Tyres (again)

Warren-Pat_01 · Guru

Tyres (again)

Aus-Kiwi · Guru

I guess the ply ratting depends on how you are intend to use your vehicle over rocks etc off road . ?? Go by what is fitted originally to your vehicle ? Then go better or higher ply depending on your use . The tyre co and van / vehicle are comprised by price and side harshness with higher ply ratings .

Peter_n_Margaret · Guru

Forget plies, base your choice on the tyre load rating.
All pressures are measured cold.
The correct pressure is determined by the actual weight of the van and the load/pressure chart for the actual tyre you use.
Cheers,
Peter

iana · Guru

Hello Warren, I ended up getting a set of Kumo A/T tires, what the salesman said made sense, they have a higher load rating, have a 20% off road to 80% on road, and have a supposed very good wet road handling. The interesting point is the tyre pressure on our ute was 38 F and 43 rear, and now is 45psi all round. Pretty sure the tyre pressure on the van is 43 all round.
You have a discovery pop top length ?, I can have a look in the camps and see what tyres they have.
Why don't you put the question up "what type of tyres are yu using" for that model caravan.

Cupie · Guru

Warren-Pat_01 wrote:
Hello everyone,
Just going on from iana's posting a few months ago & after "Searching" the files here - when we buy tyres for our vans, vehicle what do we specify to the tyre dealers? Size & LT tyres - yes.
My Nissan has LT265/70R16 tyres with 2 steel, 2 polyester, 1 nylon plies in the tread & 2 polyester in the sidewalls.
The van has LT235/75R15 tyres with 2 steel, 2 polyester plies in the tread & 2 polyester in the sidewalls. The tyres are rated at 900Kgs at 51psi, the wheels have a maximum load rating of 1000Kg. Both the van dealer & tyre dealers mentioned that tyre pressure should be 50psi.
Due to a hopefully past problem of the tyres wearing on the insides (van) I had a wheel alignment done at Warrnambool & a rotation of the tyres on the wheels here in Townsville last week. At this last action (& this dealer fitted the tyres) I found there were various ratings of LT tyres - 4, 6, 8, 10 plies. There is nothing specified on the Compliance plate other than the wheel, tyre size & a cold tyre pressure of 250Kpa (37psi)! The axle group weight is 1980Kgg, the ATM 2016Kg.
So the questions that come from these figures are -
1. is the tyre pressure of 51psi cold or hot?
2. where does Jayco get the 250Kpa (37psi) from?
3. are my tyres light-on with 4 plies?
4. as suspected many times before on this forum are Compliance plate details, figures that manufacturers dream up?
5. should I(we) be more careful when taking our vans in to have new tyres fitted & mention what the load is?

250KPA ..... My 21'6" Westport plate says 200!!!! OK if you don't mind driving with great big bags in the tyres. I have never driven with tyres that low. I checked it with Jayco many times over the years & they couldn't explain.

I drive on 280 (40psi)

BTW my 2.8T GQ Patrol recommends front pressure is 29psi (200kpa) I stick to that & 41 in rear.

Warren-Pat_01 · Guru

Thanks Peter,
I've found a chart on my van's tyres that shows the wheel/tyre size but haven't found the pressure chart yet.
The chap who did my van's wheel alignment was surprised that I had the correct pressure in the tyres - he was used to seeing almost flat tyres on vans he'd worked on!

Ian,
It sounds that you're happy - I've looked at Kumhos more than once before & they do have a good reputation. I normally stick to 60/40 on road to off road use but that is what I do. My van is 17 feet long (single axle). I've seen quite a few Discoveries on the road but they were either on road or dual axle models.

Cupie,
The difference in the tyre pressures may be due to your van having two axles - I have one. Maybe Jayco now allow us to use our Outbacks on sand dunes!!

Locals at Ceduna used to take their caravans over the sand dunes to Davenport Creek. They did it early in the morning when the dew moistened the sand. I'll get shot now as I've let the cat out of the bag & this great fishing spot will be taken over by nomads!!!!

Peter_n_Margaret · Guru

haven't found the pressure chart yet.

You will need to contact the tyre distributor.

Cheers,

Peter

Roy E · Senior Member

Warren,
I have a suggestion as to why Jayco specified unreal low tyre pressures; To stop van shaking to bits during warranty period, the tyres themselves not being under warranty.
In my Jayco Starcraft Outback, with 2, LT235/75 R15 tyres, an ATM of 2030 kg and GTM of 1861 kg, VIN plate tyre pressures are; "Tyre pressure (cold) 310 kPa" and "Tyre pressure max loading (cold) 345 kPa" that is a very realistic 45 and 50 psi. I have found, using the "4 psi increase" method that 46 psi (317 kPa) is perfect for my van.
I believe your van tyres don't take the punishment that your tug tyres do off or on road and don't need to be as rugged but correct inflation is important to prevent tyre over-heating (under-inflated) or un-necessary van stress when over-inflated.
Cheers,
Roy.

Hylife · Guru

Ignore what is on the compliance plate regarding pressures. That data is only valid if for a hypothetical example for the original tyres fitted by the vans manufacturer and every tyre differs with each batch made.

There has been an internationally recognised system specified by tyre manufacturers for well over 40 years, for your tyre pressures, load rating and speed limits and it is right there on the side of your tyres.

Step 1, What is the (real) maximum weight of your caravan loaded?
            --> divide by the number of wheels (eg, 2 or 4 for single or tandem) then add 10% for safety
                  (EG, 3,000kg fully loaded van on tandem axels = 3,000 divided by 4 = 750 + 10% = 825kg per wheel)
            --> Now you know the minimum load rating for any tyres you buy.

Step 2, What is the maximum crazy speed you intend to tow your van? Then add 10% for safety.
--> Now you know the minimum speed rating for any tyres you buy.

Step 3, Discuss these things with your tyre retailer and they will recommend tyres that meet or exceed these minimum specs, and are suitable for the types of towing you do and the places you go.
                  Having chosen to have fitted a set of the recommended tyres, "read the tyre sidewall".
            --> The tyre side wall will specify the pressure required at the maximum load the tyre is rated for.
                  (EG, the sidewall might say something like:- 55PSI at 950kg)

Step 4, Now you work out the custom pressures for your van with some really simple math.
                  Put simply, the weight percentage, is the pressure percentage.
            --> Divide the laden weight of your van (per wheel) by the maximum load rating of the tyre.
                  (Using the examples in step 1 and step 3), 750 divided by 950 = 79%

Step 5, Inflate your tyres (when they are cold) to 79% of the pressure specified on the tyre sidewall.
(Using the example in step 3 of 55PSI at 950kg), = 55 x 79% = 43PSI

Less weight equals less pressure. More weight equals more pressure.

Tread patterns, brands, tyre types (eg light truck or not) is purely person choice, so long as the tyre meets the minimum specs for load and speed rating and is an appropriate size that matches the wheel rims (usually specified on the compliance plate).