Last year I bought a set of new tyres for my GS online for 2 reasons: they were a bit cheaper than buying them from the garage (even considering that I paid 23.50 euros per tyre to have them fitted), but the main reason was that online there was plenty of choice and I could pick the brand/type I wanted, while buying from the garages they were offering either premium tyres at exaggerated prices or unknown brands, not for a cheap price, and they said they were good tyres. After all every tyres garage needs to sell what they have and they will never tell you that its tyres are bad. Anyway I found the purchase online quite easy and convenient as the tyres were delivered to the garage which after fitted them on my car, so I did not have to carry them there.