While I can't tell you
specifically about the 175/55 Vredesteins (cos they're hard to get in Oz!
) but
MOST tires that size fit Spyders without any concerns, and for those that don't just slip straight in/on, it's usually a relatively simple matter of swapping the hex head bolts in the inner fender for pan head bolts;
OR maybe fitting a washer under each of the fender mount bolts;
OR simply cutting the existing zip ties holding the wires to the fender brackets, twisting the wires around the fender bracket rods so they're away from the tire/on the outside, and fitting some new zip ties.
Seriously, the time/effort that it takes to do any of this just to
make sure the 175's fit is insignificant; just do it, I really doubt you'll ever regret it - and besides,
it's probably waaaaayyyy less effort than going to the bother of changing/cancelling your order!