speedform

So I broke a wheel at the track last week. I'm a little gun shy about going back to using the same wheel so I was wondering if anyone can point me in the right direction as to what wheel you might recommend that is both light weight, strong and won't break the bank. Thanks in advance.

2003z

iTrader: (7)

is that the enkei rpf?

I have the rpo2j and love them. about 190 each in 17x9

Moroccan_Mole

iTrader: (5)

id also look at the 5zigen fn01rc

speedform

Rpo2j? I'll have to look that one up. Thanks!

del105

iTrader: (4)

how to did you do that? Was there some sort of trauma to that wheel?

ADMAN

iTrader: (9)

Yeah, usually they don't just "break" unless he went off or it sheared frm rubbing.
Had that happen to a car infornt of me. Not fun...

So, you want price vs. weight vs. size or

speedform

No trauma to the wheel at all. Enkei is blaming the powdercoating facility that did my wheels claiming the media blasting and powdercoating process may have affected the sub- structure of the wheel.
I know sand or media blasting can heat up an object a little bit but not enough to cause this.
Anyway- I'm looking for a 17 by 8'5 or 9" wheel that might be close to the weight of the RPF1 which was 16.5 pounds.

phoenixZ33

My 5Zigen FN01RCs in 17x8 are ~18lbs and in 17x9 are 20lbs if I remember correctly. I've seen two people crack wheels in a similar fashion while autocrossing.. didn't hit anything, just noticed a weird sound and feeling, got out and noticed the spokes were broken. I forgot which wheels exactly, but Rota something or other.. split spoke design, look very similar to the one in the picture.

dwnshift

iTrader: (1)

For track wheels go with either.
Volks,BBS, or Forgelines............best bet is BBS. Their main buisness is motorsports wheels.

Vlad

Just get a new RPF1s... And don't powdercoat them this time... Baking wheel when powdercoating is sure can couse changes in structure... you shouldn't blame Enkei for that. RPF1s are the far best cost/weight ratio you can find out there.

03Z33

iTrader: (49)

You may also want to look at the Axis Reverb... it is a newer hollow spoke cast wheel that is very light similar to the advan tc-2 and the enkei rc-5. they have 17x9 coming out in low offset (~15mm) and these are cheap! only downside is that they only come in black or gold w/polished lip if you don't like that...

also if you are interested I have a set of Weds Sport TC-05's in 17x9 et20 all around that weigh about 17lbs each... I was hoping to get about $1200 for the set with some old race tires on them. These have huge brake clearance and are white.

speedform

Hey 03Z33!
Where in Socal are you located? I'm down in the LBC.

Don't think I want to risk getting another RPF1 Vlad. I got lucky the first time with no serious damage to my car or self. I don't feel like pushing my luck.

Vlad

That's your choise... I just think that people should acept responsibility for their actions, instead of finding somebody to blaim. I can't believe F1 supplier of wheels can design/produce flawed wheel. We'd hear horror stories from all directions... Powdercoating process is to blame, not Enkei.

Scott Webb

I've run Volks on the track on two different vehicles, including the Z Roadster, and I've had great luck. On my Spec Miata, I've got Team Dynamics heat-treated cast alloy wheels, and they've held up well under pretty difficult conditions, including wheel-to-wheel and wheel-to-body contact with other cars.

archman350z

Ahhh! I've been warning people about this sort of thing for some time...

If you think about what you're asking your wheels to do, I think you'll be amazed that this doesn't happen more often. Here's the 411:

The wheel you were using is a cast-aluminum wheel. Because of the crystallized grain structures in the metal (formed when the metal cools from its liquid state), they are strong as hell...but...they are also very prone to cracking and fatigue. I use the analogy of window glass when comparing cast wheels. Those that have ever tried to break a car window with a hammer know how tough it can be (glass is a very STRONG material). But when it breaks, it shatters into a million pieces. In other words, it is STRONG, but also BRITTLE.

The alternative is to use a forged aluminum or a steel wheel. Forged metals don't have a crystalline grain structure, so they are more "plastic" and not brittle. A forged wheel will actually flex as you corner, but will snap right back to shape afterward. These wheels will bend around like play-doh for quite some time before actually developing stress cracks (and ultimately failing). Steel wheels are nice and cheap, and they offer the same advantage.

For anyone regularly doing track events, I strongly encourage them to use a steel or forged aluminum wheel. These wheels will give you more warning before they fail. Forged wheels cost more because they are harder to make, but I feel the added cost is justified. A broken cast wheel during mid-corner can cost you an entire car!

Also, for those doing track events regularly: I strongly recommend you inspect your wheels periodically for tiny stress cracks. For those with cast wheels, you may want to have them Magnafluxed periodically too...the cracks that cause failures can sometimes be too small to see with your eye. Cracks will generally form in "stress concentration" areas of the wheel (this is engineering geek speak for areas that change geometry suddenly). They are most likely to occur where the spokes attach to the outer rim. Be careful not to nick or cut any part of the wheel (as these are stress concentration points).

Finally, stick with a reputable wheel manufacturer. I personally trust BBS and Rays/Volk. There is a lot of engineering that can be done to a wheel to ensure that stress concentrations are held to a minimum. The cheaper wheel shops just don't have the know-how.

03Z33

iTrader: (49)

I'm in Orange county, but I go up to LBC all the time... we should meet up sometime... if you get a chance a whole bunch of Z/G35 are meeting up at California Speedway in Fontana next weekend June 26/27 theres a nissan meet and drifting.

Wheels no matter what kind break. I've broken TE37's, BBS (on multiple occasions) both RC's and RK's... also bent the hell out of one of my rays track wheels, but thanks to it being forged it was able to be straightened.... cast wheels will definetely crack or break sooner, but forged is not in everyones budget, espeacially when you go through wheels as fast as some of us do!

speedform

Hey Vlad, chill out man. Who said I'm blaming anyone. Your getting a little defensive probably in light of the fact that your running the same wheel on your car. Great! Glad you like'm. I like them too. Enkei's a good company. I work at a major OEM design studio out here and all of the wheels on our cars, save one or two, are built by Enkei. For the most part, I'm impressed with their product. Not sure where you got this 'horror stories from all directions' thing but we powdercoat wheels all the time. Hell, sometimes Enkei does it for us.
Maybe it was the powdercoating or maybe it was just one bad wheel. Regardless, my question was to those fellow racers out there who might be running a wheel they are happy with and might recommend.
Thank-you to everyone else out there for their positive feedback. I've owned both BBS and Volks and am quite happy with their product. I was just hoping for something a little down the price scale. Of course that may be what bit me in the butt in the first place.

Vlad

Of course!!!

DmitryZ

archman,
You got the right idea and I 100% agree with you that for a track use, forged wheels are the only way to go. However, your engineering explanation is not correct. Aluminum is by nature a ductile, not brittle material. It remains ductile whether it is cast, cold rolled, hot rolled or forged. When aluminum is cast it develops a somewhat even, large crystal structure. Forged materials, in fact all metallic materials, certainly do have a crystal structure, except it is aligned to conform to the die during forging, making the part a lot stronger (smaller, directionally oriented crystals). In “geek” terms this would be: same elastic modulus but a forged wheel has a lot more toughness that a cast wheel.
It is hard to tell from the pictures, but I doubt this failure was due to fatigue. As you pointed out stress cracks generally form in areas where geometry changes suddenly, but if you look at the picture you can see that the failure occurred in the large section of the spoke in several places where geometry is constant. Also, it is extremely unlikely that a fatigue failure could occur in all the spokes at the same time.

Speedform,
You are right about sand blasting – it was not the cause. In fact sand blasting would make the wheel stronger i.e. shot peening. However, I think enkei is referring to the bake process. Powder coating takes place at about 450F, which is about 1/3 of melting point of aluminum i.e. you can have crystal structure changes as Vlad suggested. But this would only matter if the wheel was forged or if Enkei did some kind of post casting processing to increase the strength. If this was true, the wheel would not shear at the thick section of the spoke. This is what really bothers me… Looking at all the broken spokes consistently across the thick section makes me wonder. I am not sure how they cast the wheel (and this all could be complete bs) but it seems that this could be a casting problem. If the center of the wheel is the last section to be filled, there could have been some air gaps, or some sand/dirt particles that would weaken the material in that location and cause it to break. I am not saying that this would be true for all cast wheels Enkei ever made, but I am saying that this could be possible for one wheel in a very large batch that just slipped through inspection.
I am glad and surprised you were not hurt. In the future you should definitely invest in some forged wheels for the track use.

Dmitry

P.S. if possible could you post a close up pic of the fractured surface?

Vlad

wow! looks like you know your stuff

can those cracks happen from sudden twist of the wheel?

I.e. if looking from the front of the car take the bottom part of the rim and suddenly pull to the left while pulling top part of the rim to the right?