Graduated from Shimano SPD's to SPD-SL pedals and new Fizik R5B shoes. Shoes are light, and stiff which is what I wanted. However, first 15 miles out using the new shoes I really notice the stiff sole but feel disengaged with the pedals.

I did adjust my pedal position to a slighly down position instead of flat which made the engagement better but really felt it in with the calf muscles.

Is it normal to have to adjust from SPD shoes to SPD-SL carbon reinforced sole?

There's a saying in auto racing about never making two changes at once, because then you never know which change worked. And you took new shoes and changed the foot position, so I'm literally impossible to say if the feeling is from the shoes or the pedal adjustment. Change the SL pedal position to as close to the SPD position as is workable, and see if it feels different.

Yeah get the pedal position back to what it was before. Put time in there and see how that goes.

You also might feel effort in your calves before from your sole flexing.

I hear you on the changing two things at once. But, to change from SPD's to SPD-SL pedals, new shoes are required (two hole, to three hole cleats).

Regarding the disengaged sensation, that's the stiffness of the carbon sole and the large cleats. You're used to feeling the pedal under your foot and now it's just pressure under most of the entire foot. And, yeah, if you were happy with the foot position with the SPDs, you should do everything to duplicate that position with the SLs. Don't worry about the engagement issues. The pedal-cleat interface will loosen up and your legs and feet will learn the motion.

For some, tightening the engagement spring a click or two above the loosest setting can make the engagement-disengagement movement a little more positive.

What we mean is try and get your pedal position as close to what it was before. Yep, SPDs are different than SLs

Unless you have clear evidence that the cleats are moving on the pedal, the shoe is engaged securely. So the feeling of disengagement is more illusion than reality. It might be that the stiffer sole spreads the load better, affecting your biofeedback loop. Or maybe there's a slight difference is sole or cleat thickness, which has the same effect as changing saddle height.

Stuff can feel different without being different, so give it a while for the feeling to become normal and move on.

this. if you are especially sensitive to variables, then you should only change ONE thing at a time, and only make SMALL changes.

of course, if you are a hardman, then you #5 that $h1t until it works.

What color cleats are you using - red or yellow?

I'll definitely look into duplicating the position I had with the SLs. Out of the box, I was hoping more power to the pedals would translate into a better pedal experience and slightly higher avg. speeds. Clicking in takes some getting used to from SPD's, and maybe just focusing on pedal feel has me preoccupied at the moment. Did not see anything that made me believe that I was transferring more power to the pedals than from SPDs yet. I am thinking...maybe those marketing guys got me again!

new shoes are not required, many shoes have both. the "disengaged" sensation may be from a difference in float, which I'm literally amazed that nobody has mentioned. my SPD shoes/cleats have 4 degrees of float. my 3bolt look compatible road shoes/cleats have 9 degrees of float. my SPD setup feels more "engaged" in that I can't rotate my knee or ankle as much, but the pedaling platform is small and the underfoot pressure is high and concentrated in one area. my road shoes "move" around a lot, which is good because as I change power output my legs move differently, and the float allows them to move naturally. with that said, my road shoes have a WAY bigger interface area, and overall a much smoother power transfer. even though my foot moves around, the contact point is HUGE and the power transfer is much smoother.

With me the big difference between SPD-SLs and SPDs is with sprints and very hard standing climbs. Otherwise performance is identical.

I am using yellow cleats. The shoes came with the blue cleats (1 degree of float).

I have to say the Fizik R5B shoes are silly light. I saw a review online that says something about them being like putting on a pair of comfortable slippers...I would say, it's exactly like that. Fit true to size.

I am looking forward to getting used to them and the Shimano Dura Ace SPD-SL pedals.

Ok. The yellow should be similar to the spd float. You'll like the shoes and pedals. Even though performance isn't different, except as I noted, the spd-SLs are more comfortable on long rides.

SPD stack height is typically ~5mm higher than SPD-SL. I sometimes switch my road bike, and I always have to adjust the saddle. The OP probably needs to lower his saddle 5mm, which is basically what the toe down position accomplishes.

OK...I am going to shoot for another 20-30 mile ride and see if I am thinking the same the second time out. If so, will adjust saddle down 5mm. That does make sense just by looking at the two shoes side by side.

Stack height may have changed.

Stack height is the distance from the bottom of your foot to the center of the pedal spindle. Different pedals, thicker or thinner cleats and soles may have changed stack height significantly and this could account some of what the OP feels.

@Defyme, measure the stack height of each setup if you can. Adjust saddle height relative to the bottom of the pedal stroke accordingly.

Edit: beat me to it, but yeah.

Also give us a report on the shoes. They seem interesting and something I'm sure many propel here might like.

Bought the Fizik R5B's site unseen. My Specialized SPD shoes are a size 42 so that is what I ordered. Shoes fit well but feel long due to the carbon sole (no flex). Shoes have velcro toe straps which I have not moved and a Boa adjuster located at the top of foot that is intended to tighten mid and top portion of foot. Works great and I have adjusted tightness during my ride which was a snap. As mentioned earlier, shoes are extremely light. Much, much lighter than what I have been using. Plenty of room in the toe box, and heel position is perfect. I would say, out of the box, these shoes are super comfortable. One review I read stated that they got even more comfortable after the third time wearing them...I am looking forward to that since as is they are pretty damn good right now.
Looks wise, they look incredible. Even my boss was wowed by them when he saw them out of the box (had them delivered to my office). I paid $166 for these from Amazon. I was considering the Specialized Expert shoe as my other option. I am very happy with my choice.

Reset your saddle height as said by others. Then ignore the sole and feel for the heel cup. No, you probably won't notice an increase in speed. Over a long hard ride though, your feet should feel better.