The title pretty much says it all. Are cast wheels okay for HPDE track events, or are forged wheels a must? I know the fd is fairly light. I'm looking at some cast Gram Lights for sale locally.

Thanks,
Ken

 

Street tires, right?
HPDE don't care.
If you keep the car on the track, you should've be breaking rims.


-Ted

 

they are definitely ok. if you run a lot of events (10+/yr) then you should make it a prority to check the wheels for cracks, especially from behind (brake heat is intense durng HPDE's) even if they are forged wheels.

 

I personally would not have a cast wheel on a car going over 150mph. That is becuase I have seen one crack and shatter at road ATL. In land speed racing to go over 130mph you have to get a forged rim.

 

Japanese tuner shops like to do top speed runs on the freeways with Enkei NT-03's.
These rims are cast.
They do runs regularly over 300kph.
You can figure out that this is easily over 150mph.
I don't see why it's required to run a forged rim.
I'm not saying you can do this on any cast rim.
But, to make a blanket statement like that just doesn't make any sense.


-Ted

 

sorry to but in ... but couldn't you get cast wheels cyroed and they then last longer? Forging help alignes the particles for a stronger piece, and because cryo treatments are supposed to do the same, it should work, right? I mean one way is with pressure the other with changes in temperature, forging being the better.

also note that this will not give you the weight saving benefits of forged wheels, but it should take them longer to crack, and depending on your budget may be a good route.

If you plan on taking the car to the track a bit I'd invest in a set of forged wheels.

my 2 cents
Rip

 

i think it depends, not all cast wheels are created equally. I've heard that the cast Enkie wheels like the RPF1 and old RP01 aren't bad... but when you're talking a set of Fittipaldi's or Konig's, i've heard of people bending them autocrossing.

Better off getting a 2nd set of stock wheels than that.

 

Perhaps there is a rule in LSR racing that requires forged wheels for passes in excess of 130 mph?

 

No. Cryo treating a cast piece does not alter the crystal orientation, it merely relieves some of the stress across the boundaries of adjoining crytals.

When a piece is forged you get nice, smooth boundaries and transitions in the crystal structure. This results in a forged part's superior strength compared to something cast or machined.

 

Oh, I have no idea what the LSR rules are.
I just brought up the example of what the Japan tuners shop were doing in Japan.


-Ted

 

It's the quality of the wheel -- I mean Ferraris, Lambos, and Porsches still come stock with cast wheels....they all have high speed capability and I haven't heard of wheel shearing problems there. In fact, the only wheel shearing problems I have heard about are with the chromed Viper wheels.

 

I must remind everyone of this. https://www.rx7club.com/showthread.p...ight=crack+rim

 

Wow... interesting link. I've done lots of track days on stock rims... now I'm nervous.

 

Those were the original "weak" wheels that are known to fail IIRC.

 

thank you for correcting me, i'd hate to give out bad info.
Rip

 

Yep, there is a rule that states that you have to have forged rims past 130mph. it is a saftly rec. like a roll cage and fire suppression.

Although there may be some cast rims that can handle high speed runs, road racing, and auto X I personally would not trust my life with them at high speeds.

 

If you feel like reading......

Something that really isn’t being discussed here is that the forging process simply has “benefits” over casting, that’s all, and that a newer casting is perfectly safe at sustained high speeds (300KPH, 186MPH). Using a cast wheel at those speeds is not placing you in direct danger of that wheel exploding.

A quality forged wheel has its’ start from a solid hunk of raw T6061 aluminum billet. When I say raw, I’m referring to the aluminum not used in another application. I Forge has a great explanation on the website, “ The forging process, using high pressure and temperature, changes the non-directional grain structure of cast aluminum starting material to the high integrity multi-directional grain structure of forgings. The aluminum remains solid throughout the process as the forging dies come together and changes the shape of the round bar to the cylindrical shape of the wheel. This forging perform is then placed in a custom built spin forging machine to forge the rim section.”

”The resulting radial grain direction places the highest material strength in the same direction as the operating loads. The bottom line is premium strength. Then computer controlled lathes and milling machines are used to achieve the final configuration.”

While this process has its’ added benefits for us tuners, the real need for this process goes to the tractor trailers on the interstates where the amount of tonnage they carry as well as the need for fuel efficiency can play a large part in revenue created as well as the avoidance of horrific traffic accidents.

The casting process does not allow for the weight carrying capacity of a forged wheel. The most common gravity casting process as you already know consists of pouring molten metal into a mold and allowing it to solidify. It is that solidification process (as well as pressure used) that is most important. That is where the dangers of porosity (trapped air), and cracks (variances in cooling temps) can play their hand. Heat treatment helps to control the amount of variance in the wheel by uniformly reducing the residual stress form the casting process.

On an automobile, casting is a cost effective process that can yield somewhat similar advantages to forged wheels with casting’s weaknesses attached to longevity- casting has a shorter operational window / life than forging. BUT, we all know casting can be ALOT easier on the wallet. When looking for a cast wheel, look for a low pressure (less pressure, less porosity), heat treated wheel from a reputable name.

~Mike