Hi,
What do those with C15 trials bikes use for a rear tyre? I was pleased to see that mine had an MT43 4.00 x 18 when I bought it but having just taken the rear wheel out I can see that it's really too big for the frame. The tyre has rubbed a hole through the exhaust!
A 400 tyre is the standard for trials tyres, so you are lucky that it fits. Maybe when the frame was designed, Dunlop were about the only manufacturer, and they made the cross-ply Trials Universal, which could have been slightly narrower than the current types. Maybe you should consider altering the exhaust with a hammer, to fit your tyre.
If you are really competative, then the IRC tyre is the only choice, but they have gone up in price recently, to over £140.
Thanks Scifi. I'm actually totally non competitive and just want to use the bike for Green laning. Round here lots of the lanes have rock slabs and steps and the tyre of choice when I did this years ago was the MT43 rear with an enduro front.
I'd like to change to a tyre that fits a bit better as the 4.00 x 18 is pretty much tight against the front of the swing arm with little chain adjustment left. I've seen the Kenda 262 which is available in 3.00 x 18, 3.25 x 18 and 3.5 x 18 so might give one of those a go.