# Continental Tyres Run at Lower Pressures than Michelin?



## DavyS (Jan 10, 2009)

I had four Michelin Camping Agilis tyres. I tended to run the fronts at 4.5 bar and the rears at 5 bar

Last week replaced the rears with Continental Vanco Camping tyres. Because of the change I decided to recalculate my tyre pressures.

The Michelins at the front are marked 109 80psi. According to the tables that is 1030kg load at 5.5 bar. The plated max load on each front wheel is 875kg. So a rough calculation shows that the correct pressure for my van at its maximum weight is 875kg/1030kg x 5.5 bar = 4.7 bar. Which seems about right.

The Continentals at the rear are marked Max load 1030kg at 4.75bar (but can inflate to max of 5.5bar for "special motorhome circumstances" - but didnt even hint what they might be!). The plated max rear wheel load is 950kg. So the same calculation 950kg/1030kg x 4.75 bar = 4.4 bar.
So the rears to be run 0.5 bar less than the original Michelins and at a slightly lower pressure than the fronts. Which sounds odd. So if my calculations are right then the Continentals should give a softer ride than the Michelins.

This is my first year motorhoming so I would be grateful for any thoughts on the above.


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## Wizzo (Dec 3, 2007)

For many motorhomes the tyre pressures quoted by vehicle/conversion manufacturers tend to be way too high. The only way to find the correct pressures is to have your van weighed in its loaded condition at a weighbridge (individual axles and overall weight), then contact the tyre manufacturer with the actual weights.

Unfortunately one or two of the tyre manufacturers also now tend to err on the side of caution by recommending maximum pressure on some axles.

See the following site and download the guide which includes recommended pressures for motorhomes:

http://www.tyresafe.org/tyre-safety/tyre-safety-information/240-tyre-safety-information-motor-homes

On the subject of Camping tyres (CP) I find that they give a very harsh ride compared to normal commercial tyres. I assume this to be because they have stiffer sidewalls. If you run the motorhome all year on a fairly regular basis then CP tyres are unnecessary.

JohnW


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## motormouth (Jul 3, 2010)

There are many, many threads on the subject of tyre pressures. You basically ignore anything on the tyres themselves, or the plate inside the door frame, or any handbooks you may have.

Take your MH to a weighbridge fully laden with anything that you would normally take away with you, fill all tanks, make sure you and any normal passengers are in MH whilst being weighed, make sure any bikes,scooters etc are on the back if applicable.
Then get weights of front axle, rear axle and whole vehicle.

Send email to Continental with these weights, exact size of tyre, and they will respond with tyre pressures. They are one of the few that do so should solve your concerns.


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## camallison (Jul 15, 2009)

motormouth said:


> There are many, many threads on the subject of tyre pressures. You basically ignore anything on the tyres themselves, or the plate inside the door frame, or any handbooks you may have.
> 
> Take your MH to a weighbridge fully laden with anything that you would normally take away with you, fill all tanks, make sure you and any normal passengers are in MH whilst being weighed, make sure any bikes,scooters etc are on the back if applicable.
> Then get weights of front axle, rear axle and whole vehicle.
> ...


As you say, Continental respond very quickly - I asked one Monday morning by email, and I had an answer within 2 hours - not bad. The ride comfort with those pressures was superb.

Colin


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## DavyS (Jan 10, 2009)

Wizzo said:


> The only way to find the correct pressures is to have your van weighed in its loaded condition at a weighbridge (individual axles and overall weight), then contact the tyre manufacturer with the actual weights. JohnW


I did know that about the value of using weighbridges but until we are packed up and fully laden for our next trip and pass a known weighbridge, then I have to estimate.

The real point of my query was - is it likely that Continental tyres run at 0.75 bar lower pressure than Michelin for the same load. Or have I misunderstood the markings?


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## BrianJP (Sep 17, 2010)

THis subject has been covered so many times before. 

However if you want a copy of the Continental Tyre hanbook that will give you all the pressure tables you ever wanted including for Vanco campers pm me your email address and I will send it to you.


You are correct in some of your assumption though as Conti vanco's are of a more robust construction than Michelins hence their abiltiy to handle 1030kg at a lower pressure. THe higher pressures are required on the rears to allow for weight transfer under cornering and braking at least thats what Conti told me when I asked.


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## BrianJP (Sep 17, 2010)

DavyS said:


> I had four Michelin Camping Agilis tyres. I tended to run the fronts at 4.5 bar and the rears at 5 bar
> 
> Last week replaced the rears with Continental Vanco Camping tyres. Because of the change I decided to recalculate my tyre pressures.
> 
> ...


Hi, I can still fwd you theConti Handbook if you want ,but FYI assuming your MH is FWD has single rear axle and your tyres are 215/70R15 load index109 then from the Conti table if you had max loading on each axle as you suggest your pressures should be Front 4.0 Bar and Rear 5.0 Bar.
I do actually run my MH which has similar axle weights to yours at these pressures also. I did put my MH on a weighbridge once but since I could never be sure of the gross weight on any trip I assumed that each axle could have up to its max weight ( although in practice this is unlikely) . It is always safer of course to have tyres slightly overinflated rather than underinflated and I have done over 15k miles all over Europe in past 18months with no unusual tyre wear
so I assume I have got things about right.


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## DavyS (Jan 10, 2009)

BrianJP said:


> Hi, I can still fwd you theConti Handbook if you want ,but FYI assuming your MH is FWD has single rear axle and your tyres are 215/70R15 load index109 then from the Conti table if you had max loading on each axle as you suggest your pressures should be Front 4.0 Bar and Rear 5.0 Bar.


Now I am really confused cos the Continentals are marked Max load 1030kg at 4.75bar. Yet the manual you have suggests more pressure for less weight. Yes please send me the handbook, david at chobham dot co dot uk
many thanks


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## BrianJP (Sep 17, 2010)

Conti camper tyres in your size as you say are marked as max load 1030kg as they are load index109. This in the case of Contis is achieved at a pressure of 4.75Bar (69psi) as stamped on the tyrewall. They also say they can be inflated to a max pressure of 5.5Bar (80psi). If you look at the Conti pressure chart you will see that they give different pressures for Front and rear tyres with the same loading .eg for 109 tyre on Front with 2060 kg ( Axle load) pressure should be 4.75 Bar. For tyre on rear single axle with same load pressure should be 5.5Bar.
When I queeried this difference with the tech people at Conti they said that it was due to the load characteristics and weight transfer on the rear of Motorhomes whatever that means exactly.
If you are concerned Email them at
[email protected]

you will find they are very helpfull.

as I already stated I have followed there advice and pressure with no issues so far.


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## DavyS (Jan 10, 2009)

BrianJP said:


> If you look at the Conti pressure chart you will see that they give different pressures for Front and rear tyres with the same loading .eg for 109 tyre on Front with 2060 kg ( Axle load) pressure should be 4.75 Bar. For tyre on rear single axle with same load pressure should be 5.5Bar.
> When I queeried this difference with the tech people at Conti they said that it was due to the load characteristics and weight transfer on the rear of Motorhomes whatever that means exactly.


I wonder if they are basing their recommendations on the fact that motorhomes often carry weight at the back, eg. cycles, motor scooters, large water tanks, etc. Any weight placed at the back of the motorhome reduces the load on the front tyres and increases the load on the back tyres by more than the weight added. So they might argue to take the plated load figures and then increase them at the back to allow for rearwards weight loading. 
But we, of course, base our weights on actual weight (estimated or preferrably measured at a weighbridge) so dont need to make special allowances for motorhomes?
Thanks for the email address.


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## BrianJP (Sep 17, 2010)

DavyS said:


> BrianJP said:
> 
> 
> > If you look at the Conti pressure chart you will see that they give different pressures for Front and rear tyres with the same loading .eg for 109 tyre on Front with 2060 kg ( Axle load) pressure should be 4.75 Bar. For tyre on rear single axle with same load pressure should be 5.5Bar.
> ...


Nope its not as simple as that as if you give the Conti Tech people your actual weighbridge figures they will quote the pressures as in in the handbook. I think its more to do with actual weight transfer under cornering and breaking when tyres are put under greater stress than when moving in a straight line?


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## DavyS (Jan 10, 2009)

Just to draw a conclusion to this thread.
As recommended by the contributors, I took my fully laden (fuel, water, provisions, etc) Swift 590 to local weighbridge where they recorded:
Front axle = 1480kg
Rear axle = 1560kg
Using both the Continental Technical Databook and a phone call to Conti, the tyre pressures come out at:
Front = 3.2 bar
Rear = 3.9 bar
These figures are a long way from the traditional 4.5 and 5 bar I have been using so far. 
The 4.5/5 pressures have been giving me a very harsh ride, and it is very noisy inside cos of items crashing together; so I am looking to be able to drive without ear-plugs!


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## mikebeaches (Oct 18, 2008)

DavyS said:


> I had four Michelin Camping Agilis tyres. I tended to run the fronts at 4.5 bar and the rears at 5 bar.
> Last week replaced the rears with Continental Vanco Camping tyres. Because of the change I decided to recalculate my tyre pressures.


I think you have now answered your original question - "Do Continental Tyres Run at Lower Pressures than Michelin?"

I certainly believe they do, or at least Continental are prepared to quote more sensible tyre pressures than Michelin, who in recent years have insisted there should be 80 ppsi in the rear tyres, regardless of the actual loading.

Hope you find the ride more comfortable now.

Mike


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## BillCreer (Jan 23, 2010)

Hi,

The Michelin people told me that the manufactures had all agreed on the 80 psi on the rear for "safety reasons" on motorhomes.
The front pressure was used to adjust for comfort dependant on the weights given to them.

A lot of weigh bridges are geared up to give you only 2 weighs per visit. The reason for this is that they are there to measure a lorry load that is either going in or out of the yard.
Having said that, 2 is all you need so get them to weigh the full vehicle and then drive the front or back wheels off the scales, weigh again, then subtract the smaller from the larger for the other axle weight.

Sound obvious but don't expect the opertator to understand what you want.


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