Hi,
I have heard and read a lot about coilovers and wheel spacers, and honestly have no idea what they are; the pluses, and downsides, what the purposes are, etc.
if anyone can help it would be greatly appreciated,
i am also largely asking, because a car im loking at includes the following
H&R Wheel Spacers 6/front and 18/rear Bolts
and i just want to know a bit more, also does it effect psm>?
thanks

 

http://mike.focke.googlepages.com/wi...syouwantfit%3F

 

i have wheel spacers (7 mm) because the aftermarket wheels that i bought wouldn't clear the shocks unless i had rear spacers installed.

what kind of info are you looking for?

 

Wheel spacers:
A wheel spacer is a ring that sits between the hub and the wheel. It physically moves the wheel further away form the hub. A small wheel spacer (like a 5mm one) is usually just a ring of aluminium with holes drilled in it for the lug bolts to go through and a hole in the center to clear the center of the hub. Larger size spacers (like 15mm) have both stud and holes. The idea is that the spacer boths to the hub and then, using a second set of bolts, the wheel is mounted to the spacer.
Spacers can be used for various purposes. You can use them for cosmetic reasons - moving the wheels out a little will do a better job of filling out the wheel well. You can also use them for performance reasons - spacers will give the car a wider track which will improve grip levels. Finally you can use spacer to move the wheels away from part that the wheel or tire might hit - this happens sometimes with aftermarket wheels that are the wrong size for you car (like using 996 rear wheels on a 986).
Those are the positive reasons to use spacers but spacers can have negative effects. They can put increased strain on hubs halfshafts and ujoints because they effectively increase the force that a tire can exert on the chassis. They can change scrub radiuses on front axles and increase strain on power steering components. Used incorrectly they can change the handling of your car for the worst.

Coil overs:
A coil over really just means a shock surrounded by a spring. All Boxsters use "coilovers" (all McPherson struts are coilovers and Boxsters use McPherson struts at all 4 corners). However, common usage of the term coilover often means a shock with a lower spring mount that is adjustable for height. Using this adjustment one can lower or raise the whole car or any corner.
Race car mechanics use this capability to "corner weight" a car. Corner-weighting allows us to move the weight distribution around. If you add the weight on the Front Left corner to the weight on the right rear and compare that value to the sum fo the right front and left rear corners thay should be equal. This will give the car the best handling balance when turning right and left. Note that for circle track cars that only turn left corner weighting's goal is not to have equal cross weights.
So there are two reasons to have coilovers: 1) Cosmetic reasons - lowering the car makes it look better 2) Performance reasons - improved handling via corner weighting or by using stiffer springs and matched better shocks.
There are lots of coilover kits for Boxsters, ranging in price from under $1K to over $10K. Basically you get what you pay for. I recommend you always get the car corner weighted and aligned after installing or adjusting coilovers. I also recommend that you stay away from the cheaper kits. You want a kit that is properly engineered for your car which means that shocks are matched to the springs and the spring is matched to the car for the type of driving you plan on doing.
The majority of coilovers on street cars are purchased only to lower the car for cosmetic reasons. Invariably they are adjusted incorrectly. The ride height is set too low. This causes damage to the bodywork when you hit some low obstacle like a speed bump. It can also destroy the shocks if they bottom out. And since it is not properly adjusted, it actually makes the car handle worse.

Answering your specific questions:

a 6mm spacer is perfectly reasonable. You can order a Boxster with a 5mm spacer kit from the factory and 6mm is only slightly bigger - it should not be a problem. However, make sure that the wheel bolts are also 6mm longer than stock. If they use stock bolts with spacers 6mm less of the bolt will be srewed into the hub and they may be more prone to snapping off (very bad). You should be able to tell if they are long enough by removing one bolt and then screwing it back in while counting the turns that it takes. You should get at least 6 turns.

The other larger spacer, I assume is going on the rear and its purpose is probably to fit wheels on the car that were not desgined for it (probably form a 911). If they are properly designed and the correct bolts and nuts are used they should not be problematical.

Spacers that do not significantly change the track dimensions of the car (say less than 20mm change per axle) probably have no impact on the PSM at all.

 

renzop has it covered 100%, great post there.

If the car has height adjustable coilovers, that is definitely a plus as you can dial in the suspension based on what you prefer. Some aftermarket coilovers will be rebound or compression adjustable which means you can dial in the performance and handling of the setup based on your comfort preferences.

The spacers are designed to push the wheels out towards the fender and create that wider look. Just make sure, like renzop mentioned, that the correct bolts and spacer type is included.