steering wheel shakes when i get to 80kms, on porsche cayenne with aftermarket 22" wheels?

Spin balance all four wheel / tire units. If they're good, you may need a full alignment. If one tire / wheel won't balance, you may need to round (shave) the tire. Also, look for bulges in the sidewalls -- tires sometimes fail in this fashion. If you've got a sidewall failure, replace both tires on that axle, not just the failed one. If you've got different tire sets (brand, model) on front and rear axles, replace all four tires.

As everyone has noted, it sounds like a balance issue... but I will add one other note which starts with the question: Does the shaking continue to get worse above 80kms, or does it go away?

If it continues to get worse or even remain about the same, it is almost certain to be a balancing issue. However, if you get vibration at 80kms, and then at 83 or 84 it suddenly resolves, you are more likely facing an issue related to that particular wheel in relation to your suspension geometry (recall this happening with some older BMW and some BBS wheels). This is more likely with low profile tires and very light wheels.

If the later is true, the easiest fix is not driving at the speed that results in that particular harmonic cycle, but can also be minimized with different tires as well as looking at changes to soften the suspension (both of which might introduce their own issues); or looking at different wheels.

Most likely the former though.

Pete is right. Go get a SPIN balance - not a static balance. Sometimes a weight will fall off right out the tire shop door because the lead weight cracked when crimped onto the rim of the wheel. In any case, the spin balance is the cheapest and most likely solution before anything else.

Try taking the spacers out.

They may not be allowing the rim to mount firmly.

Then try swapping the fronts and rear tires.

If it is a balance, bent rim, or bulge problem, there may still be a vibration, but not through the steering wheel.

Sounds like one of the lead weights has come off. Or simply, a wheel is out of balance. Take it to your nearest tyre fitter and they will balance your front wheels for a small charge.

It's not dagerous but it will wear your tyres uneven if left not done

Cheers

Okay i have a few things

1 maybe the air pressure is off check that

2 maybe the tires need aligned

3 get a front end evaluation