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Power loss from wheels

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power wheels
15K views 83 replies 37 participants last post by  nightrunner20 
#1 ·
After I installed my 18 inch v710s. I noticed a huge power loss. Anyone else have something similar?

It looks good. But it sux...

Was already slow enough before that haha
 
#12 ·
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. :banghead:

It does look make my car look alot better.
 
#27 ·
It varies so much between brands and models, and usually the difference is pretty big too. Like, the 225/45-17 General UHP's my car came with are around 21lbs each while my 235/40-18 Michelin Pilot Sports are a full 3 lbs heavier in terms of listed weights. Weights of the wheels on the scales seem to agree with this. So even though I got lighter forged wheels that were an inch bigger in dimeter, I lost almost all of the weight advantage with the new tires. :rofl:
 
#35 ·
I have, for American purposes, a small engine in my 323ci, and am rolling on 19"s, but I have no complaints, can still easily reach 200km/hr, and am faster off the line than most...if I wanted serious hp numbers, I'd have gone with an M3.
 
#36 ·
WARNING!!! GEEK SPEAK BELOW! MAY NOT BE SUITABLE FOR THE SIMPLE MINDED!


When determining the effects of wheels on your car's acceleration, you cannot look at weight alone. The more important factor if the "mass moment of inertia" of the wheel/tire setup. By going with larger wheels, you are moving some mass farther away from the point of rotation. Think of an ice skater doing that spin move (whatever it's called, I'm not ghey). As they bring their arms in toward thier body, the speed up because their mass moment of inertia decreases. Larger wheels have the effect of the skater extending their arms out, thereby slowing down their rotation.

If the difference was proportional to the diameter, then you wouldn't see a difference in rolling speed because the larger circumference would make up for the decrease in angular rotation. But that's not case. The mass moment of inertia is proportional to the SQUARE of the diameter. The result is slower acceleration from a larger wheel even if the weight of the wheels being compared are the same.

(mass moment of intertia)=((mass)*(diameter)^2)/8

Tires have the same effect, although you have to consider the inner diameter as well. If you also increase tire width then you are increasing the weight of the tire as well as the diameter, thereby putting the double whammy on your mass moment of inertia.

(mass moment of intertia)=((mass)*((outer diameter)^2)-((inner diameter)^2))/8

So the next time you see someone rolling on chrome 22s, you have another reason to :facepalm:

footnote: I have intentionally used both mass and weight interchangeably to keep with the original terminology of the thread. I hope that doesn't confuse anyone.
 
#39 ·
Think of an ice skater doing that spin move (whatever it's called, I'm not ghey).
:rofl:

and this thread just makes me want Kosei's even more. 16.8lbs and 17x8.5 ftmfw.

or if your real concerned with the weight, get the 16x7's, they are 15lbs:4ngie:
 
#37 ·
V710's is my first pick for upgrade wheels but I've been holding it off for a while. Does anyone knows what's the weigh for the ZHP wheel and the Hamann 18x8.5 PG2's I've been using aftermarket wheels since I bought the car so I haven't track the gas mileage
 
#41 ·
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
 
#42 ·
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?
 
#44 ·
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".
 
#43 · (Edited)
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
 
#45 ·
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.
 
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