Wicked Wheels!

One of the advantages I had in the Simpson Desert Cycle Challenge was my monster wheels. I reckon I managed to cycle over 95% of the dunes, rather than having to get off, push and get back on. That really adds up over the course of the race. You can put 200 - 300 metres into a rider for every dune that you clear.

The wheels have also been great for making friends. I've had people cycle past me, do a double take, then come back and ask "What the heck are those?". People commonly ask "What size tyres are those?" - in actual fact the tyres are a normal size, it's the massive Snowcat rims that make the difference.

Years and years ago, I tried to talk my good friends Darren and Ian into entering the Iditasport. Unfortunately, they weren't that stupid, but during my research I found the Snowcats on the web. When I entered the SDCC I already had the Snowcats penciled into my list of things to get.

After a conversation with Simon @ Whicked Wheels I got a pair of 26 inch wheels imported from the US. ChainReaction in the UK supplied XT hubs and DT Swiss spokes. Simon drills the spoke holes offset from the centre; on the front wheel the rotor on the left pushes the flanges of the hub to the right, so the spoke holes are drilled to the right. On the the rear there is a rotor on the left but a much bigger cassette on the right, this pushes the flanges to the left, so the spoke holes are offset to the left. All this means that all four sides of the wheels use the same spoke length and are very easy to dish.

I bought a $100 wheel jig from ebay and made a dishing stick from piece of wood and some long brass screws. For spoke tension I saved some money on buying a tensiometer and used my friends guitar tuner which worked fairly well. I de-stressed the wheels using the wooden handle of a hammer, an idea I got from the excellent Sheldon Brown's article on wheel building. This worked far better than the old 'grab 4 spokes and squeeze' method. (I'm sure Mr Brown would be very happy to know that he continues to make a valuable contribution to cycling). No one step in wheel building is hard, but there are a lot of steps. The secret is to take it slowly.

So, with the wheels built, it was time to test their integrity. I mounted my 2.25 schwalbes with tubes and went for a 100km ride in the Blue Mountains. The 'Double-Double' circuit runs up the Oaks fire trail, up the Ingar, down Andersons then back down the Oaks. I did this a couple of times along with a number of circuits around Manly Dam. I wanted to beat the hell out of the wheels to find any issues early. I found none; the final true took 10 minutes.

The next problem was doing tubeless. Wayne (Elvis) put it succinctly on the Rotorburn forum: Tubeless, Tubeless, Tubeless. (And in hindsight I'd add "Sealant, sealant, sealant" - the SDCC has to be the best advert for Stans Sealant in the world). I bought a Stans conversion kit for my normal wheels to see how it worked, but that wasn't going to help me with my 44mm wide snowcat rims. Instead I googled 'Ghetto Tubeless" and started reading - there is a massive amount of information on the web - web pages, forums and YouTube videos.

In Ghetto Tubeless, you use a 20inch BMX tube cut in half as a rim strip. (That's cut in half longitudinally, dummy!). I drilled the rims to take Schrader valves rather than Presta. This let me get a cheap digital pressure gauge from an automotive store and I figured that the 4WD guys would have plenty of compressors with Schrader fittings. Schwalbe do a BMX tube with a threaded Schrader valve stem and I used these - the valve doesn't wobble around when you try to attach a pump or take a pressure reading. Also, the sealant gums up the valve core after a while and you need to unscrew it to clean it. I found that difficult with free floating valves. I fitted O ring top and bottom to the values to give it a bit of compliance in case it got hit by something.

I sealed the spoke holes with a couple of wraps of duct tape, then added one turn, on each of the left and right sides of the rim, of 3M 12mm double sided foam tape from that well known bike supplier, Office World. This did 2 things, Firstly, it let me stick the 20 inch inner tube to the rim - I was worried the tyre might spin on the rim at low pressure and secondly I have a theory that it helps stop burping (not me obviously, I burped freely throughout the event but the tyre didn't). The diameter of the bead is always greater than the inner diameter of rim. This gives a gap, and the gap is greater with 'non-tubeless' tyres and less with UST tyres (hence UST tyres can be a bit of a bugger to fit). The foam helped reduce this gap by 2x1.5mm = 3mm.

It's a point of pride with me that I've never used tyre levers to mount or dismount a tyre on my mountain bike, but now the tyres were fitting quite tightly and I needed strong thumbs. (Hey people take pride in curious things. I knew a guy at school who could suck a chip up one nostril and blow it out the other)

So far we have rim, duct tape, foam tape and 20inch BMX tube. Normally you'd soap up the tyre and rim strip to help it seal. Instead I painted on Stans sealant with a paint brush, an idea I got from a downhiller on one of the forums. I wanted to glue the tyre to the rim strip.

Inflation happened down at the servo. This is a tricky moment - tyres do burst - on one forum a guy reported being deaf in one ear for a month - but you still need to hold the wheel off the ground and the compressor on the valve.

I had bought a pair of 2.4 Nobby Nics for the race, but I knew that the 2.4 was too big for the rear - it fouled the seat stays. Aaron at Brookvale Bike Factory let me try his 2.35 Kenda Small Block 8 - ideal size and a great tyre.

So there we go tubeless Snowcats. I'll talk about tyre pressures on another post.

Thanks to Simon @ whicked wheels and Wayne for his emphatic directions on tubeless.

In Birdsville I sold the wheels to Andrew (rider 11). I hope he enjoys them riding on the beach in Port Fairy!