Hi Ben, had a similar problem with my SP. Went through two sets of small trelleborgs, both rubbed on the brake caliper bolts. Looked like the tyres had come out of the mold crooked. Reluctantly switched to the larger wheels (more weight) but the ride when taxiing is much improved and the larger tyres are much more puncture resistant.
Seems the quality control of the smaller trelleborgs has slippped markedly.
Cheers Pete