Stretching your Vibram fivefinger when they are too small

Fivefingers is a minimalistic type of shoe from Vibram. It emulates the physiology an feeling of barefoot running whilst offering protection to the soles of your feet. But they are really hard to get a good fit.

Vibram has detailed instructions on their site on how to measure your feet and order the correct size. My feet are just between two sizes, so I ordered the larger size, just like the website instructed.
When I got my Vibram's (these are a pair of Sprints) it was clear that they were way too large. I had over 1 cm of spare room at the heel when I slid my toes forward. Thanks to the return policy of www.zehenschuhe.de I exchanged them for a smalller size. I was quite disappointed to find out that one size down was now too small. My second toe couldn't fully extend and when stretching my toes they were clearly limited in their movement by the toe pockets.

If you want to find the right size for your Vibram Fivefingers, you have to put your feet flat on the ground. Then you grab the part of the rubber that extends slightly to the front of your toes. When you move the end of the rubber a bit back and forth, you will feel it touching and releasing the tip of your toe. When you leave the rubber alone, it should be right in front of the tip of your toe, with about 1mm play.

Luckily, it is quite easy to achieve a perfect fit by extending the toes that are not long enough. To do this, you have to stretch the rubber real hard. I used a socket wrench which I crammed into the shoe with some more objects behind it to achieve a maximal stretch. Don't be afraid to overdo it, since after the operation the rubber will come back to almost it's original size. Depending on the amount of tension on the rubber I have been able to gain a maximum of about 5mm in length gain. Other attempts only yielded about 2mm of stretch.
Whilst the shoe is stretched you have to heat the rubber with a lighter:

• hold the flame against the rubber, not just under the rubber (the tip of the flame would be way to hot)
• move the flame over all of the rubber that is elegible for stretching, starting from the forefoot area until the top of the toe
• keep doing this for 5 minutes (I know: this is long). The rubber will smell and fumes will come off. Don't worry: this is the internal links in the rubber that are breaking and will result in some amount of stretch (you can't actually melt vulcanised rubber, it's more breaking down links inside it)
• when you're done heating, put the heated area in cold water for 30 seconds. Leave the shoe under tension for another 5 minutes and then move on to the second shoe

You can do this for all toes that need extension. I started by extending the second toe by about 5mm. I walked around on the shoes for a day like that, still feeling a bit cramped on the big toes. The next day I extended those with about 3mm. When walking around like that they almost felt perfect, but the little toe was just being rubbed a bit by the shoe whilst walking. So I stretched those by a very small amount, around 1mm. 

My Vibram Fivefingers are now perfect and I can't wait to really run longer distances in them!