I had a few in my kit bag for my trip to race the World Cups this year and mid way through they hadn't seen too much use as dry tracks are few and fair between over there. I spent a fair chunk of time at Montreal riding on the hard packed greasy mud and root of Mont Royal and the Rendez on the front, in a 2.1" with fairly low pressure (around 26psi), was working fairly well over the roots. I had noticed however that the thinly spaced ramped centre knobs were clearing the mud really well in the slick mud, but the side knobs clogged easily due to their tight spacing (most likely there for cornering stability in dry hard packed conditions) and turning corners was a bit scary. The specific mud tyres that i had were 1.9" Medusa, awesome pizza cutters for proper deep mud and off camber, but roots and rocks are pretty dogdy and the rolling resistance on the fire road sections really limits the applications for these sort of tyres. I had the idea of cutting off the inner row of side knobs. About 30mins of action with some large toenail clippers (plus a trip to the shop to buy a new set when those ones broke half way through) and a couple of blisters later i had myself a custom made tyre. And i was very impressed with the pile of rubber that had collected, because you know what that means.......grams!
I tested it out and as I expected the mud cleared a lot better from the sides. I ended up using this tyre at the Bromont Canada Cup and the Mont-Sainte-Anne world cup, both in very muddy conditions, and it went a treat. I got a bit more efficient at cutting off the knobs by using side cutters instead of the trusty toenail clippers. I have even used them back at home at Stromlo and Cooma with the knobs missing and they still handle dry conditions really well, but i used a fresh one with side knobs at the world champs.
So all in all i reckon that the Rendez 2.1 up front is a pretty good all round tyre that is versatile and could minimise the amount of tyres that you carry if you travel away to a race. It is certainly not ideal for all conditions, but it is right up there for a very broad range of conditions and a very capable all-rounder.
The Rendez with to knobs cut off