Increase Wheel Size = Increase Petrol Consumption

[ChigerG]

Hey guys, i'm sure plenty of uz have upgraded from the stock rims of ur car to an increased size, but has anyone also noticed an increase in fuel consumption. my jazz from 15s to 16s now consumes an extra 0.7L/100km. doesn't seem like much but overall counts for approx 60kms less per full tank.

is it the extra traction from an increase in tyre width that requires the car to work harder than before? (previously 185 now 205) therefore an extra 80mm of rubber (20 x 4). or even the increase in wheel/tyre circumference = more travel per cycle?

share your experiences

Cheers

Rob

[94dc2tegz]

well ur only 1in increase. I'm sitting on 17's from 15's!

can't wait till i go back and feel the difference. handling is terrible.

[string]

well ur only 1in increase. I'm sitting on 17's from 15's!

can't wait till i go back and feel the difference. handling is terrible.

What sort of tyres did you have before/after?

[nd55]

In the states they re-formulate the fuel a bit for winter/summer conditions.
I don't think we get the differences to justify that, but it's another variable.

Nick.

[aaronng]

Not only more drag, but because the rims are heavier, you use more fuel when taking off from a stop (but same amount of fuel when cruising).

[SeverAMV]

try playing around with tyre pressures, you might be able to get that extra 0.7L back.

[ChigerG]

try playing around with tyre pressures, you might be able to get that extra 0.7L back.

are you suggesting higher tyre pressure than standard? anyone ever tried such a thing? just concerned about stiffer ride and loss of tyre traction/contact with the road.

[SeverAMV]

im not suggesting a higher tyre pressure than what your tyres can handle, im suggesting a little higher than what you're running now. say if you're running 30psi, i'd try to push it up to 36, 38, or even 40 if your tyre can handle it just to see if theres any notable change in fuel consumption without too much loss of contact patch. altho you wont lose too much contact patch anyway unless you bump it up to like 70psi.

[ChigerG]

ohh ok then, i'll see how it goes. 70 psi, lol sounds scary. once had a friend who over inflated his bicycle tyre, the pain he suffered from the explosion was not cool.

[Shraka]

im not suggesting a higher tyre pressure than what your tyres can handle, im suggesting a little higher than what you're running now. say if you're running 30psi, i'd try to push it up to 36, 38, or even 40 if your tyre can handle it just to see if theres any notable change in fuel consumption without too much loss of contact patch. altho you wont lose too much contact patch anyway unless you bump it up to like 70psi.

If you're gonna do this why not just go back to thinner tyres?

You'll wear the tyre out all unevenly too.

[SeverAMV]

that depends on how much you inflate it. unless you pump it to an extent where your tirys are just round and bulbous, it shouldnt cause excessive camber wear. heck, you're gonna get camber wear anyway, and dropping the tire pressure wont reduce that, it will just balance out the wear.

look at your tires when you pump it up, the shape doesnt change enough to cause much of a loss in grip, but its enough to reduce resistance enough to save some fuel, so long as you dont exceed the maximum tyre pressure of your tyre.

with my ed6 i managed to get fuel consumption down from 8L to 7.2L by increasing my tyre pressure from 32 to 40. not much loss in grip (not enough to cause you to slide), no visible loss in contact patch, just a fuel saving to be made.

[Shraka]

that depends on how much you inflate it. unless you pump it to an extent where your tirys are just round and bulbous, it shouldnt cause excessive camber wear. heck, you're gonna get camber wear anyway, and dropping the tire pressure wont reduce that, it will just balance out the wear.

look at your tires when you pump it up, the shape doesnt change enough to cause much of a loss in grip, but its enough to reduce resistance enough to save some fuel, so long as you dont exceed the maximum tyre pressure of your tyre.

with my ed6 i managed to get fuel consumption down from 8L to 7.2L by increasing my tyre pressure from 32 to 40. not much loss in grip (not enough to cause you to slide), no visible loss in contact patch, just a fuel saving to be made.

Yeah at 40psi you're not likely to wear your tyre out badly. But you will find the middle wears faster than the sides.

There's sweet spot for traction, and if you go above or below that the tyre will not grip as well. Not enough to slide around as you say, but a slight difference can be annoying.

Personally, if you really want your economy back, go back to your old smaller tyres. Your bigger rims may well have made the handling of the car worse too.

[JohnL]

Yeah at 40psi you're not likely to wear your tyre out badly. But you will find the middle wears faster than the sides.

Not necessarily. My tyres are 195/60/15 (stock CB7 Accord size), the fronts are at 38psi, the rears at 45psi (rear tyres have hopelessly soft sidewalls and need the higher psi). Wear is nice and even across the tread obn all four tyres, except the fronts have a little more wear near the inner shoulders, which I think is due to the inside front tyre running more on it's inner edge when cornering (static neg camber + some body roll causing this).


There's sweet spot for traction, and if you go above or below that the tyre will not grip as well. Not enough to slide around as you say, but a slight difference can be annoying.

Agreed. The ideal pressure will vary substantially from tyre to tyre, you have to experiment a lot to find what works for you, with your car, and the particular tyres you have. There will be a sweet spot for traction, and a sweet spot for steering and handling responsiveness. These sweet spots may or may not co-incide at the same psi.

Some people will want max traction, some max response, I'd suggest a compromise between the two, but you need to play with the pressures a lot to find what youi like the most. Some people will want max comfort, in which case they'll have to put up with probably a bit less traction, and definitely a lot less response.


Personally, if you really want your economy back, go back to your old smaller tyres. Your bigger rims may well have made the handling of the car worse too.

If the rims are too big with tyres of a ridiculously low profile then most probably the handling and grip will be worse than it otherwise would be on real roads.

[beeza]

Interesting thread,can't wait to get on the 15's light rims from these big heavy 17's.UGGGHHHHH!

[ChigerG]

i've tried changing fuels and so forth, but thats another thread for another day. i'm trialling different fuels for different results. E10 so far is surprisingly good. keep u posted, but in another thread. in terms of going from 15s to 16s the handling is better, ever so slightly heavier, but still light compared to other vehicles. the jazzes steering wheel can be flung like anything. corners can also be spiritedly driven more confidently with the extra tyre width.

[zco]

things to consider

the weight of your new wheels + tyres
rolling diametre might be wrong and you're probably travelling further than what the odo states..
are the tyre presssures the same as your old ones

[MM89]

well when you're going from stockies to lightweight rims, rims would end up being lighter even if you go up a size anyway wouldnt they? that was the case with my situation. 175/65/14 to 205/50/15, stockies to CE28N replicas..the latter was definitely lighter.

[SeverAMV]

well when you're going from stockies to lightweight rims, rims would end up being lighter even if you go up a size anyway wouldnt they? that was the case with my situation. 175/65/14 to 205/50/15, stockies to CE28N replicas..the latter was definitely lighter.

CE28N = 2.8kg per rim, replicas arent much heavier.