CMC 17" Wheel Weight & Welded Spacers

Here's another one I've been thinking about:

6.31.2 16 inch wheels must weigh 16.0lbs or more. 17 inch wheels must weigh 18.0lbs or more. One
piece aluminum spacers welded to the wheel will be included in the total wheel weight. Detachable
balancing weights will not be included in the total wheel weight..

My understanding is that this rule came about due to the availability of Z06 front wheels for the Camaros. I wasn't around at that time so correct me if I'm wrong. For the CMC mustang the wheel of choice is the Enkei RPF1 17" x 9.5" +38mm offset with a welded on aluminum spacer. Earlier in the season I had heard that that was going to be changed to a standard spacer so that we don't have to booger weld spacers onto expensive wheels.

Is this being considered for a rules update for '19 and/or the '18 national event?

Alternatively, it would be even better (for my bank account) to drop the number from 18lbs to 17lbs - but that's just my opinion.

- Josh

Z06 wheels weigh more than 18 I believe and think over 19 (I'll weigh one this weekend) so shoudln't be because of that. Sounds like it was for the Mustang and the Enkie wheel? I'm not aware of ever seeing an F body with a welded wheel. A director probably got a good deal on some lightweight 17" CCW's or something and wanted them legal at the time for the weight. Raise the weight to 19 lbs without a welded spacer.
The logic in a budget series to allow buying a $2k set of wheels and then welding on a spacer just so it's legal doesn't make sense to me.

The Z06 wheels weighed 19.0 lbs on my bathroom scale that has .5 pound resolution. Depending on the scale, you could easily get a bit above or below 19 lbs. As a strong, cheap, and readily available factory wheel that closely meets the specifications, it seems likely that it was the wheel in mind when the current CMC rule was made. The fact that it is no longer cheap or all that available isn't really relevant. The rule wasn't created around the Enkei wheel as that wheel wasn't even legal until the rule was changed to allow including the spacer weight in the calculation.

I don't think changing the allowed wheel weight (up or down) is a good idea. Up will make some people's wheels illegal. Down will send a bunch of people scrambling to buy new wheels. Allowing wheel spacers to be included in the weight is the easiest/cheapest way to get everyone to an equal spot. There are a lot of cheap wheels available for the Mustang but they are usually in the 22 lb range. There are wheels that cost a bit more but they come in below weight. The Enkei wheel costs about the same as the going rate for the a good Z06 wheel. There is really nothing in the marketplace for the Mustang that hits the sweet spot like the Z06 wheel without including the spacer in the weight.

I do think not requiring the wheel spacer to be welded to the wheel is a good idea. Welding a billet spacer to a cast wheel of an unknown alloy isn't a good plan and could even be dangerous in some cases. I also don't get the point? A light weight wheel is only legal with a spacer and checking for a spacer at impound is trivial. It also takes wheels that would be AI legal/desirable and makes them CMC only so they are harder to sell.


Richard P.

I pushed to remove the welding requirements due to safety. It’s also easy as hell to audit.
If I end up building a fourth GEN I’m going to get a Ford bolt pattern hub and axle so I can easily use and purchase the enkeis

The real genesis of the rule change was due to an Enkei RPF1 with a steel spacer that was attached to the wheel with screws (drilled the wheel and counterbore in the spacer) then plug welded so the attachment screws can’t back out or the wheel separated from the spacer, making a pseudo custom wheel).

That led to folks saying the heavier spacer “mass” was in the middle of the wheel, hence lowering the rotational inertia which created an advantage. That prompted the rule to be written around an aluminum wheel and aluminum spacer.

I’d still lobby for a permanently attached (screws plus plug weld which is easier with standard billet 6061 spacers).

Since the original steel spacer and alumunimum wheel combo was my idea and Jeremy was clever enough to try it (and McSpadden copied the idea with my CAD file for the spacer and took it to Nationals), blame all this on me... LOL

Quote:

---

Originally Posted by marshall_mosty

The real genesis of the rule change was due to an Enkei RPF1 with a steel spacer that was attached to the wheel with screws (drilled the wheel and counterbore in the spacer) then plug welded so the attachment screws can’t back out or the wheel separated from the spacer, making a pseudo custom wheel).

---

Adding holes to the center bore of the wheel scares me... and then plug welding them will locally destroy the wheel's temper.

Quote:

---

That led to folks saying the heavier spacer “mass” was in the middle of the wheel, hence lowering the rotational inertia which created an advantage. That prompted the rule to be written around an aluminum wheel and aluminum spacer.

---

How does going to aluminum solve remove the inertial advantage? I'd rather go with a steel non-attached spacer. I can make your wheels (thanks for the deal btw) work with steel spacers.

So here's the question, if I show up to COTA with aluminum spacers not welded to my wheels will I be DQ'd? I wouldn't take the risk of showing up with a car that directly goes against the rule book, if we can get clarification ahead of time against welding wheels it'd be awesome.

- Josh

yah sook make sure you get clarification on anything wheel related. I saved all Marshals approval messages on my phone when i took my setup to Utah at miller mot park just to cover my butt cause it created a firestorm online once people realized what i did to the wheels (marshals idea) to make weight. BUT it’s the budget way around spending thousands in fikse or ccw wheels.

Just to clarify the plug weld would ONLY be on the spacer, not the wheel. The only permanent modification are the tapped holes that the screws which hold the spacer on screw into.

Regarding steel vs aluminum spacers, for a given weight and thickness, the outer diameter of the spacer would be smaller on the steel spacer (advantage)...

Any mod to the wheel compromises safety IMO, I don’t understand the point of it being permanently attached, potential safety issue with no upside that I can see. If someone was protested you would audit the same way in impound, pull the wheel, dismount tire, weigh with with spacer as it came off the track.

exactly!

This horse was beat to death in the CMC forum a few years ago when the Bulletin came out allowing a welded spacer to be included in the weight of the wheel, and the subsequent "End of the season rule debate" about it.
Good read. Get your popcorn.

But, here's what I come away with.
The Enkei wheels with spacer welded come in just over 18lbs.
The only way a 17 x 9.5 GM wheel can get close to 18lbs is a set of custom wheels, which cost thousands of dollars.
So, nearly all GM's buy Z06 wheels that weight 19.5 - 20 lbs and still have to install a spacer for another 3/4 - 1 lb, and that's about 20 - 21 lbs.

A few pounds doesn't sound like that much, but it is rotating mass, so it is a big deal. Plus there is another benefit of the Enkei with spacer. In order to make the minimum , it has more of its weight in the hub. And, that one is important also.

From what I have read, rotating mass weight is a factor of 10 when compared to sprung mass. So, 8-10 total lbs of rotating mass is equivalent to 80-100lbs of sprung mass. That's a big number. Some of that would show up on the dyno and get negated , but only a portion of it. Im not an engineer, so fire away. But everything I have read, indicates that rotating weight is a very big deal. As I'm sure some already know. Or we would all be using 26 lbs wheels.

Quote:

---

Originally Posted by mach1

Any mod to the wheel compromises safety IMO, I don’t understand the point of it being permanently attached, potential safety issue with no upside that I can see. If someone was protested you would audit the same way in impound, pull the wheel, dismount tire, weigh with with spacer as it came off the track.

---

So in this scenario, a Ford can run a 16lb wheel with a 2lb spacer and get to the 18lb minimum. Great
However, there are no off the shelf, other than custom $$ GM 17 x 9.5 wheels that weigh any where close to 16 lbs or 18lbs with the proper spacer, Or 18lb that have the proper offset. They don't exist. Closest a GM car gets its about 21lbs with a needed spacer.

Rotating mass isn't a linear factor. It's exponential, and the farther out the weight is the much bigger of an impact it will have. I could google the equation, but it's out there and it's pretty simple.

Quote:

---

Originally Posted by DAlgozine

So in this scenario, a Ford can run a 16lb wheel with a 2lb spacer and get to the 18lb minimum. Great
However, there are no off the shelf, other than custom $$ GM 17 x 9.5 wheels that weigh any where close to 16 lbs or 18lbs with the proper spacer, Or 18lb that have the proper offset. They don't exist. Closest a GM car gets its about 21lbs with a needed spacer.

---

Right, same as today, ford can run a 16lb with a 2lb spacer and perhaps sacrifice the integrity of the wheel. I would hate to see a wheel fail and take out 5 cars going into T1 just because you have to compromise safety to make it legal.

I'm going to drill holes in my z06 wheels to make it an 18lb wheel.

Since the cheater mustangs are getting center of mass close to the hub, I'm going to drill into the wheel barrels.

Quote:

---

Originally Posted by Pranav

I'm going to drill holes in my z06 wheels to make it an 18lb wheel.

Since the cheater mustangs are getting center of mass close to the hub, I'm going to drill into the wheel barrels.

---

Drill em and dab some rtv in the holes, Chevy P1!

Quote:

---

Originally Posted by mach1

Right, same as today, ford can run a 16lb with a 2lb spacer and perhaps sacrifice the integrity of the wheel. I would hate to see a wheel fail and take out 5 cars going into T1 just because you have to compromise safety to make it legal.

---

Or stick to the original intent of the 18lb wheel rule and don't allow 16lb wheels. All off the shelf wheels require spacers. Including the spacer with the wheel is a goofy loop hole. And I always thought goofy loop holes don't have a place in CMC.
I supposed by welding the spacer it is a custom wheel, which by rule is not illegal.

Quote:

---

Originally Posted by mach1

Drill em and dab some rtv in the holes, Chevy P1!

---

I once RTVed a valve stem on my Honda and did a few 1/4 mile passes on it then drove home.

It actually failed but because it was an Azeni RT-615, I never noticed. Sidewalls of steel...

Quote:

---

Originally Posted by DAlgozine

Or stick to the original intent of the 18lb wheel rule and don't allow 16lb wheels. All off the shelf wheels require spacers. Including the spacer with the wheel is a goofy loop hole. And I always thought goofy loop holes don't have a place in CMC.
I supposed by welding the spacer it is a custom wheel, which by rule is not illegal.

---

So the fords have no 18lb options?

Quote:

---

Originally Posted by DAlgozine

I supposed by welding the spacer it is a custom wheel, which by rule is not illegal.

---

Doug,
The original intent of the steel spacer, attached to the wheel with plug welded screws was to create a pseudo custom wheel that met the letter of the rule.

Quote:

---

Originally Posted by Suck fumes

yah sook make sure you get clarification on anything wheel related. I saved all Marshals approval messages on my phone when i took my setup to Utah at miller mot park just to cover my butt cause it created a firestorm online once people realized what i did to the wheels (marshals idea) to make weight. BUT it’s the budget way around spending thousands in fikse or ccw wheels.

---

Marshall-will you approve my aluminum rear diff cover? I'm not aware Marshall was ever a CMC director to my knowledge to give "approval"? I'm pointing this out more because I get uneasy about anything that needs an "approval" since it's likely pushing the intent of the rules or possibly worse.

I agree with Tyler and any others that modding a wheel is a potential safety issue.

Wheel weight rule just has a better benefit for the Mustangs with the Enkei wheel option unless there is a wheel under 18 lbs for the F-body that ins't over $2k for a set (though I sure like the looks of the CCW). There are all kinds of advantages/disadvantages for each platform.
Sook-send it in for rule change request in our now non-existant silly season to get it approved to lower the wheel weight since it improves safety, lowers cost, and doesn't impact performance since people were already running the Enkei. Heck maybe you could get the rule changed before hand instead of a nod/wink approval.

I also agree with DAlgozine that it seems to be a goofy loophole that shouldn't really be in CMC. But then I'm checking to see when my custom Ford 9" with aluminum center section is going to be delivered so I can get it installed before nationals because my aluminum diff cover with a drain plug is illegal. Just doesn't make sense to replace it with a stock cover when for $3,800 I can get a stronger diff, better posi, and nearly unlimited gear options. Only downside is I have to order a new pair of CCW's for the different bolt pattern.

Quote:

---

Originally Posted by BryanL

Marshall-will you approve my aluminum rear diff cover? I'm not aware Marshall was ever a CMC director to my knowledge to give "approval"? I'm pointing this out more because I get uneasy about anything that needs an "approval" since it's likely pushing the intent of the rules or possibly worse.

I agree with Tyler and any others that modding a wheel is a potential safety issue.

Wheel weight rule just has a better benefit for the Mustangs with the Enkei wheel option unless there is a wheel under 18 lbs for the F-body that ins't over $2k for a set (though I sure like the looks of the CCW). There are all kinds of advantages/disadvantages for each platform.
Sook-send it in for rule change request in our now non-existant silly season to get it approved to lower the wheel weight since it improves safety, lowers cost, and doesn't impact performance since people were already running the Enkei. Heck maybe you could get the rule changed before hand instead of a nod/wink approval.

I also agree with DAlgozine that it seems to be a goofy loophole that shouldn't really be in CMC. But then I'm checking to see when my custom Ford 9" with aluminum center section is going to be delivered so I can get it installed before nationals because my aluminum diff cover with a drain plug is illegal. Just doesn't make sense to replace it with a stock cover when for $3,800 I can get a stronger diff, better posi, and nearly unlimited gear options. Only downside is I have to order a new pair of CCW's for the different bolt pattern.

---

Bryan,
When I'm not available to field AI questions, they defer to Michael. The inverse is true for CMC. In this case, I was also discussing with Michael at the same time since we typically talk several times per week anyway. The official "legal or not" doesn't even lie with me or Michael. It ultimately would sit with Al Fernandez and the National Office. Michael and I are simply ambassadors of the series and make the best call we can with the information provided. Obviously my discussions with Aaron were under the pretense that he executed the wheel modification exactly as we had discussed. If he had done anything outside of our documented conversation, the "approval" most likely would have no grounds for being upheld. NASA always has the ability to reach out to the series directors to point out if we are overstepping our authority. In this case, I didn't hear a peep and Aaron didn't have any issues with the wheels at Nationals.


Clarification for pushing the limits of the rules are what continue to grow series, not in inverse. There are many examples of series that don't exist anymore due rulesets that are close ended with regards to future grown and or written with a ruleset that stifles innovation.

I personally don't like it when people talk about the rules and then as a subset the "intent". If it was the intent to allow or not allow a particular modification, it needs to be clearly specified in the rules. For example, if a battery box per intent isn't supposed to be made out of 1/4" steel plate and put behind the roll cage, the rules need to a maximum weight for a battery box.. Looking at a battery box and saying it is illegal because it doesn't meet the intent of the rules is not a solid defense, IMHO. There are so many loopholes that can be closed with clarified rules. If the series is seeing rules creep with a particular item (wheels plus spacers), the rules can be changed to clearly set the allowed parameters for the wheels.

Couldn’t have said it any better Marshall. I have always thought the whole “intent” thing was kind of odd because this was the only class I have ever raced in where I have heard arguments about “intent” of the rule. Rules need to be clearly written and spelled out. If they are not then they can be creatively interpreted by anyone. But saying that it doesn’t meet the “intent” is not a strong argument at all.

Quote:

---

Originally Posted by Suck fumes

Couldn’t have said it any better Marshall. I have always thought the whole “intent” thing was kind of odd because this was the only class I have ever raced in where I have heard arguments about “intent” of the rule. Rules need to be clearly written and spelled out. If they are not then they can be creatively interpreted by anyone. But saying that it doesn’t meet the “intent” is not a strong argument at all.

---

In Aerospace, we use the "Shall"/"Should" argument.
Shall is a direct requirement that will be followed (written rule)
Should is a "it would be nice to comply, but not required" (intent)

http://asq.org/standards-shall-should

Quote:

---

Originally Posted by marshall_mosty

In Aerospace, we use the "Shall"/"Should" argument.
Shall is a direct requirement that will be followed (written rule)
Should is a "it would be nice to comply, but not required" (intent)

http://asq.org/standards-shall-should

---

We should include the intent of each rule in the rule book then. We can then change the name to the great book of guidelines - CMC edition. :)

We do the shall/should thing at my job as well, I personally don't like it. Why include shoulds from a cost saving perspective? All the shoulds that we purse really should be shalls.

Where do I go to formally request clarification? I have a question about another rule in preparation for nationals.

- Josh

Quote:

---

Originally Posted by Sook

Where do I go to formally request clarification? I have a question about another rule in preparation for nationals.

---

Josh,
Start with Michael. If you can't get Michael, send it to me. If we cannot provide guidance we will take it to Al F. He will take it to the National office, if needed.

Quote:

---

Originally Posted by Sook

We should include the intent of each rule in the rule book then. We can then change the name to the great book of guidelines - CMC edition. :)

We do the shall/should thing at my job as well, I personally don't like it. Why include shoulds from a cost saving perspective? All the shoulds that we purse really should be shalls.

Where do I go to formally request clarification? I have a question about another rule in preparation for nationals.

- Josh

---

Ideally the short answer should come from Al. The long answer should then appear as a rule change.