BBS Mag Wheel Failure
05-04-2011, 11:24 AM
#19
Three Wheelin'
Mag in general tends to be less stable than aluminum, but cracking in wheels is certainly not contained to magnesium. I've seen cracked aluminum (including forged and billet). I even saw a steel wheel crack on a 914 once, and I happened to be a passenger when we discovered it. The driver and I could hear it, and even as a passenger I could feel the vibration it was causing. When we got out of the car, we could see that the one of the front wheels had cracked more than 3/4 of the way around. The crack appeared to have started at one of the lug bolt holes and propagated around from there.
Scott
Scott
05-04-2011, 02:23 PM
#21
Three Wheelin'
05-04-2011, 04:26 PM
#22
Rennlist Member
Yea, so, this is no big deal. BBS has discontinued the MAG wheels and replaced them with the spun aluminum versions. I've had a few centers cracked, and depending on how old your wheels are, how hard you hit the curbs, and more importantly, which centers they were they will eventually crack.
The wheel centers you have are the older style where the center fits on the outside of the wheel centers, so I'm guessing these are 8040 or 8041s which are very old, in the early 90s era on 964s. I don't know whether it is true or not, but I've heard the mounting of the wheels on the outside isn't as strong as the mounting on the inside like the later wheels.
They don't just crack all of a sudden like that, they probably had a fracture that could have been seen during an inspection of the wheel. They usually start cracking from the backside, so you really, really need to inspect the wheels closely every time you have them off (each morning of a track day and again at noon).
BBS has some centers such as the 8039 centers which look exactly the same as the 8040, 8041, 8051 which are specifically for the front of a 993 to clear the 380mm brembo brakes and the spokes are thinner. They will crack eventually if you run them on the rear.
The aluminum centers are not quite as light, but they are stronger and generally have replacements with the same offset as the mag centers. You can get them from BBS Atlanta.
The wheel centers you have are the older style where the center fits on the outside of the wheel centers, so I'm guessing these are 8040 or 8041s which are very old, in the early 90s era on 964s. I don't know whether it is true or not, but I've heard the mounting of the wheels on the outside isn't as strong as the mounting on the inside like the later wheels.
They don't just crack all of a sudden like that, they probably had a fracture that could have been seen during an inspection of the wheel. They usually start cracking from the backside, so you really, really need to inspect the wheels closely every time you have them off (each morning of a track day and again at noon).
BBS has some centers such as the 8039 centers which look exactly the same as the 8040, 8041, 8051 which are specifically for the front of a 993 to clear the 380mm brembo brakes and the spokes are thinner. They will crack eventually if you run them on the rear.
The aluminum centers are not quite as light, but they are stronger and generally have replacements with the same offset as the mag centers. You can get them from BBS Atlanta.
