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      09-07-2008, 01:14 AM   #1
stevensonleehk
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Ride quality and fuel consumption of 16" vs 17"

Dear All,

I'm new to the E90 community and this forum and was just wondering whether any of you have any comments on the ride quality and fuel consumption of 16" vs. 17" rims on our cars ...

I have a E90 323i (which I presume is not available in the US) and it comes with a standard 16" rim which are ... hmmm ...revolting in terms of looks to put it lightly ... I was thinking of upgrading to 17" rims ... either style 158 or 159's ... but am worried about the potential deterioration in ride quality and fuel consumption ... needless to say, I intend to continue using RFTs ...

Would love to have some of your comments.

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      09-07-2008, 01:18 AM   #2
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Quote:
Originally Posted by stevensonleehk View Post
Dear All,

I'm new to the E90 community and this forum and was just wondering whether any of you have any comments on the ride quality and fuel consumption of 16" vs. 17" rims on our cars ...

I have a E90 323i (which I presume is not available in the US) and it comes with a standard 16" rim which are ... hmmm ...revolting in terms of looks to put it lightly ... I was thinking of upgrading to 17" rims ... either style 158 or 159's ... but am worried about the potential deterioration in ride quality and fuel consumption ... needless to say, I intend to continue using RFTs ...

Would love to have some of your comments.

I dont think you will notice to much difference in ride quality between the 16 and 17's. It really depends on the tire and also if you have Run flats now. A 17" non runflat will probably ride the same as a 16" run flat.

As for fuel economy unless you are going wider, or to a really sticky tire there wont be any change. (oh unless the rim and tire total weight is alot more one the 16 vs the 17)
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      09-07-2008, 05:42 AM   #3
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I thought the difference in ride quality between 16s and 17s was noticeable (without a significant improvement in handling) which was one of the reasons I didn't get ZSP. I don't know what your roads are like, but driving around suburban Boston is like driving across the surface of the moon, complete with craters and moon rocks. If your roads are reasonably smooth, the difference probably won't be very great.

Fuel consumption with larger wheels will be worse, particularly around town. Larger wheels (regardless of whether they are heavier or not) require more torque to overcome rotational intertia, which will impact your fuel economy in city driving. I've seen people say that they lost 2 or 3 city mpg by going from 17s to 19s, so I could see losing 1 mpg or so going from 16s to 17s. Highway mpg probably won't be affected much unless you drive like Mario Andretti. In fact, if you do a lot of straight cruising on the highway, you might see better mileage with larger wheels.
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      09-07-2008, 05:48 AM   #4
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Quote:
Originally Posted by Lassaxi View Post
Fuel consumption with larger wheels will be worse, particularly around town. Larger wheels (regardless of whether they are heavier or not) require more torque to overcome rotational intertia, which will impact your fuel economy in city driving. I've seen people say that they lost 2 or 3 city mpg by going from 17s to 19s, so I could see losing 1 mpg or so going from 16s to 17s. Highway mpg probably won't be affected much unless you drive like Mario Andretti.
I think fuel consumption depends on wheel weight, not wheel size. Use some OZ Superleggera wheels and your fuel consumption will decrease.
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      09-07-2008, 05:57 AM   #5
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Originally Posted by cstavaru View Post
I think fuel consumption depends on wheel weight, not wheel size. Use some OZ Superleggera wheels and your fuel consumption will decrease.
You can think whatever you want. Weight obviously hurts, but wheel size matters independent of weight.

And, we haven't even yet mentioned the fact that larger OEM wheels are going to be heavier. The OP is not talking about getting forged racing wheels.
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      09-07-2008, 06:52 AM   #6
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To the OP, I drive a 328 with the sports package and the 17" rft's. For the most part, driving in California is pretty good, well at least where I live so I don't really have an issue with the suspension or the rft's (knock on wood). I've also driven a loaner with the 16" rims non-sport. There is a difference in ride quality, definitely more "cushioned" and handling is not as tight but still good. I assume your car does not have the sports suspension, and going with the 17" rft's I think you'll be fine not unless you're real sensitive as to how the car feels as far as comfort and handling. The difference in feel probably won't be as pronounced because you have the non-sport suspension.

As far as mpg, as long as you're within the same or near overall diameter of your original tires and rims, you should be fine. However like the other 2 mentioned, weight and size does matter in this case. Too heavy and too wide probably will make your mpg go down. Imagine a 25lb dumbbell and 25lb barbell. The 25lb dumbbell would be easier to turn because it's shorter and less rotational torque is required, however the barbell even though it's the same weight will be harder to turn because of the increased diameter. I hope this helps a bit.
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      09-07-2008, 07:58 AM   #7
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I have a 328 with ZSP, 17" wheels and Bridgestone RFT's.

The ride is fine on smooth roads but harsh on rough roads. I have a friend that picked up a 328 with ZSP in Europe and he didn't notice the harshness until he picked up his car in California. Now he hates his RFT's.

So it depends on the roads you drive. If I lived in Germany, I'd keep the RFT's, but since I live in California with lousy roads, I'm going to replace the RFT's with Michelin PS's.
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      09-07-2008, 08:54 AM   #8
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I have a 323i. I got rid of those Style 154 ugly wheels. I found them less disgusting in appearance with time but not enough so to tolerate them any longer.

So I got a set of style 162 18" for summer and last week, thanks to a e90poster here, a used set of a 161 17" for winter.

Let me tell you that I feel that RFT is a killer in terms of smoothness and noise.

I couldn't believe how much better comfort my 18" Yokohama w4s had compared to the 16" Bridgestone EL42 RFT.

Then last week, I installed the Bridgestone Potenza RE050A RFT. Again, it is a shock. A huge step back in term of general comfort.

My suggestion; get regular tires and a kit (compressor & sealant can).


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      09-07-2008, 09:16 AM   #9
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Quote:
Originally Posted by stevensonleehk View Post
Dear All,

I'm new to the E90 community and this forum and was just wondering whether any of you have any comments on the ride quality and fuel consumption of 16" vs. 17" rims on our cars ...

I have a E90 323i (which I presume is not available in the US) and it comes with a standard 16" rim which are ... hmmm ...revolting in terms of looks to put it lightly ... I was thinking of upgrading to 17" rims ... either style 158 or 159's ... but am worried about the potential deterioration in ride quality and fuel consumption ... needless to say, I intend to continue using RFTs ...

Would love to have some of your comments.


I think it makes sense to keep 16s for winter, and with RFT tyres. In winter you don't want to be stuck on the road.

For summer I would get style 161s with regular performance tyres. 17s are best for pushing hard and can be tracked even. the 18s will give you a slightly crashier ride. But then again the 3er is a hard car to begin with. The only reason i didn't get 18s is because our roads are still bit bad and i don't want to track the rim and would rather have a bit more sidewall for protection. Besides, when driving fast, the higher sidewall makes the handling bit more predictable in how the car behaves. on low sidewall you can have tons of grip and SNAP oversteer. i like things smooth.

I actually did exactly that - 16s on winter dunlop m3 RFTs , 17s for summer with michelin ps2s. Style wise I think the 161s look best for 17in - they look bit bigger then they are and spoke thickness is just right.

No change in fuel consumption worth writing home about after switching from 16 to 17. They are similar width really, and its also about the type of tyre you get and the rolling resistance it gives, plus the tyre pressure. Get those things right and fuel consumption won't be issue if you go to bigger size. Michelin makes some very good tyres with low rolling resistance.
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      09-07-2008, 10:28 AM   #10
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Quote:
Originally Posted by Lassaxi View Post
I thought the difference in ride quality between 16s and 17s was noticeable (without a significant improvement in handling) which was one of the reasons I didn't get ZSP. I don't know what your roads are like, but driving around suburban Boston is like driving across the surface of the moon, complete with craters and moon rocks. If your roads are reasonably smooth, the difference probably won't be very great.

Fuel consumption with larger wheels will be worse, particularly around town. Larger wheels (regardless of whether they are heavier or not) require more torque to overcome rotational intertia, which will impact your fuel economy in city driving. I've seen people say that they lost 2 or 3 city mpg by going from 17s to 19s, so I could see losing 1 mpg or so going from 16s to 17s. Highway mpg probably won't be affected much unless you drive like Mario Andretti. In fact, if you do a lot of straight cruising on the highway, you might see better mileage with larger wheels.
You are half right about the rotational inertia, if the over all wheel and tire package weighs less then the original the extra inertia needed to turn the wheel is almost non existent and the op will not notice a calculable difference in fuel mileage. Unless say the overall wheel and tire package was say 5pds or more per corner.

Like you said going from 17's to say 18's or 19's is really where that inertia difference will show in both performance and in Mpg.

The real difference he would see in MPG is if he went to a much sticker/wider tire. The friction coefficient on the road would make for a much bigger drop off in MPG then anything else.
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      09-07-2008, 11:58 AM   #11
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You are half right about the rotational inertia, if the over all wheel and tire package weighs less then the original the extra inertia needed to turn the wheel is almost non existent and the op will not notice a calculable difference in fuel mileage. Unless say the overall wheel and tire package was say 5pds or more per corner.

Like you said going from 17's to say 18's or 19's is really where that inertia difference will show in both performance and in Mpg.

The real difference he would see in MPG is if he went to a much sticker/wider tire. The friction coefficient on the road would make for a much bigger drop off in MPG then anything else.
Actually, I'm completely right

If the overall wheel and tire package weighs less, it still matters where the weight is. If the weight is farther from the center of the axis of rotation, it will take more torque to get it moving. It depends on how much farther you move the weight from the center of the axis of rotation as to how much lighter the wheels would need to be to offset the increase in size.

Going from 16s to 17s, you'd need to shed about 2.5 pounds per wheel in overall wheel + tire weight in order for the rotational inertia to balance back out. Again, since we're talking about OEM wheels, bigger is going to be heavier, not lighter.

All that said, you (and everyone else) are absolutely correct tire width and rolling resistance will make an even bigger difference (did anyone mention that the OEM 17s will be wider than the OEM 16s yet?). But the OP's question was about wheel size, not tires, so that is what I was answering.
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      09-07-2008, 05:47 PM   #12
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Actually, I'm completely right

If the overall wheel and tire package weighs less, it still matters where the weight is. If the weight is farther from the center of the axis of rotation, it will take more torque to get it moving. It depends on how much farther you move the weight from the center of the axis of rotation as to how much lighter the wheels would need to be to offset the increase in size.

Going from 16s to 17s, you'd need to shed about 2.5 pounds per wheel in overall wheel + tire weight in order for the rotational inertia to balance back out. Again, since we're talking about OEM wheels, bigger is going to be heavier, not lighter.

All that said, you (and everyone else) are absolutely correct tire width and rolling resistance will make an even bigger difference (did anyone mention that the OEM 17s will be wider than the OEM 16s yet?). But the OP's question was about wheel size, not tires, so that is what I was answering.
You are 100% about the inertial difference, what I am saying that in most cases (and wheel design is also a factor) the increased weight unless its a fairly large increase will not make any calcuable difference in MPG. Its splitting hairs when you are going from 16's to 17's, I still say the extra width and tire design would make much more of a difference.

I have an actual excel spreadsheet that was built just for this purpose showing everything its on my other PC, I will try and attach it later. I did run it last night and I even put in a heavier wheel and tire combo (3pds) the difference was very minimal because the over all diameter was still the same.

The spreadsheet though you can show the wheel where it is edge weighted (a design that would put more weight out at the edges) and that does make more of a difference.

I think its all speculation though unless we know the exact wheels, their weights as well as the tires and their weights.

You also have to calculate that the tires can weigh less the bigger you go (unless you go much wider). Two tires close to the same width that just goes down and aspect ration from 16 to 17 a lot of times is lighter .

Example:

Michelin Pilot Sport A/S
215/55R16 weighs 25 pounds
225/45R17 weighs 23 pounds.

So basically the 2 pounds you gain at the outer edge from 16 to 17 wheels you lose again with the tire choice.

I know I rambled here but my basic point is we dont have enough info on the wheels and tires to count inertial rotation as a negative to MPG
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      09-07-2008, 06:40 PM   #13
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Quote:
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You are 100% about the inertial difference, what I am saying that in most cases (and wheel design is also a factor) the increased weight unless its a fairly large increase will not make any calcuable difference in MPG. Its splitting hairs when you are going from 16's to 17's, I still say the extra width and tire design would make much more of a difference.

I have an actual excel spreadsheet that was built just for this purpose showing everything its on my other PC, I will try and attach it later. I did run it last night and I even put in a heavier wheel and tire combo (3pds) the difference was very minimal because the over all diameter was still the same.

The spreadsheet though you can show the wheel where it is edge weighted (a design that would put more weight out at the edges) and that does make more of a difference.

I think its all speculation though unless we know the exact wheels, their weights as well as the tires and their weights.

You also have to calculate that the tires can weigh less the bigger you go (unless you go much wider). Two tires close to the same width that just goes down and aspect ration from 16 to 17 a lot of times is lighter .

Example:

Michelin Pilot Sport A/S
215/55R16 weighs 25 pounds
225/45R17 weighs 23 pounds.

So basically the 2 pounds you gain at the outer edge from 16 to 17 wheels you lose again with the tire choice.

I know I rambled here but my basic point is we dont have enough info on the wheels and tires to count inertial rotation as a negative to MPG
I think there's way more agreement than disagreement between us. I'm willing to bet that I have the same spreadsheet you have, and I ran it using measurements for OEM style 156s, 158s and 159s that the OP was referring to. Also ran it using the Bridgestones that are the OEM-issued tires on each of those sets of rims. The results I got showed that the moment of inertia for 17s was greater than for 16s until you used a wheel/tire combo on the 17s that was 2.5 pounds lighter.

I don't know whether differences smaller than 2.5 pounds would affect MPG to any measurable degree, but that's really moot because, as I've said twice now, the OP is talking about getting 158s or 159s, both of which are at least a couple of pounds heavier than any of BMW's 16" wheels. So, whether lighter wheels/tires would balance the equation out doesn't really matter because, if the OP buys 158s or 159s and uses the tires that come with them, he is going to have a set of wheels that are both larger and heavier than what he has now.

But, you're definitely right about 2 things: (1) if you change the tires and make them lighter, you can balance things back out, and (2) width and rolling resistance will make a bigger difference than wheel diameter by itself. But, like I said before, I was answering the OP's question.
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      09-07-2008, 09:50 PM   #14
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You won't loose ride quality, but I'd say you'd gain it. 16" will feel wobbly next to 17" or 18". I don't even think BMW offers 16" in the US on 3 series. You really don't loose any ride quality going 17" up to 18", an very little to 19".
As for gas mileage, normally I'd say who cares, but if you are in HK, gas prices may be much more than here. If that's the case, go with lighter rims and tires. Gas mileage will be affected by outer diameter and weight. Inner diameter is meaningless. Larger diameter = better mileage and slower acceleration. Lighter weight = better for both but usually less strength as long as compare cast to cast or forged to forged. Forged = less weight and more strength, but more money.

You just need to find a balance that's right for you in cost, looks, etc. Regardless, a couple pounds either way would be hard to detect in a mpg change. Usually, if you spend more to get lighter, you spend more on the lighter than you save on the MPG for the life of the car.
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      09-07-2008, 10:54 PM   #15
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Quote:
Originally Posted by Lassaxi View Post
I think there's way more agreement than disagreement between us. I'm willing to bet that I have the same spreadsheet you have, and I ran it using measurements for OEM style 156s, 158s and 159s that the OP was referring to. Also ran it using the Bridgestones that are the OEM-issued tires on each of those sets of rims. The results I got showed that the moment of inertia for 17s was greater than for 16s until you used a wheel/tire combo on the 17s that was 2.5 pounds lighter.

I don't know whether differences smaller than 2.5 pounds would affect MPG to any measurable degree, but that's really moot because, as I've said twice now, the OP is talking about getting 158s or 159s, both of which are at least a couple of pounds heavier than any of BMW's 16" wheels. So, whether lighter wheels/tires would balance the equation out doesn't really matter because, if the OP buys 158s or 159s and uses the tires that come with them, he is going to have a set of wheels that are both larger and heavier than what he has now.

But, you're definitely right about 2 things: (1) if you change the tires and make them lighter, you can balance things back out, and (2) width and rolling resistance will make a bigger difference than wheel diameter by itself. But, like I said before, I was answering the OP's question.
I agree, and I think you read the OP's post more throughly then I did since I completely missed the 158/159 part (have to stop reading during football lol).
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