Lightweight Wheels - Does it really matter?

[industrial]

Originally Posted by Dave-ROR

GRM wasn't testing no name crap wheels.... Light = less material, there's no way around that given the same manufacturing process. Less material will mean less strength given similar designs.

So the real question is which design is the strongest for a lightweight wheel?

If I had to guess, good old boring TE-37s or CE-28s. What wheels did GRM test? I can't seem to find the article.

[Dave-ROR]

Originally Posted by industrial

If I had to guess, good old boring TE-37s or CE-28s. What wheels did GRM test? I can't seem to find the article.

I can't recall. They were cast but not konig, or xxr, etc.

[CSG David]

The rigidity of the wheel takes more precedence over weight. We're talking at most 2lbs extra for some wheels. Decreasing weight while maintaining strength/rigidity means wheels will cost more just to spend more effort finding every method to shed weight without reducing that epic quality we all seek. Good wheels means more R&D and effort to optimize these factors (Volks & BBS).

Under cornering loads, a stronger wheel (usually slightly heavier) is faster than a lighter wheel. We also see a lot less bent wheels from track and street use using those "heavier" wheels. Of course, this is from an actual use and abuse perspective.

[PRORICAN]

I understand that stronger is better for obvious reasons but most "lightweight" wheels forged or not are under 20lbs. So when you guys say that tests have shown that heavier provides a faster time, are they over 20lbs? I guess what I'm trying to say is when is heavy too heavy?

PS- I've had a few brewskies so if I don't make sense don't mind me! Lol

[PRORICAN]

Also I've noticed that 90% of racing teams use lightweight wheels with success so are they all wrong? Honest question since I don't have much experience with road racing/auto-x/time attack, etc.

[CSG David]

Originally Posted by PRORICAN

I understand that stronger is better for obvious reasons but most "lightweight" wheels forged or not are under 20lbs. So when you guys say that tests have shown that heavier provides a faster time, are they over 20lbs? I guess what I'm trying to say is when is heavy too heavy?

PS- I've had a few brewskies so if I don't make sense don't mind me! Lol

We're talking only about 17lbs vs. 15lbs (if we're talking about 17x8 setups). Nothing absolutely insane. The GTI guy running 29lbs to 19lbs...uh yea, I'll totally justify that because 10lbs is absolutely wtfbbq and 19lb wheels are actually designed at a good average weight. GTI wheels are built to break sidewalks if you smash into one. j/k

Originally Posted by PRORICAN

Also I've noticed that 90% of racing teams use lightweight wheels with success so are they all wrong? Honest question since I don't have much experience with road racing/auto-x/time attack, etc.

They want light but also cheap because they have many sets of wheels for backup and replacements. They bend a lot of wheels and trash a lot of wheels as well. We're not saying uber light wheels are super weak, they are actually sufficient and respectable, however justifying that it has better acceleration and will win you close races because you saved 1lb per corner, well, that's harder to say. Also, the track surface is relatively smooth vs. public roads.

[PRORICAN]

Originally Posted by CSG David

We're talking only about 17lbs vs. 15lbs (if we're talking about 17x8 setups). Nothing absolutely insane. The GTI guy running 29lbs to 19lbs...uh yea, I'll totally justify that because 10lbs is absolutely wtfbbq and 19lb wheels are actually designed at a good average weight. GTI wheels are built to break sidewalks if you smash into one. j/k


They want light but also cheap because they have many sets of wheels for backup and replacements. They bend a lot of wheels and trash a lot of wheels. We're not saying uber light wheels are super weak, they are actually sufficient and respectable, however justifying that it has better acceleration and will win you close races because you saved 1lb per corner, well, that's harder to say.

That makes sense, thanks for clearing that up for me!

[coyote]

Originally Posted by Dave-ROR

GRM wasn't testing no name crap wheels.... Light = less material, there's no way around that given the same manufacturing process. Less material will mean less strength given similar designs.

So the real question is which design is the strongest for a lightweight wheel?

And what manufacturing process.

And what materials.

There's no comparison between a forged A6061-T66 wheel and a cast AC4C-T6 when it comes to rigidity, but people generally don't appreciate what they can't see.

For example, a 25lb Work may be more rigid than a 20lb Enkei, while a 15lb Volk could be more rigid than both. I'm not bagging any brand (as those are all good), just giving an example and obviously ignoring price.

I know you know this, but I'm making the point that material and manufacturing process is at least as important as design, unless you are saying that you'll only consider cheap cast wheels.

[coyote]

Originally Posted by ZDan

I was looking at this thread thinking to myself "I don't remember typing these things", when I realized that it wasn't me, but it was my avatar from another forum, *exactly* as I had cropped it for that forum!

Granted, I stole it from Warner Bros, but still!

Could have. I've been using that avatar in one place or another for more than a decade.

Perhaps you stole it from me?!?!

[Dave-ROR]

Originally Posted by coyote

And what manufacturing process.

And what materials.

There's no comparison between a forged A6061-T66 wheel and a cast AC4C-T6 when it comes to rigidity, but people generally don't appreciate what they can't see.

For example, a 25lb Work may be more rigid than a 20lb Enkei, while a 15lb Volk could be more rigid than both. I'm not bagging any brand (as those are all good), just giving an example and obviously ignoring price.

I know you know this, but I'm making the point that material and manufacturing process is at least as important as design, unless you are saying that you'll only consider cheap cast wheels.

Agreed. In GRM's case they tested wheels (light and heavier) from the same mfr with the same manufacturing process.

PRORICAN: Some race teams use heavy wheels, and some use very light very high end and very strong wheels that don't apply the majority. Others use cheap and light due to replacement costs. That all depends on the goals of the team in question. We run a large selection of OEM wheels on our race car because we had them laying around, soon they will be replaced with cheap and light wheels that are 15x8s to run 225s. We expect to break some over time, and we expect a lot of random damage. We aren't willing to pay for high end wheels tho :P

[Huehuecoyotl]

I have 17's that weigh 15.5 lbs(blue HLT OZ for track made in italy) and 17s that weigh 22 lbs(silver Sparco by OZ made in ROC)
I can totally tell them apart if you had me drive them blindfolded. In this case the heavier wheel is stronger for potholes, and drawing less attention than I may want day to day

[ZDan]

Originally Posted by coyote

Could have. I've been using that avatar in one place or another for more than a decade.
Perhaps you stole it from me?!?!

Ha, could be! I took down my post after I saw that exact picture as the first image on a google search. I musta just remembered scaling it down to a max size, not cropping it. I've been using it for nigh on ten years, so you have precedent. Anyway, it funny to be reading a post thinking it was mine. "When did I say THAT?!"

[OmarGC]

Originally Posted by Dave-ROR

Grassroots Motorsports tested and 100% of their tests the heavy wheels were FASTER on their test course than light weight wheels. The lighter wheels helped with braking and acceleration but they also flexed more which ended up hurting cornering.

Just sayin......

It does make a difference in feel though if you go far enough. My tires more or less offset the wheel weight savings for me...

....

[ZDan]

Originally Posted by coyote

There's no comparison between a forged A6061-T66 wheel and a cast AC4C-T6 when it comes to rigidity, but people generally don't appreciate what they can't see.

Wheels made to the same dimensions/wall-thicknesses/etc., one 6061-T6, one AC4C-T6 (A356-T6), will have PRECISELY the same rigidity/stiffness. ANY aluminum alloy will have a modulus of elasticity of 10-10.5 Msi, so the *stiffness* is the SAME for a given net shape.

Forged wheels (6061-t6) are not stiffer than cast wheels of the same design! In fact if you take advantage of the forged material's higher strength properties to take material/wall thickness out, it will be *less* stiff vs. the thicker/heavier similar-design cast wheel.

I've heard references made by reputable sources about the advantages of "stiffer" wheels, but in my experience designing and lightweighting aluminum wheel designs, even the lightest/most-flexible viable wheel design is so much stiffer than the tire, that I'd be surprised to find that it should matter much. The TIRE is moving around so much more, on the order of 10x or more deflection under load vs. the wheel, that its compliance dominates the wheel/tire stiffness.

I did see a quote from Enkei regarding the weight of the PF01 (I have these on the RX-7!). It came out disappointingly heavy relative to the RPF1 (it was supposed to be lighter), but I recall Enkei noted that it was "faster" due to being more stiff. Maybe it really is, but IMO this is possibly a story for marketing. If they did a bunch of laps on both wheels and the faster laps happened to be with the PF01 (entirely possible as the weight penalty isn't all that big), they could semi-legitimately make the case that "heavier but stiffer" was faster. But of course they are first in the business of selling wheels!

If you make a wheel twice as stiff, the overall stiffness of the wheel/tire is only going to go up by on the order of ~5%. So the payoff in overall stiffness is quite small relative to big changes in wheel stiffness.
2x stiffer tires, and overall stiffness goes up 90%. So, a stiffer TIRE, you will most definitely feel the difference. With a stiffer wheel, I seriously doubt you could feel it and any difference in lap times should, I think, be buried beneath other factors (changing track/weather/tire conditions, driver inconsistency).

I know you know this, but I'm making the point that material and manufacturing process is at least as important as design, unless you are saying that you'll only consider cheap cast wheels.

You design for adequate strength and resistance to fatigue with minimized weight taking into account material properties. The art lies in shaping the form of the wheel to minimize stresses while removing material. Of course the material properties and the shape are both critically important!