The P35 rim is so called as it has a 35mm outside profile. It has a massive 30mm internal width. This means that tyres are spread out to be even wider than they are with narrower rims. This means more air volume with the same sized tyres. Also it is possible to mount very wide tyres.
I’ve got a couple of Schwalbe Marathon Supreme 50mm size to fit on. When measured with a caliper the tyre shows as 51mm on the P35 rim
These kind of tyres will give a forgiving ride on poor roads and off the roads into the rough stuff.
When I was building this wheel I made a couple of silly mistakes. First, when I got to the stage that the wheel is “twisted” anti clock wise prior to inserting the first crossing spoke I didn’t notice that some of the nipple heads had caught on the outside of the rim. So the twist wasn’t correct, it was not far enough. This meant that the crossing spokes could not reach their correct 3 cross hole as the distance was too great. So I compounded this by only doing a 2 cross… of course it didn’t work. My only excuse is that I haven’t built a wheel in a while. In the end I started again and did it right.
Second mistake was using aluminium nipples. Normally I use “brass” nipples which seem to contain some kind of ferrous material as they can be picked up with a magnet. Why is this an advantage? If they fall inside the rim it makes them quite a bit easier to remove. With the aluminium nipples removing them from inside the rim took several minutes of shaking.
I have another P35 rim and I will be making an Alfine rear wheel with one of them, so the bike has fat tyres front and back.
Hoping to use the Karate Monkey in a couple of weekends time to do a 200km event to the lost village of Imber, on lots of tracks and military roads.