Re: wheel offset
The 5x98 is the PCD or spacing of the wheel bolt's.
A 5x100 will not fit directly onto your car, you can use "wobbly" bolt's which have a "loose" shoulder, these are commonly used in racing and are safe to use.
The offset is how far the wheel sit's in relation to the centre of the hub , body and suspension, the lower the number (mm) the wheel will sit further out to the wheel arch. It is important that the offset is within a certain range as to avoid fouling of the tyres on the wheel arches and suspension and brake componant's.
The centre bore is the diammeter of the hub where the wheel mount's, if it is too small obviously they won't fit, too big you will get vibration as if the wheel balance is out. This can be cured by using "spiggot" ring's.
It sounds like the wheel's you are interested in could be for a V.W , Audi which i would try on the vehicle with tyre's fitted to ensure any problem's before commiting to them.
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