# Boat Trailer Tire PSI???



## Incahiker (Mar 14, 2011)

Hey guys,

I have an odd situation here. I have a home made heavy duty trailer that only needs to carry a Jon boat, but was made to carry a fiber glass boat. Of course the Jon boat only weighs around 190 lbs, vs the fiber glass boat the trailer was made for. 

To be on the safe side I aired up the trailer tires up to the max 35 psi specified on the trailer tires and then took it to the lake. Lets just say that the trailer literally "JUMPED" every time I hit a bump, was not fun. I am guessing since the trailer is not even close to loaded up with it's maximum load I might need to lower the pressure. Before the pressure was on 20 and I never noticed the trailer "Bouncing" all over the place. It was pretty jarring.

What do you guys recommend, I want to get a good balance of smooth ride and not over heating the tires? Should I lower the pressure back down to 20 - 25 range?


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## dr_beerman (Mar 14, 2011)

30 should be fine


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## screwballl (Mar 14, 2011)

Mines states around 33, I keep it around 30 psi. It jumps a little but it is better to keep it close to its recommended pressure for the life of the tire. Running it too low will cause early failure and increased heat build up.


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## crazymanme2 (Mar 14, 2011)

Just keep lowering the presure & keep an eye on the heat in the tires until you get a nice ride.


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## mtnwkr (Mar 14, 2011)

screwballl said:


> Running it too low will cause early failure and increased heat build up.



If there's not enough weight to deform the tire at a given PSi then there's no worries of wear/failure or heat. I ran my old trailer with a 120lb tin at 15psi for a nice ride. My new trailer/boat combo rides at 25psi. Just keep letting out air till you find what works for you without deforming the tire where it meets the road.


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## 00 mod (Mar 14, 2011)

also if it has multiple spring, you can take one out, or find a smaller spring at a store like northern tool or harbor freight and that will soften the ride! Just couldn't go back up to a heavier boat!
Jeff


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## Incahiker (Mar 14, 2011)

Ya, it has multiple spring leafs, are they easy to adjust? I have never done it. The tire pressure on the trailer tires were at 20 and it gave a perfect ride, with them at 35 it was in the air half the time bouncing and skipping all over the road. Was kind of scary really.


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## lckstckn2smknbrls (Mar 14, 2011)

removing a few leafs from the spring is not hard you need a big C clamp and new center bolts. use the c clamp to hold the leafs together and remove the center bolt. Now remove the c clamp the leafs will fall apart. Now put the desired leafs together with the new center bolt and tighten the bolt. When tight cut off the extra threaded area.


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## screwballl (Mar 15, 2011)

It all depends on the tire type and the ratings.

Bias ply is designed with a "running pressure" or "required pressure", versus radial is designed with a "pressure range" or "recommended pressure". This is due to the way the tires are designed. Bias ply is designed so most of the weight distribution is handled by the tread and belts, which must be kept close to standard psi in order to prevent them from deforming or blowing out. Radial tires use a radius type belt that actually offsets some of the weight distribution throughout the entire tire including sidewalls, which gives it a much smoother, softer feel and tend to be longer lasting tires, but because of the distribution, this is why they have a recommended instead of required range.

Most smaller trailer tires, 12" and smaller, are bias ply and are designed to run within 10% below or 5% above the required pressure. If it says 33 psi, then you are fine 30-35psi. Any lower and the bias ply belts can separate and blow out the tire quickly. Any higher and one wrong bump and the tire blows out.

So if you want a softer less bouncy ride, look for radial tires to replace your bias ply tires. *NEVER* under-inflate bias ply tires or that soft ride turns your boat/trailer into a projectile on the road putting not only yourself but other people at risk.


Under inflating tires is the #1 reason for premature failure, trailers or passenger vehicles.


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## Incahiker (Mar 16, 2011)

Thanks for the responses.

The tires on the trailer are 14". Looking in the door on my Tacoma there is a sticker stating the recommended pressure for my tires, and they are no where near the max psi. The max psi for my tacoma tires are 35, but toyota specifically states to run the front tires at 26 psi for the front and 29 psi for the rear for optimum performance and tire life. I went ahead and lowered my trailer tire psi to 25 and it works much better.


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## PartsMan (Mar 16, 2011)

I would do a chalk test.

Draw a line across the tread. Drive around the block.
Idealy you will have the same amount of chalk worn off all the way across.
Wearing in the middle means to much pressure.
Wearing on the sides means not enough.


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## Incahiker (Mar 16, 2011)

I will try that out..

You guys with your Jon boat trailers, how do you keep your Jon boat from bouncing around? I just called our local trailer shop (very highly praised by everyone here for their custom work) and asked them about my Jon boat and trailer. I told them what my problem was and asked them if they could custom make any leaf springs and put them in the trailer. They said they could, but that it would do me no good because the boat is so light it is basically like an empty trailer and there is nothing any leaf springs could do, he said leaf springs work with the weight of the load on the trailer. He said the only solution would be to take out some pressure from the tires, just like what I was going to do anyways.

Do you guys have trailers made for Jon boats that don't bounce around with just the weight of the Jon boat on the trailer with Full PSI in the tires? If so what does the suspension look like?


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## screwballl (Mar 16, 2011)

Usually the bounce can be reduced or removed by using radial instead of bias ply tires. You can drop the pressure down a little but not too much. For 33 psi tires like mine, keep it at minimum 25 psi for shorter trips, 28-30 psi for longer trips. These boats and trailers are so light there is not really much that can be done aside from adding an extra 100-200 lbs on the trailer and using radial tires.


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## Incahiker (Mar 16, 2011)

Ok.. so you guys get bounce too? It really worried me when I hit a pot hole and my trailer bounced pretty high. Over normal bumps and what not it fairs ok, not much jumping going on, but if you hit a sharp rise or drop, or pothole the trailer gets hammered pretty good and bounce really good. I am really worried about my transom, I don't want the motor to rip out the transom when I bounce like that. It is only a 4hp mercury, but it still is more then enough weight to do some damage I would guess.


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## Hanr3 (Mar 16, 2011)

NEVER change your tire pressure to fix a suspension problem. 

You need to change your springs. That is the best way to fix your suspension problem. You could add weight to the trailer, but weight isnt cheap.


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## Incahiker (Mar 16, 2011)

Well,

I don't know what to do then. I called a place here that has been building trailers for the last 30 years in Georgia and he said that there was nothing he could do about the spring leaf / springs for the suspension to not bounce with such a light boat. He said he could custom build a trailer for the boat but it would most likely bounce just as much as the one I have right now would.

So, you guys who trailer a 150-190 lbs jon boat with no weight in it, does your trailer not hop pretty high when it hits a pot hole or a large step up in the road surface? I even heard that the harbor freight utility trailers will do the same.


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## Hanr3 (Mar 17, 2011)

https://www.etrailer.com/dept-pg-Trailer_Suspension-sf-Leaf_Springs-pt-For_Slipper_Springs.aspx

500 pound capacity, about a light as they go. 

I have either the 500 or 750 pound springs under my little 14' boat. Boat weighs 200 pounds before I added about 150 in gear, and another 80 in motor. trailer has some weight to it to. dont forget boat gas too. Add it up and figure out which one you need. 
I bought my springs at Tractor Supply.


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## lckstckn2smknbrls (Mar 18, 2011)

What weight is your trailer rated for? How many leafs are in your springs? What size are the tires?


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## Hanr3 (Mar 18, 2011)

lckstckn2smknbrls said:


> What weight is your trailer rated for? How many leafs are in your springs? What size are the tires?



No idea.

3 per spring

8", although I want 12"


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## lckstckn2smknbrls (Mar 18, 2011)

Hanr3 said:


> lckstckn2smknbrls said:
> 
> 
> > What weight is your trailer rated for? How many leafs are in your springs? What size are the tires?
> ...


Is that the op's info?
When I first got my trailer it had mono-leaf springs.


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## Hanr3 (Mar 18, 2011)

Sorry, thought you were asking me.

The original trailer that came with my boat had a single spring. Not one per side, just one spring mounted to the axle and trailer. :mrgreen:


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## DBrooke (Mar 18, 2011)

Incahiker said:


> Thanks for the responses.
> 
> The tires on the trailer are 14". Looking in the door on my Tacoma there is a sticker stating the recommended pressure for my tires, and they are no where near the max psi. The max psi for my tacoma tires are 35, but toyota specifically states to run the front tires at 26 psi for the front and 29 psi for the rear for optimum performance and tire life. I went ahead and lowered my trailer tire psi to 25 and it works much better.



In regards to your truck, I would suggest seeing what psi your tires say to go with if they are not factory originals.. EX. My truck sticker says 32 psi, but my tires are max 50 psi


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## lckstckn2smknbrls (Mar 18, 2011)

Hanr3 said:


> Sorry, thought you were asking me.
> 
> The original trailer that came with my boat had a single spring. Not one per side, just one spring mounted to the axle and trailer. :mrgreen:


I had a trailer like that for a sunfish sail boat.


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## lckstckn2smknbrls (Mar 18, 2011)

lckstckn2smknbrls said:


> Hanr3 said:
> 
> 
> > lckstckn2smknbrls said:
> ...


By mono-leaf I mean a single leaf per side.


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## screwballl (Mar 20, 2011)

For these boats, only one or two leafs are needed. The more leafs it has the higher the load/weight rating but also with our light setups, the stiffer the suspension will be. Usually 2 leaf spring setups is best for our trailers unless you have a lot of weight (15-25hp motor, full gas tank, 2+ batteries, extra decking, etc), in which case bounce should not be a problem unless you have 3-4 springs.

As for having the motor on it when towing, as long as the rear of the trailer and bunks are within 6-12" of the rear of the boat, the bouncing should not be too much of a problem. It is when you have 2-3 ft from the rear bunk/trailer when it gets to be a problem. Reinforcing the transom should provide more strength in these cases.

If you have the chance, replace 8" tires (which only come in bias ply most places) with 12" radial tires and 2 leaf springs per side. This is something I am planning in the future... That or just buying a slightly longer trailer that already comes with 12" tires which in many cases is cheaper if you have to replace a lots of components (like leaf springs, rims, tires, axle, possibly modifying fenders to take the larger tires).


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## Incahiker (Mar 21, 2011)

Thanks for all the replies. My Trailer has 2 leaf springs on each side. It also has 14" radial tires on it. I lowered the pressure to 25 PSI (from 35 PSI) and there is no deformation in the tire and it rides much, much better.


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