Audi A3 E-tron Forum

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 Post subject: Re: A3 vs Custom Rim upgrade
PostPosted: Thu Mar 09, 2017 9:34 am 
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quasitime wrote:
Not sure if this has been discussed before. But has anyone who has switched out wheels noticed a drop in fuel efficiency? I always assumed the stock rims were the way they were because of wind efficiency reasons.
That is possible, I suppose. I only had the stock rims for a couple of weeks, so I can't really be sure whether there was any difference or not. I'm going to guess not since my economy is consistent with that of other etron owners I've seen. I was far more worried about weight of the wheels compared to stock than I was about aero efficiency.

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- Arne
'16 e-tron Premium w/Nav, Scuba Blue, R8-style wheels
'84 911 Carrera Coupe


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 Post subject: Re: A3 vs Custom Rim upgrade
PostPosted: Fri Mar 31, 2017 1:48 pm 
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I've sold Audis for about 2 years now at a dealership and also a proud owner of a white 2016 Audi A3 e-tron. From my experience, there seems to be an average of 2MPG drop with every inch of wheel diameter increase. 16in wheels I've seen avg MPG of around 39-40 (without charging, only hybrid mode). My e-tron came with 17in wheels, I get an average of 36-37MPG (without charging, only hybrid mode). One of my co-worker, he installed a set of 19s from a S3 and clocked around 33-34MPG avg only in hybrid mode. Since 16in wheels get the best MPG, that's why Audi's e-tron ULTRA only comes with 16in wheels.


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 Post subject: Re: A3 vs Custom Rim upgrade
PostPosted: Fri Mar 31, 2017 6:35 pm 
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@tchu619 - How does the car know that you have installed 16's, 17's, or 19's?

I ask because I have the 16 inch wheels and my speedometer always reads higher than reality (i.e., an indicated 57 mph is actually 55).

I think that might be due to the speedometer not knowing the size of the installed tires and assuming the counted number of revolutions is for a different size wheel (poss. 17's). That would account for an error of that magnitude. It would also explain "reduced" gas mileage when you look at different wheel sizes.

Another way to think of it is smaller wheels turn over more revolutions to cover a given distance when compared to a larger wheel. That means smaller wheels produce a higher indicated speed as well as more miles covered, meaning an increase in MPG.


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 Post subject: Re: A3 vs Custom Rim upgrade
PostPosted: Wed Apr 05, 2017 1:43 pm 
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Joined: Sat Oct 01, 2016 8:13 pm
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When it comes to efficiency with wheels & tires setup, rolling mass is always key. Small wheels with more tires weigh less than bigger wheels with less tires (metal vs rubber, which is heavier right?). Less rotation mass (wheel & tire combined) requires less energy (fuel & electricity) to get it rolling and keeping it at speed. The car have no idea what size wheels you are using. It will accelerate the same regardless, but think of it as if you are lugging some extra weigh around when you upgrade to a bigger wheel setup, therefore lowering your overall MPG.


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 Post subject: Re: A3 vs Custom Rim upgrade
PostPosted: Wed Apr 05, 2017 2:12 pm 
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tchu619 wrote:
I've sold Audis for about 2 years now at a dealership and also a proud owner of a white 2016 Audi A3 e-tron. From my experience, there seems to be an average of 2MPG drop with every inch of wheel diameter increase. 16in wheels I've seen avg MPG of around 39-40 (without charging, only hybrid mode). My e-tron came with 17in wheels, I get an average of 36-37MPG (without charging, only hybrid mode). One of my co-worker, he installed a set of 19s from a S3 and clocked around 33-34MPG avg only in hybrid mode. Since 16in wheels get the best MPG, that's why Audi's e-tron ULTRA only comes with 16in wheels.


This is really helpful information.

Do you guys think the spoke design has any effect on mpg efficiency? I have no idea of how the physics of a spinning wheel's spoke's affect wind resistance, but it's interesting to think about.


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 Post subject: Re: A3 vs Custom Rim upgrade
PostPosted: Thu Apr 20, 2017 9:54 am 
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tchu619 wrote:
I've sold Audis for about 2 years now at a dealership and also a proud owner of a white 2016 Audi A3 e-tron. From my experience, there seems to be an average of 2MPG drop with every inch of wheel diameter increase. 16in wheels I've seen avg MPG of around 39-40 (without charging, only hybrid mode). My e-tron came with 17in wheels, I get an average of 36-37MPG (without charging, only hybrid mode). One of my co-worker, he installed a set of 19s from a S3 and clocked around 33-34MPG avg only in hybrid mode. Since 16in wheels get the best MPG, that's why Audi's e-tron ULTRA only comes with 16in wheels.


Unless you're also changing the tire size to something low profile for that rim size, you won't really affect anything. A 16" wheel should be fitted with tires that make it the same size as a 18" wheel with low profile tires....


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 Post subject: Re: A3 vs Custom Rim upgrade
PostPosted: Wed Apr 26, 2017 4:21 pm 
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Joined: Tue Mar 14, 2017 2:46 pm
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srwhitney wrote:
Unless you're also changing the tire size to something low profile for that rim size, you won't really affect anything. A 16" wheel should be fitted with tires that make it the same size as a 18" wheel with low profile tires....


^-This.

Unsprung weight (wheel + tire) is the only thing that could potentially cause a measurable change in MPG in a passenger car assuming tire diameter is the same or negligible. Aero on the wheels? In theory it might make a hundredth of a second difference in an Indy car race. Your etron on a daily commute? Nah.

If MPG changes are observed moving up wheel size it is because unsprung weight went up as well. Audi OEM wheels are manufactured by Ronal Wheels using casting. A larger cast wheel (the cheapest option) is going to weigh more than stock and decrease MPG. A larger, lighter wheel that has been flow formed, pressure cast, or forged (more expensive) is going to weigh less and increase MPG.


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 Post subject: Re: A3 vs Custom Rim upgrade
PostPosted: Tue May 09, 2017 1:43 am 
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Here is a setup with S3 OEM wheels. 19 inches with 235/35/19.

I haven't noticed a drop in mpg, but if it did it's very negligible. I weighted the two wheels and it's pretty much the same weight.

My original A3 etron wheels, as I recall, weight about 48 lbs with tires about the same as the S3 wheels.

Image


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 Post subject: Re: A3 vs Custom Rim upgrade
PostPosted: Tue May 09, 2017 11:26 pm 
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Those S3 wheels look awesome! Any side on shots? What tyres did you put on them?


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 Post subject: Re: A3 vs Custom Rim upgrade
PostPosted: Thu May 11, 2017 3:50 pm 
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Joined: Tue Dec 06, 2016 6:28 pm
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totalfixation wrote:
Here is a setup with S3 OEM wheels. 19 inches with 235/35/19.

I haven't noticed a drop in mpg, but if it did it's very negligible. I weighted the two wheels and it's pretty much the same weight.

My original A3 etron wheels, as I recall, weight about 48 lbs with tires about the same as the S3 wheels.

Image


I was thinking about buying these same wheels, but concerned about the ride height with 19" wheels. Do you have a side picture? Or do you think the car should be lowered?


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