[bluemax_1]

It isn't so much the suspension parts that the spacers negatively affect, it's your hubcentricity and the wheelstuds.

On our cars, spacers up to a maximum of 5mm will allow the wheel to still be hubcentered, however if you plan to roadrace, I would recommend against even that.

The main reason for frowning upon spacers is due to the stress on the lug studs or lug bolts, whatever configuration the vehicle uses, and the greatest stress is under braking (although extremely high HP cars will also generate a lot of stress under acceleration).

Think of it this way. If your car has no spacers, then you have the wheelhub, with the brake rotor against it and the wheel flush against the rotor hat. When you hit the brakes, the momentum of the car continues to push the car forward whilst the brake calipers clamp on the rotors attemtpting to retard rotation of the wheel, rotor, hub assembly. A perpendicular force results across the thickness of the studs. With the wheel flush against the rotor, the force on the studs is a shearing force, and the studs can withstand a very high shearing force.

However, once you add a spacer between the wheel and the hub, you now have this gap and for the purposes of examining the forces resulting, you can assume the gap caused by the spacer to be akin to an airgap of the same distance, because the spacer is not a part of the rotor, hub or wheel, it is loose. The force experienced by the studs now has an angular component.

It's like when you're a kid, learning about climbing trees, you soon learn that when you place your foot on the branch right next to the trunk, even smaller branches can support your weight. You may not be cognizant of the mechanics, but by doing so, you're subjecting the branch more to shearing forces. Place your weight on the branch out further from the tree trunk though, and you start applying more leverage to the branch and you won't shear it, you'll snap it, and much more easily at that.

Same principle with your wheels with spacers. Road race with spacers and after severe braking you'll start snapping studs, and losing a wheel when you're trying to slow down from 100+ to make that turn is never a good thing.

The thicker the spacer, the greater you stress the studs (and you do also increase stress on the wheel bearings and tierod ends and balljoints etc.)

There are some companies that make spacers that can be used with alignment studs. You need to drill holes in the other components to accept the alignment studs, but it removes the leverage from the wheelstuds/fasteners and the alignment studs are the ones subjected to the shearing forces (since the alignment stud/dowels now lock the components together as opposed to the generic loose spacer). Some companies make thicker wheel spacers that bolt on to the wheel hub, then have new separate studs that extend from the spacer that you now put the wheels on (H&R 25mm spacers). Do they make them for our cars? I don't know. I just stick to wheels that fit without spacers. Too many folks look at wheels as a cosmetic/aesthetic mod and will try to jump through hoops just to fit wheels that 'look cool'. For me, function before form.


Max


BTW, forgot to mention, whenever you're no longer hubcentric, your wheelstuds are going to be absorbing ALL the forces of cornering, braking and acceleration, and even just daily driving, it's only a matter of time till you snap some studs. The whole idea of hubcentering the wheel is so the wheel actually sits on the hub. The weight of the car is not carried by the studs, and the major stresses of cornering are not placed solely on the studs. The wheels studs will still see some stress from hard cornering, but the nature of the force is different and with a no-spacer hubcentric wheel, will be of a tensile nature, and the studs of course, have a very high tensile strength.

Not hubcentered though, under hard cornering, the studs are subjected to angular shear and leverage similar to the spaced wheels, all while they're being subjected to the immense and constant shearing forces from supporting the vehicle's weight.