Is 12lb total difference in weight going to affect a lot?

[ermax]

Originally Posted by rvoll

I agree. I didn't say that more traction would hurt lap times (although I can see where that would be inferred). Only that there comes a point where traction is maximized for the specific car and getting tires with theoretically more grip doesn't really help -- and in fact, because of things like weight and the shape of the contact patch and drag, may worsen lap times.

And yeah, if you really like sliding, keep the OEM Primacies as they do that well on this car. And yes, sliding can be loads of fun if that is your objective. I personally get more fun when the car sticks -- but that is me....

Gathca. I thought the test was 215 vs 215 and simply changing compounds. In that case I don't see how any UHP 215 wouldn't smoke the OEM tires (in laptimes). For sure there is a point of diminishing returns when you go wider/taller.

When trying to locate the TireRack test you were referring to I came up with this video:
[ame="https://www.youtube.com/watch?v=73Wa-uW2-dI"]Toyota 86 - Stock vs Track (Yokohama AD08R) Tire Comparison - YouTube[/ame]

215 OEM vs 225 AD08R.

[ermax]

I didn't read the whole thread but rotational mass doesn't equal static weigh. 12lbs in the wheels has more negative impact than having 12lbs in your passenger seat.

[HSUBLU]

Originally Posted by ermax

I didn't read the whole thread but rotational mass doesn't equal static weigh. 12lbs in the wheels has more negative impact than having 12lbs in your passenger seat.

take those 12 lbs of dollar bills out of the passenger seat, use them to buy a set of wheels that are 12 lbs lighter, and you've reduced both static and and rotational weights.

Sounds like a solution to me

[Tcoat]

Originally Posted by HSUBLU

take those 12 lbs of dollar bills out of the passenger seat, use them to buy a set of wheels that are 12 lbs lighter, and you've reduced both static and and rotational weights.

Sounds like a solution to me

$5448

[fatoni]

Those lighter wheels are going to raise the center of gravity and ruin the handling according to some.

[HSUBLU]

Originally Posted by Tcoat

$5448

Volks. /shrug

[rvoll]

Originally Posted by fatoni

Those lighter wheels are going to raise the center of gravity and ruin the handling according to some.

Are you kidding me? The COG, according to what I've read, is about 18" high. The mass of the car is about 2800 lbs. The mass of the wheels is about 180 lbs total. The COG of the wheels is about 12.5". For arguments sake, let's say extra light racing wheels with tires would weigh about 150 lbs. Extra wide/heavy racing wheels would weigh about 250 lbs, max. So you have an increase of about 100 lbs. divided by 2800 lbs., so your COG would rise by about 0.2 inches. And that's going to "ruin" the handling? Are you kidding me? Then you have to consider that carrying an extra 100 pounds will slow down the car and wide wheels on the front will reduce handling. So adding weight is good for performance. You got me on that one. We'd better tell all of those racing teams out there of this new paradigm.

[Vracer111]

I don't think the stock wheel/tire selection used is optimal though it works well enough. My preferred optimal setup is slightly wider and noticeably lighter 17x7.5 wheels with a slightly smaller diameter and not too much narrower 205/45-17 MAX performance tires. That combo drops over 4lbs a corner on inexpensive 17lb Enkei wheels and 19lb Continental tires, lowers the car CG ~.2", and provides better throttle responsiveness, all while greatly increasing grip and really quickening chassis responsiveness (because the 205 Continentals are more optimally matched for a 7.5" width wheel than the stock 215 tires on 7" width wheel).

The wheel and tire change is small, but the felt difference isn't. Toyota/Subaru should have gone with 17x7.5 wheels and 205/45-17 tires as the stock setup, but probably the slightly reduced load capacity and reduced ground clearance or theoretically worse fuel mileage were the reasons they didn't. For daily driving a lightweight 17x7.5 wheel with 205/45-17 Max Performance tire will make the stock setup feel incompetent - much more planted to the pavement yet also quicker to react and more precise in its reaction.

That's my two cents...

[rvoll]

Originally Posted by ermax

Gathca. I thought the test was 215 vs 215 and simply changing compounds. In that case I don't see how any UHP 215 wouldn't smoke the OEM tires (in laptimes). For sure there is a point of diminishing returns when you go wider/taller.

When trying to locate the TireRack test you were referring to I came up with this video:

215 OEM vs 225 AD08R.

Actually, it's this one...

[ame]https://www.youtube.com/watch?v=FSqWD5BSeoY[/ame]

[fatoni]

Originally Posted by rvoll

Are you kidding me? The COG, according to what I've read, is about 18" high. The mass of the car is about 2800 lbs. The mass of the wheels is about 180 lbs total. The COG of the wheels is about 12.5". For arguments sake, let's say extra light racing wheels with tires would weigh about 150 lbs. Extra wide/heavy racing wheels would weigh about 250 lbs, max. So you have an increase of about 100 lbs. divided by 2800 lbs., so your COG would rise by about 0.2 inches. And that's going to "ruin" the handling? Are you kidding me? Then you have to consider that carrying an extra 100 pounds will slow down the car and wide wheels on the front will reduce handling. So adding weight is good for performance. You got me on that one. We'd better tell all of those racing teams out there of this new paradigm.

I don't mean for racing. The teams are only concerned about time. For a street car there is no reason to ruin the center of gravity by getting lighter wheels.

[ermax]

Originally Posted by rvoll

Are you kidding me? The COG, according to what I've read, is about 18" high. The mass of the car is about 2800 lbs. The mass of the wheels is about 180 lbs total. The COG of the wheels is about 12.5". For arguments sake, let's say extra light racing wheels with tires would weigh about 150 lbs. Extra wide/heavy racing wheels would weigh about 250 lbs, max. So you have an increase of about 100 lbs. divided by 2800 lbs., so your COG would rise by about 0.2 inches. And that's going to "ruin" the handling? Are you kidding me? Then you have to consider that carrying an extra 100 pounds will slow down the car and wide wheels on the front will reduce handling. So adding weight is good for performance. You got me on that one. We'd better tell all of those racing teams out there of this new paradigm.

I think he was kidding.

[churchx]

It's not just the center of gravity, that will be ruined! Lighter wheels also don't have enough gyroscopic effect, so car will become very unstable and uncontrollable!

[ermax]

Originally Posted by churchx

It's not just the center of gravity, that will be ruined! Lighter wheels also don't have enough gyroscopic effect, so car will become very unstable and uncontrollable!

Especially when trying to ride it on two wheels.

[Yardjass]

Originally Posted by rvoll

The one point where we disagree, however, is that wider tires improve handling as a general principle. Handling, IMO, is a matter of balance. Our car is designed for 215's on the front and in my experience, the accuracy of handling degrades as you go wider on the fronts. That said, there are specific circumstances, like autocross, where a slightly wider tire may give better times. But that is the exception as not very many owners do autocross.

That's the whole better feeling vs. physically optimized concept again. Also maybe a bit because this vehicle was designed to have a certain track width and most wider aftermarket wheels that people put on them will change this slightly.


I'm not trying to say turn it into a steam roller. Eventually you will hit marginal returns and yes, you will lose out on acceleration and braking capability a lot if you stay at stock power levels. However, look no further than the BRZ race cars if you think anything even close to a stock width tire is optimized for handling.