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Tyre pressures

26K views 28 replies 18 participants last post by  marax 
#1 ·
A warning sign came up to say that tyre pressures were low ,Question is it came up in PSI then went into the metric symbol ,I know how to alter MPH and all that but i can't get it to go back into PSI any thoughts.
Thanks
 
#13 ·
Has anyone else had a problem getting the right tyre pressures ,on my A200 it says if 4 to 5 occupants it 's 38 psi all round i have been to 2 garages to correct my tyre pressures but i am still getting 37.4 or 37.6 error messages saying to correct my tyre pressures i just can't seem to get it spot on ,or is there something in the system to set those pressures i have.
 
#14 ·
I have a A 180 se auto 2018.
The tyre pressures notice in the fuel flap states, 38 psi front, 33 psi rear.
However, most tyre companies and google sites state, 36 psi front and 36 psi rear.
What do you forum members think is correct?
All the sites I have checked, and there are many, state 36 psi.
 
#15 ·
I guess the obvious answer is that the manufacturer should knows what is best for the car so provided you are using the STD spec tyre for the car I would start with these.

Having said that some people play around with pressures to find what suites them best but I just to use what it says on the car as I would forget what they are supposed to be otherwise 🙄
 
#18 ·
The "optimum" tyre pressure for a particular car, or tyre, is a balance of several factors, including grip, handling, comfort, ride, speed, loads, fuel economy, emissions, wear, ambient temperature and conditions, road surface temps etc.

Thus different numbers from different voices, they all have different priorities, there is no "one" pressure that satisfies all those factors optimally, simultaneously.

A good starting point is the label inside of the fuel flap, although that will be weighted towards WLTP & fuel economy.
 
#22 ·
Hi, first of all sorry but I'm still inexperienced with cars so I'll try to give as much information as I think is relevant. On my Merecdes Me app (A200 W177), the back two tyres are both 30 psi, whereas the front-left is 48 and the front-right is 51 psi. Everywhere I've read seems to suggest that this is too high, despite me owning this car for a few months and not noticing any issues yet (even taken in for vehicle health checks). Inside the fuel cap suggests I should have 38 front and 33 rear tyres, however I purchased the car used so I don't know if the current tyres came when built or have been switched.

I'm a bit concerned because my tyre says that the max load is 50 psi, so I'm worried that I might be at risk or damaging the trye in some way. The tyre is 225/45R18 95Y.
For what it's worth, I haven't received any tyre pressure warnings or notifications yet.

I haven't reduced tyre pressure before, just watched youtube videos, do I need certain tools? Is it a simple process? Are my tyres at a large risk at the moment?
 
#24 ·
Hi, first of all sorry but I'm still inexperienced with cars so I'll try to give as much information as I think is relevant. On my Merecdes Me app (A200 W177), the back two tyres are both 30 psi, whereas the front-left is 48 and the front-right is 51 psi.
Is the car new?

My A35 was delivered with the tyres overinflated, not as much as yours however. @Unraveller is correct though, you should read the pressures in the dash just after starting the car and before driving it. The A35 shows pressure and temps but I'm not sure if that's an AMG Performance feature.

Drive slowly to a petrol station or supermarket that sells fuel. Their tyre compressors are usually smart enough that if you punch in 35psi and the tyres are actually 50psi they will take air out to reduced the pressure.
 
#23 ·
@Unraveller

Firstly, don't blindly rely on the MMe App to give you the correct tyre pressures. It will report the pressures at the point when the car was last switched off, after a drive.

So if your last journey was during a hot sunny day, it will report those pressures at 6am the next morning, not the "actual" pressures in your tyres.

Best to go off a pencil-type tyre pressure gauge, or the tyre pressure monitor on your instruments. But these have to measured "cold" (before you start driving).

So - at 7am - go for a drive in your car, and look at the live pressures on your instrument panel.
 
#26 ·
hi I have bought before 1 year A-180 w177 style with 16'' wheels and tires 205/60/16 , now upgrade to 18'' factory and tires 225/45/18
and I want to ask who has bought from the factory A180 with wheels 18''
what air pressure writes on the sticker on the gasoline cap
because to me the sticker says whith 3 people 38 psi front and 33psi back and whith 5 people 38 frond and back
but did not mention any dimension of the tire, so I guess it's just about its size of the tires you got from the factory
in my case 16''
thanks for anser
 
#28 ·
hi I have bought before 1 year A-180 w177 style with 16'' wheels and tires 205/60/16 , now upgrade to 18'' factory and tires 225/45/18
and I want to ask who has bought from the factory A180 with wheels 18''
what air pressure writes on the sticker on the gasoline cap
because to me the sticker says whith 3 people 38 psi front and 33psi back and whith 5 people 38 frond and back
but did not mention any dimension of the tire, so I guess it's just about its size of the tires you got from the factory
in my case 16''
thanks for anser
My sticker says the same and mine came with 19" from the factory, so I guess the same pressure applies for 18"
 
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