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Old 16th July 2010, 15:48   #1
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Question Difference in Mileage with OEM Rims and After putting on Alloys

Considering the fuel prices touching skies..How many people found a difference in fuel average after putting on alloy wheels. Did it increase or did it decrease and in both cases by what margin ???


Mods: Starting this new thread as I did not find any particular thread..
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Old 16th July 2010, 16:23   #2
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hi, I drive a zen
original size: 145/80/12
Upgraded Size: 155/70/12

No difference. Its a misconception that adding alloys decreases fe.
But yes adding upsized alloys WITH broad tires definitely does decreases the fe.

Last edited by nick17s : 16th July 2010 at 16:24.
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Old 16th July 2010, 16:56   #3
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In case you are just changing the OEM still rims with alloy wheels of some good brand without opting for wider tyres, there will be slight increase in the FE. The logic behind the same is that ally wheels are lighter compared to the steel wheels which results in a lower unsprung weight.
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Old 16th July 2010, 17:33   #4
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To be honest, there is little or no difference at all. Most of it is a misconception and alloys are not that light, that they would have an impact on FE.

Some say they felt the handling get much better, as they felt less airlfow resistance, blah blah. I was quite surprised they could even feel any of that

Even if it does have an effect, the FE gain would probably be just 1%. Unless the weight of your alloys are significantly lesser than the steel rims. Then because of reduced weight, one might obviously get slight benefit
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Old 16th July 2010, 18:26   #5
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The difference is negligible if you are going for a sane upsize. If you prepare a monster truck, there will be a difference. If someone is a mileage watcher, he could alter his driving style to cover the deficit.
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Old 16th July 2010, 18:36   #6
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Does it increase FE? Yes.
Will you notice it? No. Its negligible.
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Old 16th July 2010, 19:15   #7
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I've seen any people upgrading from 145/80/12 to 165/65/13 and still say that the fuel average has not been affected? How can this be possible, you are adding an inch to rim size and broader tyres. Anyone upgraded from the said tyre size??? Please let us know your experience...
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Old 16th July 2010, 19:17   #8
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^^ Lower weight of the alloys and more mm per rotation of the tyres can give a deceptive FE reading, not to mention the ODO reading.
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Old 16th July 2010, 19:38   #9
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Just changing from steel rims to alloys (without changing tyres) would have an FE increase, but too negligible to notice. I did this on my car and could not see any perceptible difference in FE.
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Old 16th July 2010, 20:05   #10
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Few forget to calibrate the odometer after upgrading the tyres.
This has impact on the accuracy of mileage.
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Old 16th July 2010, 20:14   #11
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Quote:
Originally Posted by 911turbo View Post
I've seen any people upgrading from 145/80/12 to 165/65/13 and still say that the fuel average has not been affected? How can this be possible, you are adding an inch to rim size and broader tyres. Anyone upgraded from the said tyre size??? Please let us know your experience...
I have upgraded from 165/65/13 to 205/50/R15 and there was a definite drop in FE. Fuel average definitely is affected , but then it depends on your driving styles too.
I have pulled out the best mileage from car also running the 205/50/R15 size. So it all depends on how easy you go with the pedal and the usage of gears.

Right now with my scorp' I had changed from 235/70/R16 to 255/65/r16 and have hardly seen any difference in the FE. It has remained the same though the last two times I calculated.
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Old 16th July 2010, 20:24   #12
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Quote:
Originally Posted by rjstyles69 View Post
I have upgraded from 165/65/13 to 205/50/R15 and there was a definite drop in FE. Fuel average definitely is affected , but then it depends on your driving styles too.
I have pulled out the best mileage from car also running the 205/50/R15 size. So it all depends on how easy you go with the pedal and the usage of gears.

Right now with my scorp' I had changed from 235/70/R16 to 255/65/r16 and have hardly seen any difference in the FE. It has remained the same though the last two times I calculated.

Wow...Thats one upgrade.., what car is it ??? But, by upsizing that much it will definitely eat up your suspension, no offence here.. The upgrade has resulted in approx 7% difference in overall diameter, maximum upgrade should be limited to 3% of the actual tyre size, otherwise be ready for suspension, axle related problems and this can also cause a brake failure.
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Old 16th July 2010, 20:25   #13
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Quote:
iamswift
Few forget to calibrate the odometer after upgrading the tyres.
This has impact on the accuracy of mileage.
If we do not calibrate the Odo:

The Odo thinks that travelled distance in one rotation is:

Mileage=2x (22/7) x r

whereas the actual would be:

Actual Mileage=2 x (22/7) x R

where R > r
and in case of 13" to 14", then, R=1.077 x r

hence Actual Mileage = Odo reading x 1.077 !!

That means, if the odo is not calibrated it will show a lesser Mileage hence lesser FE !!
(In the above case, by a factor of 1.077)



But again,

for the root question,
FE up/down?

Actual energy required to run the 2 x (22/7) x R --Vs-- 2 x (22/7) x r
calculated over a common multiplier ( I think its called LCM !!) is to be debated/calculated!

But I am sure..
The energy spent on calculating will be surely be more than the actual difference (either way!) !!
:

Care

Ace.

Last edited by driverace : 16th July 2010 at 20:29.
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Old 16th July 2010, 20:31   #14
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Nicely explained.. But any ideas how can we caliberate the speedo and odo in respect to upgrade? Is that possible?
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Old 16th July 2010, 20:35   #15
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Quote:
Originally Posted by iamswift View Post
Few forget to calibrate the odometer after upgrading the tyres.
This has impact on the accuracy of mileage.

Any idea how to calibrate the digital odometer?
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