Increasing tyre clearance on '05 KH29

[Paulo]

Hi,

I’ve been unicycling here in Lisbon with my daughters for almost 2 years and owe you all a big thank you for everything I have learnt from the members of this forum. From help learning tricks, to technical information, via inspiration and motivation, and even an expensive taste for accumulating unicycles, I owe it all to you

My most used uni is a 2005 KH29 and I have been following the recent threads on the possibilities offered by fatter tyre development and the question of frame clearance with keen interest. On this subject I finally saw an opportunity to add my own small contribution to the collective knowledge, so I registered, at last, and here I am.

I had some trouble with the larger Big Apple (2.35) as it would only fit with pressure below ~25psi, and even then any sand or grit picked up scraped on the gusset. So, I took my courage in both hands and removed a good bit of the reinforcement with a half round file.

In the attached photo you can see the resulting clearance with the BA at a full 60psi – easily enough for ~2.5” tyres . As you can see there's still some triangulation left and as far as my inexperience can tell, the frame isn't flexing outwards under my 85kgs. Mind you, I ride fairly quiet rolling off-road with only the odd step or two.

There is, however, one draw back which I only discovered months later when I fitted a Magura brake: when you idle, you feel a sharp "thunk" at the end of each cycle as if someone momentarily slammed on the brake and released it. After much fiddling and head-scratching I consulted the guru whose suggestion proved to be correct: Roger (of UDCUK) says the frame twists along the longitudinal axis bringing the brake pads into momentary contact with the rim when you apply the force which makes the wheel reverse direction.

It doesn’t seem to interfere with the handling, it’s just a little disconcerting and I quickly learnt to live with it. So now all I have to do is wait for a wave of fat 29’er tyres to arrive!

Hope the above is of use to someone.