Plus sizing vs. weight diff

[Hoosteen]

Okay, I've read all the numerous posts and stickies for this subject. I know... plus sizing will decrease the acceleration of the vehicle due to the increased diameter.

However, it is said that stock wheels are approximately 23lbs each or something like it. Now I currently have protege 5 rims on i think they are 16 x 6.5 (don't ask... )

.... I'm thinking about getting new rims that are approximately 19lbs, but are 18" x 8"

Thus, I will be dropping 4 pounds of "rim weight".
I'm considering 225/45/18 tires
Will this new tire size be heavier or lighter than stock michelins..???. which i have 16s

Although this new setup will be a wider diameter: 18"
It is lighter AND wider (much wider).

So will the increase in diameter offset or even outweigh the weight savings I will be making?

So i guess what I'm saying is.... will my car be slower?

[crossbow]

Yup. Slower it will be. When stretch swaps from his 16x8's to his 18x8's, its a totally different car...even though the rx8 rims are only a bit heavier then the rx7 rims...its all due to the increased diameter.

Get the rx8 rims. Try swapping back and forth between them and the protege rims. If you don't like them, sell them (someone is ALWAYS looking for rx8 rims), if you do, keep them. Just make sure to roll your rear fenders.

[Hoosteen]

but my new rims will be lighter...

Stretch had lightweight 16's vs. heavier 18's.

In my case... I have "heavy" 16's and switching to lighter 18's

[crossbow]

Actually your increasing rim weight and tire weight.

Protege 5 rims are about 17 lbs with a 17-19 lb tire. Rx8 rims are 19 lbs, with a 25-26 lb tire.

Try it. If you don't like it, sell the rx8 wheels. If you do like it, keep them. You can also try the 16x7.5 rx8 wheels (which are 17 lbs, but wider). They usually go for 250 with tires. (Yes thats 250 USD for all FOUR with tires)

[Tire Guy]

One question, you have the Protege5 rims, but do you have the Protege5 tires? That will make a big difference in gearing as the Protege5 tires are much smaller.

The real question is, though, do you race your car? If not, you're probably not going to notice a difference in whether your car is a little slower or not. It WILL likely corner better (depending on tire choice, of course! ) What's most important to you? If you like the looks of the lightweight wheels, GET THEM and don't worry if your car is fractionally slower.

Somebody posted a spreadsheet in another thread that will help you determine the finite differences. Wish I could find it...

[Hoosteen]

well, I don't officially compete in any type of racing or autocross. But, I really do cherish the occasional punch to the wheels.

It just seems like Stretch and others have made a HUGE deal about plus sizing. I mean.... stylistically I prefer 18's to 16's. Stylistically, I prefer the more complex patterning of cast wheels than those of lightweight forged.

It just seemed that all that previous banter about plus sizing weighed heavily upon the performance of the M6. I'm no dummy when it comes to realizing my car's potential and if there is a difference, I'll probably notice it. I just remember someone spitting out a figure like 20whp loss by upsizing... now THAT'S A LOT of whp loss. My god, i don't know if that was a fair statement or if that person just pulled it out of their ass.

Toyoguy- By the way, I have the protege rims with the stock tires for the M6.

Crossbow- Also, why do tires for an 18" weigh more than tires for a 16"?

Furthermore, we're talking 19 lb 18 x 8" wheels here. That's pretty light considering some other options out there.

Toyoguy or anyone else- not to go on a tangent, but what do you think about Parada Spec II's??? did some research, seems people don't like the road noise or wet traction and the fact that its assymetrical/unilateral (something about it being backward on one side).

[crossbow]

Because the tires on the rx8 wheel are summer performance...you can replace them with T1-S's which will save a few lbs. Tire weight is by design, compound, and manufacturer. I assume your doing a straight swap from an rx8 owner, in which case your going to be getting their tires as well.

According to brillo, the stock rx8 rim weighs 21.25-21.5 lbs, with the tire weighing 25-26 lbs. You can get a 235/40/18 Toyo T1-S tire that weighs 22.9 lbs. (Remember you HAVE to roll your rear fenders).

Now I know toyoguy likes to bring up the racing stuff alot...but its more then that. Heck even steve's wife noticed the difference from the passenger seat when he swapped back. Unsprung weight is something you feel every time you touch the steering wheel. It changes the entire nature of the car. Its like a meal prepared by a chef, or a fine wine...you don't know what your missing until you try it. (Remember toyoguy is biased because he has 18's, I'm biased because I have 16's...you need someone in the middle )

Like I said, its very easy to sell back rx8 wheels, many many people want them. So it shouldn't be any problem to get them, and if you don't like them, just resell them. If you do like them, and don't notice anything, then your fine and this conversation is mute.

[6DereK6]

If your talking about the 5-spoke 18x8 RX-8 wheels with the bridgestones I put one on a scale before I put it on and it was 52lbs total. Like round cinder blocks but they look neet.

[Tire Guy]

Originally posted by crossbow@Mar 6 2005, 11:04 AM
Now I know toyoguy likes to bring up the racing stuff alot...but its more then that.* Heck even steve's wife noticed the difference from the passenger seat when he swapped back.* Unsprung weight is something you feel every time you touch the steering wheel.* It changes the entire nature of the car.* Its like a meal prepared by a chef, or a fine wine...you don't know what your missing until you try it.* (Remember toyoguy is biased because he has 18's,* I'm biased because I have 16's...you need someone in the middle )

[snapback]373566[/snapback]

I don't remember him writing that he was buying RX-8 wheels to begin with. Seems like that suggestion came from you. If he is looking at lightweight 18s, plus putting a lightweight tire like the T1-S or T1-R, why is there a disadvantage if he is lowering overall unsprung weight vs. the 16s?

Remember, crossbow, I just switched to 18s and have been touting the benefits of 18s long before I switched. For the record, my 18s aren't particularly light (they're cast wheels), but my overall package is about 3 lbs lighter than the stock 17 inch setup. Now I, like everyone else on this board, don't consider myself an average driver, but if my car is any slower with 18s, I sure can't feel it. Maybe I'm not as good a driver as I thought. My car corners better, I know that. And, to me, the proof in the pudding, is that I haven't suffered any fuel efficiency loss. In other words, I get the same gas mileage as before. Now, if my car had to slog around heavier unsprung weight, it seems like that would show itself in worse fuel economy.

My point is, if you have your heart set on a set of 18s, and if they're not outrageously heavy, then why not get them if you don't race? Even if there's a slight loss of whp, it should be offset by better cornering capability. Of course, all this depends on the wheel/tire combination you choose, but it truly bothers me when you make blanket statements saying that anyone who goes to 18s will lose performance. It's just not true. If it were, I wouldn't be posting this. I have no bias towards one particular setup or another.

[Tire Guy]

Originally posted by Hoosteen@Mar 6 2005, 01:07 AM
Toyoguy or anyone else- not to go on a tangent, but what do you think about Parada Spec II's??? did some research, seems people don't like the road noise or wet traction and the fact that its assymetrical/unilateral* (something about it being backward on one side).

[snapback]373517[/snapback]

Yokohama had just released the Parada about the same time I left Yokohama, so I don't have personal experience with that tire. I love the tread pattern, but I think what you've heard about the noise is accurate. I have heard the same thing. The only other person I have asked about the Parada was road racing on them and wasn't impressed, but on the street, the tire may be more than satisfactory. Wish I had a better answer for you. Why not consider the Proxes T1-Rs when they come out. I think you'll be impressed.