How much does wheel weight affect performance?

[venturaII]

Originally Posted by new2subaru

Wheel and tire sizes?

Motegi Forged Traklite 1, 16x7 +40, 225/50-16 (currently RT615K+)

[new2subaru]

Originally Posted by venturaII

Motegi Forged Traklite 1, 16x7 +40, 225/50-16 (currently RT615K+)

What do you think of the 16's? I'm thinking a little more sidewall would be nice for a DD

[venturaII]

I love 'em. Better ride quality, noticeably lighter weight, and still better grip. Plus I think the fat tire look of this combo looks good on the car, and the brakes fill the space inside the wheel better. The amount of sidewall a 215/45 offers is kind of ridiculous for a street driven car, especially up here in the northeast. Everyone moans and complains that going to a 50 series tire will 'compromise response' and 'dull handling', but the reality is that the tire make and model is 90% of what you're feeling regarding responsiveness - not the minuscule difference between a 45 and 50 series tire. The argument is additionally made by some that a 225 is too big for a 7" rim, but again, not the case with this combo...check out TireRack's sizing and you'll see a 7" rim is right down the middle for a 225/50, and is what they use as a base for all their measurements. And if you're still convinced you're giving up the nth degree of response, just add another few pounds of air to your tires. Never mind that there are dozens of rubber bushings in the chassis also contributing to this response 'problem'.

[nikitopo]

Originally Posted by venturaII

The argument is additionally made by some that a 225 is too big for a 7" rim, but again, not the case with this combo...check out TireRack's sizing and you'll see a 7" rim is right down the middle for a 225/50, and is what they use as a base for all their measurements.

I have 16x7 rims too and I was considering the tire dimension (205/55 vs. 225/50). Truth is that TireRack and tire manufacturers suggest a 225 size on a 7" rim. Nevertheless, I've seen pictures of this combination and I don't like it. Especially on particular tires I was considering. I think that this size is based on some general "rule" mainly for ordinary cars and there was never a differentiation for sports oriented cars. Besides, the 205 tire is lighter and given that the grip difference is very small it seems to me a better option.

[new2subaru]

Originally Posted by venturaII

I love 'em. Better ride quality, noticeably lighter weight, and still better grip. Plus I think the fat tire look of this combo looks good on the car, and the brakes fill the space inside the wheel better. The amount of sidewall a 215/45 offers is kind of ridiculous for a street driven car, especially up here in the northeast. Everyone moans and complains that going to a 50 series tire will 'compromise response' and 'dull handling', but the reality is that the tire make and model is 90% of what you're feeling regarding responsiveness - not the minuscule difference between a 45 and 50 series tire. The argument is additionally made by some that a 225 is too big for a 7" rim, but again, not the case with this combo...check out TireRack's sizing and you'll see a 7" rim is right down the middle for a 225/50, and is what they use as a base for all their measurements. And if you're still convinced you're giving up the nth degree of response, just add another few pounds of air to your tires. Never mind that there are dozens of rubber bushings in the chassis also contributing to this response 'problem'.

Thanks man! I really appreciate the feedback.

[why?]

I think 205 is better on a 16, that's what I have.

[Capt Spaulding]

ventura: is there a pic of your car on the board somewhere? This strikes as an interesting possibility. Thanks

[venturaII]

I'll take the extra pound or so penalty for for an extra 3/4+" of rubber on the ground, not to mention significantly more tire options to choose from in the autocross/trackable rubber category.

[venturaII]

Originally Posted by Capt Spaulding

ventura: is there a pic of your car on the board somewhere? This strikes as an interesting possibility. Thanks

Yeah, I think I posted one in the 16" rubber thread at one point. I'm no pro photographer though, and I have a simple flip phone, so any photo you find is going to be pretty low qual.

[why?]

Originally Posted by venturaII

I'll take the extra pound or so penalty for for an extra 3/4+" of rubber on the ground, not to mention significantly more tire options to choose from in the autocross/trackable rubber category.

if that is what you are using it for then sure, but if it is a dd like mine I want the lightest wheels and the lightest tires I can find. I wish there was lightweight 16x6.5 wheels for our cars, but their just is not.

[venturaII]

Originally Posted by why?

if that is what you are using it for then sure, but if it is a dd like mine I want the lightest wheels and the lightest tires I can find. I wish there was lightweight 16x6.5 wheels for our cars, but their just is not.

I dd mine as well. I use 205/55 on 6.5 steels for winter only. The rest of the year I use 225/50; I have a set of early spring/late fall tires (in the 340tw range)for cool weather, and a set of sticky tires (180-200tw) for warm weather/track/hooning.

[fatoni]

Originally Posted by why?

I think 205 is better on a 16, that's what I have.

why?

[nikitopo]

Originally Posted by venturaII

I'll take the extra pound or so penalty for for an extra 3/4+" of rubber on the ground, not to mention significantly more tire options to choose from in the autocross/trackable rubber category.

I measured once a 205 tire on a 6.5" rim and another on a 7" rim. The rubber on the ground is more with the bigger rim. The 225 tire will give a bit more rubber, but less than 3/4+".

[EAGLE5]

https://blog.caranddriver.com/tested...-fiber-wheels/

~24% reduction in wheel/tire weight + a ~4% gearing reduction leads to ~8% in-gear performance difference that decreases as speed increases.

As for coast down from 60mph, a ~3% difference. Considering that the gearing change means the high-revving Mustang is more in its power band and gets a gearing advantage, I'd say the coast down is a better measure of wheel weight's impact.

The GT350R weighed 3710lbs. The GT350 wheels weight a total of 58 lbs more. That's ~1.6%. Keep in mind that I rounded all my other percentages. Anyway, if you're getting ~3% difference in inertia after dropping ~1.6 per cent in curb weight, that suggests about a 2:1 ratio weight loss improvement from wheel weight versus other weight. Then again, the weight of those GT350R tires is ~4% inwards versus the GT350 tires. That also reduces the inertia. Maybe 2:1 is generous?

So ~$16,000 to reduce tire/wheel weight by ~15lbs/corner (about 24%) yields a significant difference but nothing to blow your mind.

What I suggest you all do is get some 215/35R17 Yokohama S-Drive tires on stock rims. They'll make the car feel much faster. You get a free lowering, too.

Also see this: http://hpwizard.com/rotational-inertia.html

He suggests 2:1 at most. That jives with what I'm seeing with C/D's article.