Any bike you're likely to use for road touring, urban cycling, or just getting around is likely to have a 'Presta' value on the innertube. This is the typical 'road' innertube valve. The ‘Schrader’ valve (also called an ‘American’ valve) is typical on many lower end mountain bikes and cruisers. It is also probably what came on your bike trailer.
So what?
Well, we’ve found it irksome to have to dismantle the head on our Topeak Road Morph (which has been great, by the way—we’ve had it for about five years and it has lived on various bikes since we purchased it and it still works great!) in order to inflate the trailer tires. So, since we’re lazy like that, and because the stock tires finally died on our Burley Encore, I decided to find a work around.
Burley doesn’t produce a wheelset for its trailers that runs Presta valves (Burley, if you’re reading this… take note), and I didn’t fancy rebuilding the hub around a new 20” rim (although I’ll probably eventually do this, because the spoke nipples are developing a tenacious rust anyway…) drilled for Presta valves. So, I learned about ‘valve grommets’. Essentially this is a small… well, grommet... you insert into the Schrader rim hole, converting it into a Presta rim hole.
Why do you need this? If you simply insert a Presta valve stem tube into a Schrader drilled rim you will get a tube hernia. That is, your tube will literally have a hernia out of the extra space on the valve hole. Needless to say, this is bad.
To avoid this, you attach a grommet to the hole, and presto, you have Presta!
We tried two different grommets—just for grins and giggles. The first is made by Mavic. It is plastic and easily slides into the valve hole from the outside and is held secure by the nut on the stem. The Mavic grommet was super easy to install. However, I’m curious how it will do, because the bottom of the grommet extends into the inner side of rim. I’m hoping this won’t cause pinch flats at lower PSIs. We’ll see what happens.
The second grommet was a generic one from amazon.co.uk. I was intrigued by the rubber design and thought to give it a go too. This one was a lot tougher to install (Ashley had to do it…), but it looks way more secure and there is no way it will cause any pinching problems. It took a little more finesse to get on the valve hole though.
Verdict: either will work just fine--but I'd defintely go with the generic ones on both rims if I was to it over again. Time will tell how they work out!
Now we’ve got the trailer shod with beautiful Schwalbe Big Apples. The stock tire is 1.75 on the Burleys. I opted for 2.15 as to try and provide a bit more shock absorption for the kiddos (especially over those Cambridge cobbles!). We’ll see how they work out!
Now we can pump our tires without having to change the pump! Ashley says the next trailer project is devising fenders (mudguards) that would attach to the sidewall of the trailer. (Ashley usually rides in back and I’m usually towing the trailer. This means Ashley gets soaked if she rides anywhere close to the back of me.) Let us know if you have seen anything on building fenders for kids trailers—we’d be super stoked!