Performance loss with bigger wheels?

[Steeb]

your explaination is very well thought out but i believe it would only apply if it is for certain that the replacement wheels are heavier than the stocks. while a heavier than stock 18" wheel has more rotational weight than the stock wheel it also applies to tires. a lower profile tire also has less rotational weight than the larger profile stock one to make up for the gain in wheel weight, if any.

if the lightweight 18" wheel and tire still weighed the same or less than the stock package, there would be no performance loss even with bigger wheels.

lets say u choose an 18" wheel that is 15#'s (same as stock) by choosing the correct tire size, you can save weight because of the difference in tire weight. in this example, there is no performance loss from running an 18" wheel.

this means that choosing a slightly heavier and larger wheel than stock, might mean u still end up with the same rotational weight considering the correct tire size is chosen. i dont see how you can loose performance with the same rotational weight as stock just because of bigger wheels.

doesnt gravity make weight more an issue than mass in this topic?

key to remember is that it is best to make sure your aftermarket package is lighter than your stock package and to choose the correct tire sizes or performance losses are inevitable

[jschrauwen]

Bearing in mind that I tried to maintain the integrity of the speedo, I opted for 205/40's on 17's...............guess I erred big time. Since I didn't see this particular combo addressed, I'm going to assume that this choice will translate into negative performance?
BTW - remarkable breakdown and delivery on a subject that has a lot more behind it than just BLING.....many thanks!!

[tatsu]

Dave: If it's lighter than stock, and the same overall diameter as stock or smaller, then it WILL result in better acceleration, assuming no traction issues.

Steeb: Even if the overall weight is the same, you would still theoretically be disadvantaged because the bulk of that weight would be further from the axis of rotation. However, I would think that the difference would probably be negligible enough not to be perceived by most people.

Jschrauwen: If your package is lightweight (less than 35 lbs per corner), then you should see a (slight) increase in performance, as a 205/40-17 would put down 1.8% more torque to the wheels than stock size. Your speedo would also be reading that much higher than it would be with stock size tires, but a difference that small is not worth worrying about.


As noted in my earlier post:

• ...if you are using one of the correct plus-sizes listed above as an upgrade, and the overall package is heavier, it WILL negatively affect performance. Whether you PERCEIVE the difference or not depends on how sensitive your own "butt dyno" is!

In general, I would NEVER recommend buying a wheel/tire package that is heavier than stock, unless you are willing to sacrifice performance for the sake of appearance.


(Some info from this post has been combined into my main post above...)

[Tunes67]

Ok here is a question since you opened the door How much do the stock 14" RS Rims & Caps weigh? (The stock steelies) I am planning to replace the rims eventually.. but I dont really have a need to increase size. That would just force me to get new tires again LOL. (The tires were pretty much bald when I bought the car.. didnt have the cash on hand for an immediate upgrade so I just put new rubber on)

Tunes67

[tatsu]

(Some info from this post has been combined into my main post above...)

As for the stock RS wheels - I have no idea. I imagine they would be close to the same weight as the GS alloys, since they are steel, but they could be lighter...

[Steeb]

Steeb: Even if the overall weight is the same, you would still theoretically be disadvantaged because the bulk of that weight would be further from the axis of rotation. However, I would think that the difference would probably be negligible enough not to be perceived by most people.

ok.....

So, the good news is, if you can find a plus size wheel that is the same weight as stock (I have now heard anywhere from 15 - 16 lbs.), you should be able to get a tire that will not come with a weight penalty!

well said, well said. same thing i was saying but much more easy to understand

anyway..... finding a plus size wheel that is same weight as stock, as i said in my post above. paired with a lighter low profile tire will result in no weight penalty or performance loss

so of your two statements would you agree with because we might be confusing some people here with your two contradictory statements

[tatsu]

Not quite sure what is contradictory here - if the weight is the same, but the diameter of the wheel is larger, there should, in theory, be a performance penalty because the bulk of the weight would be carried at a greater distance from the axis of rotation. In fact, even if the wheel and tire package were marginally lighter than stock, but larger diameter, you could end up with equivalent or lesser performance, rather than an improvement, for the same reason. That is just plain physics.

The point it seems you are trying to make, and I DO agree with you, is that the difference in rotational weight between two packages of equal static weight but different wheel diameters could not be PERCEIVED by the average driver.

If you are talking about a package with an average 17" wheel that weighs 20+ pounds, however, then I would say definitely yes, the difference would be noticeable.

I hope this clarifies the issue for you, and anyone else who may have been confused. For the sake of further clarity, I will edit my posts above to combine the information into one coherent package...

[Steeb]

i dont mean to single you out. im sorry if i offend u in anyway. i guess i was a bit unclear about what u meant. anyway, good topic. we dont usually get good discussions going on this board. im sure u know why...

[tatsu]

Hey, no offense taken!

...and yes, I know exactly what you mean - it's the same with any forum, really - people take questions/comments the wrong way, and get all bent out of shape about them, and the posts just turn into shouting/pissing matches.

For the record, unless someone says, "Hey, you're stupid," or something else derogatory directly to me, I just assume that they are asking an honest question or offering their opinion for discussion, and they deserve an equally honest and rational response. If someone can't be adult enough to have a discussion, rather than an argument, and feels they have to get personally insulting with someone they don't even know, then I simply don't dignify it with a response.

So feel free to fire away with any questions/comments - I welcome the feedback!

[Dave-UK-MX3-V6-SE]

You're such an idiot tatsu......









::edit::
Seriously though, thanks for the info tatsu (and everyone else!), I'm trying to get rid of these big wheels and find some lighter smaller ones... currently annoyed because a friend in our tight "cruising buddies" circle has just bought a white mx-3, just like mine!!!! i was the only one before... and the fastest grrr.... anyway.....