Bigger Size of Rims/tyres = Higher Fuel Usage

[DirtyHarry]

Hi Guys,

Just thought i would ask, say you put bigger rims on your Astra 1.8, for example (say from 15 to 17's) does your fuel usage go up slightly?

Share your observations after fitting bigger rims.

[EL BURITO]

My answer is no, difference in handaling yes fuel consumption is 6L per 100KM

[DirtyHarry]

is that for an astra 1.8 on the highway

[Red AH SRI T]

fuel consumption won't go up, because you go up with wheel size but your tyre profile becomes lower so the rolling size of the wheel & tyre is the same

[SSS_Hoon]

it can go up if the ones you put on are a lot heavier then the ones you took off, which means more power needed to move them.


you get it?


SSS_Hoon

[InsaneAsylum]

it can go up if the ones you put on are a lot heavier then the ones you took off, which means more power needed to move them.


you get it?


SSS_Hoon

no difference if the rolling resistance is the same. smaller overall wheel size will see an increase in fuel consumption

[EL BURITO]

No thats my 1.4 commbined driving

[beep beep sri]

this is a job for MYTHBUSTERS! as stated dependson the weight of the wheels and tyres.

[SSS_Hoon]

no difference if the rolling resistance is the same. smaller overall wheel size will see an increase in fuel consumption

actually there will be a difference if the 17" wheels are 5kg each heavier then the 15" he is replacing?

rolling resistance or do you mean diameter?

as if we are talking resistance that is a mythbuster episode :lol: we would need to know the stickyness of the tyres on the 15" and the 17" rims at certain temps and how much power is needed to break that traction, nah too much work just work on the assumption that they have roughly the same resistance.

but heavier yes it will have a advert effect on the fuel consumption as to how much well maybe that should be a mythbuster episode also.


SSS_Hoon

[180HOA]

LOL. I seriously doubt you'd be able to see any measurable difference. By the time you factor in variables such as driving style, road surfaces/conditions, temperature, fuel quality, tyre pressure - not to mention the probable difference in rolling diameter between old and new tyres - it's going to be impossible to measure.

Scientifically speaking, if you change your tyres and this changes the gross weight of the car and/or the grip/friction between tyre and road, then yes, there's going to be a difference, but not one that's worth losing sleep over. :p

[entice]

weight will make aq huge difference in handling.

tyre footprint will also have an impact.

ie, if you go from a 205 width to a 225, you have a 10% increase in footprint, chances are, you also get a grippier tyre, both pof which will decrease fuel efficiency.

[CJB]

well, ever since my car was playing up, which was around the same time the 17"s went on - I notice it chews the fuel a little more then it use to.

Example, it use to lift off full at around the 130km mark, now at about 70 - 100km it's off full.......


But yes, I agree, MYTHBUSTERS!!!! :p

[beep beep sri]

[QUOTE=SSS_Hoon]actually there will be a difference if the 17" wheels are 5kg each heavier then the 15" he is replacing?

5kg per wheel heavier! thats a fair bit especialy when talking rolling weight. rotating weight is the big one you want to cut down on. i race mountainbikes and its the biggest thing all of us try to cut down and im sure it'd be the same in cars.

[SSS_Hoon]

yeah i know and that is my point.


SSS_Hoon

[JasonGilholme]

Reducing rotating mass in any part of your engine is beneficial. In saying that, adding rotational mass will have a detrimental effect. Why do you think that lightened fly wheels and crank pulleys have fantastic effects??

Light weight racing wheels any day!!!

[CAL.16V]

i went from 205/55/16 to 225/40/18 and my fuel computer used to get 8.5L-10.5L and it now gets 10L-12L...... i get slightly less k's to teh tank but with the increased rolling diameter it does more k's then it accounts for so it evens out pretty much but still uses slightly more...

[beep beep sri]

you do'nt have a biggers rolling diameter because your using lower profile tyres. thats why you use lower profile tryes so that you still have the same rolling diameter.

[SSS_Hoon]

you do'nt have a biggers rolling diameter because your using lower profile tyres. thats why you use lower profile tryes so that you still have the same rolling diameter.


no that is not always the case.

i have a 14mm(or there abouts) bigger rolling diameter, its hard to get it exactly the same rolling diameter

use this to find out http://www.miata.net/garage/tirecalc.html


SSS_Hoon

[SSS_Hoon]

Reducing rotating mass in any part of your engine is beneficial. In saying that, adding rotational mass will have a detrimental effect. Why do you think that lightened fly wheels and crank pulleys have fantastic effects??

Light weight racing wheels any day!!!

lighter is not always the best actually.

yeah it makes your engine rev faster and get to higher rpm faster which can seem like its faster and got more power and it does, but you also loose torque which is more important then power.

take this for example.

my dad and his mate had minis his mate had a worked cooper s 1300cc full race engine with lightend flywheel blah blah blah, my dads mini was only the 1100 and mildly worked in same car and on uphill climbs my dad would leave him fo dead, yeah on the straighter flatter parts the other would get him but not by much and on a track like mt panarama my dad would win.

i would rather have a little less power and more torque any day of the week.

just some food for though.

SSS_Hoon

[DirtyHarry]

yeah also the tyre of tyre would depend as well right, if i put a tyre that has much better traction than the standard 15's then i should notice a slight increase in fuel consumption as like someone said before, the engine needs to work harder to break the traction i guess, also the width of the tyre will be a bit more, hence more actually traction on the road (footprint).

[SSS_Hoon]

yep and yep, but as already stated it wont or shouldnt be noticable at all, i went from 15" to 17" and my fuel econ is about the same if not better actually.

it wont be that much of a notice, it might be when you first get them i know it was for me, having to learn how to take off again was fun :lol:

SSS_Hoon

[astraman]

If you don't keep the same rolling diameter you will find that a higher rolling diameter will see you using more fuel for city driving as you will be pushing more to get to the same speed but for country driving your revs will drop as your gearing will be higher so less fuel. Don't forget if you change the rolling diameter you will need to recalibrate your speedo.

I went to 18 inch from the 16 inch on my manual astra convertible, tyre and rim combination is within 1% of the original specification.

Factor in that the style of the rim -six spoke and fitted with Hankook silica tyres - i get around 8.5 litres per 100km city driving using BP 95 octane. Using 98 Shell I get around 8.4 litres 100km, if I use 91 octane i get no better than 8.6 but struggling.

I run 38psi in the tyres and a remus muffler.