Mercedes Sprinter tyre pressures

by grahamsb Thu Oct 28, 2021 3:59 pm

I have been unable to find the definitive answer to the correct tyre pressures required on my 2021 Stanton. The dealer says inflate to pressures shown on vehicle sticker (51/55 PSI). Auto Sleeper say they are not allowed to comment! WHAT?? They only built the motorhome, but won't give any advice. Then I am told the only reliable way is to measure the weight on each axle and ask advice from the tyre manufacturer.

Lets face it, cars also carry varying payloads and you are given recommended tyre pressures based on the number of passengers. Why will no one tell me what would be recommended if I take the weight up to the maximum 3500kg. I only want a guide, because when inflated to 51/55 PSI, they still look quite "flat" at the base.

by Pete Taylor Thu Oct 28, 2021 4:17 pm

I run mine at 55 on the front and 65 on the rear.

I have semi-air suspension at the rear, as AS didn't fit the heavy-duty springs I specified.
When I replaced the tyres (originally fitted by the Mercedes factory to AS spec) the tyre place manager told me that they were incorrect spec as they were ordinary van specification, rather than Motorhome spec, which have an extra two ply casing. Good to know that AS managed to get that wrong as well; no wonder the van was sometimes slightly wayward when fully laden.

by IanH Thu Oct 28, 2021 4:18 pm

This is a subject which has been posted at least a million times!
With 999,999 different answers, most wrong!
Go to the SEARCH at the top of the page, and type in tyre pressures.
As an aside, and purely a personal not recommended pressure I've now had 5 MH's and run all at 60psi all round, NOT a recommendation, just experience.

It is a very good idea to have it weighed, 3 weights, front, rear and total on a proper weighbridge, then you can get tyre pressure recommendations, but equally importantly you'll know what it actually weighs!

by PLOUGHLIN Thu Oct 28, 2021 4:55 pm

Which Stanton do you have MAM 3200kg or 3500kg? Continental Tyres?

MIRO Front 1360kg, MIRO Rear 1561kg

Max Axle Front 1860kg
Max Axle Rear (3200kg) 2000kg, (3500kg) 2250kg

If Continental look up for tyre size in Manual in Factsheet section.
page 80 onward here:- https://blobs.continental-tires.com/www8/servlet/blob/476070/960c00deff28484e7fbdec87d1d00583/download-technical-databook-data.pdf

by grahamsb Thu Oct 28, 2021 6:39 pm

Pete Taylor wrote:I run mine at 55 on the front and 65 on the rear.

I have semi-air suspension at the rear, as AS didn't fit the heavy-duty springs I specified.
When I replaced the tyres (originally fitted by the Mercedes factory to AS spec) the tyre place manager told me that they were incorrect spec as they were ordinary van specification, rather than Motorhome spec, which have an extra two ply casing. Good to know that AS managed to get that wrong as well; no wonder the van was sometimes slightly wayward when fully laden.

That's interesting about the type of tyres fitted. Mine are ContiVanContact 200. Does that mean they are standard van tyres and should have different ones?

by PLOUGHLIN Thu Oct 28, 2021 7:09 pm

What is the Load rating? If 121/119 They are 10 ply.

by Cymro Thu Oct 28, 2021 7:18 pm

Have a look at this:

https://www.autosleeper-ownersforum.com/t34062-continental-rear-cp-tyre-pressures?highlight=pneu

Many Forum members advocate using tyres which manufacturers claim are designed for the usage characteristics of motorhomes (e.g. stronger sidewalls to combat sitting stationary for weeks when loaded).

Personally, I'd go for CP rated tyres, and then calculate the pressure from the manufacturer's table.

Cymro

by grahamsb Fri Oct 29, 2021 9:50 am

PLOUGHLIN wrote:What is the Load rating? If 121/119 They are 10 ply.

Mine are 7 ply, Load Range "D". Max pressure 80PSI.

Not very scientific, or technical, but how "Flat" should the tyre look at the base, if correctly inflated?

by PLOUGHLIN Fri Oct 29, 2021 10:46 am

Don't recognise D rating. What does your tyre size say?

Mine are Continental Conti Van Contact Four Season 235/65 R16C 121/119N M+S

by Paulmold Fri Oct 29, 2021 10:58 am

Strange that AS wouldn't comment. This was their reply to another owner on another forum...

“The correct pressures should be shown on a label on the passenger side cab door pillar, near the lock striker plate. The label is fitted by Peugeot (or FIAT) and gives their specification for tyre pressures.
The figures are based on maximum axle mass and are unaffected by the conversion into a motor caravan. If the label is missing it will be necessary to ask your Peugeot (or FIAT) dealer for advice. They will be able to identify the information based on the 17 digit VIN.”

I guess the same applies to Mercedes.

by grahamsb Fri Oct 29, 2021 12:14 pm

PLOUGHLIN wrote:Don't recognise D rating. What does your tyre size say?

Mine are Continental Conti Van Contact Four Season 235/65 R16C 121/119N M+S

I have had another look and in a smaller font 235/65 R 16 C 115/113R

by PLOUGHLIN Fri Oct 29, 2021 12:30 pm

grahamsb wrote:
PLOUGHLIN wrote:Don't recognise D rating. What does your tyre size say?

Mine are Continental Conti Van Contact Four Season 235/65 R16C 121/119N M+S
I have had another look and in a smaller font 235/65 R 16 C 115/113R

For Continental that is an 8 ply tyre, load rating is perfectly adequate for a Stanton (3500kg) load with appropriate pressures. The Equivalent CP tyre is also 8 ply with same load allowance.

For your Maximum axle load, Front 3.5 Bar (51 psi), Rear 4.25 Bar (62psi). With measured actual load could be reduced.

by grahamsb Fri Oct 29, 2021 12:34 pm

Paulmold wrote:Strange that AS wouldn't comment. This was their reply to another owner on another forum...

“The correct pressures should be shown on a label on the passenger side cab door pillar, near the lock striker plate. The label is fitted by Peugeot (or FIAT) and gives their specification for tyre pressures.
The figures are based on maximum axle mass and are unaffected by the conversion into a motor caravan. If the label is missing it will be necessary to ask your Peugeot (or FIAT) dealer for advice. They will be able to identify the information based on the 17 digit VIN.”

I guess the same applies to Mercedes.

On the Merc the labels are on the driver's side. With a full load, the pressures are Front 51 PSI Rear 55 PSI. The dealer recommended these pressures, since they had no other information. The person I spoke to at Auto Sleeper said they are told not to comment on tyre pressures.

I have maintained these pressures, but what concerned me was the degree to which the tyre is indented at the bottom. Perhaps I should look again after a journey at speed, when the tyres have warmed up. I have to admit I have always set my car tyres 10% below the recommended pressure to obtain a more comfortable ride. On this much heavier commercial vehicle, which is our home on wheels, I would like to get it as right as possible. I am also aware/concerned that there is no spare wheel and hence my added caution. (Annoyingly, the Auto Sleeper spec for the 2021 Stanton states "Alloy wheels, plus spare wheel and carrier". When I raised this with the dealer, they said "Look underneath, there is nowhere to fit one")

by grahamsb Fri Oct 29, 2021 12:41 pm

PLOUGHLIN wrote:
grahamsb wrote:
PLOUGHLIN wrote:Don't recognise D rating. What does your tyre size say?

Mine are Continental Conti Van Contact Four Season 235/65 R16C 121/119N M+S
I have had another look and in a smaller font 235/65 R 16 C 115/113R

For Continental that is an 8 ply tyre, load rating is perfectly adequate for a Stanton (3500kg) load with appropriate pressures. The Equivalent CP tyre is also 8 ply with same load allowance.

For your Maximum axle load, Front 3.5 Bar (51 psi), Rear 4.25 Bar (62psi). With measured actual load could be reduced.

The plies on the tyre are listed as :- Tread 2 Polyester + 2 Steel = 1 Polymide. Sidewall 2 Polyester

by BornAgain Fri Oct 29, 2021 1:40 pm

As has been said, there are many, many, posts on this but it’s actually not that difficult. Weigh the motorhome and get the data from the Tyre manufacturer. If they are Continental Vanco the pressure tables are readily available and they will also confirm in writing if you are still worried. The tyre pressure plate relates to the commercial vehicle loads and it is questionable whether it is appropriate for a coachbuilt motorhome.

What is more puzzling is that the dealers and AS main workshop don’t seem to have a clue. I was at Willersey a few years back and they pointed to the Tyre which was marked 60 psi (I think). This is irrelevant on the Vanco Tyre as it relates to USA specification.

The bigger problem is trying to get the pressure monitor recalibrated for lower pressures but that’s a different topic.

by Caraman Fri Oct 29, 2021 5:44 pm

The figures in Continental's Data Book are not their own. They are the ETRTO's figures which are used by ALL tyre manufacturers. But these are not real world figures as they assume the axle mass is not a gram higher than the stated figure and is equally distributed between the wheels which it will never be. As it is far more dangerous for a tyre to be under inflated for its load than overinflated, a higher pressure should always be used. The question is how higher? Some tyre manufactures will give a higher real world pressure but in my experience Continental doesn't which is misleading. TyreSafe who are sponsored by the tyre manufacturers including Continental recommend the pressure should be set using the ETRTO's figures for an axle mass that is 10% higher and they use this in their on-line calculator.

The tyre pressure label on a car normally shows the front and rear pressures for a small load and a full load. I don't know what is shown on the M-B Sprinter but on the Peugeot Boxer all that is shown is the recommended front and rear pressures for when the front and rear axles are both at the MTPLM. These pressure are real world so above the ETRTO figures.

The key is to fully load the motorhome for a trip and take it to a weigh bridge to measure the vehicle's total mass and the two axle masses. This is to make sure that none the vehicle's MTPLMs are being exceeded and to determine the actual axle mass that can then be put into TyreSafe's on-line calculator to give the tyre pressures. It really is that simple.

by Caraman Sat Oct 30, 2021 8:45 am

Caraman wrote:The figures in Continental's Data Book are not their own. They are the ETRTO's figures which are used by ALL tyre manufacturers. But these are not real world figures as they assume the axle mass is not a gram higher than the stated figure and is equally distributed between the wheels which it will never be. As it is far more dangerous for a tyre to be under inflated for its load than overinflated, a higher pressure should always be used. The question is how much higher? Some tyre manufactures will give a higher real world pressure but in my experience Continental doesn't which can be misleading. TyreSafe who are sponsored by the tyre manufacturers including Continental recommend the pressure should be set using the ETRTO's figures for an axle mass that is 10% higher and they use this in their on-line calculator.

The tyre pressure label on a car normally shows the front and rear pressures for a small load and a full load. I don't know what is shown on the M-B Sprinter but on the Peugeot Boxer all that is shown is the recommended front and rear pressures for when the front and rear axles are both at the MTPLM. These pressure are real world so above the ETRTO figures.

The key is to fully load the motorhome for a trip and take it to a weigh bridge to measure the vehicle's total mass and the two axle masses. This is to make sure that none the vehicle's MTPLMs are being exceeded and to determine the actual axle mass that can then be put into TyreSafe's on-line calculator to give the tyre pressures. It really is that simple.

by BornAgain Sun Oct 31, 2021 7:59 am

It seems sensible to add a margin to the pressures in the data tables noting, however, that if you weigh the van with full water, full fuel and some waste you will be at a lower weights most of the time.

by Caraman Mon Nov 01, 2021 9:47 am

BornAgain wrote:It seems sensible to add a margin to the pressures in the data tables noting, however, that if you weigh the van with full water, full fuel and some waste you will be at a lower weights most of the time.

Not quite right. If you weigh the motorhome with a heavy load behind the rear axle it will result in a lower front axle mass. If you remove some of this load and even more so if you move it forward, which is a good thing, it will result in a higher front axle mass. So the front axle mass when the motorhome is fully loaded may not be its highest mass which is the mass around which the front tyre pressures should be set. Peugeot recommend that when the front axle is loaded to its MTPLM of 1850 kg, the front tyre pressures should be for an axle mass that is 7% higher if its a C tyre and 15% higher if its a CP tyre. TyreSafe are somewhere in between with 10% for both types of tyre.

by BornAgain Tue Nov 02, 2021 2:09 pm

If you remove weight from the back surely the the C of G shifts forward and the front end weight stays the same? Fuel tank is towards the front so that’s 100 kg slowly reducing. Anyway, it seems sensible to allow margin in the pressures. The weight distribution on the wheels will differ.

by Caraman Tue Nov 02, 2021 4:41 pm

BornAgain wrote:If you remove weight from the back surely the the C of G shifts forward and the front end weight stays the same? Fuel tank is towards the front so that’s 100 kg slowly reducing. Anyway, it seems sensible to allow margin in the pressures. The weight distribution on the wheels will differ.

Consider your motorhome as a see-saw pivoting on its rear wheels. Increasing the load behind the rear wheels makes the front go up which decreases the front axle mass. Decreasing the load behind the rear wheels makes the front go down which increases the front axle mass. This see-saw effect is exacerbated in coach built motorhomes like ours due to their long rear overhang which provides considerable loading opportunity e.g. waste water tank, toilet cassette, bike rack, kitchen lockers and a shower compartment that can be filled with stuff.

by BornAgain Tue Nov 02, 2021 8:32 pm

Yes, provided the weight you are removing is from behind the rear axle. Fuel and LPG are forward. Not sure about the water tank as our Broadway has been traded in so I can’t check. Older Bourtons had a forward supplementary water tank. Anyway, 200 kg in 3500 is not a lot.
What I do know is that the rear weight was close to the maximum axle load so I couldn’t reduce the rear tyre pressures but the front axle was much lower and reducing the pressure resulted in a big gain in ride quality.

Mercedes Sprinter tyre pressures

Mercedes Sprinter tyre pressures

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