W140 tyre pressure

Ben Longden

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Just a stupid question....

The tyre placard for my W140 states the pressure to be 27 PSI.
So, being a "do it by the book" bloke, I ran the tyres at that pressure for the past three years, clocking up around 50,000km.

This is the tyre print I noticed the other day...

W140tyreprint.jpg


My question is, if the advised pressure of 27PSI gives a wear pattern like this, showing a tad of underinflation, then what pressure should I really be looking at running the tyres?


(By the way, I have taken her to the blacksmith and had her reshod.)
 

Silver_Star

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When the tyres needed changing, was the wear even across the tread or were the outsides worn more than the centre?

Also does the hand book/service schedule call for the wheels to be rotated front to back?
 

Alex M Grieve

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the recommended tyre pressures are in a table on the inside of the fuel filler flap That shows different pressures recommended for different load states and speeds.

Many tyre fitters don't even bother looking and fit new tyres at 30 all round - which generally works well and seems to do no harm.

You are right in thinking that yours have been under-inflated.
 

Mic

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Do tyres not change their profile when hot and travelling at speed and in a straight line such that the centre of the tread becomes more in contact with the road compared with the outer edges ?

Mic
 

Alex M Grieve

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Do tyres not change their profile when hot and travelling at speed and in a straight line such that the centre of the tread becomes more in contact with the road compared with the outer edges ?

Mic

yours might well do that Mic! ;):rolleyes:;)
 

brandwooddixon

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Personally I'd have thought that was slightly under inflated.
My CL (basically an S class) recommends 29 front and 32 rear for comfort and somewhat more for speeds over 130mph.

I do, however, tend to run my tyres at 32 front and 34 rear as it gives me an improved steering response and I don't have to worry too much if I load the boot up.

I suspect that the comfort setting is slightly under inflated, hence why it has to be increased at higher speeds in order to reduce heat stress in the tyres.
 

Mic

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Do tyres not change their profile when hot and travelling at speed and in a straight line such that the centre of the tread becomes more in contact with the road compared with the outer edges ?

Mic

My C140 was not here yesterday so I could not comment on your 27psi but I have now checked on the inside of the fuel flap and the recommended pressures for my C140 for low loads and ''low'' speed are 30psi front and 32psi rear.......higher pressures for higher loads and high speed.
I will therefore, as Brandwooddixon, have set the pressures at 32psi front and 34psi rear as I always set my tyres at 2psi above the minimum recommended.

Mic
 

television

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27 is too low for any 140, and one can see that from the tyre print. I also suspect that the outer part of the tread is more worn than the centre I run the fronts at 30 on mine, any more and the ride gets hard, any less the the danger of rim damage on pot holes.

I think it is always worth having your own tyre gauge in order to keep some consistency in the readings. A good one cost about £7 -£10
 
OP
B

Ben Longden

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  • Thread Starter
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Thanks...

All four tyres are the same, and rotated every 10,000 km religiously.

The pressure gauge is the same one used over the past few years at the same servo, and I know its accurate, cos I met the bloke testing the digital machine... so 27 really IS 27 PSI...

The wear rate on all four shoes is identical. Severe outer tread wear, and bugger all on the inside... indicating even to me they are under inflated, at the advised pressure.

Mic, with your pressures, are you getting even wear?

As an aside, I checked the pressures on the reliable gauge the day after her trip to the blacksmith... both on the left were 38psi, and both on the right were 30. So it pays to double check the tyre fitter...


For your info, here is the tyre placard..

W140pressureplacard.jpg
 
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television

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I have not done a high enough mileage yet to know how all 4 tyres are wearing, but at ½ way through their life I adjust them to balance any wear.

Interesting cars though with tyre pressures.

Just last week I had to mount a kerb and I felt the tyre bottom out on the rim with 29 in the fronts, so I blew them up to 33 and the ride was very hard, I later dropped them 29/30 and the ride was good again. wear wise as said its too early yet as I have only been 4k on the new tyres
 

Mic

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I have done about 7.5k miles on the tyres and so far as I can tell the wear is even......probably too soon to tell to be absolutely certain.
If the wear is uneven it is not dramatic.

Mic
 

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Those figures are interesting , mine shows 30 to 32 unloaded for the front and 36 when loaded, OK this is for the CL the same as Mics.
 

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These do seem unusually low numbers Ben.

Do other 140 owners use these pressures, or is this for the Australian market I wonder?

Yes that really surprised me Alex, I would have almost argued on those figures.

The wheels would not last long in the UK roads with such low pressures

Maybe the air is heavier down under :rolleyes::rolleyes:
 

kth286

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I have a 1995 124 coupe with 320 engine.

The filler flap shows 35 front and 36 rear.

Full load shows rear needs increasing to 46 !!!!!!!!!!!!!

The picture on the flap label is of a saloon.

They are far too hard for me and I use 32 all round with normal
tyre wear as expected.

I would be interested in other owners of the 124 coupe with 320
engine, their recommended tyre pressures.
 

television

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I have a 1995 124 coupe with 320 engine.

The filler flap shows 35 front and 36 rear.

Full load shows rear needs increasing to 46 !!!!!!!!!!!!!

The picture on the flap label is of a saloon.

They are far too hard for me and I use 32 all round with normal
tyre wear as expected.

I would be interested in other owners of the 124 coupe with 320
engine, their recommended tyre pressures.
So you use pretty much what we all use then David
 

AndyjamoS500

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W140 Tyre pressures

Good subject, ive found my W140 very sensitive to tyre pressures. I drive a 1998 S500 and my fuel flap pressures have 4 settings

Upto 135mph light load 30 front 32 rear
Heavy load 30 front 38 rear

Over 135mph light load 36 front 36 rear
Heavy load 36 front 44 rear

I run in the lowest settings as it ruins the ride otherwise

Have just fitted a brand new set of Kuhmo KH31's and they suit thus car very well, incredibly comfortable & quiet
 

television

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Good subject, ive found my W140 very sensitive to tyre pressures. I drive a 1998 S500 and my fuel flap pressures have 4 settings

Upto 135mph light load 30 front 32 rear
Heavy load 30 front 38 rear

Over 135mph light load 36 front 36 rear
Heavy load 36 front 44 rear

I run in the lowest settings as it ruins the ride otherwise

Have just fitted a brand new set of Kuhmo KH31's and they suit thus car very well, incredibly comfortable & quiet
Then the same as my findings :D that extra 2lbs can ruin the ride, I have never known a car to be so sensitive
 

Mcobinad

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I have to go and check my tyres straight away. Some great recommendations here.
 
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