A few "throwing stars" questions

[rtowle]

Excuse my lack of knowledge.

Are throwing stars only available from the M5 E34 cars?

What sizes are out there?
Are they tough to find, or are they readily available used?

Rich

[kipwinger]

e31, e32, and e34 models came with throwing stars I believe. All the upper crust of the 5, 7, and 8 lines of course.

The sizes range from 17x8 to 17x9 and the offsets range from 10mm to 26mm.

The 17x8 et 20 wheels are fairly common. The others are not.


*the offset information may be off but, it's close. Damn you memory*

[e34moneypit]

There are two factory 17-inch wheels for the E34 M5: M System I (http://www.bmwmregistry.com/images/E34-M5wheel.jpg) and M System II (http://www.bmwmregistry.com/faq/M_System_II_Wheel.jpg). Both are a two-piece wheel with a forged five-spoke center and a cast rim covered by an outer cover. The only difference is the design of the outer cover: "turbine" for the M System I and "throwing star" for the M System II. This outer cover is interchangeable between the two M System wheels, making updating form the earlier style to the later style an easy (and therefore common) procedure.

All 3.6-liter M5s (with the exception of North American-spec 1993 models) are equipped with 8x17-inch M System I wheels carrying 235/45ZR17 tires. In some markets outside of North America, the rears could be upgraded to a wider 9x17-inch version with 255/40ZR17 tires as an extra-cost option.

All 3.8-liter M5s built before May of 1994 (as well as North American-spec 3.6-liter M5s produced for the 1993 model year) are equipped with the later M System II design. Wheel size remained 8x17-inch all around or, as an extra-cost option, the wider 9x17-inch version could be specified in the rear. These 9x17-inch rear wheels (carrying wider 255/40ZR17 tires) were fitted to all pre-5/94 3.8-liter M5 sedans equipped with the optional Nürburgring Package, as well as all pre-5/94 E34 M5 Tourings (whether optioned with the Nürburgring Package or not).

All M5 sedans and Tourings built after May of 1994 were upgraded to staggered M Parallel Spoke wheels measuring 8x18-inches in the front and 9x18-inches in the rear. These carry 245/40ZR18 tires on all four wheels. Note: Though nearly identical in style to the 18-inch M Parallel Spoke wheels later used on the E38 7 Series, the E34 M5 wheels have a different matte silver finish and a unique offset.


Taken from the M Registry website

E31's had staggered throwing stars, and I believe, as someone already said, e32's had them as an option.

[540msportva]

The 1995 540i Msport also came with the M system II design with the throwing star cover. They were also the 17x8 all around.

Just had to step up for the forgotten one.

[BruinBimmer]

The 1995 540i Msport also came with the M system II design with the throwing star cover. They were also the 17x8 all around.

Just had to step up for the forgotten one.

Was totally about to do that. Beat me to it... But at least someone is standing up for our rare species.

[BigRedSeventy1]

Was totally about to do that. Beat me to it... But at least someone is standing up for our rare species.

represent :alright

[kalevera]

Not all are forged, some are cast, google it as there are a few good pages discussing how to determine which is which.

[bubba0966]

There are two factory 17-inch wheels for the E34 M5: M System I (http://www.bmwmregistry.com/images/E34-M5wheel.jpg) and M System II (http://www.bmwmregistry.com/faq/M_System_II_Wheel.jpg). Both are a two-piece wheel with a forged five-spoke center and a cast rim covered by an outer cover. The only difference is the design of the outer cover: "turbine" for the M System I and "throwing star" for the M System II.

Really not sure why the M Registry is saying that the M-System's are a 2 piece wheel with a cover. They're a 2 piece wheel when the cover is installed, the wheel itself is only one piece, either cast or forged.

And yeah, they were available in E31/E32/E34 fitments both forged & cast in both 17x8 & 17x9 sizes.


M-System forged vs. cast comparison guide, from another M-Sport owner...

http://www.cscoupe.org/misc/tstars/tstars.html

[mossyoaks]

Which one is more 'desirable'?

Forged or Cast?

[kipwinger]

Forged.



Casting
The quality of cast wheels varies dramatically, depending on process, and sometimes on variables beyond the control of the manufacturer, such as ambient temperature or even humidity. In general, pressure casting, in which the metal is pumped into the mold, is better than just pouring it in. Castings tend to be porous -- some carburetors actually leaked fuel through the metal, with no crack or visible flaw present. Porosity is bad, because it means there are places where the metal isn't in direct contact with more metal on all sides. Voids, which tend to form in the spaces between crystals (a chicken and egg situation), are where cracks begin. Larger, chunky grains may beget larger voids, and cracks along crystal boundaries will have farther to travel. All these points mean that cast wheels must contain more metal to achieve an acceptable strength, and are thus heavier. Still, cast wheels can be made to a high standard with attention to quality processes. The vast majority of alloy wheels are cast, and provide many years of good service.

Forging
Forged wheels take advantage of what happens when metal is cold worked. Cold working doesn't necessarily mean you'd want to touch the materials while they're in process, it means the procedures are done at a temperature below the point where the metal starts to melt and regrow a new crystal structure. Just as the spaces between a metal's crystals may hold flaws, the crystals themselves are full of imperfections called discontinuities. They may take a variety of forms, but discontinuities all share one important quality. By traveling through the crystal lattice of the individual grains, they allow the metal to change shape without fracturing like a diamond. When a load is applied to a metal object, it deforms slightly. When the load is removed, it regains its original shape. This happens because discontinuities move a little, and move back. If the load is high enough, the discontinuities will move until they reach the edge of their crystal, or until they run into another discontinuity.



Generally, discontinuities move one atom at a time, and their movement is guided by the regular structure of the crystal. If a discontinuity in the structure runs into another, the regularity is interrupted, and they may become tangled, and can't return to their starting position. This has two effects. 1) When the load is removed from the metal, it will not return to its original shape. 2) The metal is more resistant to deformation in the future, because there are fewer discontinuities available to move around. This description of the process is a single case of what is actually happening by the billions.
What we can measure is the average of them all. The idea behind forging is to get, on average, the right number of discontinuities tangled around each other, with crystals oriented in the right direction, so that the metal is very strong and resistant to further deformation. This is a delicate balance, because too much cold working makes the metal brittle, so that it fractures instead of absorbing loads. You can see how this works for yourself: Bend a paper clip back and forth many times until it breaks. It begins soft, then gets stiffer, before finally fracturing.



Forging also changes the shape and alignment of the crystal structure. When molten metal solidifies, its grain structure is non-directional, amorphous, grains in the sense of "grains" of sand. As metal is forged, these grains are stretched in the direction of deformation, making them more like the "grain" of wood. The metal is formed so the grain goes in the directions where strength is needed most. Think of particle board versus real wood. One is cheap, heavy, and easily formed into a variety of shapes. The other is strong and light. The forging process, because of the vast pressures involved, also compacts the metal, eliminating porosity and the voids that can be a source of cracks or corrosion. The result is that less metal is required to achieve a given strength, meaning lighter, stronger wheels can be made.

Billet
Billets, raw blocks of metal as it is purchased from the manufacturer, are generally significantly cold-worked in manufacture. However, the cold working is done in one direction only, as the material is rolled or extruded into long bars in a continuous process. This means the grain of the metal has only one orientation. A billet wheel is like cutting a part out of an ordinary piece of lumber, whereas a forged wheel is like growing a piece of wood to exactly the shape you want.


Taken from modified.com

[bubba0966]

Which one is more 'desirable'?

Forged or Cast?


As was said already the forged versions are much preferred. But I've honestly yet to see a cast set for sale or on someone's car in pics. Only pics of a cast M-System I've ever seen are in that link I posted on the visual differences in the forged & cast versions.

I'd wonder what a set of cast M-Systems would go for.

[nirvana19]

Which E32s had the M-System wheels as an option? Was it perhaps a BMW individual option? I wasn't aware of this, I can't recall any E32s with them from the factory but even if I had seen one I would have probably assumed they were added later...

[Dvsm50e34]

In Australia the M5's. 540i's and 535i Sports all came with 17x8 and 17x9 at the rear :D

[Sixdown]

The E32 did come with M-System II Throwing Stars as an option, and also M-System I, but apparently only in Europe.

http://www.realoem.com/bmw/partxref.do?part=36112227745&showus=on&showeur=on&series=E32


Not entirely sure of how accurate the numbers are.
http://www.gearfx.com/bmw/partnumbers.gif

[BruinBimmer]

Really not sure why the M Registry is saying that the M-System's are a 2 piece wheel with a cover. They're a 2 piece wheel when the cover is installed, the wheel itself is only one piece, either cast or forged.

And yeah, they were available in E31/E32/E34 fitments both forged & cast in both 17x8 & 17x9 sizes.


M-System forged vs. cast comparison guide, from another M-Sport owner...

http://www.cscoupe.org/misc/tstars/tstars.html

Damn if the forged 17X9's are 21 lbs my forged 17x8's are probably less than 20... so now I'll feel guilty if I get any other wheel. Not much else lighter than 20 unless you pay over $700/wheel.

[bubba0966]

Which E32s had the M-System wheels as an option? Was it perhaps a BMW individual option? I wasn't aware of this, I can't recall any E32s with them from the factory but even if I had seen one I would have probably assumed they were added later...


I couldn't find any US model E32's with M-System's on realoem. Was able to find them on some Euro 735's though.

[kipwinger]

As was said already the forged versions are much preferred. But I've honestly yet to see a cast set for sale or on someone's car in pics. Only pics of a cast M-System I've ever seen are in that link I posted on the visual differences in the forged & cast versions.

I'd wonder what a set of cast M-Systems would go for.

I've seen them almost as often as the forged sets. I think that they are less visually appealing in the slightest way possible.

[warhammer23]

.... 8x17-inch M System I wheels carrying 235/45ZR17 tires. In some markets outside of North America, the rears could be upgraded to a wider 9x17-inch version with 255/40ZR17 tires as an extra-cost option...



Just to be sure 100% , i ask.

Currently i have these rims (e34)
-front 8,5j x 17" with 235/45/17 tyres
-back 10 j x 17" with 245/45/17

I want to put the M-System rims and to use existing (dimensions) tyres . My only worry is the ratio at the back.. 45 (mine) vs 40 (from what it recomends here (http://crass.on.ru/bmw/wheels/style/style_021.htm))
Can i? Thankyou.