Sole stiffness faster? Anyone got any data?

When I started cycling seriously, I progressed from tennis shoes to some pretty flexible touring shoes to pretty stiff cycling shoes over the course of a year or so then on to clip in pedals a year or two later (I started at the end of the toe strap era . . .). Stiffer soles are definitely faster when comparing floppy to stiff. But, once you get to comparing among various racing level shoes, I don’t think there is a whole lot of power differences from stiffness alone. Once you’re in to “real” shoes, fit and comfort are the differentiation.

Ah yea, you’re coming from the same place then! Definitely give the sworks 7 a shot if you have the opportunity. Be aware that there are chafing issues though. For me, it was the top of the shoe and the tendon at the top of the ankle. For other people it was the outside front ankle. Fortunately with specialized and my LBS it’s a satisfaction guarantee issue and I tried it for about two weeks before I had to return it for the chaffing issue. Other than that issue it was the best shoe I ever tried.

How do you even quantify sole stiffness? The shoe manufacturers just assign a number to the stiffness of the sole. But they give no idea what that number even means. Does a Specialized 13 have any relation at all to a Giro 13? Is a 10 twice as stiff as a 5? I’d bet not. And how big a flex is a given number? Is a 10 = 1mm, 10mm, 0.1mm? Who knows. Without any more information these numbers are basically useless. Just get a modern shoe that is comfortable. I have the S-Works 6, S-Works 7, and S-Works Exos. I can tell a big difference in comfort (the Exos are the best by far for me) but I can’t tell any difference in flex. Other fit related stuff but not flex.

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A bit of a bump…

I know nothing but thought this was interesting…I just rode with an old friend who has long ties to Dave Simmons of Simmons Racing back east as a skater. Stiffness while important is but, one aspect of the system. How much the foot moves or not in the shoe I think is where real gains can be made or lost as far as power transfer/efficiency are concerned. Again, I’m not an expert. Just parroting here and only trying to provide a different direction in the discussion. Here is one of his pair.

i dont have any data except for what’s already posted out there; my data is the feeling of when you wear a stiff shoe and the bike just flies beneath you. it makes a big difference IMO.

I think you just saved me some $ !

I’m thinking about new shoes - currently have some old Shimano RP3 and was looking to upgrade - but from everything I read, the only upgrade would be a cosmetic one - there doesn’t seem to be any advantage in the more expensive shoes.
I see the argument about more stiffness = better power transfer, but curiously there are no numbers indeed. Same for aero claims. Pretty amazing quite frankly !

Considering clipless pedals are no faster than flat pedals (where I assume one would wear ordinary sneakers) I can’t see how sole stiffness who have any effect on speed.

@PawelKozela I don’t think shoes make a difference in terms of actual measurable watts…well, actually, I know they don’t because I’ve tested it. Same with cranks. Even the most flexy cranks don’t make a measurable performance difference.

But, but, BUT…definitely shoe comfort can be ‘make or break’. Very important. I know I’ve told this story before but once upon a time I won a North American Championship and that victory required a substantial solo effort during which I started to get ‘hot foot’. I had never experience this before and in fact had always held a low opinion of people who complained about ‘hot foot’. But on this day it really did feel like my foot was on fire. I mean, it made my eyes water. It was really uncomfortable.

After the race I couldn’t feel parts of my foot. My big toe was numb for 18 months.

So SHOE COMFORT can make a difference. After that experience I would say its definitely worth a few extra bucks to get a more comfortable shoe. On the other hand (foot?) if you are just doing 100k races or 90 minute crits…probably doesn’t matter.

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This thread was bumped up at the same time as this bike radar article which references a University of Colorado study which determined shoe stiffness was insignificant.

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So I’ve gone from a not that stiff shoe to super stiff Bonts. I think a super stiff sole makes peddling a little different and for me, better. Maybe a good analogy would be if you imagine deadlifting with bare feet on a concrete floor vs on a 1 inch foam matt. I think my max deadlift would be the same outhouse 2 surfaces but over time I think I’d be more efficient and be able to apply force more efficiently and biomechanically more soundly on the concrete floor. Unfortunately these things can’t really be quantified but for me they are there. (the Bonts were only about £200 too which isn’t so bad)

The summary of that article is there’s no measurable performance difference between plastic and carbon sole cycling shoes. However, there’s a significant difference from a cycling shoe to a tennis shoe. You need a stiff enough platform to spread out the load to the pedal.

Also, a good fit and arch support matter. Otherwise your foot acts like a damper which will cost you energy and create pain.

So just find the most comfortable shoes you can. If necessary you can swap the insole to get better arch support (which depends on your specific arch shape).

Good fit is what n=1 I found felt like it made the difference, albeit in a lighter, stiffer soled shoe. Any kind of wide feet, and cycling shoes get tricky in my experience - I ended up going for size (length), and buying a shoe stretcher!

I wouldn’t disagree with that study. What they didn’t study though is how pedal stroke is effected after 6 months on a totally solid platform vs a slightly bendy one. For me (20 years of riding) a super solid peddling platform has improved my pedal stroke. Some things are hard to measure in a 3 week lab study.

Stiffer soles are more comfy over ultra distance type durations.

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I don’t really buy into the sole stiffness thing either, but surely there is an effect on speed between flat pedals and clipless pedals, especially when you’re going fast. I mean, there is already an effect of the sock length and material. The airflow around the pedal will change. And normal sneakers are likely more bulky and a lot less aero then thinner, smoother cycling shoes.

If we’re strictly talking downstroke, I’ve definitely lived through not stiff enough tennis shoes then the gains of going to a stiffer dedicated cycling shoe. It seems like the consensus is that once you’ve made that jump, going from stiff to stiffer may be marginal, with comfort becoming the more critical factor.

For completeness, what the thread seems to ignore is the rest of the stroke, esp. when comparing flats to clipless pedals. I hope we can agree that gaining more control through the rest of the stroke, esp. the upstroke, is a big benefit that clipless brings that you can’t get with just a flat.

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Yes, I think we all agree that cycling shoes vs tennis shoes, there is a difference. Now that I think about it, I quite often go on longer rides on my gravel bikes - with flat pedals, I’ve never seen a big difference in average power (estimated). But there is definitely one in comfort and when climbing.

However, between different cycling shoes, it seems that between the cheap and most expensive models, it’s completely negligible. Again - from power transfer perspective. Comfort is another thing of course !