Tyres for caravans

[millard1399]

G'day All,

I had to get a spare wheel made up for the van. Not easy to track down the old 13" Holden wheels. Did the rounds of local auto wreckers, but nothing going. Eventually popped in to a local garage where I'd often seen a couple of Toranas hanging around. Asked did he know where I could look, and he says he might have one out the back. Came back with one, in usable but not great condition. Tyre was way past it, but rim was salvageable. He wants $40. I dunno where else to go, so I cough up.

Off to the tyre shop to discuss another tyre. No second hand tyres available. Don't come across second hand 13" tyres much to build up a stock.

But he can give me a new light truck tyre for $80, plus another $14 for a tube, because the rim is not the proper tubeless type. So he strips the old tyre off and comes back out with the rim. Not looking good, I thinks. He says, no no, just take it home and clean up all the rust inside and give it a paint job with any old paint, and bring it back...



Back the next day to have the tyre and tube fitted. For my $80 I end up with a Nankang tyre.

A Nankang??!! Never heard of 'em! What the heck is a Nankang?! Sounds like something you step on in a cow paddock! "Don't you come in the house with any of that nankang on yer boots, Bluey!"

So I go home and do some research on the internet. Nothing polarises people more than cars and car bits. Looked at all the forums where Nankang got a mention, and there were as many people who thought they were ok, as there were who thought they were crap.

There's not a lot of brands of 13" light truck tyres. Nankang, Maxim, Kumho, Goodyear. Somebody on a forum said they'd bought the 13" Goodyear Wrangler L/T tyre last year for $117. About 50% more in price than the Nankang.

The Nanakangs have a coding of 165R13C. Trying to find out what that meant was another challenge. Eventually found this info (the Nankangs are in the fourth group)...

Tyre sizing systems: (from the website - www.bobjane.com.au/4x4-commercial-sizing.html)

When it comes to commercial and 4x4 tyres, there are four different sizing systems:

1. European Metric
2. Light Truck High Flotation
3. Light Truck Metric
4. Light Truck Numeric

All sizing refers to the performance requirements of both the vehicle and the tyre, in line with the varying applications for these types of vehicles.

1. European Metric

Example: 185R14XCD

185 = Section Width in millimetres
R = Radial Construction
14 = Rim Diameter in inches
XCD = Tread Pattern

2. Light Truck High Flotation - This sizing system evolved in the mid 1970s as lower aspect ratio tyres became more popular on 4x4 & Commercial vehicles.

Example: 31x10.50R15LT

31 = Tyre diameter in inches
10.50 = Section width in inches
R = Radial Construction
15 = Rim Diameter in inches
LT = Light Truck construction

3. Light Truck Metric - This sizing system was introduced to mirror the system used for sizing passenger tyres.

Example: LT235/75R15

LT = Light Truck designation
235 = Section width in millimetres
75 = Aspect Ratio
R = Radial Construction
15 = Rim Diameter in inches

4. Light Truck Numeric - This older system is still widely used, mostly on commercial vehicles.

Example: 7.50R16C

7.50 = Section width in inches ( or 165 = Section width in millimetres)
R = Radial Construction
16 = Rim Diameter in inches
C = Camionette (Light Truck/ Commercial)

-------------------------------------------------

And then there's the whole different argument about what pressure to put in the tyres. Man-oh-man, there's a gazillion different opinions out there.

Found these two guides...

The following is from the NRMA caravan info site:

"4 psi rule":

"Tyre pressures - do-it-yourself check

It is impossible to list the correct pressures for every caravan, due to variation in size, load, etc. This easy check will help you find the best pressure for your caravan tyres.

1: First inflate the tyres to the pressure recommended by the manufacturer of the trailer or the tyre you are using. Secondly, tow your trailer for a distance of 100 km, preferably on a highway.

2: Recheck the tyre pressures immediately after pulling over and compare them with the pressures you had at the start of your run. If the pressures are right, the hot readings should be 4 psi (28 kPa) higher than the cold readings.

3: If there is a greater than 4psi (28 kPa) difference between these pressures, the tyre temperature is too high and the pressure needs to be increased. If there is less than 4 psi (28 kPa) difference, the pressure needs to be lowered.

4: Large 4WD tyres will have a differential of 6 psi (42 kPa).

5: Be sure to use the same accurate gauge for both readings."

-----------------------------------

And this one from another forum...

"Another way to find out approximately what pressure you should run is from a very simple formula derived from the tyre specifications:

max tyre pressure and max load rating are shown on the side wall of the tyre. Plus you need to know the weight of the van you'll be towing...

max tyre pressure divided by max load rating times actual load per tyre

for example: 450Kpa / 950kg x 450kg = 213kpa (30psi)"

----------------------------------------------------

Still gotta change the two tyres on the van. Dunno which ones to get. And dunno what pressures to put in 'em.

Life wasn't meant to be easy.

cheers,
Al.

(ps. Two days after I got the spare wheel sorted, somebody about an hour away from me listed two 13" caravan rims in "reasonable condition, light surface rust, could do with a repaint." $60 for a Buy-it-now deal for the two. Just the rims - no tyres. Got no takers. None.)

[kylarama]

Nankang is owned by Yokohama, it's their budget brand. Their even made in the Yokohama factory.


Check to make sure the offset is the same as your van wheels.

My old boat trailer ran 13 inch pre HR (1966) Holden rims. Tried to fit a set of LH Torana rims that I bought, only to discover they hit on the back of the guard. Turns out these rims had a 20mmish deeper offset.

Before the rebuild I changed the Wheels on the Millard as the old ones wouldn't hold air. Both were stock early Falcon rims, one had a 195 wide tyre fitted, the other a 205. The 195 just cleared the plastic guard and the 205 rubbed on it. Original tyres for these were 185 wide and the plastic guards showed signs of tyre rub marks over the course of its life.

Seems Millard don't allow much for tyre clearance. I've now fitted a wider axle to fix this, which should also accommodate the deeper offset late model Falcon wheels.

Might be worth a test fit now instead of finding out your spare doesn't fit in the middle of nowhere.

[ronaldjohn]

Apr 27, 2010 20:13:30 GMT 10 millard1399 said:

G'day All,
Back the next day to have the tyre and tube fitted. For my $80 I end up with a Nankang tyre.

A Nankang??!! Never heard of 'em! What the heck is a Nankang?! Sounds like something you step on in a cow paddock! "Don't you come in the house with any of that nankang on yer boots, Bluey!"

cheers,
Al.

Nangkang have been around for a while
In 2003, they were one of the few companies putting out white walled tyres.


That wheel belongs to this.


They have been on that car for 7 years ;D

Cheers,
Ron

[mike]

G'day Al, ;D

Thanks for all that info on van tyres: I know, hours of research!!
But invaluable.

I put 40psi in our van tyres. I've checked at Goodyear and Jax (and two other caravanners) and they recommended 40psi on my inquiry.

I have 14inch Holden HJ rims.

Kylarama: I can't quite understand what you write about in talking about "offset".
Is it the depth of the tyre that rubs on the guard?
Is it the position of the rim in relation to the studs?

I have an 'odd' spare rim on the van at the moment: can't fit a hub cap on it. Very strange. Not unsafe just odd because all rims were supposed to be the same.

Am I looking for problems here, or should I just leave it alone?

Cheers ;D ;D ;D
Mike

[kylarama]

Apr 29, 2010 23:17:30 GMT 10 mike said:

Kylarama: I can't quite understand what you write about in talking about "offset".
Is it the depth of the tyre that rubs on the guard?
Is it the position of the rim in relation to the studs?
Cheers ;D ;D ;D
Mike

Wheel offset is the distance from the centreline of the wheel to the mounting surface of the wheel.

HQ - WB Holden and XR - EL Falcon std Wheels have an offset of around +13mm. Which means the wheel mounting surface is 13mm towards the kerbside (front) of the wheel from the centreline. Commodore and AU Falcon onwards have a +45mm offset.

FE-HR Holden 13inch rims are +6mm

HK-HG Holden 14 inch rims are +30mm

HQ-WB Holden rims are +13mm

VB-VE Commodore rims are +45ishmm

XR-EL Falcon rims are +13mm

AU-FG Falcon rims are +45ishmm

Holden Torana rims are also 13 inch dia and have the same stud pattern as FE-HR's, but I'm pretty sure the offset is +13mm.

'Back Space' is the easiest way to work out what will fit on a trailer or caravan. On the back of the rim put a straight edge across the tyre and measure down to the wheel mounting surface.

With a tyre on the measurements will be around the following (can vary with tyre width).

FE-HR 105mm
HK-HG 135mm
HQ-WB & XR-EL 120mm
VB-VE & AU-FG 145mm

The above sizes will vary on factory and aftermarket mags, which are generally wider.




This pic might help.

Hope this helps.

[millard1399]

I checked today to see if the spare wheel fitted ok, which it does. ;D

But I noticed there is a different gap on each side between the inside of the tyre and the inside wall of the mudguard. About 30mm on one side, and about 50mm on the other. I guess this means the axle is about 10mm off centre, something I never figured on checking during the restoration.

But it means I'm restricted about what tyre width I can put on one side. The spare is 165mm, and leaves a 40mm gap on the narrow side of the van. The wheels already on the van are 175mm and leave a 30mm gap on the narrow side. There are rubbing marks on the inside of the plastic mudguards on the narrow side, so it looks like a 185mm wide tyre or greater can cause problems if there's too much lateral movement of the axle.

I presume an axle should be centred, or is there a valid reason for it not to be??

cheers,
Al.

[kylarama]

Apr 30, 2010 22:41:33 GMT 10 millard1399 said:

But I noticed there is a different gap on each side between the inside of the tyre and the inside wall of the mudguard. About 30mm on one side, and about 50mm on the other. I guess this means the axle is about 10mm off centre, something I never figured on checking during the restoration.


Al.

Axle should be centered, but it could be a number of things.

Did you check this with the same wheel? Wheels could have different offsets.

Measure back to the chassis rails. There maybe some variation in the plastic inner guards.

Axle may have shifted on the leaf springs. The axle has a 'axle pad' welded on to locate the centre bolt in the leaf spring, but you can still get a bit of play in hole in the axle pad. Measure from the brake backing plate to the leaf spring U bolts to make sure measurements on both sides are the same. If not loosen U bolts and shift axle.

Leaf springs maybe leaning to one side. Could be bent spring hangers or twisted leaf springs (probably not though). Most likely could be worn bushes, ie. bush holes have become elongate.

Ultimately on a single axle van 10mm offset will not affect anything so you could leave it. The axle on my 6x4 trailer shifted about 15mm 6 years ago and I've never fixed it.

[mike]

Hey hey kylarama, ;D ;D ;D

Thanks for that. Makes sense, but not obvious to the casual caravanner, yet could be crippling on the roadside if it doesn't fit!!

So much to learn... and here's the place to do it.

Cheers ;D ;D ;D
Mike

[maxbicyclemax]

hello mike
with regards to this

I put 40psi in our van tyres. I've checked at Goodyear and Jax (and two other caravanners) and they recommended 40psi on my inquiry

the tyres on my van are 65psi 850kg maximum
i recon my van weighs about 1500kg single axle so 750kg per tyre. i equate that to 55-60psi. (using millards formula)
plus 55-60 psi looks right. bit of a tyre bulge. any less looks flat, any more and thats maximum which would worry me.

my question is, what weights do you have that people suggest 40psi?
cheers
max

[millard1399]

G'day mbm,

When I set off on the big trip in May, I had no idea what pressure I should start with on the Millard. So I used mike's suggestion of 40psi as a starting point. Then at exactly 100kms later, I checked the pressures using the "4psi Rule" (described above in this thread). The hot pressures were 43psi, which according to the rule meant they were slightly overinflated to start with (...maybe the starting point could have been down around 38psi or something like that).

What I like about the 4psi rule is that it gives you "real-time" feedback on how the pressure is going in your tyres while you are actually travelling. You could do the same pressure check every day on the road if you wanted to. I never bothered with the pressures again after that first check, and the van seemed to be quite happy to run that way. My Millard has a tare of 820kgs and when loaded was probably another 200kgs or so.

The 4psi Rule seems to get favourable comments on other forums as well.

cheers,
Al.

[mike]

Greetings Al and mbm, ;D ;D ;D
mbm: 40psi was the figure Jax told me they were putting into the tyres when they fitted new Sumitomo tyres. (I was told by them that Sumitomo was Dunlop in Japan).

Whether or not the tyre fitter who was doing the job knew what he was telling me was going to be relied upon by me, I don't know.
The figure of 40psi had been mentioned in three other places tho' so it didn't seem 'out of whack' with the figure that I expected when I asked the question.

I had intended to get back here to this forum sometime soon though, and now's as good as any.

We've put about 2000km on those new tyres.
At 40psi, our van probably weighs in at 1500kg loaded, and those tyres (like others before them...) looked 'normal': which means bulging a bit where contact is made with the road.
On closer inspection, on site, I noticed small amounts of what looked like a black powder around the outside of the rim, just where the tyre fits into the rim. What I reckon was happenning was that the tyre was 'rolling' sideways on the rim and wearing the wall of the tyre for just the 5mm of remaining rim edge.
Then, on the sidewall, I could read "Max 450Kpa or 65psi at 850kg on a single axle COLD". This means that when HOT, the tyre could still be safe at even higher pressure?
I reckon that at 40psi, for the weight, the tyres are UNDER-INFLATED, and rolling sideways left then right when cornering. It would explain the long splits in the sidewalls of the previous tyres we had on (which were retired with quite good tread, but those tyres were also 9yrs old.)
So I had decided to increase the pressure to 50psi cold, and continue to watch the rim sidewall wear.

Re-visiting this thread today, I'm going to give Al's 4psi rule a go because it provides a 'measure'.

When I use the formula method above in Al's first Post here..
Taking the 'reading' from the sidewall of the tyre..
450Kpa/850Kg x 750Kg (or ACTUAL load on ONE tyre) = 400Kpa!!!
Strewth! Thats close to 60psi!! [397Kpa = 57.5 Psi]
Nb (1 psi = 6.8948 KPa)
Hey mbm, you could be right!!!! 55-60Psi!!!!

Looks like 50Psi would still have been too low.
60Psi ... Holy dooley!
Well gents, what do you reckon?
Right now I'm thinking 60Psi WITH a 4Psi rule check after 100km!
Hell, I'll probably have to get a weigh-bridge measure of the weight of the van because my guessed loaded weight gets close to the max limits for the tyres: If I've under-estimated the weight.....

Again, I think its lousy that even the tyre retailers don't know their stuff, well enough to provide advice based on scientific testing of the product they are selling to us.

By the way, isn't it hard to find a servo that you can get air into the tyres of the van... because they usually tuck the "Air" pump into a corner where its too hard to get the van into. I've worked out my 'ease-of-access' favourites round Sydney and they get my business. It is still a problem when touring. ;D

Cheers
Mike ;D ;D ;D

[Deleted]

I used the calculation method to find tyre pressure and as I am able to weigh each wheel load separately I worked out that I needed 47 Psi in each tyre, this works out well, the tyres stay cool and the van rides smoothly. I overcame the problem of access to garage air outlets by buying a reasonably priced 12 volt compressor and tyre pressure gauge which I carry with me in the van . now I can inflate van or car tyres cold and know that the pressure is accurate. (some garage gauges are way out of calibration).

Frankidownunder.

[mike]

Frankidownunder, ;D
Good to know someone has used the calculation method successfully! ;D ;D ;D
I have a 12v pump but its always been for 'emergencies' only, because it doesn't have a secure connection to the tyre valve, and I don't want a completely flat tyre.
But I'll take your point and start and use it ... if servos are not convenient, especially as tyre pressures are experimental at the moment.
Thanks
Cheers ;D ;D ;D
mike

[pisces51]

G'day All,

I've resurrected this old thread to add some "useful" info into it.

I had new tyres fitted to the wheels of my vintage van this week. The wheel rims are 15" FJ Holden, and apparently 15" tyres are not all that common these days. I couldn't get Light Truck Commercial tyres, and had to settle for standard radials. The old tyres had only done about 15,000 kms since I fitted them when the van started to be restored, but were now 8 years old, which is the maximum years my tyre sevice man says they should be used before replacing. I don't want a blown tyre to cause expensive damage to my van, so I'm happy to replace the tyres when they are due, irrespective of wear.

The tyre shop didn't have any new 15" tyres in stock, and had to order them in. When I got the wheels back home, I checked the date stamped on the new tyres out of curiousity, and discovered they were manufactured in Week 24 (mid June) in 2018! Heck, they've been sitting in a warehouse somewhere for 10 months already!! So I've already used up 10 months of the next 8 years allowance, and I haven't even done a km yet.

Something to mindful of the next time you have new tyres fitted.

cheers,

Al. 

[Mustang]

The tyres on Winnie have done 500km & are already old, I don't see any perishing or deterioration but I guess the road worthy inspector will knock them back?
I should take your advice, the 13" LT are only $90.00ea fitted.

[snoops]

I’m sure the Tyre sellers would love us all to replace tyres at 8 years, regardless of condition or wear. I’m the first one to replace tyres as needed but if they showed no signs of cracking then I’d still use them. Sidewall cracks will always be the first sign as they flex more than any other part of the Tyre. If I had to replace all my tyres at 8 years, I’d be broke - the wellys on my 101 are over $800 each and are currently 10 years old. No signs of cracking anywhere, I’ll keep them as long as I can. Do about 5,000km a year so hopefully another 5 years in those. Van tyres are cheaper yes, but the HO8’s set me back around $180 each IIRC so wouldn’t be in a hurray to replace them at 8 years either to be honest. There is no legislation requiring tyres to be replaced at a timed interval (no matter how much the Tyre sellers would like this).

Could be said it’s cheap insurance but I have 5 vehicle, 2 trailers and the van and I’ve never had a Tyre go flat or blow out because of age - oldest I’d have would be 15 years on my Series 3. I buy top quality when I do buy them, and they’ll last heaps longer than 8 years.

Just my 2 cents, I have no issues if others do this and are happy to, but I wouldn’t myself,

[78466noM]

The tyres on the F350 are 21 years old made the 2 month 1978 changed the steer tyres very small age cracks not cheap to go with the original type was much dearer but when I change the rear tyres as well I should be able to get an engineer to drop the gross weight down a little as max weight for the new ones are 50kg less for a single wheel and if I remember correctly 70kg's less per duel whee than the old ones and if I loose 55kg the rego drops by half. Since it is used as a private vehicle and I will never have it at max or even close best I have done is about a ton it is legal to carry a 2.5ton load on it's tray. It's registered gross weight is 4545kg's

      I have put this in mainly though talking to old tyre people and to check the load rating in this instance it works for me but if the old girl was loaded to the max weight it would be over weight by a few kg's not a lot but in the event of an accident I may or not be covered by insurance .

[Mustang]

We still see shredded truck tyres here in Qld.
Are retreads still used for trucks?

[78466noM]

Retreads are still used on trucks and trailers not as steer tyres but as drive tyres and trailer tyres two main causes of exploding retreads are previous repairs letting go puts air under retread but the main one is under inflation. last one I had blow took out the plastic guard, add blue filler and large fire extinguisher also put deep dent in fuel tank . The f350 will have new tyres all round they can still blow but the chance of that happening are extremely low compared to a retread.