Carbon Sole shoes

I'm preparing for a 250mile ride over 2.5 days in July and currently using a set of M520 SPDs and Lidl shoes. As I've been hiting bigger distances I've found my knees have started to hurt a bit and I can't seem to find the sweet spot for cleat setup so am probably going to get a proper bike fit. However before I do I might as well treat myself to a pair of Speedplay Zeros and some new shoes - hoping the psychological boost will out weigh the lack of training 
I understand that carbon sole shoes are stiffer and that should help to eliminate hot spots and increase power transfer but are there any disadvantages to them. Are they really only for racers (which I'm definitely not!) or would another type of shoe be better suited for me.
Cheers
Jim

I understand that carbon sole shoes are stiffer and that should help to eliminate hot spots and increase power transfer but are there any disadvantages to them. Are they really only for racers (which I'm definitely not!) or would another type of shoe be better suited for me.
Cheers
Jim
Cannondale Synapse 105
Giant FCR3
GT Avalanche 3.0
Canyon Nerve AM 6.0
Giant FCR3
GT Avalanche 3.0
Canyon Nerve AM 6.0
0
Posts
Carbon in shoes is not necessarily used for it's lightweight means but for it's increased stiffness and reduced thickness (compared to an already good nylon sole). The stiffness of of the sole and the reduced stack (distance from the ball of your foot to the spindle of your peddle) will really make your foot feel and act like the peddle itself. This is maybe hard to imagine as a big advantage when trying different shoes at your LBS but it's very noticeable when riding. You really don't need to be a pro to feel the difference. That said look for a shoe that in the first place supports your foot well, and fits snugly yet comfortably. If you can afford it (because you will have to vector in road specific pedals too, which is the other have of the equation) then go for carbon, if not you'll still be alright!
Good luck with training too.
I fancy the titanium ones with Lake shoes but the cost has always been prohibitive
MTB is going on ebay shortly though
Just don't do what my mate did with his. He skipped over the instructions and put them in the oven at 150deg c instead of 70. OOPS.
F*cking Fast 29er
Rapid Rose Roady
Bionicon Beast
Rockhopper Communter
Toasty warm when you put them on, but I don't think I changed the fit much by pressing on the mouldable parts.