cobalt

I manufacture magnesium castings for a living. Incredible material. Alloy used for wheels plays a critical role along with the design, casting process and heat treatment cycles. Most of your F1 wheels are made of a zirconium based rare earth alloy called ZE41AT5, very expensive the additive runs around $15 a pound and requires roughly a 17% addition to quantity poured. It has great yield strength but not much tensile strength. All Magnesium alloys are susceptible to impact damage, and corrosion from the elements. It is easily used in F1 where cost is less important than weight savings and wheels are expendable.

IMO when I first saw these wheels I though the spoke design was not adequate for the loads required. I guess I was correct in my assumption. The biggest issue with magnesium is that no matter how well the processing was done you can only work to minimum requirements and magnesium can achieve strengths similar to cast aluminum more often than not it falls short.

I will say that based on what I have seen over the years the fracture in the picture above is more likely a case of improper heat dissipation. The material looks as though it had been annealed from prolonged exposure to high temperatures exceeding 500 degrees. The shinny exposed metallic look to the broken areas is a giveaway. If this material was properly heat treated and in sound condition the broken areas would look a creamy mat color and not shinny silver. This might also be a result of the CF not being able to transfer the heat across the barrel of the wheel. Although thicker spokes would have added little extra unsprung weight and given far great strength to the design.

As far as proprietary alloys there aren't many configurations that haven't been tried. One very popular alloy many years ago was called almag 35 more of a high concentration magnesium based aluminum alloy very strong and stable although it is heavier than your average mag alloys.

deputydog95

If that's what magnesium "does", then why use it? Seriously? Unless you're changing the wheels out for every event and throwing the old ones away or sending them back to the factory for inspection, why would anyone want to use a wheel that they know is going to crack at some point? I would rather have 10% more weight and the confidence that the wheel probably isn't going to shatter... Although I guess that's why they're not using magnesium anymore. What can't figure out is why you would keeping using magnesium after you kept breaking wheels... One is a defect, two is a problem. Time to dump the set.

deputydog95

I just came back from running Daytona this past weekend. The OZ's with pilot cup's were great! The feel from my 19" cargraphics with street tires to the OZ's was a tremendous improvement.

cobalt

Magnesium is best suited for racing where every ounce makes a difference. For the weekend warrior I agree it doesn't make much sense. Although aluminum will do the same exact thing if temperatures are allowed to get to high. Annealing any metal will cause it to loose its strength. ie world trade center collapse. Sorry for the example but it makes the point. I have seen aluminum wheels fail just the same because they were allowed to get too hot for too long. Proper brake venting heat dissipation is critical. Design has a lot to do with it also.

deputydog95

I'm totally with you on those points. Although I'm sure F1 teams have dozens of sets of wheels to work with. For the DE guy or street driver, using something that will probably fail doesn't make sense. Unless you're being paid to race, a few extra ounces won't matter

ricster

" For the DE guy or street driver, using something that will probably fail doesn't make sense. Unless you're being paid to race, a few extra ounces won't matter"

Well said!! I have a friend who worked for Flying Lizard race team and he told me they use BBS wheels because they are the best.....so if its good enough for them its good enough for me...and you.

I recommend BBS LM wheels for your car.

cobalt

F1 teams also inspect everything thoroughly before and after each use. The old 917/935 wheels were mag alloy. I have a friend with a Jagermeister 935 and he had his original wheels refinished. They were quite solid and held up well because of the design. Far more strength in the spokes thickness to the barrel and much better brake cooling.

I would not discount mag for AX or DE. I would recommend inspecting your wheels every chance you get but I recommend that for any wheel mag or alum. There are varying grades in quality of alum wheels also. Low profile tires and stiff sidewalls can cause factory wheels to fracture just from impact and these are high strength aluminum. Mnay people use the 993TT hollow spoke wheels for DE and they are notorious for fracturing.

I have many friends that own vintage race cars and take them to historic races. More times than not the mag parts are replaced with aluminum copies. Although these guys are out there for fun and bragging rights where safety takes priority over weight.

TB993tt

That is a very good question

The mag centerd wheels were Porsche993GT2 Speedlines, the ones with the 5 spoke mag centres. I bought a set second hand for my 993tt which I adorned with GT2 arches. I didn't really know anything about cracking magnesium back then and soon learned.
I loved the look and since no one else made anything which looked the same I persevered..... It was the rears which cracked, one really badly and potentially dangerously. I ended up leaving them in my garage for most of the time and used 996tt alloys instead. Someone kindly alleviated the problem by breaking into my garage and stealing them - I didn't really shed any tears, they shouldn't be used on road cars really without the aformentioned inspections/xrays etc and were/are an accident waiting to happen.
I hope the new Dymag alloy holds up !

deputydog95

Isn't Fiksi out of business now? I know someone with someone wheels that were sent in for repair and now no one has been answering the phones for a couple weeks.

Where do you get a low profile jack? It is a such a pain in the *** to get my car jacked up as I have to drive up on a couple small sections of 2x4 and then race to jack the car up before they've been sitting on those narrow 2x4's for too long.

rennschnell

I'm a little late to this post, but didn't BBS switch from a magnesium center section to an aluminum forged center on there modular race wheels about 5yrs. ago?

Also, how are the CCW modular wheels? I see/hear that alot of folks are using them mainly due to price, but they look pretty rough. I've seen a few up close and the bolts look like grade 8 from the local Homedepot with nylon locking nuts. On the CCW website they have a video showing you how to do your own wheel repair at home.

http://www.ccwheel.com/files/technical.php

Two things that concern me are, the tech is using a 3/8" drive impact gun on full blast to run down the nuts and uses his finger to smear the silicone seal. Doesn't seam like a very high tech wheel for a Porsche. I've seen the guys from BBS and Fikse at the Daytona 24hr years ago replacing wheel parts and both used hand tools. Both used a 12 point bolt, looked like an aerospace type. I guess when you watch a video on how they hand build a Porsche Motorsport, AMG or Katech engine you would expect the same materials, care and similar modern technology to be used on your aftermarket wheels. If you paid an extra $2k for titanium connecting rods, but then bought the cheapest aftermarket wheels available for track use, would you expect them to perform equally as your engine with the titanium rods?

Just my two cents here, great discussion about wheels. Funny you read about wheels on other forums and it's all about the latest color or chrome the wheel company has available.

cobalt

Interesting link thanks for posting.

I wouldn't be so concerned about the impact driver. I would assume it is set to the appropriate torque and is designed or set up for its intended purpose and supplies specified torque with each pull of the trigger. I don't necessarily agree with their approach regarding the time needed for the silicone to set and the way they torque the bolts. I would still stagger bolt torquing after the 4 are tightened and I am surprised to see they are using Silicone #II vs Silicone # I or more like other brands that use a silicone based gasket.

altonj

Ok,

here is how to do it....

Assemble the wheel torquing each fastener in a criss-cross patern to its specified value. Be it a 6mm BBS fastener or a 1/4 inch or 5/16 fastener. The use a silicone "adhesive" and not a silicone "sealant" to fill the valley and seal the wheel. We have had excellent success with the products from Dow and good success with the products from Loctite.

DO NOT use air tools. The torque values for the small fasteners are very low 12-14lb feet depending on where you source your fastener and its nominal diameter.

Cheers

333pg333

Out of curiosity, what are Dymag saying about all this???

TripleM

I like Carbon products for body panels but not for wheels, cant justify the existence of it really..
Forged LW Alloy is the furtherst I'd go..

Griswald

I'll say up front that there are many, many great wheels out there.

I've run CCW's for a number of years for track and AutoX. I've NEVER had a problem - period. As for looking rough, well, all of them I've seen look good to me. Value for the money I'll put them up against anything. Those of us who have raced Vipers and Vettes as well as PCars are well familiar with them. Do I sometimes run something else on my street car that is 3 piece, color matched, really, really 'pretty' etc. - sure. But for hard core use I like the CCW's - and even for street use.

Understand please, I'm no lapdancer and have no vested interest in CCW but IMHO they make a great product for the money.