Tyre Pressure recommendations

[clk320x]

Running 36 front , 44 rear.

Anyone tried another combination and got good results?

18" alloys

Cheers

 

[AMGeed]

Rears in particular are too high unless you are driving around fully laden at high speed all the time.
I run my E55 on 18s at 35/35 and that is heavier than a CLK.

I'd drop to the suggested 31/31 like your fuel cap shows.

 

[clk320x]

Rears in particular are too high unless you are driving around fully laden at high speed all the time.
I run my E55 on 18s at 35/35 and that is heavier than a CLK.

I'd drop to the suggested 31/31 like your fuel cap shows.

I thought as 44 is shown on bottom for 4 pas, 130+ should be safe to fill to that? Will reduce it anyway but shouldn't be dangerous should it? Maybe use more fuel/increase tyre wear?

Cheers

 

[AMGeed]

My interpretation of your fuel filler is that if you have a fully laden car and intend reaching speeds of 130mph+ then set your tyre pressures as you have at 36/44.

But if you only have a couple of people in the car and little in the boot, put less air in......... to the recommended 31/31. If the tyre looks bit soft with 31/31, increase it a little but I wouldn't be putting 44psi in my rear tyres unless I was doing vmax

 

[markjay]

You have to try it.

I ran the W203 on the higher figure in the range and it felt just right.

I tried the same on the W204 but it was very bouncy - it seems much happier at the lower figure in the range.

Incidentally... in spite of the suitcases, you can run the car with the pressures within the range to suit your driving style even if the car is not fully loaded - that's official.

The higher figure in the range is for generally more sporty feel and also for motorway driving. Not only for when carrying heavy load.

 

[190]

I thought as 44 is shown on bottom for 4 pas, 130+ should be safe to fill to that? Will reduce it anyway but shouldn't be dangerous should it? Maybe use more fuel/increase tyre wear?

Cheers

Safe as in not exceeding the maximum pressure for the tyre but not necessarily safer for the car dynamically compared to the correct pressure. The Tyres won't warm up for one and the rears in particular will have a reduced contact patch when almost 50% over inflated.

Higher pressures will use less fuel due to low rolling resistance but the rears are likely to wear in the centre of the tread.

For me the worst results of excessively high pressures are the loss of ride comfort and additional wear on suspension components.

 

[PobodY]

I run mine at 44/44 and it seems fine. - I don't know if it's related, but my fuel economy figure seems to have gone up for a long run on the motorway.

I think the maximum pressure on the tyre is closer to 70psi.

 

[clk320x]

You have to try it.

I ran the W203 on the higher figure in the range and it felt just right.

I tried the same on the W204 but it was very bouncy - it seems much happier at the lower figure in the range.

Incidentally... in spite of the suitcases, you can run the car with the pressures within the range to suit your driving style even if the car is not fully loaded - that's official.

The higher figure in the range is for generally more sporty feel and also for motorway driving. Not only for when carrying heavy load.

Yeh the car seems a lot more boucny on country roads but a quick motorway blast it felt better than before..

Decisions decisions

 

[markjay]

Yeh the car seems a lot more boucny on country roads but a quick motorway blast it felt better than before..

Decisions decisions

This might not be of much assistance... but Russian ZIL trucks had a tyre pressure system that allowed the pressures to be changed from the cabin by means of an engine-driven pump feeding the tyre through the hub. Great when moving from mud or sand to paved roads and back.

 

[magpiemalemerc]

My C-class estate 220 with 18 " wheels says 36 psi all round unless the car is full and its a much higher pressure.

 

[PobodY]

This might not be of much assistance... but Russian ZIL trucks had a tyre pressure system that allowed the pressures to be changed from the cabin by means of an engine-driven pump feeding the tyre through the hub. Great when moving from mud or sand to paved roads and back.

I'm sure I've seen that on other 4x4s as an after-market accessory.

 

[clk320x]

Haven't bothered dropping pressures yet

Car seems happy on motorway, all be it ride slightly harder but I've also noticed slightly better fuel economy?

 

[PobodY]

I'd leave it unless you find the ride too hard. - This isn't F1, so tyres don't fall out of their optimum performance because the pressure is 10PSI too high or they're 15 degrees too warm.

 

[190]

If you want to put some numbers on the fuel saving then a 10% increase in tyre pressure equates very approximately to 0.75% increase in MPG.

This is not a fixed and guaranteed return as the contribution of rolling resistance to overall fuel usage varies with speed. At motorway speeds aerodynamic drag swamps rolling resistance so the benefit from high inflation pressure will diminish.

As with most things there is also a point of diminishing returns for pressure vs rolling resistance so each 10% increase in pressure results in a smaller and smaller reduction in rolling resistance. 44 psi vs 31 psi (42%) will not result in 4 times as much fuel saving as a 10% increase.

The effect on vehicle handling is what would worry me more. Increasing pressure reduces the tyre contact patch, which will decrease the available traction. Taken to extreme and 42% sounds extreme to me, there must be some impact on vehicle dynamics and safety.

Looking again at the recommended pressures I wouldn't run higher pressures at all but if you must, I can't see any possible justification for exceeding 34 F 39 R

 

[Petrol Pete]

I'm sure I've seen that on other 4x4s as an after-market accessory.

Standard on US military spec Hummer H1. I believe it can be ordered on some new Hummers.

 

[Petrol Pete]

If we are being pedantic and need tyre pressure to remain as close to cold setting the tyres should be filled with Nitrogen gas.

 

[magpiemalemerc]

I had my car done on the hunter alignment and my toe on the front was out passenger front side the rest of the readout goes beyond my knowledge.but the guy said not to worry about the numbers in RED as it's the toe alignment that matters most.

 

[190]

If we are being pedantic and need tyre pressure to remain as close to cold setting the tyres should be filled with Nitrogen gas.

I thought Nitrogen fill was about leakage rates and freedom from moisture content. Nitrogen still has to obey the gas laws so pressure will rise with temperature Approximately 0.1 bar for each 8 Deg C rise.

 

[markjay]

I thought Nitrogen fill was about leakage rates and freedom from moisture content. Nitrogen still has to obey the gas laws so pressure will rise with temperature Approximately 0.1 bar for each 8 Deg C rise.

Apparently the temperature does go up more on an air-filled tyre, hence the pressure goes up quicker:

https://youtu.be/knHeUF9JLzg

But the conclusion is that while the science is correct, Nitrogen-filled tyres still make no noticeable difference in real-life tests.

 

[markjay]

Or try this....:

https://youtu.be/bCnWvMleVD0