Not 29er, but may still apply. Recently got a couple of new decathlon tyres (26 x 2.0) for one of my clunkers. Back one straight on, runs peachy. Front one more wobbly than a wobbly jelly. Tried adding some soapy water to the mix, no use. Removed and tried again with soapy water, still the same. Ran it for a while, but the 'hump' was noticeable and getting annoying. Anyways, had another spare front wheel in my store, so gave that a go. Tyre went on nice and true, no messing with soapy water. Seems a slight variation in wheel size is enough to cause an issue. Just a heads up - don't assume the tyre is at fault!