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      03-23-2013, 04:36 PM   #45
Dackelone
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Quote:
Originally Posted by ///1M
So if the 19" 1M stock wheels are 26 lbs each, what's a good 18" lightweight alternative for the street?
I met a guy in Switzerland who went with 18" wheels - he had a P3 gauge vent and he claimed his 0-100 kph (62 mph) was under 4 secs with the 18's. So he runs them in the summer months. He said his car accelerates faster with the lighter 18" wheels. He also said the OE wheels were quite heavy.
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      03-23-2013, 06:45 PM   #46
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Quote:
Originally Posted by Dackelone
Quote:
Originally Posted by ///1M
So if the 19" 1M stock wheels are 26 lbs each, what's a good 18" lightweight alternative for the street?
I met a guy in Switzerland who went with 18" wheels - he had a P3 gauge vent and he claimed his 0-100 kph (62 mph) was under 4 secs with the 18's. So he runs them in the summer months. He said his car accelerates faster with the lighter 18" wheels. He also said the OE wheels were quite heavy.
I take it his car was not tuned?

That would be amazing, really!
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      03-23-2013, 08:43 PM   #47
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For an OE wheel, that's quite light for the size, especially considering the standards wheels sold in Germany (TUF?) have to adhere to. To put it in perspective, coming from the Mazda world, here are a few OE Mazda wheels
Mazda3 17x6.5+52 = 21lbs
Mazdaspeed3 18x7+5x = 26lbs
US-Spec FD Rx7 16x8, which was praised for it's lightness for a production car = 16lbs IIRC
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      03-23-2013, 11:22 PM   #48
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Quote:
Originally Posted by Dackelone View Post
I met a guy in Switzerland who went with 18" wheels - he had a P3 gauge vent and he claimed his 0-100 kph (62 mph) was under 4 secs with the 18's. So he runs them in the summer months. He said his car accelerates faster with the lighter 18" wheels. He also said the OE wheels were quite heavy.
P3 reads wheel spin, so the 0-100 kph function is not accurate. The hipocracy of the M3 competition package is the 359M wheel isn't forged and is heavier than the non-competition package 19" 220M wheel which is forged.
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      03-24-2013, 03:40 AM   #49
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Quote:
Originally Posted by heli_ben View Post
Who here is a good enough driver to feel 5lbs a corner on unsprung mass? (on a car with street / road focused suspension)
Anyone who pays attention to turn-in and how the suspension behave on road.

Quote:
Originally Posted by neech View Post
Well the common thought is that (at least for handling) every pound of unsprung rotational mass you shave off is equivalent to 10x that in sprung weight. so 5lbsx4 cornersx10 = 200lbs in total chassis weight. Can you feel the difference around the road course between having a passenger or not?

Now imagine shaving off 10 lbs off each corner. Yes, wheel weight is a big deal.

Unsprung weight by itself (shocks, suspension components, brake calipers) is a 4x ratio IIRC.
Quote:
Originally Posted by blueshark View Post
Interesting.. How does the math work?
Quote:
Originally Posted by neech View Post
Well i'm not sure where the 10x comes from but the general principal has to do with the moment of inertia (MOI) / angular momentum. MOI is the amount of force required to change the angular momentum of an object about a fixed axis, or change the axis of rotation. These are what "gyroscopic" forces are.
When you accelerate/brake/turn, not only are you changing the velocity of the wheel (as if it were in your trunk) but you must change the angular velocity AND also the axis of that velocity, which both require significant energy. Think about when you're holding a spinning bike wheel by the hub, how hard it is to change the orientation... And that's 3-4 pounds at a relatively slow angular velocity.. Now take 60 lb car wheel/tires, multiply that by 4 corners, at 20-100mph... That is a significant moment of inertia.

I think the 10x is a pretty rough guesstimate though, not sure where that came from.
After doing a whole lot of research before I purchase my wheels, I think it is almost like Chinese whispers and ended up with something some dramatic like 10x the weight. I have heard people talked about 5x 8x and 10x. The math on angular velocity once you do the sum it range from 1 at the centre of the wheel to about 2.5 times (IIRC) at the edge of the wheel at an average around 2x. So, the more accurate saying should be, "if you save each kg in each wheel, that's equivalent to saving 8x that weight". That is calculating by 2kg in each wheel with a total of 8kg, and not 8kg of unsprung mass saved and equivalent to 32kg.

However, the other thought is that it is about the suspension behaviour when reducing unsprung that people are talking about the x5 x10 improvements.

Quote:
Originally Posted by heli_ben View Post
I can certainly feel 200lbs. However we've changed rims on my race car with a similar %'age mass reduction and we couldn't really see it in laptimes, and I don't think I can feel it.

I don't think it's that simple.

For sure it's always good to cut mass wherever you can, especially in rotational and non-rotation un-sprung mass... but I think on a road car, it's primary use is in the bar, not on the track! :-)
The advantage of reducing unsprung is not weight reduction from the total mass but suspension behaviour. Now, theres where probably the x5 or x10 possibly comes in. The suspension controls the sprung and the unsprung mass - if there is a proper suspension tuned to the reduction in weight, there is where the advantage comes in. My car has 40kg of unsprung reduced from brakes and wheels, and you can certainly feel the difference in ride and grip. Your suspension basically works better as there is less momentum to deal with. However, to truely extract the performance on track, you will need to tune the suspension accordingly. You will probably see more improvement on the road than track when there are more bumps.

Quote:
Originally Posted by gatorfast View Post
People put way too much emphasis on wheel weights. Ive switched from "heavy" factory wheels to lighter after market wheels and noticed no difference.
How much lighter?

Quote:
Originally Posted by Dackelone View Post
I met a guy in Switzerland who went with 18" wheels - he had a P3 gauge vent and he claimed his 0-100 kph (62 mph) was under 4 secs with the 18's. So he runs them in the summer months. He said his car accelerates faster with the lighter 18" wheels. He also said the OE wheels were quite heavy.
+1.
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      03-25-2013, 02:11 AM   #50
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I think it is good weight on 1m original rim to be 9 on 10 "and low ET

have ordered other rims to my this year

Oz Superforgatia mblack 8.5x19 et29 10x19 et23 think they will weigh between 17-18lbs

8.5x19 et 49 7.34 kg
10x19 et 61 8.03 kg
this in the Porsche rims spec, lightweight to be 19 "

hope I get rims this week

/ JimmyObergsweden
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      03-26-2013, 08:29 PM   #51
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Quote:
Originally Posted by Oberg View Post
I think it is good weight on 1m original rim to be 9 on 10 "and low ET

have ordered other rims to my this year

Oz Superforgatia mblack 8.5x19 et29 10x19 et23 think they will weigh between 17-18lbs

8.5x19 et 49 7.34 kg
10x19 et 61 8.03 kg
this in the Porsche rims spec, lightweight to be 19 "

hope I get rims this week

/ JimmyObergsweden
Super-light, but why the heck are this so skinny in front! Errrr. Also, they're a bit 'money'.

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      03-27-2013, 02:24 AM   #52
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Quote:
Originally Posted by Mahlzeit View Post
Super-light, but why the heck are this so skinny in front! Errrr. Also, they're a bit 'money'.

tirerack
I know :/ do you think it works with 10x19et23 front too? Yes it is a lot of money :/
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      03-27-2013, 03:12 AM   #53
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Z4M wheels are in the 26lb range.

If you want real, track proven wheels go APEX.

Their ARC8 wheels can be had for close to 18-19lbs in 17" sizes.

The EC7s are a bit heavier
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      03-27-2013, 12:29 PM   #54
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Quote:
Originally Posted by Oberg View Post
I know :/ do you think it works with 10x19et23 front too? Yes it is a lot of money :/
I'm not offset expert - but very interested in the answer you get.
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      03-28-2013, 08:03 AM   #55
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Quote:
Originally Posted by Oberg View Post
I think it is good weight on 1m original rim to be 9 on 10 "and low ET

have ordered other rims to my this year

Oz Superforgatia mblack 8.5x19 et29 10x19 et23 think they will weigh between 17-18lbs

8.5x19 et 49 7.34 kg
10x19 et 61 8.03 kg
this in the Porsche rims spec, lightweight to be 19 "

hope I get rims this week

/ JimmyObergsweden
Quote:
Originally Posted by Mahlzeit View Post
Super-light, but why the heck are this so skinny in front! Errrr. Also, they're a bit 'money'.

tirerack
Quote:
Originally Posted by Oberg View Post
I know :/ do you think it works with 10x19et23 front too? Yes it is a lot of money :/
Not that much money compare to the fis, but not sure how the strength will compare.
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      03-28-2013, 08:48 AM   #56
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Quote:
Originally Posted by Mahlzeit View Post
Super-light, but why the heck are this so skinny in front! Errrr. Also, they're a bit 'money'.

tirerack
Quote:
Originally Posted by Oberg

I know :/ do you think it works with 10x19et23 front too? Yes it is a lot of money :/
The stock rear wheel at 19x10 fits up front with minimal rubbing on stock rear tire size so yes this should work.
At the very least go with a 9" up front or 9.5" .

I put some 19x8 E46 m3 wheels on my car for a day to pass an inspection. They looked ok in the rear at 19x9.5 but the fronts looked horrible. Wrong offset and super skinny wheel and tire.
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      04-13-2013, 01:33 PM   #57
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I'm not sure that's right. The 220 are 1/2 narrwer but come it at about 23.3 lbs front and 25.5 lbs rear.

http://www.m3post.com/forums/showpos...&postcount=306

So about 8 lbs lighter per set v. #359. I also understand the 220 are forged and the 359 are not.

Quote:
Originally Posted by Dackelone View Post
^^That sounds about right.

M wheels are always lighter than normal BMW wheels. IF you look at the Felgenkatalog you can see that the "normal M wheels (type #220) weigh in at 13.26 kg or 29 lbs each. And those #220 wheels are half an inch narrower than the M Y-spoke #359 wheels on the M3 (comp pak) and 1M.

http://felgenkatalog.auto-treff.com/

So the 1M wheels are 3(+) lbs lighter than normal bmw wheels.


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