What's the point of double-sided SPD pedals if SPD pedals with platform are more convenient and lighter?

Question

Briefly

I don't get it. Why would anyone want to use dual-sided SPD pedals—such as PD-M520 (left of the image), PD-M8000, PD-M9000, PD-M9100, ...—when single-sided SPD pedals with platforms—such as PD-EH500 (right of the image) and PD-T8000...— are available?

Within the same design line and in one snapshot for comparison (the two models pictured), the latter is even lighter—383g instead of 425g.

(I'm not sure why the other models that are two-sided yet are built around a larger frame exist — such as PD-M8020 and PD-M9020 — but that's a topic for another question.)

Rotational Symmetry

We can use rotational symmetry as a guideline while discussing pedal designs. Rotational symmetry is how many times one can orient a pedal with it "looking the same" within one full revolution.

SGo4

The Crankbrothers pedals have SGo4 (belong to a symmetry group of order 4). If the present orientation of a pedal is not right, you need to spin it by no more than 45° to one side or the other, and you'll be ready to engage.

Editor's note: This is only true of the Eggbeater line of pedals. All other Crankbrothers models are SGo2 because of the surrounding platform.

SGo1

The Shimano SPD-SL, Look Keo, and Look Delta pedals belong to SGo1. There is just one position for clipping in, but that's not a disadvantage because in all three, the rear of the pedal is heavier than the front. The position of the pedal can be predicted, and this can be done (crucially) while looking up rather than down.

(In my limited experience, an SGo1 pedal will not always "lean back and be ready for clipping in." That possibly has something to do with the viscosity of the lubricant inside as well as how cold it is. These issues are also a topic for another question.)

SGo2

Like a rectangle, SPD pedals belong to SGo2. As with the Crankbrothers' SGo4 (which resembles a square), we cannot predict their resting position. Since the SGo2 pedals could be at an arbitrary orientation, the rider may need to rotate a pedal by as much as 90° to one side or the other until the pedal is ready for engaging (and the rider would truly like to be able to clip in without looking).

Question

The platform SPD pedals have a built-in weight because the platform side is heavier so they're always ready for clipping in (leaving aside viscocity, ambient temperature, as well as factory quality control). Plus they provide the option to use regular shoes or boots.

So, once more, why would anyone want double-side SPD rather than single-side SPD with a platform on the other side? Aerodynamics?

Future Questions

I am curious about the following two questions. I do not intend to ask them imminently. You are more than welcome to elaborate on either/both of them and ask.

1. Suppose I buy a pair of SGo1 pedals. Since the rear is heavier than the front, I expect them to lean back to just the right position, but one of the two in the pair I bought doesn't. Should I return the pedals? Should I heat it and try again?
2. Shimano makes some models including PD-M8020 and PD-M9020 that have SGo2 symmetry (we can't predict their orientation), yet that have a large frame. Suppose I don't care about the risk of impact (because I'm using SPD to ride on snow/ice and not in forests) and will (hopefully) always be clipped in, what's the purpose of their existence? In particular, does the frame make it easier to clip in without looking?
3. My clothes, boots, and wheels have reflectors. My bike has front/rear strong lights. Yet the tell-tale sign for motorists that a cyclist is ahead is the characteristic up-down motion of the pedals. Do I really need to be concerned if I use either PD-M8000 or PD-EH500 (neither has reflectors), or does only the PD-T8000 make sense in an urban environment?

Answer 1

Hybrid SPD pedals are somehow "weighted": the heaviest item (that defines the rest position of the pedal) is the rear of the mechanism rather than the platform. In "calm situation", you need to approach the pedal by the rear if you intend to clip, and by the front with regular shoes. But in practice, you develop muscle memory, and it's difficult to change your habits depending on the shoes you wear. And in moving conditions, because there's still some inertia in the pedal, it's very difficult to "predict" which side of the pedal will present itself (see first edit).

With hybrid pedals, if you have cycling shoes with rigid soles, having the platform side instead SPD side is also be very unconvenient. They just slip on the platform side, and are damaged by the spikes. A similar reasoning applies if they are used with soft soles: the SPD side is one pressure point that is quite uncomfortable, and with hard soles, the SPD side doesn't provide a lot of grip.

As other have said, the advantage of double-sided SPD pedals is that you just don't bother on which side it is and you just clip in. That is critical when you stop in the middle of technical steep climb. The 90° angle of rotation you mentioned is not a problem in practice. Maybe a bit in the beginning when you don't approach the pedals correctly. But if you approach them from the rear, they align themselves.

To conclude: hybrid pedals are for me an acceptable compromise only if you want to be able to use your bike with regular shoes and you don't do anything technical (because you can't count on muscle memory). I also find them annoying in urban settings, with frequent start and stops: they are often in the "wrong side", and the conditions are not so good to "flip" the pedal. For the rest, you're better off with either pure platform pedals, or double-side SPD (or Crank Brother, or any other good brand of pedal).

EDIT: I made the experiment on my trekking bike that now on my trainer. The pedals are hybrid SPD/platform (PD-M324), the experiment was to simulate a start: you start with one pedal up and make one half turn as quick as possible. At the end of the half turn, because of the rotational effects (due to the crank, but also that the pedals themselves are not "neutral"), the other pedal keeps turning, and faster than expected: the weight that is supposed to stabilize the pedal is actually having opposite side effects: centrifugal effect pushes it "outside" the rotation (which means up when the crank is up), and when the crank rotation stops, you have a rotational effect on the pedal itself: the "weight" that is outside the rotation wants to continue straight, but because the pedal is held in place, it creates a rotational effect on the pedal, which can cause them to make one or two additional turns. If you try to clip-in at this moment, it's then in practice impossible to know which side will be on top.

Answer 2

I had the platform one side pedals on my previous bike and went to the SPD both sides for my new bike. I think it depends on how you use the bike.

I bought the platform one side as my entry to clipless pedals. I am a recreational rider, but I thought there would be times I wanted to ride for transport, would not want to put on bicycling shoes, and would appreciate the platform being available. After 4 1/2 years on that bike I had ridden for transport (we were down a car for some reason) three times. In all three cases I had elected to wear cycling shoes and clip in. One of the features of SPDs is that you can reasonably walk in them enough to go to the hardware store. If I were using the bike routinely for transport I would want to be able to ride in normal clothes and platform pedals would be required.

Although the platform pedals are weighted, I found that it took some time for the pedals to align, so starting from a stop you had to clip in at the proper point in the cycle. I got used to it so it worked most of the time, but sometimes I would have to kick the pedal to get it in the right orientation. With the two sided pedals I just put my foot down and it clips in. I don't think the size of the angular correction is important as long as you always get the side you want without thinking about it.

You should use what works for you, but this is why the two sided ones work for me. I don't count weight to that resolution.

Answer 3

Finding the right side is not that easy.

With the SPL SL style Look Keo Blade Carbon pedals on my road bike finding the right side is always a hassle and makes starting in traffic very stressful. With double sided mountain bike pedals (Shimano SPD, Look Quartz etc.) you just step onto the pedal and are locked in in basically all circumstances. Kind of makes me miss the double sided Speedplay Zero pedals I had on the road bike.

Platforms are more prone to ground contact. Since the platform is rather wide it tends to strike the ground earlier in tight turns. I’ve found this to be a real problem when (temporarily) riding road bikes with platform pedals.

Answer 4

I tried SPD/platform pedals on a borrowed MTB when I was used to SPDs (both sides) on my hybrid. They were horrible - I clipped in when I didn't want to, and not when I did. The weighting wasn't adequate to be sure where they'd end up in rough terrain.

The whole experience made me quite reluctant to put SPDs on my MTB at all, though I finally got to like them when riding solo, much less in a group where stops can be sudden and unpredictable.

I'd be tempted to ask the opposite question - why do people ride with those nasty compromises when you can choose something better? Choose from:

• good platform pedals
• reliable SPDs (both sides, like M520, which are 380g)
• something like M424 with SPD on both sides and a cage to press against. This is OK for short rides in soft soled shoes or hiking boots. I wouldn't recommend them in smart shoes with rather smooth soles. I used to ride unclipped with my daughter in a child seat on the back, then clip in after she got off. For family holidays when I'd only be riding with her on there, I fitted platforms.

Picking up on your edits, and using your terminology:

• All my SPDs with SGo2 symmetry rotate naturally to the right position on contact with my foot (no looking down)
• I've never ridden with CrankBros SGo4 symmetry so can't be sure, but Id expect them to do the same.
• SGo1 as implemented in pedals has the unique property that it has two stable positions, only one of which is desirable at a given moment.

Answer 5

I can find few reasons

1. Safety redundancy. If one side gets clogged or broke, one can easily kick-to-rotate to engage in the other slot.
2. Size. The whole assembly is smaller than SPD/platform one. It allows sharper tilts without touching the ground.

SPD pedals are not meant for casual rides; they are meant for dedicated rides. The SPD/platforms are somewhat crossbread, or cat-dog, mixing both together at some compromises

1. The pedal size is compromised. It is slightly bulkier increasing risk of hits (Curbs, ground, stones,...).
2. Weight. For the same-grade materials the bulkier design means extra weight.
3. Price. For the same weight the bulkier design needs to opt for ligter materials to keep the durability.
4. Quality. For the same weight and price the lower-grade materials and/or components are used to keep the product within profitable margin.

Answer 6

If you always use SPD shoes, double sided SPDs pick up either side and are a lot easier to use.

I had ones with "rat trap" platform one side, (and added toe clips/straps) and SPD the other, because sometimes I needed to use normal shoes and sometimes SPDs. The left pedal always hung in just the wrong orientation for a quick pickup until I weighted its toeclip with an old (heavier) 50p piece.

Bike shop owner kept laughing at this modification ... until I pointed out it was the cheapest component on the bike!

Answer 7

I'll focus specifically on the SPD pedals with mini-platforms in this answer. It also applies to Crankbrothers' Candy models.

---

The mini-platform on the PD-M530, PD-ME700, PD-785, PD-985, PD-M8020, PD-M9020, PD-M8120, and PD-M9120 models are nice to have for some riders for the following reasons in comparison with the sans-platform models:

• A larger contact area with the shoes gives better stability and underfoot feel, especially with less stiff shoes designed for casual mountain biking.

• One can rest a foot on top of the pedal when unclipped (eg. while cornering on loose terrain) and have the platform to rest on.

• It is easier and more comfortable to ride these pedals with sneakers or running shoes.

• The platforms protect the working parts from rock strikes etc. In the event of such a strike, the angled faces of the mini-platforms tend to deflect rocks more than the head-on faces of race-style pedals.

However, there are also some downsides:

• Worse mud and snow clearance.
• The platforms add a decent bit of weight (84 grams for PD-M9100 vs PD-M9120).

Shimano PD-M9120 mini-platform pedal	Shimano PD-M920 race-style, sans-platform pedal

Generally, the mini-platform pedals are better for casual riders or those riding more technical terrain. The added weight is less of a concern, the tendency for shoes to be less stiff pairs well with the added contact area, and the protection & foot stability lead to a more comfortable and safer riding experience (marginal difference at best to be fair).

For XC racers, gravel & road riders, or riders on mellower terrain, the weight savings and mud & snow clearance benefits may be more important. Racers and roadies also tend to wear stiffer shoes, so shoe-to-pedal contact is less important because the entire shoe is now acting as the platform instead.

Ultimately, it is up to personal choice.

I run the mini-platform pedals on both my mountain and road bikes (PD-M9020). I wanted the foot stability benefits on the MTB, and I wanted to be able to semi-comfortably ride with running shoes on the road bike for commuting purposes. I am wearing intermediate-stiffness carbon-reinforced shoes for both riding niches.

---

I may elaborate on the large-platform SPD pedals such as the Shimano Saint PD-M820 and Crankbrothers Mallet, Mallet E, and Mallet DH later on. Hang tight for that.

Answer 8

I don't get it either. Double-sided SPD pedals provide a far easier way to attach pedal reflectors, which are required by law in many cases and heavily advisable if not required too. Pedals such as PD-T8000 already have reflectors built in around metal protection. Some earlier models like PD-M324 require external plastic reflectors that are very quickly broken, so the best solution in these cases is adding reflective tape because it's far more durable and if it ever breaks, easier and cheaper to replace because it's wide available in 5 meter long rolls and a pedal requires only 2 centimeters.

For poor SPD/platform duals like PD-M324 there is one drawback: the weight is rotationally symmetric so you never know which way the SPD side is and which way the platform side is. Thus, when starting riding the bike, it's possible you try to accidentally attach your SPD shoes to the platform side which obviously won't work. Then you need to remove your foot from the pedal for a half-rotation and try attaching again.

However, for good SPD/platform duals like PD-T8000, the pedals have very low-friction bearings and the weight is slightly asymmetric. For example in the case of PD-T8000, the SPD side points backwards and the platform side points forwards when at rest. Then when attaching your shoes, you choose the side using leg motion: move leg forwards and you get SPD side, move leg backwards and you get platform side. Easy and over 99% success rate.

It's very useful that you can use your pedals too without SPD shoes. I can think of at least two circumstances where it's useful:

• Maybe you want to use your bike for few kilometer long shopping errands. Then having to use SPD shoes would be ridiculous
• Maybe you want to occasionally ride in very cold weather, so cold that normal SPD shoes won't work (you would freeze to death) and your only option is very expensive shoes like 45nrth Wolvhammer or Wolfgar, or non-SPD-shoes which are available for very cold weather far cheaper. If you ride only occasionally in very cold weather, it isn't useful to buy the very expensive cold-weather SPD shoes, and thus, you want to use regular cold-weather shoes and you need platform sides on the pedals

Answer 9

Why would anyone want to use SPD pedals... when SPD pedals with platforms (such as PD-M9120—right of the image) are available.

Another aspect to consider aside from the techinical aspects: vanity. I imagine a large number of people are put off because, although convenient, it's not a very "pro" look.

Answer 10

Dual-sided SPDs are for those who rides exclusively clipless. This will happen when you stop looking at your rides as a light hobby and start putting some serious work into it.

The weight of the pedals is a serious consideration and premium dual-sided SPDs will be lighter than any platform pedals.

If we are going to talk about rotational symmetry SGo2 provides reasonable balance between complexity, weight and usability.

From physics and usability standpoint SGo3 is optimal because it is much easier to get clipped into such configuration. But this adds weight and manufacturing complexity.

Answers to additional questions:

1. I had SGo1 pedals (PD-EH500) and those needs to be properly tuned so platform moves down. You need to use them a little bit so grease breaks down and enables smooth rotation.
2. Large platform helps to clip-in faster and also helps to transfer power from the shoe to the cranks.
3. Pedals reflectors are myth, use bright clothes with reflective stripes and constant running red tail light. Also, tune up your front light spot to 3-2-1 rule: observe-process-react. For example, if you see a giant pothole you have enough time to evade or jump over it. Never ride in black/dark gray clothes in the night. I have done many 100+km rides in the night in-and-out of town roads.