Low Tyre Pressures and Fuel Consumption?

JohnnyN

What effect would low tyre pressues have on fuel consumption? I normally run my tyres at 36psi and I hadn't checked them for a VERY long time. I found them showing 24psi when I checked them today. My petrol usage has been horrendous for a while now and i'm starting to wonder if this has had anything to do with it?

:wtf:

JohnnyN

Just researched this a bit and found the Michelin website has this,

Low pressure and the effect on your fuel consumption:

A set of under inflated tyres will have the effect of causing the engine to work harder and this will increase your fuel consumption or decrease your fuel efficiency. A set of tyres that are 10psi under inflated will have the same effect as increasing the cost of fuel by 3p per litre. (based on £1.00 per litre)

And this from Toyo,

http://www.toyojapan.com/tires/pdf/TTT_19.pdf

pottsey

crikey johnny you have your tyres hard ,i thought having mine at 30 was bad enough mind you im running on 40's so it would seem harder.i checked mine a couple of weeks ago both fronts were down to 22 and 24,one of the back was 24 the other was 19,no wonder the back end was sliding about in the snow lol

JohnnyN

Going by the Owners Manual, the GSi wheels with 215/45/17are meant to be inflated to 36psi unless I misunderstood?

notsure.gif

Daz

I'd say 36 is a tad high for normal driving,,maybe ok if ure fully loaded.....but your not...

i Used to run my vec at 28 with 18's otherwise it would tramline like hell

pottsey

JohnnyN said:
Going by the Owners Manual, the GSi wheels with 215/45/17are meant to be inflated to 36psi unless I misunderstood?

notsure.gif

ohhh bugger if thats the case i better stick some more in

Daz

2.5 24v V6 GSi 98 - 02 36 32 36 45
2.5 24v V6 GSi Estate 98 - Onwards 34 34 36 48

However....the 2.5 lump is lot heavier than the 2.2,so i think i would drop the front down to 32 aswell...

JohnnyN

Here's the figures from my book. Just been out to the car and I'm a little up to what it recommends:

z22se: Tyre Size 215/45/17:

For upto 3 Persons - 33 Front and 38 Rear.
Full Load - 36 Front and 45 Rear.

Looks like i've got to let a little out the front and add a bit to the rear tomorrow.

Daz

What 17" wheels did they fit to the z22se cars then john..??....as if they wernt fitted as standard there would be no reccomended pressure for them.....

I think i'd be running them at 32 all round in all honesty...

JohnnyN

Just edited above post with a copy of the Owners Manual.^^^

pottsey

would the 215 45 17 be the veccy c tyres

Daz

That with dunlop sp 9000 tyres only.....whack em all to 32 and see how it goes john.....

JohnnyN

I did wonder about that. What's so special about the Dunlop SP9000?

Daz

DUNLOP - SP9000
The Dunlop SP9000 is a state of the art high performance tyre. The tread pattern of this tyre fans outwards utilising a totally new silica compound for the tread. Features:

* Directional, silica compound tread pattern
* Massive grip and precise handling control, wet or dry
* High resistance to aquaplaning
* Rock solid stability at high speeds
* Stunning looks
* Shorter braking distance and reduced fuel consumption

JohnnyN

Blimey that sounds like a bit of an animal!

So you reckon to go with 32 all round then?

Daz

I would john and see how it goes......Ive got alys at 32 on her coupe and she got 215/40/17 on there...they seem to be wearing well and we get 45 to gal on a run.so fuel economy is good too

BURT150

I allways go high to 40psi that way with the negative camber on the back of lowered vectras with low profiles you get a bit more even tyre wear dunno..

Not saying that 32 is wrong tho!

rushy

Some Vec C's running the 19" snowflake have to be run in the low 40's. I'm on 225/45/17's and run around 38 on the front and 36 on the rear, my MPG drops quite a bit when I get down into the low 30's.

vocky

I ran 32psi all round on my old vec when it had gsi wheels :thumbup:

guy_27

I check my tyre pressures weekly and before any long drives. Running on 215 /35 /18

I run mine at 38 all round for daily driving.
40 all round for long trips. which gives me the best fuel economy (seen over 900km to a tank several times and also got over 1000km to a tank before)

For sprinted drives Its 38 up front and 36 in the rears.