailer weight) to 800 lbs (trailer weight only).

The air bag solution worked perfect. Increase air pressure when loaded, decrease when not loaded.

By far the smoothest riding trailer I have ever pulled, whether loaded or unloaded.

Worth the cost and effort involved, which I did not consider to be excessive compared to leaf, but truth be told I never did a direct $ to $ comparison.

Sounds like folks who have experience carrying boats warn about damage to the craft if not properly supported / cushioned. May have to factor that into final design and cost comparisons.

Great info!

 

[honda250xtitan]

Try it out first and see if you're actually disappointed with the ride and tune from there. The biggest issue with trailer designed leaf springs, in off road applications, is their SPRING RATE, specifically it's too high. Removing a leaf will help soften the rate up, but could be bad for the springs LOAD RATE. Quick break down if needed; Spring rate is how much weight it takes to deflect the springs 1 inch. Load rate is how much weight the springs are designed to support safely.

2.5K is pretty close to the 3.5K so you should be decent to start, unlike many who end up with a 1-1.5K trailer on 3.5K springs, their spring rate is just never going to reach it's potential for the off road conditions and the springs won't deflect much to conform to rough terrain. On my last trailer, that weighed in at 1K pounds, I switch to 1,350 lb springs that were the same length as the stock ones, so kinda short at like 27" eye-to-eye. They rode great though, combined with the tires at low 20 PSI. No shocks, no fanciness, just derated springs and a little better spring rate.

Is your leaf pack a 3 leaf, 4, 6, etc? If it's a 3 leak pack, I'd be weary of removing one leaf...that might put you under a safe load rate. If it's 4 or more leafs...I'd think you'd be closer to safe by removing one but it depends on the pack setup and how the load is dispersed on the additional springs.

Cool thanks!

It's a 4 leaf. 1750 per pack. 25 1/8" eye to eye. One way to find out i suppose lol.

 

[Jmanscotch]

Cool thanks!

It's a 4 leaf. 1750 per pack. 25 1/8" eye to eye. One way to find out i suppose lol.

With a 4 leaf pack, I wouldn't hesitate to remove a single leaf, but try it out as-is first and see if it's even worth the hassle.

I don't know the exact math here, but keep in mind a 4-leaf spring pack rated at 1750 lbs won't be divided evenly between the 4 leafs, aka each leaf isn't rated for 437.5 pounds. The main leaf spring carries 100% of the 1750 lbs as it's the only leaf that bridges the mounting points to the axle. The other 3 leafs (in a 4 pack) just help distribute that weight along the main leaf spring and thus it'll perform more reliably (as well as serve a purpose for spring rate).

My point is, if you remove one of four leafs from each side, don't think you are reducing the weight carrying capacity by 1/4th. This is where I'm unsure of the exact math, but I'd assume removing one leaf (the shortest) would only reduce the springs rating by 5-10%, and by that I mean they maybe more likely to fail when pressed to the max, but technically should still be rated to carry the same weight. Maybe someone more knowledgeable in the mechanical engineering realm of things can enlighten us on the exact effects of such a modification.