Install cleats and engage pedal in shoe 1. Put the crank in a fixed position, put the end of a tape measure in a fixed location on the inside sole of the shoe, and measure to a fixed point near the top of your bike. Repeat for pedal and shoe 2, using the same fixed locations. Take the difference between both heights as the stack height.

I have nothing to add about your specific shoes, but for info I routinely adjust saddle height depending on which pair of shoes I choose to wear. I have Northwave Tribute (tri shoes) and Fizik R5b (road shoes) and there is a significant difference in stack height. I'd say at least 1cm which is totally noticeable if I try to ride without adjusting. I use identical cleat configurations on both (speedplay with 3 hole adaptors).

Cheers, Rich.

Appreciate this method but 1) it's not exactly feasible with these shoes due to the tongue and boa systems, 2) the margin of error we are talking about is likely <10mm so it makes measuring to an arbitrary point fall within the +/- variance that could invalidate any measurement.

Carbon sole thicknesses for high end shoes are often around 6-7 mm total. For lower end shoes with nylon soles, 8.5-10 mm. The potential difference in two different carbon soles is likely small. Have you looked at the insoles?

Thinking about it more there can be a mm or 2 difference in the lasting board and maybe another mm in the upper material wrapped around the lasting board

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Ed O'Malley
www.VeloVetta.com
Founder of VeloVetta Cycling Shoes
Instagram • Facebook

The RC9 does have an extra low stack height. I don't know about your model years, but the current RC7 has a stack of 8.8 mm while the RC9 is 4.7 mm.

Interesting, thanks Ed. I think I may have exaggerated with my bold claims of 1cm difference in height!! Certainly, it is enough that I need to compensate, especially when I go from the high stack Fizik with the seat post set up correctly and swap to the lower stack Northwave. I can tell straight away that my saddle is now too high and it is uncomfortable to ride without dropping it.

I should get the calipers out and quantify this. I have read that the Fizik lower end shoe like my R5b has really high stack - even though it is carbon - and saw 9.7mm written somewhere. If my Northwave were on the lower end I could easily see 5mm difference. I'm using the same plate adaptor and cleat on both pairs but I guess I might use slightly different shims on one vs the other (Speedplay).

If it proves nothing else to me, it is that saddle height matters a lot!

Maybe the fizik really is that thick...

I wonder if your saddle height is a little too high in either case if a 5mm difference feels that consequential to you?

If the sc9 is really 4.7mm I think they must last the upper directly to the carbon sole. Pearl izumi did this first with their p.r.o. leader. I did not know anyone else had followed suit. That would explain the tpu plastic part around the outer perimeter of the sole.

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Ed O'Malley
www.VeloVetta.com
Founder of VeloVetta Cycling Shoes
Instagram • Facebook

Have you tried contacting Shimano customer service? While a CS agent may not know the information off-hand, the product manager/developer should have those stack heights readily available.

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Shawn
TORRE Consulting Services, LLC
http://www.TORREcs.com