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[bank3r]

Sorry, if there is already a thread about this but I didn't find it anywhere?

So do you guys think that putting a 19" wheels on your car makes your car's acelleration becomes slower?

[M3 Piotr]

Lots of 19s are lighter than OEM wheels. Not sure about helping too much with acceleration, but it helps with the unsprung weight, when wheels are lighter.

[Year's_End]

Would you have to factor in the lower side walls on tires equipped with 19s? Does that affect acceleration, or does that only apply to cars with higher outputs where a large sidewall is necessary to get an effective launch?

[E90SLAM]

i'd say is all down to tires....even if u have very light wheels...but shitty tires....ur acceleration is not going to be any better.....but wider does help launch better and grip on dry conditions.....

[poldim]

A tire with a small sidewall will have a lot of metal reinforcing the rubber, the farther the weight is from the center of the wheel, the more energy is used to accelerate it. Just because 19" your wheels weight, say, 15 pounds, doesn't mean they will accelerate faster than a 18 pound 17" wheel.

Also, remember that we have run flats, so when you go to a non-runflat tire, that helps.

MZ6ZoomZoom:
Some informational posts taken from other threads regarding the subject. They may be slightly edited. If you feel like you have more information, contact me.

Quote from: stretch

Ugh, I keep trying to resist posting to this thread.

Can't do it anymore.

The average 20" wheel is 35lbs. The stock 16" wheel combination WITH tires is 39.4 lbs. So you're almost as heavy before even mounting tires! I tried looking up tire weights, and realized that no respectable manufacturer makes the size you would need. So you're forced to buy shit tires. Kuhmo doesn't even make the "MX" in a 20" size because no respectable performance driver would be on 20's. But their 712's are available in SUV sizes, and the 255/35/20 is 30lbs. T1-S's also come in that size, but no smaller width. These are essentially SUV tires, they're heavy because they're designed to support a lot of weight. Falken doesn't even make Azenis in a size over 17" because again, no respectable racer (autocrosser) would use wheels larger than that.

The only reason to run large wheels is to run large brakes, and the 3's brakes are completely adequate for track use (when used with track pads) even under 16" wheels.

Anyway, back to weights. You're going to run 35lb wheels with 30lb tires, totally 65lbs compared with 39.4lbs stock. This is not like adding a 200lb subwoofer in the trunk (which is pretty stupid), this is far worse. The thing about wheels is you have to spin them, and that takes much more effort than it does to move an object that isn't spinning. You're dealing with the polar moment of inertia.

I won't bother explaining it since I doubt you care (and Crossbow already touched on it), but here are some numbers for you.

In fact, just for fun I looked up how much straight-line performance you'd lose by switching from 16" wheels to 20" wheels if the wheels weighed the same. It'd be about like adding 200 static weight to the car, which would take an additional 11ft-lbs of torque (roughly 15hp @ the rev limiter) to compensate and get the same acceleration as a stock car. That's bad enough.

But no 20" wheel is as light as the stock 16's. Your combination will weigh 65lbs, remember?

That's like adding nearly 800lbs of static weight to the car. Think about that number. That's almost 30% of your car's entire weight. In order for the car to accelerate like it did STOCK, you'd have to gain back 42ft-lbs of torque over the ENTIRE rev range. At the rev limiter, you'd need to be making 55 extra horsepower. Not gonna happen without forced induction. So basically, you'll need to supercharge your car to keep pace with a stock Mazda3 on 16" wheels.

Bling bling though, right?

Now you know why people with big rims get laughed at. Clowns wear big shoes too, but they're supposed to be funny.

Oh, and that's assuming you get the tires to fit in the first place, and then manage to make it over a pothole. You should aim to keep the volume of air in a tire constant when plus-sizing, which is why you should always upgrade to a wider wheel and wider tire when plus-sizing (a reason why Porsche uses hollow spokes!). Due to fender size constraints, you can do neither, and your brand new $4000 wheels will be bent in no time. The sidewall on 35 profile tires has to be very soft to be compliant, and your car will look like the rims are touching the ground. You know the look- like the tires are low on air. Take a turn and it looks like the rim scrapes, hit a pothole and the rim breaks. Utterly stupid looking.

Oh, and I almost forgot to mention- that extra 800lbs of equivelant weight that you're adding to the vehicle? You're going to have to slow it down, too. Good thing the Mazda3 has awesome brakes, cause you're going to need every ounce of them to stop your car in just routine traffic.

Here's a link for you to read:

Plus-sizing for dummies: a dozen reasons not to go bling-bling with large wheels.

MZ6ZoomZoom:
Quote from: crossbow


Any increase in unsprung weight is multiplied by a variety of factors.

Did you know that a mere 2 lb increase in tireweight on a 19 inch diameter tire is equivilant to 200 lbs of additional static weight?


Quote from: crossbow

http://www.mazda6tech.com/index.php?...d=16&Itemid=32

And here's the direct formula.
http://www.mazda6tech.com/files/rotational.xls

Its quite accurate based on 1/4 and 0-60 times. Having experienced the opposite effect on my car (dropping 40+ lbs of unsprung weight), I can definitely say unsprung weight is one of the most important aspects of a cars performance. Combined with proper tires, it has the ability to make or break what makes a car great. Heavy wheels and tires make the car feel slow, the steering heavy, reduce braking performance, acceleration, and the overall effect of suspension on the car.

Lightweight wheels and tires (smaller diameter then stock, lower profile rubber, lightweight forged wheels), make the car feel hundreds of pounds lighter then it actually is, give a very light steering feel (feels nimble as hell), and increase braking performance, acceleration, and require the suspension to do far less work to maintain the car's manuverability.


Quote from: crossbow

Remember that though you can maintain the same overall ratio, you are still pushing the tire weight further away from the center of the wheel hub. Because of rotational inertia (insert smart math forumla's I don't understand here), this means that even if you have wheels of identical weight, your still increasing the inertia (and torque required to turn the wheel) by 6-8% (per inch of additional wheel diameter).

So technically to maintain the exact same performance specs (And its effect on unsprung weight) while increasing grip/aesthetics, you'll have to REDUCE the weight of the larger wheels over stock. Aka if you went with a nice set of forged SSR GT2's (18x7.5) which were around 18 or so lbs, its possible to maintain the exact same or better characteristics as a stock configuration while increasing aesthetics.

Because of rotational inertia, the importance of tire weight becomes absolutely critical on a 19 or 20 inch wheel. (Because its on the outside of the rotational mass) A mere lb of additional tire weight can have a drastic effect on the car.

Article on Unsprung Weight and Rotational Inertia
http://www.mazda6tech.com/index.php?...d=16&Itemid=32

[Big Windy]

as posted ^, it has to do with rotational inertia. bigger rims are going to negatively affect acceleration. you can offset this with the right tires, etc.

[daixloxbmw]

agreed with the previous statement!

its not just about the total weight of the rim, its about where that weight is. a bigger rim will always have more weight further away from the center even though the overal weight might be lower than a smaller rim.

think of it this way, what is easier to swing 360 degrees; a 2 ft long sledge hammer or a 20ft long bamboo pole? the bamboo pole might be lighter overall, but most of its weight is beyond the 2 ft mark.

[addy85]

im lost, I got 19's with Nixon tires lol so hopefully im in good shape!!!!!!!!

[Revlis]

Lower unsprung weight is good, and remember over all size of a 19" wheel and tire package VS 18" wheels doesn't really change much. 1-2% or so with a conservative package. So no worries. It's not like your wheels and tires are actually 1" larger over all than previous set.

[bank3r]

I believe the OEM wheel weight around 34lbs w/o tire?

I order the CSL 19" which weight 25.5 lbs w/o tire.

And I am also going from 7" runflat to 8.5-9.5" max performance summer tire.

So If the tire and the wheel is lighter and the width is wider, it should definately help my acelleration?

[poldim]

Originally Posted by bank3r

So If the tire and the wheel is lighter and the width is wider, it should definately help my acelleration?

Wrong. Read above statements about the radial center of mass.

40 pounds on a 10 inch radius is the same as 20 pounds on a 20 inch radius. The further the center of mass is from the axis of rotation (radius), the more torque is required to accelerate it (torque = force * distance, so in this case, torque = force * radius).

[Revlis]

Originally Posted by bank3r

I believe the OEM wheel weight around 34lbs w/o tire?

I order the CSL 19" which weight 25.5 lbs w/o tire.

And I am also going from 7" runflat to 8.5-9.5" max performance summer tire.

So If the tire and the wheel is lighter and the width is wider, it should definately help my acelleration?

Originally Posted by poldim

Wrong. Read above statements about the radial center of mass.

40 pounds on a 10 inch radius is the same as 20 pounds on a 20 inch radius. The further the center of mass is from the axis of rotation (radius), the more torque is required to accelerate it (torque = force * distance, so in this case, torque = force * radius).

If the tire and wheel package is lighter, and the tire is a little wider then yes, you can expect some small improvement in acceleration due to improved traction. Assuming of course that you don't have some magic wheel with all it's weight on the perimeter. The increased traction from a wider tire will likely (unless you buy crap tires) give you a slightly larger contact patch allowing more power to be put down.

The discussion above regarding radius and mass is valid however I don't believe that it necessarily amounts to a noticeable difference in every day driving. It's something that could be instrumented and measured in a lab sure, But real world performance wise not so much. It's not as though the 19" aftermarket wheel that weighs 8lbs less than the 18" OEM somehow has significantly more mass around it's perimeter. In fact it likely looses some mass at the rim canceling out whatever losses were present due to the increased moment.

[bavarian19]

For most setups, a 19 inch forged wheel and some good tires can improve your acceleration and handling in comparison to OEM.

Just be careful with your choices. Plus sizing wheels will not always yeild better results. I decided to go with 230's and 235/265's, which means I went up size on both the rims and tires.

I have not noticed a great difference (if at all) of acceleration, but grip has vastly improved.

[E90330iS]

good article

[poldim]

Originally Posted by Revlis

If the tire and wheel package is lighter, and the tire is a little wider then yes, you can expect some small improvement in acceleration due to improved traction. Assuming of course that you don't have some magic wheel with all it's weight on the perimeter. The increased traction from a wider tire will likely (unless you buy crap tires) give you a slightly larger contact patch allowing more power to be put down.

The discussion above regarding radius and mass is valid however I don't believe that it necessarily amounts to a noticeable difference in every day driving. It's something that could be instrumented and measured in a lab sure, But real world performance wise not so much. It's not as though the 19" aftermarket wheel that weighs 8lbs less than the 18" OEM somehow has significantly more mass around it's perimeter. In fact it likely looses some mass at the rim canceling out whatever losses were present due to the increased moment.

Check out the link to the excel file form the article: http://www.mazda6tech.com/files/rotational.xls

It shows the affects of changing tire/rim weights. With a 5 pound decrease per wheel, its like removing 60 lbs of chassis weight. Its not immensely significant, but if the car is daily driven, on fuel efficiency and acceleration.

You can play around with it and actually input your original tire size and weight and the new ones and see what you come up with.

[bank3r]

I went with the 19" 235/35 and 265/30, so i am hoping for a better grip while not effecting my acceleration. And from what you guys has discussed, i am sure that this new setup will be better....

[blakjack23]

I just went from 16 inch 156's to 19 inch CSL reps. I only put them on today, but so far it does seem like my car is a tad slower. But it also seems like my car was lower while I was driving, which is the oppositive of what my before and after mesurements of the body height said, so it might just be mind tricks since I was reading that cars are slower with larger rims before I put mine on. I do think the ride is a lot smoother with the non-rft tires though. I could throw the end out around a corner the same with the old narrow tires and the new wide tires about the same.

[Revlis]

Originally Posted by poldim

Check out the link to the excel file form the article: http://www.mazda6tech.com/files/rotational.xls

It shows the affects of changing tire/rim weights. With a 5 pound decrease per wheel, its like removing 60 lbs of chassis weight. Its not immensely significant, but if the car is daily driven, on fuel efficiency and acceleration.

You can play around with it and actually input your original tire size and weight and the new ones and see what you come up with.

Very interesting... I know unsprung weight is the devil... Interesting link.

[poldim]

Originally Posted by blakjack23

I just went from 16 inch 156's to 19 inch CSL reps. I only put them on today, but so far it does seem like my car is a tad slower. But it also seems like my car was lower while I was driving, which is the oppositive of what my before and after mesurements of the body height said, so it might just be mind tricks since I was reading that cars are slower with larger rims before I put mine on. I do think the ride is a lot smoother with the non-rft tires though. I could throw the end out around a corner the same with the old narrow tires and the new wide tires about the same.

The ride improvement is probably lacking because you went to a 19 inch wheel, very little side wall...