Secondly, both fronts were Michelin PS4's with about 3.5-4mm of tread. I obviously need at least one new one, but would you replace both fronts at the same time? The difference in tread depth is making me a bit cautious, but is it something to worry about?
If it was 5mm then i'd just replace 1, but at 3.5mm there's not that much life left so better to replace both (and you could always get another rim and stick the 3.5mm one on as a full size spare)
