Over pressuring tyres

[MattSoanes]

I've heard it mentioned about over pressuring tyres to gain M.P.G. Does anyone know just how much more pressure you would need to put in to make any real difference without making your tyres going bang??

[markbivvy]

I've heard it mentioned about over pressuring tyres to gain M.P.G. Does anyone know just how much more pressure you would need to put in to make any real difference without making your tyres going bang??

:good:

only know of 2 things over inflated tyres cause.

bad road handling,uneven ware.

[HDAV]

In my car it is recommended 36 psi for optimum economy but does make the ride worse....... 32psi normal

[J@mes]

:good:

only know of 2 things over inflated tyres cause.

bad road handling,uneven ware.

 

 

+1, and I'm not sure what the 5-0 would have to say if you were involved in an accident and had drastically over inflated tyres, which to be fair is what you would need in order to notice a difference in MPG.

 

be more gentle on the brakes and throttle, plan your driving better. Best way to gain MPG.

[Edward]

I put 34psi in my fezzas tires with the compressor at the farm, drove home and thought '****' the steering was really dangerously light and I felt every single bump, got home used a digital pressure gauge and it was 47psi so the compressor wasnt far out

[Cookiemonsterandmerlin.]

Overinflation causes the centre of the trye to go bald very quickly.

 

Cheers OTH

[ziplex]

I usually check the pressures every month or so on the Freelander, (rarely need air), but hadn't done so for a while, my mpg had dropped from approx 37mpg to approx 33mpg over a period of a few weeks and on finally getting 'round to checking them the nsf was 25psi and the nsr was 17psi, for what reason I don't know It didn't adversly effect the handling but it put a big dent in the fuel economy. Usual pressures are 32psi all round.....I tend to make time to check them now. Thw government done some sort of 'green' campaign a while back suggesting you over inflate by 2 psi to improve fuel economy IIRC.

[vulpicide]

It would adverselly affect the handling if you had to brake or swerve in an emergency situation.

[4eyes]

You should not really over inflate road tyres. If you do you distort the shape of the tyre footprint; the part of the the that contacts the road. Essentialy the centre of the tyre is rounded out and the footprint is reduced.

 

The reduced footprint means that less of the tyre is in contact with the road. Less contact equels less drag hence why you get an increase in MPG. However be warned- a smaller footprint means handling will suffer, in particular braking. The size of the tyre fitted to your car has been calculated to give a good balance between it's weight and power so that the footprint is sufficient to make it handle and more importantly stop in time. Given that's is coming to winter I would want all the grip I can get thanks. Added to that the tyre will wear faster so is it really worth it? Plus if plod finds out, proberbly after you were involved in a crash because you could not stop in time, be ready for a thick ear and to be assigned the balme!

 

FYI - a standard road tyre can withstand upwards of 150 psi before it goes bang. However, I seriously suggest you do not try it. Look on YouTube instead

Edited October 25, 2010 by 4eyes

[Tom&Dexter]

Good reply 4Eyes

[al4x]

to the OP obviously everyone is describing what happens if you over do it, however with road tyres you do have a lot of leeway on a 4x4. I had a set of BFG's that despite being inflated to the correct pressure on a fourtrak kept wearing both outside edges. From memory if I kept them about 5psi over what daihatsu recommended it stopped and I gained about 2mpg, the tyres had written on them that they could be inflated to 61psi so I wasn't too concerned and road handling made no difference at all

[wymberley]

Hi,

Listen to 4eyes. Also, and particularly if you're talking off road, it's no bad thing to get your tracking checked on a frequency basis. It's usually free if there's no correction needed and it can save you money by not having to change your tyres prematurely.

Cheers

[Browning]

to the OP obviously everyone is describing what happens if you over do it, however with road tyres you do have a lot of leeway on a 4x4. I had a set of BFG's that despite being inflated to the correct pressure on a fourtrak kept wearing both outside edges. From memory if I kept them about 5psi over what daihatsu recommended it stopped and I gained about 2mpg, the tyres had written on them that they could be inflated to 61psi so I wasn't too concerned and road handling made no difference at all

 

 

I keep my BFG & Grabbers at 5psi over, as recommended by a couple of the 4x4 forums and the guy who fits them (4x4 specialist). Never noticed any negative wear or handling capabilities.

[4eyes]

 

I keep my BFG & Grabbers at 5psi over, as recommended by a couple of the 4x4 forums and the guy who fits them (4x4 specialist). Never noticed any negative wear or handling capabilities.

 

 

Appologies. When I first posted I had in my mind bog standard car tyres, and I stand by what I have said above. +/- 1 or psi is not goging to make a differnece in mosts cars. +/- 5psi will howver start to show effects. As stated in of the above posts, when 5psi is lost it affects the MPG, reducing it. This is due to the tyre now having a larger footprint and therefore producing more drag. +5psi over the recommended pressure and you will start to see the effects above. However, the effects are proportional to the tyre wall. +5psi will have more of an effect in a 30 profile tyre than it will in a 55 profile tyre.

 

This is where the difference comes from with 4*4's. Large profile tyres, thus the increase in pressure is negligible. Given that the same tyre might be fitted to different vehicles (different axle wirghts) then obviously there will not be a standard cover all pressure for that tyre. So, with the same tyre on each vehincel. say putting 38psi in a Shogun and 34psi in a Defender may give you the same footprint. Bit faffy to work out the right pressure based ons tyre size and axle weight but everything is related. The OP suggested addiging additional pressure to wahat I (possibly wrongly) assumed were standard tyres. If this is the case then I still stand by what I said. If the the tyres are STANDARD for the vehicle and the manufacturer of the car says upto 35psi then stick to it (+/- 2psi for atmospheric differences and/or a c**p pressure gaugue)

[al4x]

the other side with 4x4's are some of the tyres are designed for a large weight carrying ability, that is why the BFG's are rated up to levels as high as they are to cope with say a defender or pickup with a ton on the back.

[Dunkield]

I always <slightly> over inflate my cars tyres, I prefer the feel of my car like that and it doesn't have adverse affect on handling or tyre wear.

The recommendation is to do that with a bit of a load on anyway, so how many people inflate/deflate their tyres when driving loaded up or not?

Another issue is the accuracy of the gauges at petrol stations, although I use the pump to inflate my tyres I check the pressures with a Masta gauge (just because I have one left over from my racing days) if you rely on the gauge at the petrol station you may find the pressures you are running aren't what you think they are anyway.

[ProteuS]

For off road tyres doing a lot of road miles i'd say you might want to up the pressure a reasonable bit to help with the fuel and make them feel less sloppy. obviously check your wear. I was reccomended by a good friend to run the landcruiser (vredestein wintracs) around 40, as with the standard pressure they wear unevenly. If you're running muds you won't be driving like a loon on the roads anyway so a little extra pressure won't do any harm.