Shimano Flat Pedal Shoes: GF400 or GF600?

Shimano's Fresh Flex

Shimano's new GF400 and the GF600* flat pedal shoes are excellent. They have impressive sole durability that will satisfy lovers of the Michelin-soled GR7. They have a level of traction that puts them into the conversation with high end flat pedal shoes from Five Ten, Ride Concepts, and Giro. All with Shimano's typical quality, attention to detail, and fit.

I'm wearing my usual size 43 in Shimano's more casually constructed high performance shoes. I bring up the size early because if the question is 'should I check out Shimano's new flat pedal shoes?' my answer is yes. If it's a question of choosing the GF4 or the GF6, stiffness is the most important differentiator. At 185 lbs in my size 43s, your experience may differ. The GF6 weighs 461 grams per shoe whereas the GF4 is 445 grams in size 43.

*Interchangeably referred to as GF4 / GF400 and GF6 / GF600

These shoes share a few features, including the ULTREAD GF rubber compound for the similar but not identical soles, which I'll discuss more below. The detail I always enjoy is the raised and padded inner ankle, which I never fully appreciate until I wear shoes without it.

The laces were what I loved most on my first ride and they're a step up from those on Leatt's 2.0 Flat Shoes. The Shimano laces are lighter feeling and hold even less water yet they share the "tie-once (not too tight) and go ride functionality." I do a lot of pedaling from a standing position and hike-a-biking so it's always a bit of a surprise when I don't have to tighten my lace-up shoes on a ride. They are not as stretchy Giro's Latch shoe laces, but that's a battle of unicorns for another day.

Soles & Treads

If you often hike-a-bike, the performance of the GF6 pushes ahead of the GF4. The subtly different tread details on the toe make an appreciable traction difference when hiking up steep and loose terrain. Coupled with the increased stiffness and support of the GF6, I'll choose it over any other shoe if I know I'll be hiking a lot.

I've recommended the Shimano GF series shoes to quite a few flat pedal converts who want lots of grip but miss the more direct power transfer of clipped-in shoes. Thanks to the high-traction rubber of the ULTREAD GF tread, there's no lack of grip despite the reduced compliance in the pedal-shoe interface.

Shimano only rates the GF6 as a Level 3 on their stiffness chart. This is a much lower rating than an all around clip-in shoe like the ME5 that Cooper just reviewed, only one level above the rating of the GF4 (Level 2), and the same rating as the previous top-level GR7/GR9 shoes. I'm suspicious because the GF6 feels much stiffer than those other flat pedal shoes and much more similar to a trail use clip-in shoe

The GF6 is stiffer than any other flat pedal shoe I wear. This is noticeable when standing and climbing my bike up steep sustained sections, hiking, and on long janky hardtail descents where my feet don't get as sore. If I'd only reviewed the GF6 I'd be tempted to credit the latter to the EVA rubber section of the sole damping vibrations, but the GF4 shares this feature.

The EVA section functions similarly to Giro's patented Mute foam midsole, but the damping effect is less noticeable. Giro's explanation of Mute best sums up the concept either way: "It's a patent-pending slow-rebounding foam-injection-molded midsole layer meant to dampen the bounce from hard landings and punching through chunder-ridden trail sections."

Other Shoes

Let's say you're signing up for the 365-day flat pedal challenge and trying to choose a pair of shoes. The GF4 and GF6 both have tenacious traction. The GF4 has a more forgiving flex that will likely better suit lighter riders and those with smaller feet, while the GF6 will better suit those looking for stiffness closer to a clip-in-like shoe.

For the wet weather grip and trail damping, I give the nod to the Giro Latch. That Tack rubber grip, holy sh*t (speaking of, worst shoes I've ever had to scrape clean of dog crap). That aforementioned Mute foam midsole is a considerable comfort boost in the jankiest terrain. The stretchy laces are a luxury, but at a few costs. The Giro shoes rob some efficiency while climbing due to the impressive damping, and the treads wear much faster. Stiffness-wise, they're similar to the GF4.

My favourite shoes to slip into remain Crankbrother's Stamp lace. The soles are nowhere near as grippy as Giro's Tack Rubber or Shimano ULTREAD GF but they're suitably grippy. The soles conform enough to my pedals that, even on the greasiest days, I can achieve a magic balance of being able to move my feet around and stay glued to my pedals.

For folks looking for maximum traction, these will not be the first choice and that's where I always suggest the Giro Latch. Compared to the Shimanos, I'd always choose the Stamp Lace over the GF4 but I've been consistently finding that I'm grabbing the GF6 over anything. On proper rides on my hardtail, my feet feel less beat up compared to descending in the Stamps and I notice the difference in climbing efficiency compared to the Latch on both my hardtail and full suspension bikes.

Insoles

Part of the cost difference between the GF6 and GF4 is the included insoles. The GF4 has a standard floppy insert while the GF6 includes a more structured form. I pedaled in both setups in both shoes, and the only benefit I noticed from the stock GF6 insole is that it absorbs less water.

I've written plenty about Esker's Canadian-made wool insoles so I'll link and move on with my shoe review. To make things fair comparing stiffness, I ran the same pair of Esker The Approach insoles in both shoes. There's an increase in support over the stock inserts but more important for me is the moisture and temperature managing characteristics. The smell management is nice, too.

Price Aside

The Shimano GF6 is a more expensive shoe than the GF4 to an extent that I don't think is reflected in the performance improvement, unless a rider is looking for a stiffer interface. In that case the GF6 is the winner, no contest. I assume this stiffness difference is why Shimano does not offer the GF6 in sizes smaller than a European 38. While the GF4 covers a range of 33-48, the GF6 only covers a range of 38-48.

Given the nice blend of stiffness, grip and quality construction of the GF6, I'm surprised Shimano doesn't offer it in a Euro 49 and 50. I think it would be the perfect flat pedal shoe for mountain bikers with large feet. Five Ten sells the Freerider and Freerider Pro in sizes up to 50 as Giro does with the Latch. Considering my experience with the support of the GF6, it would be a competitive option.

Shimano's soles taper as you approach the arch and have less pedal pin and body contact for riders who pedal more ball-over-axle. I didn't find this to be a grip or support issue at all.

Some shoe rubber seems to work better with threaded machine screws but I tend towards pedals with smooth pins as I find they allow shoe soles to interface more predictably and wear longer. Of the pedals I've used, the Wolf Tooth Waveform had the most natural landmarking, but the Shimano soles provided excellent traction with a range of different sizes, shapes, and pin types.

While they are much less expensive, I'd choose other shoes over the 150 CAD | 110 USD Shimano GF4 but would still recommend them for riders with smaller feet or who prefer a more flexible sole.

I really enjoy the pedal interface, grip, and efficiency of the 220 CAD | 160 USD Shimano GF6. They are a big jump up in price from the GF4 though, which I'd have a hard time justifying in terms of added features, except for riders chasing a stiffer flat-pedal-shoe interface.

Price considerations aside, both shoes are excellent on the trail.

Shimano Gravity Flat Pedal Shoes