Power loss from wheels

Another way to lighten up and regain that «lost» acceleration is to switch your current tires. As said above, the weight of tires varies a lot from one model/brand to another -- just check tirerack.com to see what I'm talking about. Also, there's a pretty big variance depending on the width and profile. Plus, since the tires are on the outside of the wheel, there's more weight to be put in motion, affecting acceleration too. What you could do would be to change your tires for a lighter model or something a bit narrower. An added plus would be no rubbing. You can also go for a lighter set of wheels and use spacers to get that stance.

GL anyway !

Cool33

I never felt any change from my stock 18's to my 710 19's. Ride quality didn't really change nor does going/stopping. My fuel economy is still awesome as I get 32-36MPG running in the country canyon roads and 24-29MPG the rest of the time in 30 highway/30 city/40 country. Could there be a coincidental problem happening at the same time?

Hey guys,

Were you running 17" before? Our 18" 710's are just about 23~24 lbs, around the same, or a bit less than the weight of the 18" BBS CH, depending on the finish.

Imagine holding a 10lb weight with your arms fully extended, as opposed to holding it close to your chest. Even though the mass is the same, it takes a lot more energy depending on the positioning. It's the same idea with bigger wheels, the actual weight could be the same as a smaller wheel, but if there's more of it on the outside, it would take more energy to get the wheel turning.

Tires would also have quite an impact. Lower profile tires are concentrated along the outer edge of the rotating mass, further contributing to the lack of throttle response you're feeling. Then factor in the weight difference of different tire manufactuers, mkodama mentioned a difference in 3lbs between 2 tires of the same sizes, that's an additional 3lbs added in the worst place possible, just from the tire model.

This is one of those things that nobody can avoid, can't really fight physics

-Steve@VMR

Originally Posted by rovert

I never felt any change from my stock 18's to my 710 19's. Ride quality didn't really change nor does going/stopping. My fuel economy is still awesome as I get 32-36MPG running in the country canyon roads and 24-29MPG the rest of the time in 30 highway/30 city/40 country. Could there be a coincidental problem happening at the same time?

The adverse affects on acceleration/braking does not vary by engine type. It affects an M3 the same way it affects a 318. But because an M3 has so much more power available, the effects are less noticable, i.e. the change is a smaller percentage of the car's performance.

Changes in fuel economy are tougher to nail down because of different driving styles. You'll see lower MPGs during acceleration, but only marginal changes during cruising. During coasting, you might actually see a slight increase in MPG. So when you look at your average, well let's just says "results may vary".

Yeah I understand physics and I won't in no way argue that...haha...I guess having a 330 helps a bit in masking the effect of upsizing/weighting. My friend with a 330 had the stock 17" M68's and changed to 19" ACS with very little difference to him as well and he's a very good driver at knowing how to balance his car on it's toes.

dude you have to go with 17lbs or so on rims, tires around 25lbs, then you'll be fast and stop on a dime, there are both 17" and 18" with or very close to that weight just do your homework, forget the looks thats second or third mine are 17x9 at 17.4lbs had style 119 17x8 at 23lbs

Originally Posted by dkirby147

The adverse affects on acceleration/braking does not vary by engine type. It affects an M3 the same way it affects a 318. But because an M3 has so much more power available, the effects are less noticable, i.e. the change is a smaller percentage of the car's performance.

Changes in fuel economy are tougher to nail down because of different driving styles. You'll see lower MPGs during acceleration, but only marginal changes during cruising. During coasting, you might actually see a slight increase in MPG. So when you look at your average, well let's just says "results may vary".

I'm not really getting your point.
Let's think about wheel(metal part) and tires(rubber part).
So when you're going a next size wheel, you should go next lower size tire(Aspect Ratio or height)?! Right?
So your wheel+tire diameter is staying the same, so your speed indication didn't change or in other words you don't need update your speed reading ratio(conversion). BTW the speed of rotation would be same at any point of the wheel/tire.
So you're believing , that is bigger wheel will move mass rotation. I don't see how. The change(+_ 3-4 lb) would not significant, to compare to mass of the vehicle itself. Even more, the mass should almost compensating, by less rubber would use with bigger wheels.

Originally Posted by BMWespresso

dude you have to go with 17lbs or so on rims, tires around 25lbs, then you'll be fast and stop on a dime, there are both 17" and 18" with or very close to that weight just do your homework, forget the looks thats second or third mine are 17x9 at 17.4lbs had style 119 17x8 at 23lbs

more info on your setup. that sounds

this is exactly the reason I traded out my 19s for my 18" OZs

I my 18"s

Originally Posted by phlfly

I'm not really getting your point.
Let's think about wheel(metal part) and tires(rubber part).
So when you're going a next size wheel, you should go next lower size tire(Aspect Ratio or height)?! Right?
So your wheel+tire diameter is staying the same, so your speed indication didn't change or in other words you don't need update your speed reading ratio(conversion). BTW the speed of rotation would be same at any point of the wheel/tire.
So you're believing , that is bigger wheel will move mass rotation. I don't see how. The change(+_ 3-4 lb) would not significant, to compare to mass of the vehicle itself. Even more, the mass should almost compensating, by less rubber would use with bigger wheels.

He is jsut saying, when buying bigger wheels, if you buy lighter tires, with a slightly smaller diameter instead, the change won't be as drastic.

Yeah i noticed a power loss when i went with my 19" Beyern Mesh Staggered setup. Doesnt really bother me much b/c the loss wasnt too bad or wasnt HUGE. Not enough to piss me off anyhow but what DOES bother me and sucks A LOT actually is that Gas Mileage went down SO much and sucks so much harder than before! oh well its the price you pay for the looks i guess

Yea can't fight physics. And yes I used to have 17s on. I love the wheels though. Just going to get headers or something

Originally Posted by phlfly

I'm not really getting your point.
Let's think about wheel(metal part) and tires(rubber part).
So when you're going a next size wheel, you should go next lower size tire(Aspect Ratio or height)?! Right?
So your wheel+tire diameter is staying the same, so your speed indication didn't change or in other words you don't need update your speed reading ratio(conversion).

This is all correct. As a general rule, you should size your wheels and tires such that the tires' outer diameter is as close to OE as possible.

Originally Posted by phlfly

BTW the speed of rotation would be same at any point of the wheel/tire.

Yes and no. The angular speed is the same at any point of the wheel/tire, but the linear speed is not. Regardless, my previous posts address how increased mass moment of inertia affects acceleration and braking... not steady speed.

Originally Posted by phlfly

So you're believing , that is bigger wheel will move mass rotation. I don't see how. The change(+_ 3-4 lb) would not significant, to compare to mass of the vehicle itself. Even more, the mass should almost compensating, by less rubber would use with bigger wheels.

If you keep the same tire OD and width then you are correct that the mass moment of inertia of the tires would decrease, but not enough to compensate for the increase in mass moment of a heavier (or even equally heavy, but larger diameter) wheel. As far as it's significance to the bigger picture, that depends on several other factors. A lighter car, a less powerful engine, a lower drag coefficient, or less rolling friction would all increase the percentage change in acceleration/braking due to a change in mass moment of inertia. As I said before, the effects would be more noticable on a 318 over an M3. Ultimately, it's up to the driver, if he/she notices or cares about any performance degradation. What's insignifcant to you, might be significant to someone else.

For the record, I can't wait to retire my 17" M68s for 18" TR Motorsports MT1s. Just waiting for the funds.

Originally Posted by E46Kris

more info on your setup. that sounds

This are 17.4lbs APEX ARC-8 17x9 $259 each, they are also working on 18" sizes, light as well remember around 18lbs, I'm runing 245-40-17 all four corners
Read a bit, they are awesome

here are pics from n2Bimmer
http://forum.e46fanatics.com/showthr...light=apex+arc
and drivrswntd
http://forum.e46fanatics.com/showthr...light=apex+arc

http://forums.bimmerforums.com/forum....php?t=1225763
http://apexwheels.blogspot.com/

Originally Posted by 5MT_E46

I guess we are in the same boat. Got my V710 in 18 for a month.
Gas miles from 25-28avg down to 22-23 avg. Wont go over 26mpg on road tirp that I always avg 28-29mpg. Car feels powerless, brake seems doesnt stop the car at all, where with my old stock 17 my brake can grip and stop on dime.

It does look make my car look alot better.

While there's no doubt that adding a few pounds to taller wheels will make some difference (though I wonder how many of us could pick it out in a blind A/B driving test?)... there's no way that you're going to drop that much fuel economy just because of heavier tires/wheels, particularly on the highway. There, once you get the heavier wheels/tires up to speed, there's no additional penalty (minus a very, very insignificant penalty for curves). If the tires are a LOT wider than the originals, you may be pushing more air... but the weight can't possibly be causing that kind of change in gas mileage. I'd look for some other factor that is killing your mileage.

Maybe you just drive faster now that your car is sexier?

Originally Posted by habbyguy

Maybe you just drive faster now that your car is sexier?

Nope, you drive slower so everyone gets a longer look.

would the size + weight of the rims affect Dyno results?? I'm getting a dyno tonight and I know my rims + tires are super heavy and 19", so on the street I do feel a big loss in acceleration, but I still want accurate dyno results.

what do you guys think?

Originally Posted by ChrisTKHarris

Or just get lightweight wheels.

What rims are these and what is there weight? They look sharp (I am a fan of the lip )

Originally Posted by BMWespresso

This are 17.4lbs APEX ARC-8 17x9 $259 each, they are also working on 18" sizes, light as well remember around 18lbs, I'm runing 245-40-17 all four corners
Read a bit, they are awesome

here are pics from n2Bimmer
http://forum.e46fanatics.com/showthr...light=apex+arc
and drivrswntd
http://forum.e46fanatics.com/showthr...light=apex+arc

http://forums.bimmerforums.com/forum....php?t=1225763
http://apexwheels.blogspot.com/

thanks for the information, they look fantastic.

OK, so how many "HP" are we talking around here? I had intake, header, and thn I upgrade for CSL reps, does that mine that my car is as fast as before the mods with 17s?. If yes, then when a noob asks, "what can I do to make my car go faster?" the first answer should be "Lighter wheels!". Because to be hones, 5 to 10 hp is not noticeable except on dyno or track, so If you guys are "feeling" it that means it must be good at least 15 hp.