# Thread: Trailer tires; how much pressure

1. ## Trailer tires; how much pressure

I noticed one of my boat trailer tires didn't like the extreme cold and his flat. I can't seem to read the side of either tire.

What's a safe 'ball park' amount of pressure to inflate to?

2. ## Re: Trailer tires; how much pressure

Originally Posted by John Smith
I noticed one of my boat trailer tires didn't like the extreme cold and his flat. I can't seem to read the side of either tire.

What's a safe 'ball park' amount of pressure to inflate to?
About the same as the back wheels on your car as a starter f' ten.

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## Re: Trailer tires; how much pressure

True trailer tires here in the states run much higher pressures than car tires. - I have seen typically around 60 PSI for real trailer tires.

I made the mistake once of setting the pressure in my trailer tires close to car tire pressure (around 35 PSI). It was not long (actually a very short period of time) before I was off on the side of a highway with a blown tire, mangled fender and black rubber streaks on the side of the boat. I learned my lesson quickly.

4. ## Re: Trailer tires; how much pressure

The amount of pressure required is entirely dependent on the load.

There is a load/pressure chart for every tire made. Finding it is the trick, sometimes we have to use empirical data.

Look at this chart for example, and note the maximum pressure listed on the sidewall is 80psi, yet the operating pressure for a given load could be as low as 35 psi
https://www.michelintruck.com/refere...tion-tables/#/

5. ## Re: Trailer tires; how much pressure

May I recommend that you not guess? The same size tire, depending on load rating can vary by 100% or more. If you can't read the info, check with a flashlight & magnifying glass. If you still can't - you may need to pull it off & check the inside.

6. ## Re: Trailer tires; how much pressure

#4 has it right.

without a chart for your tire/application, I gotta say that it's right when it looks right.
Trailer tires (generally) fail when the oscillation between the loaded (bulged sidewall) and unloaded positions overworks the material and boom. Inflate until you have just a touch of sidewall bulge left (kinda how your car tires look when inflated to the pressure listed on the doorjamb), and you're pretty close to correct.

Better to be a few psi over then a few psi under, from the tire's perspective anyway. Your boat probably prefers a few psi under.

7. ## Re: Trailer tires; how much pressure

The trailer manufacturer should be able to tell you -call or check their website.

Thanks all

9. ## Re: Trailer tires; how much pressure

If your tire is that old and worn - you may want to consider new tires...

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## Re: Trailer tires; how much pressure

Originally Posted by Canoeyawl
The amount of pressure required is entirely dependent on the load.

There is a load/pressure chart for every tire made. Finding it is the trick, sometimes we have to use empirical data.

Look at this chart for example, and note the maximum pressure listed on the sidewall is 80psi, yet the operating pressure for a given load could be as low as 35 psi
https://www.michelintruck.com/refere...tion-tables/#/
Yes, and

"If your tire is that old and worn - you may want to consider new tires..."

Yes.

11. ## Re: Trailer tires; how much pressure

Some people here like to go for fairly low tire pressure on their boat trailers, since many of these are much too stiffly sprung. Lots of trailers are rated at a ton when the wooden boat weighs 1/4 of that at most.

But I tend to run them fairly hard, usually at 40-55 for a 60psi trailer tire. I worry that running them too low will increase heat and wear on the sidewalls. I also always pump up the spare that is mounted to the trailer tongue somewhere. If you see a lot of cracking in the sidewalls, buy new tires before the old ones fail.

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## Re: Trailer tires; how much pressure

Trailer tyres..?
I have several trailers...a cargo trailer , max load half a ton 10 cwt, 500 kg
the boat trailer , max load with small euro car tyres, typically 13 inch citroen eurowheel fiat renault, less than a ton .
a canoe trailer , also with 13 inch car tyres
posh Swedish fibreglass homologated registered approved etc etc maybe 750kgs payload, , three quarters ton again 13 maybe 14 inch i havent looked lately.
all I run at as PM said standard rear car tyre pressure, 25 lb to max 30 lb ..2.0 metric. A 26 ft touring caravan. again as above.

never ever had any problem from the tyres.. even the boat and trailer all up weight is less than a ton and i have always run it at 30lbs 2.0, 2.1
I am more concerned about balanced load + 50 kg on the hitch, and general condition than actual pressures.

13. ## Re: Trailer tires; how much pressure

Jonboy - what you have are automobile tires on your trailers, not trailer tires. I also moved to auto tires for my old San Juan 21 trailer, as they handled the weight and long trips better than the cheaper trailer tires. But auto tires have much lower maximum pressure ratings than trailer tires, so there's no direct comparison.

14. ## Re: Trailer tires; how much pressure

Trailer tires have other significant differences from drive vehicle tires. Not the least of is the depth of tread being deliberately less to reduce tread "squirm" thus lessening the tendancy to "fishtail" behind the towing vehicle, sidewall stiffness is another.
With a 500 pound tow you would never know the difference, but with a 5000 lb tow, you definately will. The tires on my smallest trailer (maybe 500 lbs, boat and trailer) I run at 20 psi which is probably more than they need.
(On my "race car" which shows 50 psi printed on the sidewall, I run between 23 and 26 psi depending on conditions)

15. ## Re: Trailer tires; how much pressure

There's a good article about this in a recent issue of Small Boats Monthly. I encourage you to subscribe and read it. There are important notes about how to read the labels on the tire of safety and how to know when to replace a tire, even if it looks good to the eye.

A well respected tire store here in Oregon advised me to pay more attention to the shape of the tire (the crown) versus the actual pressure. Mr Tire said the tire should be flat on top, not curved. The weight of the boat will determine the amount of air needed.

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## Re: Trailer tires; how much pressure

We have always run tires with the L/T designation on our trailers with very good results,but where we live our trailers other that boat trailers tend to see rough paved as well as dirt roads.
If you know the axles loaded weight the tire mfg. should be able to give you a number +/- a couple of PSI.
When I went with taller and wider tires on my 50 year old pickup I had no idea where to start so i emailed Cooper tires tech. people with axle loads tire size and rim width and they responded within 24 hours with inflation data for front and rear axles that were very accurate, on a side note the last set of Coopers I ran lasted 70,000 miles and when replaced had enough tread left that they will be used as tires on our utility trailer for another few years.

17. ## Re: Trailer tires; how much pressure

Depends on the tire size, 8 inch, 12, 14? They usually run higher. 5 years is a good time to replace, 6 years is max.

From the article. "Imprinted on every tire is a lot of useful information on its size, type, load range, pressure, and date of manufacture. All trailer tires are marked with ST—Special Trailer— and they are not at all like vehicle tires. Trailer tires have strengthened sidewalls that keep the trailer from swaying in turns and allow them to carry the often very heavy combined weight of trailer and its load."

https://smallboatsmonthly.com/article/trailer-tires/

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## Re: Trailer tires; how much pressure

Originally Posted by Bruce Bateau
There's a good article about this in a recent issue of Small Boats Monthly. I encourage you to subscribe and read it. There are important notes about how to read the labels on the tire of safety and how to know when to replace a tire, even if it looks good to the eye.

A well respected tire store here in Oregon advised me to pay more attention to the shape of the tire (the crown) versus the actual pressure. Mr Tire said the tire should be flat on top, not curved. The weight of the boat will determine the amount of air needed.
I've been told the same. Good test (if you can find the place to do it) is to drive on dirt road, then a short distance on pavement. If dust wears off the middle, lower the pressure; off the edges, increase pressure. Goal being uniform tire wear across the tread. I run mine at about 30 lbs (rated 60), and check the temperature every time I stop. They seem to run about the same as my truck and car tires (pretty warm, but not hot).

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## Re: Trailer tires; how much pressure

Originally Posted by Canoeyawl
(On my "race car" which shows 50 psi printed on the sidewall, I run between 23 and 26 psi depending on conditions)
If it was dry-slick, we'd get down to 4 in the left rear, and 8 to 10 on the right

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## Re: Trailer tires; how much pressure

As Thorne said, most small boats are underweight for the designed trailer axle suspension. I run them soft for a short jaunt and drive slow to avoid it jogging up and down and getting damaged. Usually stop after a short while and recheck the load straps and feel the wheels outside the bearings for heat.

Torque figures

Wheel Bolts

AL-KO

M10 - 40 lb. Ft / 54 Nm
M12 - 65 lb. Ft / 88 Nm
M14 -108 lb. Ft /146 Nm

Indespension

M12 - 55 lb. Ft / 74 Nm
M14 - 60 lb. Ft / 81 Nm

Avonride

M12 - 65 lb. Ft / 88 Nm

Ifor Williams

M12 - 65 lb. Ft / 88 Nm

Wheel Nuts

Peak Trailers

M12 x 1.5 - 75 lb. Ft / 102 Nm
M16 x 1.5 - 145 lb. Ft / 197 Nm
3/8" UNF - 45 lb. Ft / 61Nm
1/2" UNF - 80 lb. Ft / 109 Nm

Indespension

3/8" UNF - 42 lb. Ft / 57 Nm
7/16" UNF - 50 lb. Ft / 67 Nm
1/2" UNF - 56 lb. Ft / 76 Nm
5/8" UNF - 85 lb. Ft / 115 Nm

Avonride

1/2" UNF - 65 lb. Ft / 88 Nm
5/8" UNF - 79 lb. Ft / 108 Nm

Tightening sequences:

4 Stud

5 Stud

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