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      04-23-2010, 07:50 PM   #1
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Need Advice with a 19" Forgestar wheels (Ride quality & Performance)Z4 M Coupe

Hello all,

I just received my 19" Forgestar wheels Hyper black.... and I pull out the scale an weighted them.

Front = 19X8.5 25lbs

Rear = 19X10 26lbs

Has anybody noticed a significant ride quality using 19"? I think that the OEM wheels weight 1/2 lbs less than the 19" Forgestar.

I don't want to compromise the acceleration on the Z4 M Coupe by going with 19" wheels... so if anybody out there with this setup (19" wheels) has some information, it would be really appreciated.
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      04-24-2010, 11:47 AM   #2
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19" wheels vs. 18" wheels in general are heavier, require more expensive tires, have inferior ride quality, and offer no improvement in handling. Their advantage is purely appearance. It's your choice.
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      04-24-2010, 04:06 PM   #3
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Quote:
Originally Posted by car62 View Post
19" wheels vs. 18" wheels in general are heavier, require more expensive tires, have inferior ride quality, and offer no improvement in handling. Their advantage is purely appearance. It's your choice.
Definitely a GENERALIZATION. ....and NOT my experience at all. Actually quite the direct opposite for me.
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      04-24-2010, 08:52 PM   #4
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I guess that my inexperience made me buy 19" thinking that becasue the Forgestar (Front 24.5 lbs Rear 25.lbs) are almost the same weight as the OEM, I wouldnt notice a difference in ride quality. Anyway, I will post some pictures once they are installed and post more coments about the ride quality.
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      04-24-2010, 11:19 PM   #5
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I'd say quit worrying and give them a try. They are already considered "used" so slap them on the car and try them with an open mind. Since the weight is the same, the difference should be almost negligible. Ride comfort might be a little rougher but I bet it will look sweet. Just watch out for those pot holes.

Also it looks like it won't be a problem since soon you'll have a big leaf blower on your car
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      04-25-2010, 09:37 AM   #6
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you are sooo right... the looks will be just sweet I can't wait to have them installed. 10 days for the tires to arrive and then picture time.
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      04-25-2010, 10:07 AM   #7
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Is that a promise for a photoshoot? I want multiple angles, an amazing background and Beautiful Models throwing them self over the car!
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      04-25-2010, 03:36 PM   #8
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How is this for a start
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      04-25-2010, 07:23 PM   #9
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I have the exact same wheels. I love mine. I do feel like I feel more things on the road now but I don't mind at all. Also the wider rear tires grip better
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      04-26-2010, 11:12 AM   #10
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.5lb is negliigible...I tracked my vmr 30lbs vs my vs7 20lbs on the 1/8th w/ no difference in time. and that's 10lbs a corner. the feel is a different story
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      04-26-2010, 11:24 AM   #11
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Awesome... thanks guys... This helps a lot... I decided to go with the Hankook Ventus V12 tires for now... I assume that becasue they are not run flats that might also help to keep the weight down??? maybe?
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      04-26-2010, 11:25 AM   #12
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cant wait for the pics
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      04-27-2010, 07:11 AM   #13
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Is the car Sapphire Black or Carbon Black? There was one Carbon Black car made for North America - LM08354 is the serial number.
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      04-27-2010, 01:56 PM   #14
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Quote:
Originally Posted by car62 View Post
Is the car Sapphire Black or Carbon Black? There was one Carbon Black car made for North America - LM08354 is the serial number.

The car is Sapphire black... so I hope it looks good Black on Black...
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      04-27-2010, 04:09 PM   #15
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The same brand and width tire will be lighter in 19" than 18" due to differences in sidewall height so comparing rim weights do not tell the whole story when it comes to total wheel weight. Actually, the real variable is the rotational intertia, but you won't find specs on that.
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      04-27-2010, 11:48 PM   #16
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thanks for all the info guys! Once the car is ready, I will post the pictures....
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      04-28-2010, 07:23 PM   #17
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Quote:
Originally Posted by lucid View Post
The same brand and width tire will be lighter in 19" than 18" due to differences in sidewall height so comparing rim weights do not tell the whole story when it comes to total wheel weight. Actually, the real variable is the rotational intertia, but you won't find specs on that.
Very misleading statement. Metal weighs more than rubber. See Car and Driver Magazine May 2010, page 34, for a detailed test and explanation of the negative effects of increasing wheel sizes.
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      04-28-2010, 07:40 PM   #18
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Quote:
Originally Posted by car62 View Post
Very misleading statement. Metal weighs more than rubber. See Car and Driver Magazine May 2010, page 34, for a detailed test and explanation of the negative effects of increasing wheel sizes.
1lbs of iron and 1 lbs of cotton candy - which is heavier?

Actually lucid is right about the idea that people can't merely compare the weights of the rims and dismiss the weights of the tires. It makes me laugh when people spend a lot ot money to buy lightweight forged rims only to combine them with heavy tires.

Except that, same brand/model and witdh of tires, 19" usually weights more than 18" or at least weighs about the same because the sidewalls need extra stiffening.
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      04-28-2010, 09:42 PM   #19
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Quote:
Originally Posted by car62 View Post
Very misleading statement. Metal weighs more than rubber. See Car and Driver Magazine May 2010, page 34, for a detailed test and explanation of the negative effects of increasing wheel sizes.
Nothing misleading about anything I wrote. You just don't know how to interpret it. Same brand, same width, same rolling diameter tire usually weighs less in 19" than 18". Compare the PS2, Goodyear F1 Asymmetric, PZero, Ventus V12 or Contisportcontact3 weights in 245/40/18 and 245/35/19 (tirerack or manufacturer's specs) and you'll see. This is true for most tires, but not for every tire; some are about the same.

Also, a tire is not merely made of rubber. And, a high quality forged Al barrel is rather thin (<3mm) and lightweight for instance. See detailed discussion and first order approximations on total wheel weight and rotational inertia here: http://www.m3post.com/forums/showthr...weight+inertia From an acceleration point of view, it is more or less a wash.

From a merely weight perspective, the difference in the 18" and 19" tire weights is often ~1lb. The difference between the same model similar strength similar offset forged 18" and 19" rims is also about 1lb (RAC RG63 is a good example, and BBS RGR might be another one). Even when there is less difference in tire weighs, the whole thing is still not a big deal as long as you chose the right rims.

Anyway, the point is, as I said earlier, if you want the "whole story" on wheel size and acceleration, you need to consider these kind of details. I don't need to read a car magazine to think through any of this.

And, as pointed out above by another person, "metal weighs more than rubber" is a meaningless statement.
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Last edited by lucid; 04-29-2010 at 06:57 AM..
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      04-28-2010, 09:45 PM   #20
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Quote:
Originally Posted by GP20 View Post
Except that, same brand/model and witdh of tires, 19" usually weights more than 18" or at least weighs about the same because the sidewalls need extra stiffening.
You are correct that some tires weigh about the same, but I have not seen a tire weigh more in 19".
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      04-28-2010, 09:51 PM   #21
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Quote:
Originally Posted by Panchio View Post
Hello all,

I just received my 19" Forgestar wheels Hyper black.... and I pull out the scale an weighted them.

Front = 19X8.5 25lbs

Rear = 19X10 26lbs

Has anybody noticed a significant ride quality using 19"? I think that the OEM wheels weight 1/2 lbs less than the 19" Forgestar.

I don't want to compromise the acceleration on the Z4 M Coupe by going with 19" wheels... so if anybody out there with this setup (19" wheels) has some information, it would be really appreciated.
Sweet, nice to see a fellow Calgary Z4 enthusiast. You'll definitely have to come out to a meet/cruise this spring or summer. I can't wait to see your car!
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      04-28-2010, 09:56 PM   #22
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Quote:
Originally Posted by lucid View Post
You are correct that some tires weigh about the same, but I have not seen a tire weigh more in 19".
...and it's not just the weight of a 19;
it's also where the weight is located.

The barrel, which for arguments sake, is the same on a 18 & 19,
has now moved out closer to the perimeter, which compounds the problem.
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