My new Shimano-hubbed Sunrim Cr-18 wheelset arrived the other day, and to my chagrin – it’s not drilled for Schrader valves, but presta valves (those tall, thin metal ones with threads). Nothing is wrong with presta valves – in fact they actually retain air better at high pressures – but the availability of tubes for wider tires is somewhat limited.
So what does one do to remedy this problem, short of replacing the rims? Well, you drill the valve holes out, of course. Presta valves are 6mm wide, with a 6.4mm (1/4in) valve hole. In contrast, Schrader valves are 8mm wide, and have an 8.3mm (21/64in) valve hole. Luckily for me, the Cr-18 rims are wide enough to accommodate this wider hole; don’t try drilling out thin rims, or those rims with a strongly arched profile, or you may end up weakening the rim significantly.
Flat profile rims; its easily drillable.
Select a few dill bit sizes for stepped drilling – this will prevent the bits from binding and ruining the rim. I chose 3 bits: a 7/64in bit, a 9/32in bit, and of course the 21/64in bit.
If there is already rim tape, peel it back with a tire lever and commence drilling. Once done, it should be noticeably larger:
File off the burrs in the metal to prevent punctures, and the job is done.
Then try fitting in a Schrader valve tip, just to check to see if it all fits in neatly. If you have trouble getting in the valve, try making sure the hole was drilled straight, or possibly go for the slightly larger 11/32in bit.
Now that I’ve drilled out these new rims, I’m all set to replace the old wheelset. The old Shimano/Araya combo has conducted me very “wheel” over the past 5000km and 5 years, and supported another 5000km or so for the 13years before that. 10 000kms and 18 years later, though, it is time to move, lest something *does* in fact break during our Italian trip.
Araya Wheelset: 1994-2012
$10 Craigslist sale, anybody?
Here are the new beauties: I’ve finally made the switch over to 8 speeds and double walls.
Update 16/10/17: Wow, 4 years later and this is still the most popular page on my site! The Camping In Taiwan store has changed some URLs, so I updated them accordingly.
Update 13/05/13: It has been noted by someone that the company’s policy of shipping their adaptors in simple sealed, unpadded envelopes can cause problems – the unpadded envelope may rupture, leading to package loss. I suggest voicing any concerns with shipping to the owner.
An $8 piece of equipment which I highly recommend to any canister stove or lantern user is this butane canister refill tool. I managed to find it from the Camping In Taiwan website/webstore, here (scroll down).*
With butane, there are two standards: the wide and squat EN417 threaded style canisters used in camping applications, and the thin and tall bayonet-style butane canisters often used in home applications. This above tool allows anyone to refill their isobutane/butane blend EN417-threaded canisters with the bayonet type butane cartridges. The benefit of using these bayonet cans to source fuel is obvious: they are cheap, cheap, cheap! But, because they have a bayonet fuel mount, then this adapter is needed. The adapter converts the large nozzle on these butane cartridges into a smaller nozzle – just large enough to fit into an EN417 valve and refill your favourite isobutane cartridge.
If you are partial to using the small isobutane canisters (like me – I always use the 113g/4oz. cans), so that you aren’t carrying the heavy and larger 227 or 450g cans, then using this refilling adapter will save you even more. Lets do some math:
MSR Isobutane (113g): $4.90
Primus Isobutane (450g): $10.00
North 49-branded Bayonet Canister (227g) : $2.99
Generic Bayonet Canister (227g): $1 to $1.50ea (look for these in 4-packs @ your nearest Asian food market)
These work out to (g per $):
MSR: 23.1 g/$
Primus: 45.0 g/$
North 49: 75.9 g/$
Generic: 227.0 to 151.3 g/$
The substantial savings become obvious when comparing like that. Note also how much more you get per dollar when using the larger isobutane canisters compared to the smaller ones. Asian markets carry lots of the bayonet cans at dirt cheap prices, since curved woks won’t work on regular electric stove elements, and the butane home ranges are often used instead. But seeing as I don’t live near any Asian food markets, I recently have relied on Canadian Tire’s North 49-branded bayonet cans as fuel (and sadly, have been paying the mark-up on price).
The break-even amount I have found is 2 full refills, using my MSR 113g and the North 49 refills. The adapter has already paid for itself a few times over.
Here’s how you use it. You’ll need a kitchen scale, the adapter(duh), a threaded isobutane canister, a butane refill, access to a freezer and a marker.
1. Weight a full EN417 isobutane cartridge. If you don’t have a full can, you can often find the full weights online. I have recorded this weight on the can’s bottom, for future reference:
2. After a few weeks, once your can has been mostly used up, weight it again:
3. Now, put the empty can into the freezer, and let it chill. This will help create a pressure difference, and drive the butane into the canister far more quickly.
4. Remove from freezer, and place the adapter into the valve hole.
5. Take the bayonet can and place it into the orifice in the adapter. Press down firmly. If you don’t it may leak a bit of butane gas (you’ll smell it). Hold it down for a few seconds.
6. Place the refilled can onto the scale, less the adapter. Aim for a similar weight to that of the full canister. Try not to go over. Under filling by any amount is fine, and overfilling by a few grams shouldn’t matter either.
As in the above picture, I’ve managed to over fill. By adding these extra 11 grams, I have increase the total fuel by ~10%. Since this refilled can is just pure butane now, instead of the usual isobutane/propane mix, the cold-weather performance should be noticeably less exciting. Butane boils at 0C @ sea level, and so this technique will really only work for spring/summer/fall use. Isobutane boils at -12C, and Propane boils at -42C, and so these fuels should work much better in the cold.
However, this allows us to exploit the higher boiling point – we *can* over fill by some degree with impunity. This can occur without the canister bursting because pure butane won’t make as much vapour pressure at room temperature as isobutane/propane will. Slightly overfilling is a good way to cut down weight if you should need more fuel – more fuel for less space and per packaging weight. A way to do this with minimal risk is to let both cans reach room temp, then try at filling a little more. The pressures should equalize to a safe level, and you should still get a little extra fuel added. BUT if something does go wrong, I don’t take any responsibility.
* This is not an advertisement for Camping in Taiwan, nor have I had any compensation for this review.