Tyres on a twin-axle caravan - different brands per axle

[Shaino]

Hi All,

Planning to replace tyres but £100 per tyre is a bit expensive for the budget. So I've been thinking about changing on one axle for now and on the other one a couple of months later.
Same specs but the load rating (going with a higher one).

Are there any concerns with such an approach? Does it matter on which axle the new tyres go first?

Thanks all.

 

[otherclive]

Hi All,

Planning to replace tyres but £100 per tyre is a bit expensive for the budget. So I've been thinking about changing on one axle for now and on the other one a couple of months later.
Same specs but the load rating (going with a higher one).

Are there any concerns with such an approach? Does it matter on which axle the new tyres go first?

Thanks all.

No real concerns but why not buy all together in a couple of months time. Just put the money to one side until you are ready to buy all four. Might even obtain a discount for a bigger purchase depending on what and where you buy.

 

[Shaino]

No real concerns but why not buy all together in a couple of months time. Just put the money to one side until you are ready to buy all four. Might even obtain a discount for a bigger purchase depending on what and where you buy.

Don't want to make another mega tyres thread
* Current tyres are still OK this year but all of them need to be changed next year
* For some reasons Bessacarr spec'ed tyres with absolutely 0 weight margin on top of the van MTPLM, which I find inadequate

I'm having a long journey in France very soon and just want to minimise the risk. It doesn't look like I have an urgency to change all of them now but replacing 2 will give me some peace of mind (and less burden on the budget)

 

[ProfJohnL]

Its worth noting that in some european countries and I think France is one of them that states tyres on the same axle must matched.

Seems the decision may have been made for you.

I'm not sure your logic about the load rating on the tyres is correct. No tyre manufacturer would be silly enough to give a tyre a rating value and not engineer into the design enough extra capacity to deal with that stated load under normal road conditions, where the dynamic loads caused just through normal driving are quite surprisingly bigger than the static load.

The problem would of course be exacerbated if the caravan is already overloaded, but them your opening a another can of worms about the safety and legality of that.

There's no harm in going for a greater load margin, which may well cost more, but is there any tangible benefit of over specifying?

 

[Shaino]

Its worth noting that in some european countries and I think France is one of them that states tyres on the same axle must matched.

Seems the decision may have been made for you.

I'm not sure your logic about the load rating on the tyres is correct. No tyre manufacturer would be silly enough to give a tyre a rating value and not engineer into the design enough extra capacity to deal with that stated load under normal road conditions, where the dynamic loads caused just through normal driving are quite surprisingly bigger than the static load.

The problem would of course be exacerbated if the caravan is already overloaded, but them your opening a another can of worms about the safety and legality of that.

There's no harm in going for a greater load margin, which may well cost more, but is there any tangible benefit of over specifying?

Just out of curiosity is there any other caravan model whose tyre specs are exactly caravan's MTPLM?
I just want to have more than 0kg margin just in case I buy too much wine in Auchan

 

[Hutch]

Just out of curiosity is there any other caravan model whose tyre specs are exactly caravan's MTPLM?
I just want to have more than 0kg margin just in case I buy too much wine in Auchan

Up grade the car tyres then. 😃

 

[Hutch]

I rem Buckman, stating he wanted to upgrade his tyres on his Buccaneer, and had problems.
Out of interest , what load rating do your standard ones have??.

 

[Shaino]

Out of interest , what load rating do your standard ones have??.

82 with MTPLM 1900

 

[otherclive]

Just out of curiosity is there any other caravan model whose tyre specs are exactly caravan's MTPLM?
I just want to have more than 0kg margin just in case I buy too much wine in Auchan

I had a Bailey with a payload upgrade to 1400kg but Bailey said nothing about upgrading the tyres from 1420 kg to a higher load index. I know my weighing is very accurate but I could not guarantee to be within 20 kg in 1400kg so I fitted a higher load index caravan/trailer specific FRT tyres.

 

[JTQ]

Just out of curiosity is there any other caravan model whose tyre specs are exactly caravan's MTPLM?
I just want to have more than 0kg margin just in case I buy too much wine in Auchan

Hymer with both our SA vans had specified and fitted tyres with a load rating correct for the van's maximum loading, not adding an arbitrary margin on top of those the tyre maker's testing etc yielded.

It's a concept I totally agree with, not seeing a logic to add arbitrary margins on margins but probably it's my aviation background where the components' ability has to be known.
I also realise the tyre's compliance is all part of the caravan's suspension, and fitting higher load rated tyres than needed will very probably lead to a harsher "ride", not something our fragile van structures need. So, I don't think Hymer and the tyre makers have got it wrong and I need to up my tyres load rating, just as I don't do so with our cars.

With caravan tyres there is a "hidden" margin in that few of us will fit tyres rated only up to 60-62 mph, more typically we have tyres capable of carrying their rated loads at way higher road speeds than the van will ever see.

That said I am aware that TyreSafe the charity take a differing point of view in respect to caravans and don't trust the tyre maker's knowledge, testing etc.
LINK
Some tyre brands nor would I, but respected international industry leading brands, I think they are up to "speed" on the ratings of their tyres.

 

[Buckman]

I rem Buckman, stating he wanted to upgrade his tyres on his Buccaneer, and had problems.
Out of interest , what load rating do your standard ones have??.

Yep on our 2000kg twin axle we had Falken 175 / 65 R14 VAN01 90/80 tyres fitted at a cost of £266.52. I don't think the Falkens are a budget tyre?

Not sure how any budget tyre could cost +£100 each? The tyres were fitted by Protyre at their depot.

 

[otherclive]

Yep on our 2000kg twin axle we had Falken 175 / 65 R14 VAN01 90/80 tyres fitted at a cost of £266.52. I don't think the Falkens are a budget tyre?

Not sure how any budget tyre could cost +£100 each? The tyres were fitted by Protyre at their depot.

Falken are a well respected mid range tyre owned by the Japanese company Sumitomo. I have had them on Saab 9000, Nissan Note and on Pajero off roader. No complaints at all.

 

[Shaino]

Had another thought on this.

A twin-axle caravan needs to sustain a tyre blowout to a point that you can safely brake from 60mph and park without other tyres blowing in a row. Something around 150-300 meters, I suppose.

This means the remaining 3 tyres must have load index high enough to bear the caravan weight. So in my case I need 160kg (1900/3 - 1900/4) margin to the minimal load index 82. Or in other words, a load index for 1900/3=633kg. Which is 92. Plus extra margin for wine. So 93 then.

 

[otherclive]

Had another thought on this.

A twin-axle caravan needs to sustain a tyre blowout to a point that you can safely brake from 60mph and park without other tyres blowing in a row. Something around 150-300 meters, I suppose.

This means the remaining 3 tyres must have load index high enough to bear the caravan weight. So in my case I need 160kg (1900/3 - 1900/4) margin to the minimal load index 82. Or in other words, a load index for 1900/3=633kg. Which is 92. Plus extra margin for wine. So 93 then.

Might be better to fit TPMS that gives warning of tyre problems prior to blow out. Plus you assume the remaining three tyres have no in built load margin.

 

[JTQ]

Was just chatting to father in law and saying i would add one of these. We don't use the radio but if we came to sell the van, would like it there still so this seems like the best option!

Had another thought on this.

A twin-axle caravan needs to sustain a tyre blowout to a point that you can safely brake from 60mph and park without other tyres blowing in a row. Something around 150-300 meters, I suppose.

This means the remaining 3 tyres must have load index high enough to bear the caravan weight. So in my case I need 160kg (1900/3 - 1900/4) margin to the minimal load index 82. Or in other words, a load index for 1900/3=633kg. Which is 92. Plus extra margin for wine. So 93 then.

You have overlooked that the van's weight does not move so the remaining three tyres bear the weight equally; in reality the lone remaining tyre on the punctured side will bear nearer double its normal load.

Load rating IMO is more about what the tyre can carry operating normally at up to the rated speed. Its not IMO the maximum it can bear for the very short time it takes to slow down and seek somewhere safe.

 

[Shaino]

Well yeah it's some margin here, some margin there. We can calculate the centre of mass, momentum, wind, speed etc but there are always some unknowns.

If the van is on a straight line the weight is distributed equally . If the van is turning or the Earth is curved enough then one of the sides bears more weight - could be the one with the 1 tyre, could be the opposite one.
Assuming those cases are equally probable it makes sense for me to provide more support for the remaining tyre (i.e. have it with a higher load rating)

As your van loses speed its load become more equally distributed across 3 remaining tyres as the other factors become less impactful. On the other hand , as there are less dynamic forces then the "built-in" load margin will be used to bear the increased load per tyre.

 

[otherclive]

Well yeah it's some margin here, some margin there. We can calculate the centre of mass, momentum, wind, speed etc but there are always some unknowns.

If the van is on a straight line the weight is distributed equally . If the van is turning or the Earth is curved enough then one of the sides bears more weight - could be the one with the 1 tyre, could be the opposite one.
Assuming those cases are equally probable it makes sense for me to provide more support for the remaining tyre (i.e. have it with a higher load rating)

As your van loses speed its load become more equally distributed across 3 remaining tyres as the other factors become less impactful. On the other hand , as there are less dynamic forces then the "built-in" load margin will be used to bear the increased load per tyre.

It seems to me that you have already answered your own question and your mind was made up anyway. But in reality caravan tyre blowouts are rare on well maintained tyres, and a TPMS goes a very long way to preventing one should you get a puncture.

 

[Buckman]

When we had a blow out on our twin axle a couple of years ago, I was unaware and probably drove for 2 - 3 miles before someone advised us about the tyre. Before our next trip we bought a TPMS.

 

[otherclive]

When we had a blow out on our twin axle a couple of years ago, I was unaware and probably drover for 2 - 3 miles before someone advised us about the tyre. Beforfe our next trip we bought a TPMS.

What did you do wrt the three remaining tyres?

 

[Buckman]

What did you do wrt the three remaining tyres?

I looked at them?

 

[JTQ]

When we had a blow out on our twin axle a couple of years ago, I was unaware and probably drove for 2 - 3 miles before someone advised us about the tyre. Before our next trip we bought a TPMS.

That you were not aware suggests that technically it was never a "blowout" but a disintegration arising from running too long underinflated where the heating up breaks down the tyre's material and structure.
The normal outcome from an undetected puncturing, and fully endorses the advice to fit a TPMS, safer and come well save buying a tyre, just getting it repaired which if not detected and run into the damaging the tyre is not an option.

 

[Buckman]

That you were not aware suggests that technically it was never a "blowout" but a disintegration arising from running too long underinflated where the heating up breaks down the tyre's material and structure.
The normal outcome from an undetected puncturing, and fully endorses the advice to fit a TPMS, safer and come well save buying a tyre, just getting it repaired which if not detected and run into the damaging the tyre is not an option.

Definitely no tyres were under inflated as they were checked just prior to setting off. As we never had a TPMS at the time, I used to check them religiously before setting off. We had only travelled about 4 - 5 miles on the motorway. Cheap Ovation tyres were probably the cause.

 

[otherclive]

Definitely no tyres were under inflated as they were checked just prior to setting off. As we never had a TPMS at the time, I used to check them religiously before setting off. We had only travelled about 4 - 5 miles on the motorway. Cheap Ovation tyres were probably the cause.

I think that under inflated could mean the you picked up a nail en route which started to deflate the tyre hence causing the tyre to overheat. 4-5 miles is the normal distance for a tyre to reach stable temperature so picking up a penetrant early in the journey could easily lead to deflation and overheating.

 

[Buckman]

I think that under inflated could mean the you picked up a nail en route which started to deflate the tyre hence causing the tyre to overheat. 4-5 miles is the normal distance for a tyre to reach stable temperature so picking up a penetrant early in the journey could easily lead to deflation and overheating.

No nails seen, but is possible. Tyre was shredded, but no idea how far I had travelled with it deflated as that would have shredded the tyre anyway. No damaged to caravan.

 

[ProfJohnL]

Just out of curiosity is there any other caravan model whose tyre specs are exactly caravan's MTPLM?
I just want to have more than 0kg margin just in case I buy too much wine in Auchan

Fact 1. You should not overload your caravan, therefore the specified combined tyre rating only needs to include your MTPLM. Loading your caravan above its MTPLM is illegal. Do not even think about doing it. When you are detected it will cost you a lot more than savings you might make on the wine you anticipate buying.

Fact 2. Tyre manufacturer's are not daft. Non of them would set out a load limit on a tyre, without allowing for the dynamic loading it could expect to see within its envelope of operation. Thus you should not need a tyre rated above the caravans specified MTPLM.

Fact 3, there is no harm or reason not to use a higher rated tyre, but it offers no functional benefit and might cost more so this points is a matter of personal preference and how deep your pockets may be.

Whether there are any other caravans with a zero combined tyre load margin over the MTPLM or not does not set a presidence. If a tyre is incapable of carrying the maximum load its manufacture specifies, it's not fit for purpose and should not be sold.