# Change tyres to allow greater payload?



## rosalan (Aug 24, 2009)

At the Newark Motorhome Show I had my van weighed. The front was fine but the rear was 30kg overloaded. I was advised that if I changed my rear tyres to a wider tread on the same rim, I would be well within the acceptable weight distribution. I cannot understand how changing my tyres can alter the axle weight. Can someone explain this to me?

Alan


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## listerdiesel (Aug 3, 2012)

If the overload was based on the axle weight as per the vehicle plate, then bigger tyres would make it worse as they are heavier. Then you need the axle weight uprated by SVtech if possible.

If the overload was based on tyre rating and you were still within the axle weight limit, and IF the load rating of the bigger tyres was higher than the existing, then it could work.

Peter


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## HurricaneSmith (Jul 13, 2007)

Because it's not true. Weight is weight and can't disappear.

By fitting a wider profile type you would only be spreading the load, but those wider (heavier) tyres would probably only be increasing the weight and exacerbating things.

(Done it again ............ Taken too long to type, but it's the same advice.)


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## aldra (Jul 2, 2009)

We upgraded the rear axle payload but not the overall weight via SVTec

Air suspension raised the payload from 3700 to 3850

The higher rated tyre increased the payload to the back axle to 2240

The overal weight of 3850 remains the same

Aldra


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## mgdavid (Nov 27, 2014)

Peter's explanation is spot-on :smile2:


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## rosalan (Aug 24, 2009)

I am now truly confused, while my confidence in Peters advice will never waver and neither will the logic behind it, which is clear to me. Like Sandra says, SVTec weighed and checked my van with its air bag suspension and Conti tyres. He pointed out the weight limit of the tyres (something like 1090 printed on the tyre) and stated that being 30kg overweight on the rear would not be likely to raise a problem, if I increased the tread width on the same rims, I would be well within my permitted weight of 3800+ kg.

Alan


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## Webby1 (Mar 11, 2012)

*Tyres*

We uprated our Coral exactly like Aldra.

Total to 3850 but changing to 225 tyres with 112 loading allowed rear axle to

go to 2240 rather than 2000.

With our bicycle rack we needed the extra on the rear axle.


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## Stanner (Aug 17, 2006)

It seems from what you say that it is the tyres that are overloaded not the axle.

I.E. you have more load on the rear axle than can be carried by the load index of the tyres that are fitted.

IF that is the case fitting tyres with a higher load index should solve the problem.

That can either be the same section tyres, but with a higher load index, or wider section tyres with a higher load index.

Which basically what Peter said in the last bit of his post.


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## peribro (Sep 6, 2009)

I wonder if your van is overweight on both the tyre load rating as well as the axle weight limit. My understanding is that VOSA examiners will allow you a degree of tolerance (5%) on the axle weight limits but I'm not aware that any tolerance would be allowed (for obvious safety reasons) on the tyre weights. It could therefore be for that reason that you were told that sorting out the tyres would deal with the problem as 30kg over on the axle limit is less than 2%. For what it's worth I've preferred not to rely on the 5% discretion and have used SVTech to increase the rear axle limits on my last two vans despite being less than 5% over.


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## listerdiesel (Aug 3, 2012)

109 Load rating is 1030kg per tyre, so four of those will give you over the 3850kg mentioned, but not by a huge margin. Enough to be fully legal but I'd want more margin than that for comfort.

Unless you have twin rear wheels? 

Peter


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## mgdavid (Nov 27, 2014)

All we can do is 'seem' and 'wonder' and 'guess' and 'maybe'; we need the details.
- what are the weights on the VIN plate?
- do you have twin rear wheels?
- can you confirm the load index of the tyres currently fitted?


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## aldra (Jul 2, 2009)

Alan

SVTEC know their job

If Gareth or Steve have informed you

That's what's needed 

The DVLA take their word for it

And they wouldn't sign of anything that isn't legal and verified

So we are legally 3850

The maximum we can load on the back axle, with air suspension and uprated tyres is 2240
The overall weight of 3850
Is the combination of back and front axle

So if the back axle is 2240 and is loaded to that

The front must be 1610 maximum

To be within the total payload of 3850

It seems simple to me

Am I missing something ???

Aldra


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## mgdavid (Nov 27, 2014)

aldra said:


> .........
> So we are legally 3850
> The maximum we can load on the back axle, with air suspension and uprated tyres is 2240
> The overall weight of 3850
> ...


Yes you are missing something.
The max GVW is NOT the sum of the two axle weights.
The front axle has a max design loading.
The back axle has a max design loading.
These are both independent of the overall vehicle GVW.
You can look at VIN plates to confirm this - if you understand what each line on the VIN plate means.
My GVW is also 3850.
Front axle 1950
Rear axle 2000.

If you think logically about it, the GVW could never practically be the sum of the axle weights - you could never load the MH that accurately to get a perfect balance.


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## aldra (Jul 2, 2009)

Wel I might be missing something

But I have a plate which tels me

Legal and authorised by the DVLA
That I can carry 2240 on the back axle

No doubt from the assistance of air suspension and weight rated tyres
And my overall weight is 3850
So if the back axle weight is less than 2240
And the total weight is 3850 or under

I'm legal0

Aldra


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## mgdavid (Nov 27, 2014)

aldra said:


> We upgraded the rear axle payload but not the overall weight via SVTec
> Air suspension raised the payload from 3700 to 3850
> The higher rated tyre increased the payload to the back axle to 2240
> The overal weight of 3850 remains the same
> Aldra


what you have written is erroneous.
The 'payload' is neither 3700 nor 3850 - you may mean GVW.
If you have upgraded then you will have been given a new VIN plate; what was on the old one, and what does the replacement have on it?
(all the figures).


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## rayc (Jun 3, 2008)

mgdavid said:


> Yes you are missing something.
> The max GVW is NOT the sum of the two axle weights.


But it can be equal to it. The Fiat Light Chassis has a front axle limit of 1850kg and the rear 2000kg. SVtech offered to upgrade my 3500kg GVW to 3850kg with no increase in axle limit weights as long as air suspension was fitted. I declined because of the load balancing problem you refer to.
I spoke with Alan after his MH was weighed by SVtech at Newark show. I think his situation is that he had previously taken advantage of the upgrade to 3850kg that I had declined i.e his GVW was 3850kg, his front axle 1850kg and rear 2000kg and air suspension was fitted.
I believe that when weighed he was within the front axle and GVW limits but the rear axle was 30kg over. SVtech told him they could upgrade the rear axle limit if wider [225 instead of 215] tyres were fitted. I presume that would give him a GVW of 3850kg, front axle 1850kg and rear axle 2200 kg.


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## aldra (Jul 2, 2009)

You are right

I think

Let's start again

Our van is officially upgraded to 3850 

The maximum load permissible on the back axle is 2240

The total weight must not exceed 3850

This has increased our payload as previously our total weight was 3500

And our tax has reduced>
Aldra


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## rayc (Jun 3, 2008)

aldra said:


> And my overall weight is 3850
> So if the back axle weight is less than 2240
> And the total weight is 3850 or under
> 
> ...


As long as the front axle is not loaded to its limit as well. If you were to load the MH so that the rear axle weight is 2240kg and take advantage of the 3850 GVW then the maximum you can have the front axle loaded to is 3850 - 2240 i.e 1610kg which is well below its limit of 1850kg.


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## aldra (Jul 2, 2009)

I understand that Ray

If we need a Higher ratio on the back, ie up to 2240 it reduces the front maximum 

But our van with a back garage and twin beds seems to tend towards an overloaded back 

We notice many vans that are riding very low on the back axle

Aldr


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## mgdavid (Nov 27, 2014)

excellent, I think we all agree now :grin2:

Don't keep mentioning the cheaper VED at 3850 or someone in authority will catch on and change it :frown2:


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## rosalan (Aug 24, 2009)

I am indebted to Rayc for both his clarity when speaking to me about this and also his explanation here.
I aired the topic as it was one that I had not heard discussed previously and that could possibly be beneficial to others.

Alan


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## rosalan (Aug 24, 2009)

I have just received this email from SvTech regarding my vans weight...The best option in this instance would be to reposition weight toward the front of the vehicle, however on occasions this is easier said than done.
Should you wish to consider an uprate on the rear axle, you would need to fit rear axle air assisted suspension and change the rear tyres from the existing 215/70R 15 (109 LI) to 225/70R 15 (112).
This change would allow for an increase in rear axle to 2240kg.

Which I think is what Sandra said.

Alan


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## aldra (Jul 2, 2009)

It was

But no one listens to me:frown2:

And here I am

Knowledgeable, agreeable (sometimes)

And ignored:crying::crying:

All together now

Sad>>
Sandra


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## Webby1 (Mar 11, 2012)

*Tyres*

Sandra

You were right and clear from the start.................and I tried to confirm it in my post.

I don't understand sometimes why people not only disagree, but with a tone that seems very provocative.......................I know some motorhomers consider that FUN ..............but to me it's too much like being at home ????


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## rosalan (Aug 24, 2009)

Webby1 said:


> Sandra
> 
> You were right and clear from the start.................and I tried to confirm it in my post.
> 
> I don't understand sometimes why people not only disagree, but with a tone that seems very provocative.......................I know some motorhomers consider that FUN ..............but to me it's too much like being at home ????


Did you say 'FUN' in big letters? Is it permitted to say that on this newly designed forum?
Alan


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## GIBOO (Feb 1, 2015)

What about doing away with the spare tyre? I'm beginning to investigate the possibilty of doing this by using a tyre repair kit, which you can get for motorycle tyres. I do not know how much my spare tyre weighs but if this works there will be quite a saving in weight.


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## listerdiesel (Aug 3, 2012)

GIBOO said:


> What about doing away with the spare tyre? I'm beginning to investigate the possibilty of doing this by using a tyre repair kit, which you can get for motorycle tyres. I do not know how much my spare tyre weighs but if this works there will be quite a saving in weight.


That is fine until you try to get a tyre repaired that has goo inside it, or the tyre gets damaged beyond repair. Then what do you do?

A spare is like insurance, you rarely need it but when you do it is invaluable.

Peter


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## GIBOO (Feb 1, 2015)

listerdiesel said:


> A spare is like insurance, you rarely need it but when you do it is invaluable.
> 
> Peter


Thats a very good point.


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## rosalan (Aug 24, 2009)

Only by chance I caught the sidewall of my rear tyre on a sharp kerb in Spain on a Saturday night. It made a small but physical hole in the sidewall.
I later discovered that if I had not just bought a spare, that would be real trouble.
The goo will not mend a hole and without a spare, the breakdown service does not work, for where can they get an exact replacement (especially on a Sunday morning), As it was it took me a whole day to eventually find a replacement on the Monday and in France.
I know the spare is heavy, I know it is expensive and I know that it is a pain to fit into the garage and secure it but you will never find me driving without a spare in future.

Alan


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## listerdiesel (Aug 3, 2012)

rosalan said:


> I know the spare is heavy, I know it is expensive and I know that it is a pain to fit into the garage and secure it but you will never find me driving without a spare in future.
> Alan


Amen to that!

We carry two spares for the big 6-wheel trailer, and a spare tyre carcass for the Discovery if we are going into southern France.

The Mercedes has sufficient weight capacity for it not to be an issue, thank heavens, and we have a spare for that too :grin2:

Peter


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