Monday, August 24, 2009

Bear with me.

Maxxis 29" welter weight.

wtb DH 26" tube.

Maxxis free ride 26" tube.

So, been having a few punctures. Front wheel fro most part: odd pinches on the side of the tube. Low pressure, fat rim, tube stretched too far? perhaps. Options were to stop running the fat rim, go tubeless, or use a fatter tube. Or maybe a different tube?

Tubeless with a pinned and single wall rim strikes me as unlikely. Especially as the bead seat is best described as roomy. Not using the fat rim is an option. I have a spare whub, and a spare bonty duster rim. But i like the fat wheel. Hmm.

Different tubes seemed to be the thing. I was initially thinking of running the same freeride maxxis tube i have in the endomorph front wheel. Then i weighed it. 400g. A wtb 29er inner tube is shy of 200g, as is a maxxis 29er welter weight tube. Jeff uses light 26" tubes in his uma 29er wheels. I suspect i have a few kg on jeff, but i also reckon the tubes are stretched beyond what they can take and still be robust at low pressure. So, i put a 26" wtb 'downhill' tube in, inflated to 18psi and went for a ride today. Inverted commas are because i doubt a downhill run would be possible with such a light tube. Maybe the thicker tyres help, maybe...

It was when i was halfway to where i was going i realised that i didnt have a puncture repair kit, tool, or indeed a pump with me. Clever.

Oh well, if it was a long walk back, it was a long walk back. I needed to know how the tube would hold up to being slammed into pointy rocks.

All too soon, i found out. A short uphill on double track, with a sharp left hander over and up some sharrp rocks delivers you onto a nice wee trail. THUD! rim hits the rocks with total compression of the tyre. I wait, holding my breath.

No puncture.

This is good. The fat rim stays, and i gain only 20g on the front wheel. Acceptable.

Interestingly, when compared the wtb 29" tube and 26" tube are about 1 cm different in width, but obviously the 29" has a greater diameter. If you blow a 26" tube up to the stage it is round and won't fold if you lean it against the wall, it is very close to being 700c rim diameter. So i'm guessing the extra girth is all good.

Or maybe it was all the talc i used...


muddy runner said...

Is this a 'guess what happened next?' pic??!!

muddy runner said...

..and what the tape for - instead of rim strip/tape?