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Thread: CMC 17" Wheel Weight & Welded Spacers

  1. #1

    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
    CMC #50

  2. #2
    Senior Member Carroll Shelby
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    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.
    Bryan Leinart
    CMC #24

  3. #3
    Senior Member Carroll Shelby RichardP's Avatar
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    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.

  4. #4
    Senior Member Grass-Passer
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    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
    Tyler Gardner
    CMC #13 2015-2017
    SM #013 2018
    www.dfwmustangs.net

  5. #5
    Senior Member Carroll Shelby marshall_mosty's Avatar
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    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
    Last edited by marshall_mosty; 07-20-2018 at 06:21 PM.
    Marshall Mosty
    AI/SI Texas Regional Director
    2011 NASA-TX American Iron Champ
    AI #67 "Mosty Brothers' Racing" (RIP)

  6. #6
    Quote Originally Posted by marshall_mosty View Post
    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.

    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
    CMC #50

  7. #7
    Senior Member Grass-Passer Suck fumes's Avatar
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    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.
    “A man with no enemies is a man with no character.”
    ― Paul Newman

  8. #8
    Senior Member Carroll Shelby marshall_mosty's Avatar
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    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)...
    Marshall Mosty
    AI/SI Texas Regional Director
    2011 NASA-TX American Iron Champ
    AI #67 "Mosty Brothers' Racing" (RIP)

  9. #9
    Senior Member Grass-Passer
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    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.
    Tyler Gardner
    CMC #13 2015-2017
    SM #013 2018
    www.dfwmustangs.net

  10. #10
    Senior Member Grass-Passer Suck fumes's Avatar
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    exactly!
    “A man with no enemies is a man with no character.”
    ― Paul Newman

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