I bought a Raleigh Motus this summer, for leisure cycling on tow paths, etc. Now that winter is here and the paths are muddy, it’s sliding all over the place on the standard CST Zeppelin road tyres. The tyres are 700x40c on 622x19C rims. What are the largest/ widest/ chunkiest tyres that I could fit on these rims? I realise I should probably have bought a mountain bike not a tourer like the Motus, but it was too good a deal to miss. Any guidance will be most welcome.