Comments: I thought the SP3s were great until I tried the SP4s. I use them for all running events from 5k to marathons as well as off trail. I use them with or without socks and for training on and off the track. I have had mine for a year and would run 30-90k per week in them depending on the race I'm training for. I have had no repetitive injury problems, blisters etc. maybe a bit of stone bruising on mountain runs. SP4 are my go-to shoes.
From: Adrian, New Zealand
Comments: I ran my first half marathon in these shoes, i will definitely stick to shorter races in them, 10k max! The toebox is so wide my feet began to slide a bit and by mile 8 every step was getting increasingly painful. I train in gel nimbus usually but these fit your foot drastically different. Ran just under 1:22 but with my stride altered due to pain i will have to run another half soon in different shoes to see how much they affected my time. On the plus side if i used them for 10k or below i wouldve pr'd, u can barely tell u are wearing shoes they are so light, could be the best road racing shoe for 5k, 10k distance. Worth the money but not meant for half marathons.
From: Adam, Manchester, CT
Comments: The worst of the Piranhas. The forefoot grip is improved but at the expense of it being a very noisy shoe. On tarmac it sounds like velcro. The counter is too high now: it is nearly 1/2 inch taller and 1/16th further foreward so it rubs on your Achilles tendon. The tongue is very small and fiddly. For road races this may be an improvement but for triathletes it makes transition nearly impossible. The print on the outside of the toe box shows through onto the inside and so catches on any up-pointing toenails inside. Get some PS3s if you can. Or wait for Asics to rebadge it as the SP5.
From: Eric L, New York
Comments: The toe box is very wide, also the shoefitr recommended a size 10 per my nike pegasus in 9.5, and recommended a size 9.5 per nike streak xc 9.5. Regardless I returned the size 9.5 for a 9, they run big, if you wear nikes usually. This is the lightest racing flat I can find that has at least 20mm heel stack height. So there is a decent amount of shoe here, and yet it is as light as most 10k racing spikes, so ideal for the roads or a 10k on the track.
From: Bowling Green, Kentucky
Comments: After checking out the reviews here on RW and other places I decided to try this flat out. For me it is true-to-size. I used them on a 10K this weekend for the first time. I was actually quite impressed about how little sore my legs were after the race. I think I could get away with running a half marathon with them. I'm a mid-foot striker and have a BMI of 24,5 so I'm not a light runner. I run about 70 miles a week. I'm a sub 3 marathoner. Ive tried several really light shoes like the Nike Mayfly and Universe 4. This shoe is best of them. The toe box is more narrow than the Universe 4.
From: Espen, Norway
Comments: I run around 55 miles per week. I have 4 pairs of the SP3 and still love those shoes and will probably order another pair since they are on sale. I just received my SP4 shoes and these are THE BEST racing flats I have ever worn. 4.2 ounces each and they have a ton of support...you glide like a gazelle during the run. I just got back home from an 11 mile run wearing these...right out of the box. No foot pain or your usual "gotta break them in" feel. They are a smooth shoe. Plenty of room in the toe box and feel softer in the insole area than the SP3's. Don't hesitate to invest in these...you'll have the competitive edge and people will envy you while wearing these kicks. BUY THEM. Kudos to Asics for delivering a stellar shoe.
From: Jason H., Chicago, IL USA
Comments: I am 14 years old and am in 8th grade,I run over 42 miles a week at a 6 minute mile pace or less. I just came back from the National JR Olympics for x-c. I ordered these shoes on a Monday morning and got them on a Wednesday afternoon the shipping is great and the fastest free shipping i have ever seen. The shoes are as lite as a feather and have more support than the Piranha sp3. On the down side they are an extremely wide shoe with a huge toe box, when you lace them up tight the upper toe box either bunches up or down. If Asics wants to sell more shoes they would stop making them for big foot and make them for the skinny runner who is interested in a light weight road flats.I would never train in these shoes for they would break down in a week, and you would probably hurt yourself. I would only run road or track races in these from 3200m to half marathon. Overall a great shoe, but extremely wide.
From: Dominic H., Harvey's Lake, Pennsylvania, USA