Fork change

[Jorin]

Can a 650c fork be swapped on a 'bent with a 20" front wheel? I know that this will raise the BB height... which should make it quicker by cutting down frontal area. My concern is first handling (it will change, but will it be rideable) and are there other technical problems with making the switch? The bike I am looking to do the conversion on is an Optima Lynxx, which comes with some rear suspension.

[BlazingPedals]

With a curved frame like an optima, the larger wheel may hit the frame behind the head tube. Raising the headset will have the effect of relaxing the steerer angle, which will tend to increase trail, which will serve to make the steering more sluggish. At a guess, it'd still be rideable, but you may or may not like the new handling. Regarding the rider recline angle, you will be reclined more, so make sure you'll be able to see over your knees. Of course, the seat will be higher too, but you knew that!