cobba
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Posts: 30
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Post by cobba on Dec 22, 2012 20:38:11 GMT -12
My 12 foot tinny is on a proper dinghy trailer. The trailer had 8" wheels with motor scooter tyres which is OK towing from the house to the water 2km away, but looked a bit of a worry for highway motoring, so I've put in an axle with 13" wheels and 165 radials. Now the big question is tyre pressure for such a light load. I've got them at 32 psi but haven't tried it out yet.
What tyres and pressures are you guys running on?
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Post by chillidog on Dec 22, 2012 21:36:56 GMT -12
Ya know thats a really good question, to be honest my trailer is new , but I'll be phoning them up to ask  |
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Post by 1650bullet on Dec 22, 2012 22:52:39 GMT -12
I have the same size tyres on my trailer towing a Quintrex 3.85 mtr Explorer trophy with 25 mariner. All up weight including trailer is just under 390kgs. I have always run 32 psi and the tyres are evenly worn all the way threw the tread pattern. The tyres are 11 years old now and still going. The boat has always been kept undercover. If we go away for a weekend we load all our camping gear in the boat and i run 40psi so it rides better on the road.
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Post by Rex NZ on Dec 23, 2012 8:14:13 GMT -12
Pressure depends on weight & suspension type
Steel leaves have a modest spring rate & travel well, so you'll want firm tyres.
My ballpark numbers for single axle leaf suspn on 13" rims
* 1000+ kg kurb weight go 45psi
* 500- kg kurb weight go 25psi
Conversely, Dura-torques have high effective spring rates & basically don't travel, rather they are vibration dampers, so you want mushy tyres
My ballpark numbers for single axle dura-torque suspn on 13" rims
* 1000+ kg kurb weight go 30psi
* 500- kg kurb weight go 15psi
8" tyres have a small footprint & will want higher pressures than 12"/13"
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cobba
New Member
Posts: 30
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Post by cobba on Dec 23, 2012 15:15:38 GMT -12
I've just had another look at the tyres and they're 155s. Interesting about the different pressures for different suspension types, I didn't know that. Mine is leaf springs and with 32psi there's only about 80mm tread width touching the road but it seems to ride ok. I'll try 25psi and drive over some bumps and take it for a blast down the motorway and see how it handles then recheck the pressure when hot.
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cobbadog
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Woof Woof !
Posts: 32
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Post by cobbadog on Dec 30, 2012 18:14:17 GMT -12
I used to work in the tyre industry here in Oz for too long. I would not drop the pressure below 30 psi will only hurt the tyre. I understand that you have very little weight on the trailer and it may bounce a little bit but it is better than causing tyre failure. Like us we only have to travel 2 klms to the boat ramp but I still run 30psi in our tyres and have done so for amny years. So many I now have to replace the tyres due to age. Yep tyres can get too old.
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Post by Rex NZ on Jan 5, 2013 7:04:10 GMT -12
Did some destructive testing of tyres back around 1991 using a car transporter heavily loaded
* Cross-ply tyres would heat & heat until they ruptured the sidewalls.
* Radial tyres with only 4 ply construction would last better, but readily ruptured their tread face when inflated to the top of their pressure rating.
* 8 ply radial constructed tyres outlasted everything else
Later did some further study around 1997 using heavily loaded courier freight vans
* Found that commercial 8 ply radial constructed tyres run at the top of their pressure rating (65-70psi) were prone to rupture their tread faces. Further found that dropping the pressures back & letting the sidewalls flex made them last until worn out.
* 8 ply commercial tyres run at modest pressures turned out to be the most indestructible, unsurprisingly, & the most expensive.
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cobba
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Post by cobba on Jan 5, 2013 10:59:12 GMT -12
I'm going on holiday with the dinghy tomorrow so I'll have a good chance to try out tyre pressures. And as for old cross-ply tyres - I'm about to dump a pile of them from Jowett Javelins and Bradfords, all with excellent treads but cracked sidewalls due to old age.  |
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cobba
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Posts: 30
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Post by cobba on Jan 16, 2013 16:03:30 GMT -12
Well I did about 200km with 28psi in the 13" radials. There might have been a slight bounce in rough potholed surfaces but otherwise it was all good so I'll keep it at 28psi and watch the long term wear.
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cobbadog
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Post by cobbadog on Jan 17, 2013 12:48:37 GMT -12
When checking the wear pattern, check the tread depth on both sides of the tread and also the centre. If the outsides are wearing faster than the centre then you must increase tyre pressure. Of course if the opposite is happening, centre wearing faster than side , drop the pressure.
Next, if you find that one side of the tread is wearing faster than the rest of the tyre you have a bent axle or it is not set square across the trailer to the coupling and you are dragging it sideways.
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