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Reviewed: DMT Prisma Shoe – Speedplay Sole

DMT Prisma Shoe - Speedplay SoleOne of the best developments in shoe design we’ve seen in the past few years is the return of four-bolt soles on the bottom of cycling shoes. This design means those who ride on Speedplay pedals don’t need the three-bolt plate that attaches to the Look three-hole bolt-pattern sole common throughout the cycling world. The reason we’re excited about this development is we’re Speedplay users. It also might be we think that if we can lose weight and increase efficiency just by switching shoes, we probably should do it. So praise is due to DMT for making shoes with Speedplay-compatible soles. The Prisma is their high-tech cable-lace shoe, though it shares a sole with their Radial model, which uses three Velcro straps.

DMT Prisma Shoe - Speedplay SoleBy bolting the four-hole Speedplay cleat directly to the shoe sole, Speedplay riders are reducing their rotating weight (according to published statistics) by 24g per pedal, from 162g per pedal to 138g, as well as their stack height by 3mm, from 11.5mm to 8.5mm.

We’ve found no shortage of people who believe that reducing rotating weight is very important, much more important, some say, then reducing static weight. And when you’re pedaling, you’re lifting each pedal 90 plus times a minute. In terms of acceleration, probably everyone has noticed the difference between a lighter wheel and a heavier wheel, a lighter tire and heavier tire. All the same we haven’t found a formula. Makes sense to us, when we first switched to super-duper lightweight carbon soled cycling shoes, they felt much lighter in the hand, but it certainly doesn’t feel as dramatic as when we switch from our training wheels with the 300g tires to our race wheels. We’ll go with lighter being better because we’ve seen that even half a watt of energy saved can reap huge dividends over the course of an hour.

DMT Prisma Shoe - Speedplay SoleAs for the importance of reducing stack height, and the resulting “rocking torque” (energy lost due to moving back and forth over the pedal spindle), here, too, we’ve had trouble finding proof. There is plenty of anecdotal evidence. Take a look at the blocks people often affix to their kids’ trikes and little bikes. Think about doing that to your pedals. Do you think you’d be faster if your feet were much closer to the pedal? Most say yes, even if we’re talking about three millimeters, not three centimeters.

In terms of equipment, the Shimano Dura Ace AX crank and Dyna Drive pedal of 1982 put the ball of the rider’s food at the axle by using a possibly revolutionary dropped pedal and oversized spindle. We think this was ridden by Alexi Grewal to the Olympic gold medal in 1984, but haven’t found any pictures of Alexi’s bike from the side. But the biggest evidence is found in the evidence of clipless pedal evolution since Look debuted the first successful clipless pedal in 1985.

The original Time pedal system, a shoe and pedal combo that debuted in 1988, was created by the same person who designed Look pedals, and he was trying to improve his basic idea by addressing both stack height and bio-mechanical needs. It called for a two-piece cleat that would get the shoe sole closer to the pedal axle, with part of the cleat in front of the axle, and part behind. Richard Bryne debuted the Speedplay pedal in 1989, and based his design off the four-bolt system that Time used for the same reasons Time did. He explained his thinking, “Time’s pattern spread the mounting bolts further apart so that the pedal could be positioned nearer the foot. Look’s pattern positions the front bolt too close to the rear bolts, preventing a low stack height. When I realized that I could integrate both patterns into my design I did it.” Time’s two-part cleat stayed through the 1990s and into the twenty-first century, but it suffered from a problem; to take advantage of the lower stack height, you needed either a Time shoe or another company who was willing to work with Time by bonding their upper to a Time sole. Of course, savvy Speedplay users could have also reduced their stack height with the same shoe.

While Time retired their original design in the early aughts, the need for the four-hole pattern sole seemed to just about vanish. There was a small demand kept alive by Speedplay users who were going to custom shoemakers to get soles pre-drilled for Speedplay cleats. As this was going on, Shimano, Look, and the few others left on the market were trying to figure out how to reduce the stack height of their pedal systems. And Speedplay demand was increasing.

Somewhere in the middle of this timeline, USA Cycling’s Project 96 came and went. The point was to develop cutting-edge gear to give Americans an edge at the 1996 Atlanta Olympics. Don Lamson developed an integrated shoe/pedal system for the team.

So, moving onto the shoe, we’re assuming that slightly lighter is better and that a lower stack height is better. Bryne also thinks its more aerodynamic and has had some success testing out his theory.

DMT Prisma Shoe - Speedplay SoleThe DMT Prisma shoes with the Speedplay sole are pretty light. Our left shoe, size 44.5 weighs in at 291g, the right at 296g. The insoles are 17g each. The carbon sole is said to be 3.5mm thick at the cleat area. Right away, we’re adding weight because the insoles are too wimpy for our needs; we replaced them with our custom insoles. And we’re adding stack height by .29mm because it is recommended everyone install the Speedplay Carbon Sole Wear Protector Shims, which are .29mm thick and weigh 7g apiece (Speedplay claim these reduce wear on their pedals and on three-bolt to four-bolt adapter plates as well). You’ll also need slightly longer than standard 15mm cleat fastening screws, aka Speedplay 4×15-8 Screw Pack, 4mm longer than the standard, and resulting in a negligible weight gain.

DMT Prisma Shoe - Speedplay SoleWe’ve spent most of this review discussing the sole and what goes on underneath, but what’s above the sole is what will determine whether or not you’re going to like this shoe. This is where most of the comfort is. The shiny synthetic upper looks like Patent leather. It’s a good look, but the stuff also seems fairly tough; we barely noticed any stretch even though it feels pretty soft. All the shiny material made us think the upper wouldn’t breathe well. We were wrong on that. Maybe the stuff breathes well, maybe the mesh panel on the inside of the shoes do a great job venting; either way, the shoe never got hot on us.

A feeling of lightness goes beyond just the shoe’s overall weight. It also has to do with the fit. The heel cup feels wide and soft relative to what we’re used to, and the ratcheting wire lace system doesn’t come up very high on our foot. We were concerned that this meant it would feel like our foot wasn’t snug in the shoe. Then we set the Velcro strap on the bottom of each shoe so it just took up loose space, as it was too low to really do much to hold our feet down. And when we ratcheted the lever, what DMT calls RAM+VTR (Rotary Activated Mechanism + Variable Tension Regulator), and tightened the shoe against our feet, we didn’t feel like our foot was firmly in place when the lace felt taut. We had the sense that our foot was definitely at the narrow end of the range of adjustability for the 44.5 size.

DMT Prisma Shoe - Speedplay SoleWhen the lace felt taut, we’ also had a sensation that the plastic ratchet lever was flexing. This, too, was a bit unsettling. We’ve used the Boa cable-lace system, are very comfortable with it, and never experienced a similar sensation when tightening down with the disc. At the very least, we want to have two extra “laces” along with the ratchets in a drawer or travel bag just in case. They’re easy to replace and the lace can be inserted and removed by hand quickly; the shoes even come with the tool. It also, btw, comes with a nice travel bag.

While we didn’t feel secure in the shoe, we rode them and sprinted on them anyways. Our feet felt secure. Not like they were clamped into place, but snug and secure and weren’t going to move. Same when grinding away up a climb at a 50rpm cadence. Since we’re used to our feet feeling bound, this was a new sensation, though we did get used to it.

We’re skeptical about published shoe stack heights. Like for this shoe. 3.5mm is really thin. We’re not sure they can really control manufacturing that precisely. This isn’t just a complaint about DMT, but for all shoe manufacturers, especially those that use what we think of as “half a T-beam” construction; a sole platform that is on top of a much narrower cleat platform. When we look at our digital calipers, it seems that 3.5mm is the thickness of the sole, the cleat plate starts another few mm below that, and that the distance between the cleat and the sole increases the further back you move the cleat. Wish we could be more definitive here, but without drilling holes through every shoe, it’s going to be hard to measure.

Because of this skepticism, we didn’t initially lower our saddle height the 3.44mm thickness we measured of our Speedplay three-to-four bolt adapter plate. We didn’t lower it at all. And our first rides on the DMTs, we couldn’t notice a change in overall extension.

What we did notice was a change in how our calves engaged the pedal stroke. It didn’t feel like they were moving as much. Perhaps we could have moved our cleat forward, but we’re pretty sure the cleat was in the same position relative to the balls of our feet. The second thing we realized is that we needed to laterally adjust the cleat position. We typically find that we need to push the shoe to the far end of its lateral travel in order to minimize Q-factor. With the different positioning of the plate, we had the cleat in the middle of its lateral travel and still were just about hitting the crank arms.

On our first four-hour ride on the DMTs, we realized that while the shoe stack height might not be 3.5mm, the shoe and cleat combo of the DMT shoes and Speedplay four-bolt cleat definitely possessed a much lower stack height than we were used to. Our back was aching until we lowered the saddle. Even if the stack isn’t quite what they advertised, our previous shoes soles are constructed the same way, a sole platform on top of a cleat platform, and then the Speedplay adapter and then the Speedplay cleat.

After a few months of riding the DMT Prisma Speedplay shoes and swapping shoes around and back and forth to figure out relative merits of our old versus this new, we’re pretty happy with the Prismas. The upper feels good inside the shoe, very few seams, it doesn’t seem to stretch at all, and it looks good. The cable lace and ratchet system doesn’t over-tighten or pinch our feet in any way; very comfortable. Still not sure how we feel about not sensing our feet are bound, but it’s definitely different; people who feel their feet are squeezed into most cycling shoes will probably love how the DMT upper feels. The carbon-fiber sole is plenty stiff and the shoe has a pretty low overall weight. As for the issues of stack height and rotating weight, we’re still inclined to believe it makes a difference, but it’s a difference that is probably less important than the overall fit and comfort of the shoe.