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Wheel spacers on a wk2

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wk2
95K views 65 replies 35 participants last post by  Cheenah 
#1 ·
Has anyone installed wheel spacers on their wk2 with stock wheels. If u have, would love to see pics, on the fence about installing on my 16 75th Anni. Thanks in advance!



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#11 ·
So I installed my bora spacers yesterday, 1.25" in the back and 1" in the front...love the new stance, really makes an aggressive difference, was just curious for any of you who have them, as far as checking torque down the line or any crazy horror stories, Bora says to check torque after 5 miles but I was just curious on anybody else's methods...thanks in advance


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#24 ·
i have them (see sig) love the stance - the stock stance is very "soccer mom" but after spacers its the aggressive offroad vehicle it should be

i should get my pocket flares this week and will see how they look with the new flares - hopefully they still are even with the edge of the new flare.

no vibes or other issues even out west on interstates w/ speed limit at 80 (so I'm going about 89...). no trimming the lugs either (stock 18)
 
#25 ·
I have been debating whether wheels spacers are safe or not. During my brief research I found a FAQ from an online store "Maximum Motorsports" which explains the forces applied to the studs/spacers. Seems interesting and I though I would share. I'm not sure if I have to provide a link to the site or if it is allowed on here but here it is.

Moderators feel free to delete this post if I'm violating any rules.

After reading Q&A's regarding wheel spacer I feel more comfortable in ordering a set of Boras.

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:

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.
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.
 
#36 ·
Increasing the length of the wheel studs to use a wider wheel spacer has no appreciable effect.
Not true. Whenever a spacer is added, wheel studs or bolts must be lengthened the same amount. Lots of us use spacers behind our race wheels in road racing, not to fill out wheel wells but to clear modified suspensions or big brakes. Spacers must be hubcentric or the wheels will never properly center on the hubs resulting in high speed vibration. Wheel bolts or nuts do not center the wheel, the fit between the hub and the center of the wheel is what centers the wheel. The nut/bolt just hods everything together.

In racing, open face bolts are required so that safety inspectors can see see that the stud is at least flush with the outer face of the nut, preferable protruding. For wheel bolts there is a calculation that is used, but typically anything that gives 6 full turns before tight is legal in racing. And no racing body allows wheel adapters- the pieces that first bolt to the hub, then wheels bolt to the adapter. Not sure why, but I'm sure there's a safety reason for it.

Then there's the change that's made to the suspension geometry with spacers. Moving everything outward does in fact change such things as scrub radius which changes how a suspension operates. It can also add different loads to wheel bearings. Will you notice this on the street? Probably not, but in a race car at speed it will make a stable car quite squirrely at speed. Not to say it shouldn't be done, I ran 25mm H&R spacers on the rear of my old BMW X5 4.8is and 15mm on the front, but it did make the front end darty until I realigned it with the spacers in place. And I'd like to do something on my current JGC, as soon as I can find longer studs to make up the difference of the spacer thickness.
 
#26 ·
another thing, though I used the term spacer too ..... spacers and adapters are different beasts. adapters bolt to the hub, then the wheel bolts to the adapter ... no movement

spacers are just that - a plate that you place over the hub, then bolt the wheel to the lugs and sandwich down onto the spacer. imo... no way i'd use these
 
#27 ·
I would agree with most all of that writeup on how the wheel/hub joint behaves. One thing I think most people assume is that the studs carry some shear load from wheel to the hub or vice versa, but bolts are never used to carry shear in any proper design. In this case the friction due to clamping force carries all shear. If during analysis of the joint during the design the shear load were too great for the friction joint then shear pins would be required.

The other thing to consider when using wheel spacers or extension adapters is the load on the wheel bearings. In addition to the vertical load applied to the bearing from the car's weight there is a moment applied because the bearing is not located at the center of the wheel. This moment is increased when spacers are used and, depending on the thickness of the spacer can decrease the lifespan of the wheel bearing. Lucky for us, car suspension designers usually spec out parts that can handle several times the expected design loads (factor or safety) so the effect is rarely noticed. If you're using wheel spacers keep an eye out for the possibility of a failing bearing as the miles click away.
 
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