[keefer]

would be surprised if anyone tells you any different, but I think it is quite a big problem.
you must make every effort to get rid of any contamination on the tyre
wash them thoroughly use brake cleaner even but I would not ride it while it is on there. also are you sure that none has got onto the disk ?
again be very careful.
if you must use wd40 to clean in such areas then apply it to a cloth then apply the cloth to the wheel