Question: I saw your article on why not to convert my 26in bike to 27.5in wheels. What about taking a Santa Cruz Superlight frame — meant for 29in wheels — and getting one of each wheelset (29in and 27.5in)? What are the tradeoffs in trying this setup?
The bottom bracket height will decrease, which is likely to result in more pedal strikes when riding through technical terrain.
Unlike attempting to cram a slightly larger 27.5in wheel into 26in frame, neither tyre clearance nor tyre interference at maximum suspension compression will be problematic – so that's something in the plus column. Sadly it's probably the only positive aspect about such a conversion.
While downsizing presents less clearance issues – and is also safer in terms of interference problems at the fork and rear end – you would also be lugging around more bike than you need. The geometry of the Superlight, as with the overwhelming majority of 29ers on the market, is designed solely for 29in wheels.
Some marketing-types like to tout their 27.5in models as having "the best attributes of big and little wheels". But a 29er to 27.5in conversion is likely to have the worst elements of both.
You'll lose the roll-over benefits of larger wheels, you'll be riding a heavier frame (longer tubes equal more weight) with a longer wheelbase, than would be required of a purpose-built 27.5in rig, and you’ll be smacking pedals like an angry Ike Turner. While this might not be a recipe for disaster, it’s surely a recipe for a bad time.
As I wrote in my article about 26in to 27.5in conversions — there’s an every-growing number of dialled 27.5in models on the market. Take one for a test ride and base your judgements on that. (The Superlight now comes with 27.5in wheels in small and medium sizes, and the Bantam is also a worthy single-pivot, 27.5in model.) This way you can get a true apples to oranges comparison, rather than a cobbled together apples to apple-orange-chimera-hybrid-unholy-monster test.
So slow your roll and leave well enough alone.