Option magazine wheel test: weight vs. rigidity
10-06-2008, 06:51 AM
#11
So the lightweight wheel will show an obvious difference in acceleration on the street (according to the driver), well that decides it for me. In an engine with less torque I would guess the difference would be even more apparent.
I don't race, no tracks near me, and if I did it would be for fun and not to beat others because I am never going to be that good behind the wheel. So the four tenths of a second gained by the rigid wheel will not make up for the tiny extra grin factor of better acceleration.
Interesting read though. I would also venture a guess that the difference in rigidity become more apparent the wider wheel you go, and less apparent with narrower wheels.
I don't race, no tracks near me, and if I did it would be for fun and not to beat others because I am never going to be that good behind the wheel. So the four tenths of a second gained by the rigid wheel will not make up for the tiny extra grin factor of better acceleration.
Interesting read though. I would also venture a guess that the difference in rigidity become more apparent the wider wheel you go, and less apparent with narrower wheels.
10-06-2008, 09:42 AM
#13
Registered User
Curious comment about braking instability. I wouldn't expect much effect, lowering the nose very slightly, in a straight line. Maybe he means braking into a turn?
10-06-2008, 10:01 AM
#14
When it comes to wheel rigidity. many tend to assume that production method (cast vs. forged) dictates the overall rigidity. In the case of technologically advanced manufactueres, this is not the case at all. Rigidity depends on the design of the wheel. Regardless of whether the wheel is cast or forged, if the same design and raw materials are used, the rigidity factor will be equal. Furthermore, the weight will not be affected neither. The majority of Enkei wheels are cast. Although, the generalized stereotype in the U.S. seems to be that forged is superior to cast, wheels such as the GTC-01 is equal or suprioer in strength to many other forged wheels out on the market due to Enkei's MAT technology. This MAT technology enables Enkei to produce wheels in which both strength and lightweight attributes can coexist in a balanced manner.
Ask any engineer if he will take a cast part over a forged part and they'll take forged every time, EVEN if the supposed material properties (strength, ductility, etc, etc) are exactly the same for both parts.
Why? Casting flaws are typically significantly higher in number and larger in size than flaws in forgings. Forgings will occasionally have pitting but most usually have cracks more than anything. Casting flaws can be on the surface but many are interior to the part. A cast part will not have the same rigidity as a forged part if they are dimensionally equal, mainly due to those flaws.
I don't care how you're casting a particular item - you'll NEVER have the strength of a forged wheel, period. Your material might theoretically be as strong but in real life, your casting flaws will require you to downgrade the strength of the material.
In my work, we can use a minimum safety factor of 3 for a forging. For a casting, we do a safety factor of 6 (minimum). In other words, we will allow stresses in a forged part to be 33% of the yield strength. In a cast part, it's half that (17%, roughly). That doesn't mean you can't make a strong, lightweight cast wheel, it just means that you've got to do an amazing job with the casting to keep it as light and strong as a forged wheel.
10-06-2008, 10:57 AM
#15
Originally Posted by JonBoy,Oct 6 2008, 12:01 PM
In my work, we can use a minimum safety factor of 3 for a forging. For a casting, we do a safety factor of 6 (minimum). In other words, we will allow stresses in a forged part to be 33% of the yield strength. In a cast part, it's half that (17%, roughly). That doesn't mean you can't make a strong, lightweight cast wheel, it just means that you've got to do an amazing job with the casting to keep it as light and strong as a forged wheel.
10-06-2008, 01:52 PM
#18
Originally Posted by JonBoy,Oct 6 2008, 10:01 AM
This is a bunch of baloney.
Ask any engineer if he will take a cast part over a forged part and they'll take forged every time, EVEN if the supposed material properties (strength, ductility, etc, etc) are exactly the same for both parts.
Why? Casting flaws are typically significantly higher in number and larger in size than flaws in forgings. Forgings will occasionally have pitting but most usually have cracks more than anything. Casting flaws can be on the surface but many are interior to the part. A cast part will not have the same rigidity as a forged part if they are dimensionally equal, mainly due to those flaws.
I don't care how you're casting a particular item - you'll NEVER have the strength of a forged wheel, period. Your material might theoretically be as strong but in real life, your casting flaws will require you to downgrade the strength of the material.
In my work, we can use a minimum safety factor of 3 for a forging. For a casting, we do a safety factor of 6 (minimum). In other words, we will allow stresses in a forged part to be 33% of the yield strength. In a cast part, it's half that (17%, roughly). That doesn't mean you can't make a strong, lightweight cast wheel, it just means that you've got to do an amazing job with the casting to keep it as light and strong as a forged wheel.
Ask any engineer if he will take a cast part over a forged part and they'll take forged every time, EVEN if the supposed material properties (strength, ductility, etc, etc) are exactly the same for both parts.
Why? Casting flaws are typically significantly higher in number and larger in size than flaws in forgings. Forgings will occasionally have pitting but most usually have cracks more than anything. Casting flaws can be on the surface but many are interior to the part. A cast part will not have the same rigidity as a forged part if they are dimensionally equal, mainly due to those flaws.
I don't care how you're casting a particular item - you'll NEVER have the strength of a forged wheel, period. Your material might theoretically be as strong but in real life, your casting flaws will require you to downgrade the strength of the material.
In my work, we can use a minimum safety factor of 3 for a forging. For a casting, we do a safety factor of 6 (minimum). In other words, we will allow stresses in a forged part to be 33% of the yield strength. In a cast part, it's half that (17%, roughly). That doesn't mean you can't make a strong, lightweight cast wheel, it just means that you've got to do an amazing job with the casting to keep it as light and strong as a forged wheel.
10-06-2008, 02:21 PM
#19
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So ... they measured rigidity by the lap time and the ever so accurate butt dyno?
What was the point of this again? Oh yeah, to sell heavy wheels. I'll take 2 sets then.
What was the point of this again? Oh yeah, to sell heavy wheels. I'll take 2 sets then.
10-07-2008, 03:36 PM
#20
[QUOTE=budgy,Oct 6 2008, 03:52 PM]got another question, maybe you know this too.