Video of How to Fit a Tire (example - Marathon Plus)
I've encountered cyclists struggling to fit tires, particularly the stiffer Marathon Plus, and also for Brompton where the size of the depth from top of rim to the bottom of the well is relatively large and so the tire's little stretch isn't enough and brute-force usually fails.
The "Wave" method is to push the bead of the tire into the well, it will tend to bounce back out of the well so takes multiple waves, progressively flipping a bit more of the bead over the rim. The TRICK is to NOT USE STRENGTH, because all that strength does is firmly lock the bead over the rim so when you use the WAVE it too tight all-over to really be moved much into the well. You need JUST enough tension at the bead-rim boundary to tend to keep the bead where you put it, too much tension and it won't move, too little and it will just bounce back out of the well. There's no skill initially required, as initially if you've pushed too little of the tire over, the first couple of waves are not doing much but then later it will be doing it enough. With practice one remembers how much force your thumbs should be applying before the first wave, I'd say about 10%-20% of max thumb strength.
Multiple Waves, little strength, and just be patient. At no time should strength be used, a child's hands could do this method.
For a new tire about 4-10 waves are needed, in the video this is using an old tire and this example only 2 waves needed.
In the video I've omitted some commonly-known facts like the tube needs to be partially inflated so it tends to not get caught.
Vancouver, Washington and Ocean Shores, Washington, USA
2 - 2007 Custom Bike Fridays, 2 - 2009 Bike Friday Pocket 8's, Gravity 29'er SS, 2 - 8-spd Windsor City Bikes, 1973 Raleigh 20 & a 1964 Schwinn Tiger
I don't have any Marathon Plus tires around any more - they were just too hard to deal with - but I will give this technique a try with a Std. Marathon 20" tire the next time I have to replace a tire here at home.
Thanks for the video. When I mount a tire, I make sure the bead is down in the well, but I invariably force the bead over on the first try, often with the help of not so muffled grunting and a few choice words.
I like the idea of going back down to re-position the bead at the bottom and keep doing that in "waves".
I must try that technique. It is not like I am looking forward to my next flat, but I am sure this will help.