I order all my bike parts online from Roseversand. They ship to Switzerland and cleverly bypass all customs charges (not duties, just charges) by automatically removing the 19% German MWST and adding the 8% Swiss MWST to the invoice. They charge 1% for doing this.
Then the goods arrive directly to you in Switzerland without any customs intervention as the tax is pre-paid to them.
For (trekking bike) tyres:
http://www.roseversand.com/products/...yres/trekking/