I've been getting about 19.51/100 km on gas, and having changed from B'stone RE92 215x 15, to the above in 225x16, I'm still getting 19.5.

BUT, the distance travelled is as measured by my odometer, and the circumference has gone from 2020mm to 2120mm, so I'm travelling 4.9% more for the same indicated distance, and the same fuel. So my fuel consumption has improved by 4.9%.

Also the ride, noise, and especially the grip is much better. V happy with these tyres. This is on a dual-fuel TW wagon.

hey man why are you gettin 19.5 per 100km thats just horrible, im getting 13.4 on lpg city driving thats with supercharged engine

also i dont understand what u mean with circumference, why would it change? you realize that overall diameter should stay the same if you have selected the right tire, as in if you go for larger rim then usually you have tyre with smaller profile to compensate in order to keep overall diameter the same....

The circumference is not the determining factor with this issue. What you really need to know is the rolling radius - the distance from the centre of the wheel to the ground. Maybe the Michelins bag out more than the older tyres. Not saying that you don't get better mileage, but this is what you really need to know.

If you want good fuel economy, pump them up to 45psi.

Just don't expect much grip, and i'd probably not drive it in the wet.

If you want good fuel economy, pump them up to 45psi.

All joking aside, no - just no.

Hang on a sec, what is a circumference of a circle? Doesn't that equal the distance covered per rev? Circumference = 2xPIxR so if R increases, so does circumference. Cooperplace, are you sure the originals were 215 wide in 15" diameter? What are the tyre profiles?

yea but the overall R wont increase because tire will have smaller profile to compensate for larger rim.

Hang on a sec, what is a circumference of a circle? Doesn't that equal the distance covered per rev? Circumference = 2xPIxR so if R increases, so does circumference. Cooperplace, are you sure the originals were 215 wide in 15" diameter? What are the tyre profiles?

a thousand apologies: old RE92s were 205/65, 15", new tyres are 16", 215/60. On new wheels, clearly. I don't know what the rolling radius is, I just measured the circumference. And on the old, worn tyres, it was 2020mm, on the new ones, 2120. I'm assuming that the extent to which these tyres bag out under the weight is about the same (bad assumption??). But they definitely have better grip, ride and noise.

wow Andrei, 13.4, that's v. good mileage, I am jealous, mine is factory std. Impco mixer system, bog-standard engine. What sort of system do you have? And how much supercharger boost?

I admit I don't drive it all that easily, but I could be worse: the old RE92s had done 74,000km and still had a lot of meat on them.

thanks

Peter

a thousand apologies: old RE92s were 205/65, 15", new tyres are 16", 215/60. On new wheels, clearly. I don't know what the rolling radius is, I just measured the circumference. And on the old, worn tyres, it was 2020mm, on the new ones, 2120. I'm assuming that the extent to which these tyres bag out under the weight is about the same (bad assumption??). But they definitely have better grip, ride and noise.
that is a way too big a difference. may even be illegal. do a search on here for wheelmaster and use it to find appropriate 16" tyres. 215 60 is ok on 15" rim but you went up an inch. try 215/55r16. andrei use wheelmaster as well to better understand tyre sizes. there are no sizes that exactly match when up sizing or downsizing.

I ususlly get 11L/100, petrol '99 verada. How much stuff do you have loaded up in your wagon and what sort of driving do you do? Busy stop start traffic?

If you want good fuel economy, pump them up to 45psi.

Just don't expect much grip, and i'd probably not drive it in the wet.

Actually, that is far less dangerous than running 20psi, or even 27psi.
About 150psi may start to damage a tyre. 45psi is nothing.

Higher pressures are better for wet weather driving because it makes the tread pattern open up and the tyre can displace more water.
Run low pressure and the tyre becomes concave against the road surface and the tread closes up. This traps the water between the tyre and road and can more easily cause loss of traction.

IMO, error on the high side of tyre pressure is much safer.


As for your tyres, what is the factory tyre size on your tyre placard?
Reason I ask is because, on paper, 205/65/15 = 647.5 diameter while 215/60/16 = 664.4
The difference is 16.9mm and I think you are supposed to keep within 15mm of the overall diameter.
So you may be putting your speedo out by an "illegal" amount.

As for 19.5L/100km, that sounds steep to me, but if you work out $ per 100km you beating me by about 40% :)

I had mixer system before aswell, i could easily get 14.5 city driving when car was auto & N/A, i strongly suggest you have it tuned by LPG mechanic, my guess is your O2 is out of whack, this is what happened to me, at one stage i was getting really bad economy similar to yours, ended up being lazy o2 sensor making car run rich as hell.

illegal? no, they're listed in the book as a standard size. Too big a difference? No, instead of the speedo reading 8% too fast, it now reads 3% too fast. I've gone from one standard size to another.

what is the factory tyre size on your tyre placard?
Reason I ask is because, on paper, 205/65/15 = 647.5 diameter while 215/60/16 = 664.4

As for 19.5L/100km, that sounds steep to me, but if you work out $ per 100km you beating me by about 40% :)

these are a factory size

I had mixer system before aswell, i could easily get 14.5 city driving when car was auto & N/A, i strongly suggest you have it tuned by LPG mechanic, my guess is your O2 is out of whack, this is what happened to me, at one stage i was getting really bad economy similar to yours, ended up being lazy o2 sensor making car run rich as hell.

interesting, I've taken it to a number of LPG specialist mechanics, they all say that's what they get, and that the mixture is fine

these are a factory size
Just because it's factory off another Magna doesn't make it legal. It's legality is compared to what's on your placard. So if your placard says your car comes standard with 205/65R15 tyres, and you currently have 215/60R60s on, they're illegal. You can go 15mm larger than what's on your placard: you've gone 16.9mm larger.

illegal? no, they're listed in the book as a standard size. Too big a difference? No, instead of the speedo reading 8% too fast, it now reads 3% too fast. I've gone from one standard size to another.
unless you have an awd, veranda or magna sports or s1 vrx, or ralpartl your oem size is 205/65r15 and your speed is calibrated for that. just because a tyre/wheel combo is standard on one make/model does not mean it is standard on all makes/models. that 15mm rule is adr. if ur speedo was registering 8pct too fast then your odo would have clocked 8pct more kms making it look more efficient than the new one.

... Also the ride, noise, and especially the grip is much better. V happy with these tyres.
that's interesting, my dad has the Primacy's on his Euro (came standard in i think 245/45 (or 40) R18) and they're quite a noisy tyre.. i have the sportier version (Sport Pilot 3- in a 235/40R18 profile) and IMO it's a little quieter, but still a noisy tyre.. then again, it could most probably be because they're in an 18" profile than a 16" profile

Actually, that is far less dangerous than running 20psi, or even 27psi.
About 150psi may start to damage a tyre. 45psi is nothing.


Agreed. In terms of tyre damage 45psi is nothing.

At 45psi the tyres can feel like they've got more grip but when they lose traction they lose it suddenly and all at once. Low pressure will cause a blowout but in my opinion a driver lured into a false sense of security by overinflated tyres is just as dangerous.

Agreed. In terms of tyre damage 45psi is nothing.

At 45psi the tyres can feel like they've got more grip but when they lose traction they lose it suddenly and all at once. Low pressure will cause a blowout but in my opinion a driver lured into a false sense of security by overinflated tyres is just as dangerous.
Underinflation will increase braking distance in emergency situations. It is just the physical nature of tyres causing a cupping effect in the contact surface when looked front/rear on. Properly inflated tyres to between 35 and 40 psi will reduce the cupping effect.

ok, thanks for clarifying that

Saw the Mythbusters Tyre pressure test.....
Search it.....

Results are in.
35 psi (control)
tyres at 10psi = 3.7% increase in consumption
tyres at 30psi = 1.2% increase in consumption
tyres at 40psi = 6.2% decrease in consumption
tyres at 60psi = 7.6% decrease in consumption.

However, they they did remark at 40 psi you are more likely to get a puncture. Which argues the point over a 40 psi tyre pressure.
I just avoid gutters and driving for the Apex Cornering.....Stick to the 40 PSI and stay on the well worn parts of the road, to avoid punctures.

They also left this out of their test, a cold tyre @ 38 PSI will be 40 psi at working temps. So 40 psi is actually 42 when they warm up.

As for 19 litres per 100, get another LPG workshop, that's total Baloney. 7-8 K's (12-14 l/100) per litre should be acheivable. Less if Phang it.

I'm averaging 14 l/100, and If I could be bothered I could get a lot less than that, but that's no fun...............

Good luck

BTW 19l/100 = 12 mpg. Thats really, really, really, really bad. 12 l/100 is about 20 mpg much better, and 10 l/100 (23-24mpg) on the freeway is excellent.

you talked me into it. I'll get another LPG workshop to look at it. The people who have been servicing it are Southern Autogas, who claim they did all of Mitsi's factory installations on Magnas and 380s, (if wrong I'm sure someone of this forum will correct this) so I assumed they knew what they were talking about.

isn't 19l/100km about 14.8mpg? not very good, either way.

so, does anyone know of a gas place in Adelaide who they recommend?

Sorry if thats inaccurate, the online calculator I used must be Fubar.... My smartphone is in my car......

Edit.
We are both correct, I used US Gallons, you calculated European Imperial.

Saw the Mythbusters Tyre pressure test.....
Search it.....

Results are in.
35 psi (control)
tyres at 10psi = 3.7% increase in consumption
tyres at 30psi = 1.2% increase in consumption
tyres at 40psi = 6.2% decrease in consumption
tyres at 60psi = 7.6% decrease in consumption.

However, they they did remark at 40 psi you are more likely to get a puncture. Which argues the point over a 40 psi tyre pressure.
I just avoid gutters and driving for the Apex Cornering.....Stick to the 40 PSI and stay on the well worn parts of the road, to avoid punctures.

They also left this out of their test, a cold tyre @ 38 PSI will be 40 psi at working temps. So 40 psi is actually 42 when they warm up.

As for 19 litres per 100, get another LPG workshop, that's total Baloney. 7-8 K's (12-14 l/100) per litre should be acheivable. Less if Phang it.

I'm averaging 14 l/100, and If I could be bothered I could get a lot less than that, but that's no fun...............

Good luck

BTW 19l/100 = 12 mpg. Thats really, really, really, really bad. 12 l/100 is about 20 mpg much better, and 10 l/100 (23-24mpg) on the freeway is excellent.

All tyres' pressure will increase to a degree when they warm up due to the steel belts in them flexing and friction from road surface. Under-inflated tyres will pressure will increase more due to extra flexing of the belts (the section in contact with the road is larger due to flattening of the tyre). This extra increase in temperature and hence pressure is what causes a blowout.

Oh, I thought it was heat and flexing ruining the structure and strength in side wall.

My old Verada on the mixer LPG used to run 13-13.5L/100km with essentially a stock engine aside from the full exhaust. Just for a comparison sake.

I also always run 38psi as recommended by my tyre dealer, that is on 18's though. That said, I always ran 38-40psi on my 16's on both this car and the Verada, and found it to be in the optimum range for economy and tyre wear. Anything below 36psi is too soft for my liking.

Sorry if thats inaccurate, the online calculator I used must be Fubar.... My smartphone is in my car......

Edit.
We are both correct, I used US Gallons, you calculated European Imperial.

yes, that makes sense. either way it's crap mileage, I'd love to get better

My old Verada on the mixer LPG used to run 13-13.5L/100km with essentially a stock engine aside from the full exhaust. Just for a comparison sake.

I also always run 38psi as recommended by my tyre dealer, that is on 18's though. That said, I always ran 38-40psi on my 16's on both this car and the Verada, and found it to be in the optimum range for economy and tyre wear. Anything below 36psi is too soft for my liking.

Hi Lugo, was that round town? I'd love to get 13-14. And it's hard to imagine that the full exhaust would make that much difference.
Re tyres I'm running 36 -38 so I don''t think that is likely to be a cause of any big difference.

Any luck with this excess LPG fuel consumption.

Hi, sorry for the hi-jack but...




They also left this out of their test, a cold tyre @ 38 PSI will be 40 psi at working temps. So 40 psi is actually 42 when they warm up.



This tyre would be over-inflated. To find the correct tyre pressure firstly inflate to whatever pressure you like, it's best to do this when the car hasn't been driven for several hours. Then drive the car for about an hour and measure again with the SAME pressure gauge, you are aiming for a 4 PSI increase on radial tyres (6PSI for LT construction tyres on your fourby). If it has increased 2 PSI then it is over inflated, if it has increased 6 PSI then it is under inflated.
This takes a bit of mucking around but it definately worth it when you get the extended life out of your tyres. The change in temperature during the day will also affect this (if extreme) and if one tyre is in the sun and the others aren't, this one will read high aswell.
BTW I have 245/55/17's on my V6 Sedan and I run about 40 PSI to work and back, and around 42 on the highway.

Cheers!

Any luck with this excess LPG fuel consumption.

got it back from ABBA today; apparently the gas system diaphragm was stretched or something, they fitted a new one, still couldn't get it within spec., ended up going back to old one which they shimmed and then it wasn't too rich. Previously it was too rich on running, OK on idle. So they tell me. Am waiting to see how it goes. Certainly drives A1. Abba seem nice people, will go back to them. No charge for a loan car, which makes for more convenience. Recommend them.

consumption after 1 tank, around town: 16.3l/100k. The is MUCH better than the 19 -19.5 I was getting.

16's around town is heaps better, Hopefully you'll be getting 12's on a long trip....

So you're saving $3.00 per 100, it takes a bit to get the service fee's back unfortunately

yeh, it'll take quite a while to get that back, but it's also running better, seems to somehow feel cleaner or crisper as it revs out, not surprising I guess, it was way too rich. Plus I've got the satisfaction of knowing that I'm better for the environment..........