Increase mpg just by pumping up tyres

[philepo]

Hi, I've increased my mpg from an average of about 31 to 34 just by pumping up the tyres from 30/33 fr/r psi to 35/35 fr/r psi.

This seems safe to me, but would 40 psi be pushing it???

It's a w202 c200 auto.

Cheers.

(PS I need a tow bar if anyones got one going)

 

[cplnoonoo]

Your saving in fuel will probably be wasted when you consider how the tyres will wear across the centre much more quickly. May slightly increase the braking distance also as there is less contact patch between rubber and road.

 

[kwakdonut]

The more you pump the tyres up, the better your economy BUT you will also affect braking, handling and steering. It will also wear your tyres prematurely. You will also be more likely to get a puncture or worse still, a blow out - Do not keep pumping them up!!

I would stick with the recommended pressures and adjust maybe no more than +/- 2psi.

My E320 pressures should be 29 Front 30 Rear but find that 31 Front 32 Rear helps with tyre wear (less shoulder wear on the fronts) and does not affect anything adversely.

 

[philepo]

wear

Fair comment, but...

The wear on the fronts when at correct pressure was on both shoulders. The back psi is only up by 2.

The manufacturer has to balance ride comfort with other factors so I would make an educated guess that the stated psi is chosen to also include favourable ride comfort, which I am not that bothered about.

I will stick with plus 2 on the rear and plus 5 max (may drop to 2 also) on the front an report in 2 years time (unless I forget... which I wil!)

 

[kwakdonut]

I am a mechanical engineer so do kind of know what I'm talking about lol!!

If you want to improve your fuel economy;

1) make sure the car is serviced regularly
2) don't fill the boot full of sh1t!!
3) drive it gently!!

 

[philepo]

me too

I am a mechanical engineer so do kind of know what I'm talking about lol!!

If you want to improve your fuel economy;

1) make sure the car is serviced regularly
2) don't fill the boot full of sh1t!!
3) drive it gently!!

I am too, but not in the automotive eng world, which is why I am guessing rather than stating fact. But I do remember a module from my eng degree on auto stuff and ride comfort is a factor in choosing tyre pressures so it isn't that clear cut, but I do appreciate what you say .

 

[grober]

There is a recommended "range" for normal running and slightly higher pressures for prolonged high speed running or heavy loads [ this may involve rather higher pressures on the rear than necessary for load purposes]. However running your car routinely at these higher pressures should do no harm other than reducing the ride comfort and possibly causing a change in the tyre wear pattern. Its best to maintain any pressure differential between front and rear [if one exists] since this can effect stability- [something to do with relative tyre slip angles evidently ] Excessive increase in pressure will bring as many disadvantages as gains as has been said.

 

[davidjpowell]

I once drove a Escort with overinflated tyres to reduce the weight of the steering. I had a very bad moment on the M18 which involved going sideways at a shade over 80 mph. Would never drive a car with overinflated tyres.

It's just dangerous IMO.

 

[kwakdonut]

I don't think there are many problems experimenting with your tyre pressures within the given ranges. I understand what you are trying to achieve and are willing to sacrifice some ride comfort for perhaps, better economy. You obviously understand the implications of excessive pressure so if I was you I would just go with whatever you're happy with.

 

[iscaboy]

worth pointing out that under-inflated tyres are more dangerous than overinflated.

if you want a guaranteed accident just lower the pressure on one rear wheel on a front wheel drive vehicle, at some speed you will rather suddenly develop instability, another 5 mph and you lose it.

 

[kwakdonut]

worth pointing out that under-inflated tyres are more dangerous than overinflated.

if you want a guaranteed accident just lower the pressure on one rear wheel on a front wheel drive vehicle, at some speed you will rather suddenly develop instability, another 5 mph and you lose it.

Good point

 

[iscaboy]

Can see from the left you and I both ride bikes.

The average biker has forgotten more about tyres / pressures / etc than the vast majority of car drivers will ever know.

 

[Ashley]

I get a 7mpg difference on Motorway cruising at 75mph running my 235/45/17s at the Max Load pressure rather than the 'normal' (48mpg rather than 41mpg) 32F and 41R. Everyone takes huge pleasure in telling me 'it knocks the centres out the tyres quicker' but I've never noticed. Whilst not cruising I generally drive like I stole it and as I have the engine re-mapped and pushing lots more power out I get about 8k miles from the Goodyears F1 Assymetrics (97 load ratings as opposed to the 94's) before they are 'slicks'. I'm actually here to see which tyres people recommend for grip and precision. Personally I think the Michelin Sport SP3's are the best closely followed by the Goodyears with Bridgestone RE50A's next but as I get the Goodyears for £102 a corner and the Michelins would be £145 I stick with the Goodyears. I use 2 sets a year I'm an expert . Right... off to find the appropriate thread

 

[Bellow]

For what it's worth, I just took my tyres back to 2bar from an experimental 2.15bar. At 2.15 bar they were horrible. Harsh, and skittered across the road in cornering. Very light car mind you.
Bear in mind if you bin it at ultra high pressures in the wet, your insurance company will disown you.

 

[kwakdonut]

Can see from the left you and I both ride bikes.

The average biker has forgotten more about tyres / pressures / etc than the vast majority of car drivers will ever know.

Forgotten? Are you sure lol! I am a stickler for making sure my bikes tyre pressures, condition etc are spot on. The average bike tyre contact patch is about the same area as your hand so is even more important!!

There are plenty of bikers on here too so am sure they will put their input in!

 

[kwakdonut]

For what it's worth, I just took my tyres back to 2bar from an experimental 2.15bar. At 2.15 bar they were horrible. Harsh, and skittered across the road in cornering. Very light car mind you.
Bear in mind if you bin it at ultra high pressures in the wet, your insurance company will disown you.

Another good point!

 

[Bellow]

worth pointing out that under-inflated tyres are more dangerous than overinflated.

if you want a guaranteed accident just lower the pressure on one rear wheel on a front wheel drive vehicle, at some speed you will rather suddenly develop instability, another 5 mph and you lose it.

The roads are littered with the above. Crawling around 60mph bends at 30mph because they are convinced that is the limit of the car, not realising it is the limit of the under-inflated tyre(s).

More lazy ignorance we have to contend with...

 

[Sorry Pete]

I routinely use the upper-limit pressure. I find very little difference in-cabin re comfort, and only slightly lighter steering as a result.

 

[wemorgan]

I over-inflated my tyres by 10% and hardly noticed any variation in fuel economy, or none that was greater than the change due to air temperature and my speed. I've kept them as they are as wear looks OK, but in general I feel that 'safe' changes in tyre pressure are at the fringes of achieving good economy. IMHO.

 

[Bellow]

Possibly the benefits and effects vary with aspect ratio (profile). Low profiles benefit less I'd say, while taller tyres are sharper for some more pressure but on any tyre more than a small amount of over-inflation soon gives all the drawbacks with no increase in benefit.