renvagn

Is anyone aware of any after market billet hub failures in racing or track used cars?

There are two manufactured types I have come across with the differences being 7075 aluminum and 6-7 oz heavier than the other, which is 6065 aluminum. What are your thoughts. Revolving weight is allways the most significant, but not if strength and ultimately safety is compromised. I have been told that 18" wheels and grip will put a fair amount of stress on the part.

Thanks.

RedlineMan

Hmmm...

If you're worried about rotational inertia, you probably don't want 18s anyway. BOAT ANCHORS. You have to spend that 18" money wisely to avoid it, and it can be BIG MONEY. The hub is so close to the rotational center that weight is probably not significant. I'd opt for strength AND toughness, for sure.

slawek

Racers Edge billet hub failed on my 944 with 18" wheels during race. Karl still is waiting for answers from his LAB. I would like to know if the wheel diameter has to play with the failure, since my 18" wheels are very light--front 18lbs. Anybody has any thoughts on that-- metallurgic engineering brains here? Cheers

Cory M

Are you sure you got the 6065 alloy number right? I couldn't find anything listed for it in the ASM material data center. In general 7075 is stronger than the 6000 series, although either option should be stronger than the factory hubs because they are machined from wrought aluminum rather than cast. I designed and built some hubs for a formula car once and ended up selecting a 2000 series aluminum because of its high strength at elevated temperatures, we were using carbon brakes that got pretty hot.. I wouldn't worry too much about 6-7 ounces on a production based car. Is there much of a difference in the designs? If so you may want to select the one that has the least number of sharp inside corners and the best surface finish...

Cory M

The big wheel diameter is going to make a much bigger difference than the weight o the wheel/tire. All of your lateral cornering loads, and longitudinal braking loads are tranfered from the tires contact patch - a biiger wheel = a longer lever and a bigger moment acting on the part. Do you have any pictures of the failed part?

slawek

Unfortunatly I didn't snap any shots of it-- it was ugly thought, spindle destroyed, but the hub was strong enought-- it didn't come apart and the wheel didn't brake off.

renvagn

Thnaks for the info, keep it flowing. I had heard wispers of some failures. I agree with John. The weight issue I believe will be somewhat minimized do to it's smaller circumference location when compared to the greater diameter and weight of the wheel/tire, hence the need to go with lite weight wheels, which I will. I don't do rice.

Slawek, What wheel were you using? Why would you suspect a liter wheel would produce more stress on the hub than a heavier one??

slawek

I'm using approx 19lbs front and 20-21lbs rear wheels from ccw, volk, bbs. Did I say lighter wheel will put more stress? If I said that I was wrong-- havier wheel will put more stress on the hub. Any more thoughts on this?

renvagn

I would agree with the heavy wheel generating greater stress, But this doesn't seem to be a contributing cause to your failure. Where did the break on the hub occur?

Cory M

I wouldn't worry too much about the weight of the wheel - wheel diameter, wheel offset (affecting scrub radius), the capabilities of your tire, the weight of your car, weight distribution, tracks you drive, your driving style, etc, etc, will have a much greater effect.

Oddjob

Not sure the lever arm is changing much, if the tire OD is similar (e.g. between a 245/45/16 and a 245/35/18). Also, lateral grip is arguably similar between tires with the same size contact patch.

I would entertain the idea that the reduced sidewall height on the 18s (vs 16s) increases impact/shock loading on the suspension, since there is less rubber sidewall to flex and absorb/dampen that type of loading. Similar effect as caused by replacing all factory rubber suspension bushings with solid/spherical bearings and bushings (which may increase risk of failures of control arms, trailing arms, suspension pickup points, hubs, etc).

JoeMag

I had some 18 fikse fm-5's crack. ...actually, noticed one rear spoke cracked and found one other on another wheel. fikse totally took care of it and I got 4 new centers and barrels swapped free of charge. from the originals to the replacements, the webbing on the back of the spokes had been increased.

Cory M

Yeah, if the OD and contact patch stay the same you're right. There will be some effect from a stiffer wheel with a shorter sidewall tire, but the point I was trying to make is that the weight of the wheel itself is not the critical factor here.

RICHVIZZ951

Personally I have never seen a hub fail at the track on a 944 (doesnt mean they dont), spindles Plenty, hubs no, although have seen many pics of failed hubs on rennlist, search there are threads out there on this. I replaced my hubs with Karls Racers Edge ones as well, never had an issue with his either, Very nice pieces he sells. They really arent too too expensive, better to be safer than not. I always ran 18's.

slawek

I just installed these hubs spring '08 from Racer's Egde and did 3 races before inner bearing went south. My RE hubs weren't the only ones failed-- even at the same race!!!