assumingthe ratio of the 215 is 80%,, I figure the difference is about 7.5%! Workmates older Hilux has huge tyres and is hoovering petrol at an alarming rate. Surely putting it back on 'normal' size tyres should help consumption by needing less throttle at road speed! Cheers.
xacoon,
Jun 25, 6:14pm
ahhh, so the lux with the bigger feet has worse consumption! sooo many variables.
mugenb20b,
Jun 25, 6:46pm
I had exactly those tyre sizes on my old Surf (2.0 litre EFi petrol, auto). I went from 215 15 to 31 x 10.5 x 15. Made absolutely no difference in fuel economy 14 litres per 100km at all times.
mrfxit,
Jun 25, 7:03pm
My 88 2.4T diesel was on 215/80/15's (std factory size) has been on 31/10.5/15's since I got it & regularly get 9.5L to 10L per 100kms
muzz67,
Jun 26, 4:58am
Thanks guys. Workmates truck is 2litre carbed petrol and manual. 14l/100km is about what he's getting. Wouldn't a carbed engine be less thirsty if the manifold vacuum was decreaced by less throttle, even if the revs wereslightly higher tho!
zephyrheaven,
Jun 26, 7:25am
Different kettle of cylinders but my 3L Diesel economy didnt change when I went to 35's from factory
mrfxit,
Jun 26, 9:39am
Tyre size DOES very often make a very noticable difference to economy with PETROL engines. Most petrol engines DON'T have the torque to ignore tyre sizes unlike most diesel engines . particularly 4 cyl & under 3ltr.
mrfxit,
Jun 26, 9:41am
Borrow a set of the correct size wheels & go on a couple of trips with BOTH sets of tyres. Make sure the trip route is EXACTLY the same as reasonable for distance & traffic flows. *** Small petrol engines in "work vehicles" (in particular) can often go ONE size up or down without having a noticeable impact on fuel usage./ 2 sizes up or down WILL clearly effect economy.
spottie,
Jun 26, 4:50pm
That's right you will have to measure the consumption over the same known route. The 31's will be larger in diameter so your odometer will be out compared to the 215's.
Check the speedo difference. Low torque motors suffer very badly from over loading. Remember what happens when push biking on the flat & then have to go up a steep hill NOW . stick on a heavy back pack & do the same hill Same with small cars & trailers Small motors & bigger wheels Driving in too high a gear for the slope Carting 4 ppl instead of 1
da de do dah.D'OH
mrfxit,
Jun 26, 6:39pm
Once upon a time . I had a Holden station wagon with 202ci motor & auto Std 205/70/14" tyres Auto busted so dropped in a toyota 5 speed box.
Didn't know that the auto's had a 2.9 ratio diff & the manuals had a 3.45 ratio diff Car was a real pig around town & mostly stayed in 3rd gear as 4th was far too high Got given a pair of 225/50/14" & that made a HUGE difference to town driving & take offs
mrfxit,
Jun 26, 9:12pm
Both ways make a difference on up or down size = more fuel. All things being exactly equal for true road speed/ load/road type condition etc etc. Sometimes . it can offer better economy up or down sizing or make it worse, but that is mostly dependent on the exact vehicle concerned & how it's being used.
Only real way to find out is to try it over a few trips making sure the trips are done as much as possible the same way. Width does have an effect but to a far lesser degree.
It's a bit like 4x4 driving in seriously muddy tracks, sometimes it's better to have skinny wheels that cut through the crud to harder ground & sometimes better for wider tyres to float through. Theres a lot of varibles & each suits a particular vehicle in a certain situation better or worse, but in general for small engine/low power vehicles, it's best to stay with the same rolling height & just go 1 physical size wider. Same torque ratios (motor/ gearbox /tyre height combo gearing ratios) Same speedo ratios Same basic tracking Same basic guard/suspension clearance Better traction working within the factory suspension settings
snoopy221,
Jun 26, 9:35pm
Juss gonna pop in here and put in MY DAMN 10 CENTS WORTH _k why! because 1) the original poster has been around here LONG enough that his question DESERVES A COMPETENT ANSWER. i.e.Different kettle of cylinders but my 3L Diesel economy didnt change when I went to 35's from factory
Quote zephyrheaven (599 )9:25 am, Sat 25 Jun #7 KNOW.NO OFFENCE TO OLE MR.(LOL) BUT. THIS KETTLE OF CYLS. IS PETROL. IT HAS A WELL. VARIABLE VENTURI . AIR VALVE SECONDARY CARBURETOR. I.E. This kettle of cyls is BASIACLY sitting too high on the secondary at road speed due to tyre drag. This gives a secondary opening with LOW AIRSPEED AND RELEVANT BAD FUEL MIXING. AND yes muzz Have seen more than 1 get a TAD thirsty on em. either a carb recalibrate. or back to std. K all No flame. but. DIDYA READ IT AS I DID! AND.take the carb secondary opening relevant to load as well. me and zeph do NOT argue much. AND i think well all have been commenting_ minimally of late_ However.Different kettle of cylinders but my 3L Diesel economy didnt change when I went to 35's from factory Agreed jimmy James. Tis a diff kettle. Hopefully ole muzz67. I MAY! have explained the kettle a tad. Again no offence mrfxit. Mind you_ i think ya been around LONG enough not to TAKE ME DAMN FENCE.LOL
mrfxit,
Jul 30, 5:09am
Part of the confusion is because of the difference between diesel & petrol motors. Eg: our Nissan bluebird Attessa 2Ltr Petrol . Has it's best usable torque is between approx 2000rpm & 4000rpm with only slightly less usable torque either side of that rev range. My Hilux Surf 2.4ltr turbo diesel . Has it's best usable torque between approx 2000 rpm & 3000 rpm, With stuff all usable torque either side. 1: The nissan REALLY notices the effect of having 4 ppl in the car 2: The Surf couldn't care less Where the surf with the same load (or empty) still takes the same amount of effort on the same hill, the Nissan definitely notices it with the load & takes more effort Despite the Surf having a far bigger & heavier body then the Nissan. . Oh & this is a personal observation from many years of driving all sorts of vehicles. The 2 vehicles above are really just an example . Also, those of us with turbo diesel motors, also know that they operate very differently compared to petrol turbo motors, (torque curves/ outputs etc etc)
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