Jogging Stroller Tires question?!?

so… we found a great stroller at a great price, it is an InStep Suburban Safari, the blue one with 12'' swivel wheels. i like everything about this stroller, except i find that the wheels (all same size) are a bit too small for our terrain…i was wondering if i can replace the tiny wheels with the 16'' tires most jogging strollers have? also, since the tires are all the same size, that means they are connected on the same height, so i guess i wouldnt be able to leave the front wheel as it is and just replace the back tires with some larger ones? is replacement at all an option? or are they permanently fixed?

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