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3rd January 2019, 17:39
#1
Regular Member
Which wheel Size for Best Economy?
Hi Which is better for fuel economy,16 inch or 17 inch alloys?
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3rd January 2019, 17:44
#2
16, as they'll be narrower and have less rolling resistance.
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3rd January 2019, 22:54
#3
Originally Posted by
LastOne
16, as they'll be narrower and have less rolling resistance.
wheel diameter wouldn't have any influence on tyre width.
there are a number of factors that would effect the economy. rolling radius would probably be the biggest, and the rolling resistance, as said, so you'd need to be more specific as to tyre size, rather than wheel diameter.
because........SIGNUM!
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4th January 2019, 08:08
#4
Originally Posted by
bonehead
wheel diameter wouldn't have any influence on tyre width.
there are a number of factors that would effect the economy. rolling radius would probably be the biggest, and the rolling resistance, as said, so you'd need to be more specific as to tyre size, rather than wheel diameter.
Rolling resistance is friction (in simple terms), brakes use friction to stop you. A narrow, hard tyre will have less rolling resistance than a soft, sticky wide tyre.
Think bicycle tyre. 26 inch diameter 1.6 inches wide pumped up to 60psi will have less resistance than a 16 inch 255/40 tyre.
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4th January 2019, 20:12
#5
Originally Posted by
fatfred
Rolling resistance is friction (in simple terms), brakes use friction to stop you. A narrow, hard tyre will have less rolling resistance than a soft, sticky wide tyre.
Think bicycle tyre. 26 inch diameter 1.6 inches wide pumped up to 60psi will have less resistance than a 16 inch 255/40 tyre.
Rolling radius is basically the circumference of the wheel with tyre fitted and inflated, commonly used in motorsport rather than aspect ratio. A lot of competition tyres look odd when you look at the tyre size as they have the diameter as part of he size rather than the profile in order to work out the rolling radius, so instead of 225/45x17 you would have 225/635x17 with 635 being the total diameter in millimetres, from this you can work out how far the wheel will roll per rotation using Pi and work out your top speed at max revs in each gear (theoretically).
Obviously the total diameter will also have an effect on economy with a longer roll per rev using less fuel, but you would also use more fuel to get up to speed as the relative gearing will be higher so it's a bit of a double edged sword.
The difference between for instance 205/55x16 which has a total diameter of 632mm and a circumference (rolling radius) of 1985mm and 235/40x18 has a total diameter of 645mm and circumference of 2027mm so will roll 42mm further per rev. This is wheel speed of course, you would need to calculate in the gear and final drive ratio to relate it to road speed, but bigger diameter overall will result in less engine revs for the same speed therefore better economy at that speed.
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4th January 2019, 23:52
#6
Originally Posted by
Steel
The difference between for instance 205/55x16 which has a total diameter of 632mm and a circumference (rolling radius) of 1985mm and 235/40x18 has a total diameter of 645mm and circumference of 2027mm so will roll 42mm further per rev. This is wheel speed of course, you would need to calculate in the gear and final drive ratio to relate it to road speed, but bigger diameter overall will result in less engine revs for the same speed therefore better economy at that speed.
Agreed but also take on board that a wider tyre had more rolling resistance.
As an ex mountain biker turned road cyclist you wouldn't believe the difference an extra inch makes!
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4th January 2019, 23:53
#7
Originally Posted by
fatfred
Agreed but also take on board that a wider tyre had more rolling resistance.
As an ex mountain biker turned road cyclist you wouldn't believe the difference an extra inch makes!
Vectra VXR estate 2007 Sapphire Black
Teapot Tuned 255/300
Eibachs B8's, fully loaded factory options
Tech2 & MDI diagnostics + SPS
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5th January 2019, 07:54
#8
Regular Member
Originally Posted by
fatfred
Agreed but also take on board that a wider tyre had more rolling resistance.
As an ex mountain biker turned road cyclist you wouldn't believe the difference an extra inch makes!
Oh you are awful but i like you
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21st January 2019, 20:24
#9
Regular Member
just read these threads and i suppose theres pro's and con's to the size of tyres with regards to resistence on the road but i wonder in the real world would it make that much of a noticeable difference with the mpg
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21st January 2019, 20:49
#10
Originally Posted by
got3dogs
just read these threads and i suppose theres pro's and con's to the size of tyres with regards to resistence on the road but i wonder in the real world would it make that much of a noticeable difference with the mpg
Exactly, besides which the circumference is all going to be around the same. Theres only 2 size settings available but i dont know what the actual figures are for them but so many wheel tyre choices but only 2 selectable for the speedo to read.
Vectra VXR estate 2007 Sapphire Black
Teapot Tuned 255/300
Eibachs B8's, fully loaded factory options
Tech2 & MDI diagnostics + SPS
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