Are Wheel Spacers Safe?

Discussion in 'General Automotive Questions' started by bit182, Aug 4, 2018.

  1. bit182

    bit182 In First Gear

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    When I bought my Ranchero the guy gave me a set of really wide (fantastic looking) tires with Mustang rims. The only thing is that they require wheel spacers to put them on. I've seen a lot of different opinions on whether spacers are safe or not. Can anyone give me a bit of info on whether they are safe to use or not?
     
  2. 5.0 Chero

    5.0 Chero MODERATOR Staff Member

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    http://www.maximummotorsports.com/tech_wheels_spacers.aspx

    Mustang Wheel Spacer Tech

    Are wheel spacers safe?

    Yes. When properly installed they are just as safe as wheels installed without spacers.

    Will wheel spacers cause my wheel studs to bend?

    No. The load from a wheel is transferred to the axle/hub through the friction of the clamped joint, not through the wheel stud. A wheel stud can only bend if the lug nuts are not properly torqued, in which case the wheel is about to fall off, anyway.

    The Physics of Keeping the Wheels On

    • As long as the wheel, hub, and spacer are stiff enough to prevent flexing and loss of clamp force, the cause of most wheel stud failures is under tightened lug nuts (not enough clamping force) or over tightened lug nuts (the stud has been stretched past it's elastic limit, so the clamping force goes away). Therefore, properly installed wheel spacers are perfectly safe.
    • The wheel stud applies a clamping force that holds the wheel to the hub. When the lug nuts are tightened, the wheel studs stretch elastically, like very stiff springs. The lug nuts should be tightened until the stud is at 90% of its elastic limit. This will provide the greatest possible force to hold the wheel to the hub.
    • The amount of clamping force at a joint is important because of the coefficient of friction (Cf). The more clamping force applied to the joint (in this case the joint between the wheel and the hub), the more force required to make the wheel slip relative to the hub. Unless the wheel slips on the hub, there cannot be any bending load on the stud.
    • Coefficient of friction -- There is friction between the wheel face and hub face. This friction can be measured, and it is called the "coefficient of friction". The coefficient of friction (Cf) is the ratio of normal force, at the intersection of two surfaces, to the lateral force required to slip the bodies relative to one another. As an example, good street tires have a Cf of 0.9. This means that if there is a 100-pound vertical force applied to the tire, the tire can generate 90 lbs. of cornering force before it slides.
    • When the car starts moving, the stress applied to the stud does not change appreciably, unless one of two things happens:
      1. The vertical component of any external force applied to the wheel is so great that the clamping force is not sufficient to hold the wheel in place, and it slips on the hub. At this point the stud is loaded in bending and in shear, and may yield, or even break.
      2. Some portion of the clamped joint, wheel, or hub is not stiff enough to prevent flexing, and allows the tension load on the stud to drop to zero. With no tension load on the stud, the clamped joint is no longer tight. The wheel can then move relative to the hub, and place a bending load on the studs.
    • Inserting a wheel spacer between the hub and wheel changes nothing about these physics.
    • The hub center of a hubcentric spacer does not hold the spacer on the hub or reduce the chance of stud failure. There is never any load on the lip of the wheel spacer. For there to be a load on the lip, the friction force in the joint must have been completely overcome. The lip on a hubcentric wheel spacer serves only as an aid for wheel installation.
    • Increasing the length of the wheel studs to use a wider wheel spacer has no appreciable effect.
     
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  3. 1965 Ranchero 66G

    1965 Ranchero 66G In Maximum Overdrive PLATINUM MEMBER

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    What about excessive stress on the bearings.
     
  4. ribald1

    ribald1 Banned PLATINUM MEMBER

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    Thin steel ones, like 1/4 or 3/8" are probably safe, but there are too many videos of them coming apart (granted on a drag strip) for me to believe that they are as safe as not running them.
    Aluminum I wouldn't use.
    The issue is that when they crack the only evidence is a lug nut that needs snugged a little when checking the torque as you can't see the things.
     
  5. bit182

    bit182 In First Gear

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    Thank you. That is great info. I'm a little concerned about the spacers as they are aluminum. I need to find someone who would be willing to put them on the right way for me. Not many places want to do it.
     
  6. bit182

    bit182 In First Gear

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    Yeah, the spacers he gave me are aluminum, which concerns me a little bit. hmmm...going to need to think on that one for a bit. Thanks for the response.
     
  7. 5.0 Chero

    5.0 Chero MODERATOR Staff Member

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  8. 1965 Ranchero 66G

    1965 Ranchero 66G In Maximum Overdrive PLATINUM MEMBER

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    Porsche also has a better engineering and quality control than after market.
     
  9. handy_andy_cv64

    handy_andy_cv64 In Maximum Overdrive SILVER MEMBER

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    If you do use aluminum ones (or even ferrous ones), you want billet over cast. Cheapies are usually cast.
     
  10. ribald1

    ribald1 Banned PLATINUM MEMBER

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    Billet aluminum units engineered to a very specific application are a far cry from the Chinese 'universal' junk out there.
    Not long back a video of one of those Chinese units failing was posted here.
     
  11. 1965 Ranchero 66G

    1965 Ranchero 66G In Maximum Overdrive PLATINUM MEMBER

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    I think if I'm not mistaken, that was on the track, pretty entertaining.
     
  12. beerbelly

    beerbelly In Maximum Overdrive SILVER MEMBER

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    I figure someone needs to pipe up about the reason wheel spacers are needed, and damn the torpedoes. I figure this is because folks want to use modern factory wheels on their older cars, either because they they like the look of them on a 40+ year old car, or maybe they got a good deal on them. Being an old fart, I just don't get it; why not get a period-correct wheel from the era of the car? The offset of the new factory wheels is very shallow compared to the muscular old deep dish wheels from back then, and my personal opinion is that it makes the cars look like they're on roller skates, or tippy. But hey, that's just me, and no offense.
     
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  13. ribald1

    ribald1 Banned PLATINUM MEMBER

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    Too late Mr. Belly.
    I am offended that you asked that no one be offended.
    What gives you the right to ask people to not be offended? Isn't being offended a constitutional right? This is America Dang It! and we will be offended any time we dang well please!
     
  14. handy_andy_cv64

    handy_andy_cv64 In Maximum Overdrive SILVER MEMBER

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    A guy I know from Fullsizebronco.com knows the guy that owns that car, and my friend called it that the wheels wouldn't handle the stress.
     
  15. Clark

    Clark In Maximum Overdrive

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    I ran 1/2" thick wheel spacers on a '82 VW Rabbit for years with no issue. Granted the VW weighed nothing compared to a Ranchero. Also, I had a shop machine my spacers out of aluminum plate with centering on the VW hubs/drums. I don't know if there is a centering lip on your wheel hubs.
     
  16. HuevosRanchero

    HuevosRanchero In Maximum Overdrive

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    have had spacers on my 2003 mach 1 wheels on my 'chero since before 2007......still no problem...
     
  17. ForistellFord

    ForistellFord In Maximum Overdrive

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    Sure, but are they quality, or Chineseium?
     
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  18. 1965 Ranchero 66G

    1965 Ranchero 66G In Maximum Overdrive PLATINUM MEMBER

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    Could have been Taiwanesium.
     
  19. 1979 RANCHERO GT

    1979 RANCHERO GT In Overdrive

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    They're Illegal in my state. Fail on the safety inspection.
     
  20. ribald1

    ribald1 Banned PLATINUM MEMBER

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    If the government doesn't like them, they must be something everyone needs.
     
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