Recently my 29-er (nimbus 700c rim, 2.1 Notos tyre) has been getting regular punctures, something like 4/5 over 10 ish rides.
They’re in different places, I’ve checked the inside of the tyre and the rim and found no sharp objects.
The actual punctures are all the same, a hole leaking air preceeded by a line of smaller holes, maybe an inch long.
Could they be the ‘pinch punctures’ I’ve heard mentioned here?
On the last one there was also a matching abrased line on the outside of the tyre (on the side wall)
I suspect the slim nimbus rim is a little small for a 29-er tyre, but, then again, it’s worked OK till recently.
Also, when inflating the tyre should I err on the side of under inflating, or over inflating, to cut chances of more punctures of this kind?
I’m finding all these punctures a real pain and would appreciate any ideas.
This may seem like a silly question, but have you got rim tape on? I left mine off on a 20" Nimbus rim and I got loads of little holes all the way around it from the spoke holes. if you hav then try thicker tape??
Pinch punctures in most cases are where the tyre is underinflated and the walls of the rim puncture the tube.
I prefer a high pressure for 29ing as I can’t hop up curbs at speed very well so I kind of pummel into and over it. Makes for a smoother more responsive ride too.
Someone is bound to be able to give a better reply!
Sounds like a pinch flat scenario, in which case you should raise your tire pressure.
None of the spokes are pushing up into the rim tape are they? If you’ve recently tightened up the spokes, then the end of them can be poking out through the nipple too far and push up the rim tape. You can then pinch flat on the spoke end, which gives you a hole (or several evenly spaced holes) either on the outside or inside of the tube close to the middle.
When I’ve seen normal pinch punctures, they’ve usually been long holes, often one on either side, where the rim hits the tube.
If you sidehop with a narrow rim and a fat tyre, it’s easy to pinch on one side. Have you been practising big sidehops? I found the notos rolled sometimes if the pressure was too low and that could lead to pinch flats.
The way to avoid pinch flats is to pump up a bit more. It’s worth having a big pump at home with a pressure guage, so you can quantify how much you’re pumping it up each time.
Cheers for the advice.
I have got rim tape, though I’m going to buy some more as it’s looking raggy.
I’m pretty sure the spokes aren’t stuck up, but I’ll check them at the next puncture repair.
Concerning pressure, I don’t have a guage so just do it by feel. Also use a hand pump which limits how high I can go.
However, yesterday went to my brothers and used his foot pump/guage- turns out that I’m on psi of around 30, when the tyre wall says 40-65.
So I put it up to 50 psi and will try it out today. If the punctures stop them I guess it’s time to buy a track pump and keep the psi high.
Can someone just confirm that the right inner tube for 29-ers is 700 x 35-45? Thats what it says on the tube box, but the tubes seem a bit tight when I put them on.
Sounds like you’ve found and fixed your problem. Pinch flats are usually elongated as you describe. Can I assume that the 1" line of damage is on the side of the tube and is parallel to the rim?
This might seem a little obvious in hindsight, but the weight a tire carries on a unicycle is roughly twice what it would be on a bike. Since most of the tires we use were designed for bike use you should stay at the top end of the pressure range, or even overpressure it a little, if you want to avoid pinch flats.
Then again, raggedy rim tape can be a problem too. Though at 30 PSI I doubt you’ve got enough pressure to sag the rim tape enough to have a hidden spoke puncture the tube. That’s a problem that is occasionally a problem on high pressure (over 90 PSI) tires.
Re: 29-er puncture problem
Another good trick is to line a tire with talcum powder before
inserting the tube, and I always line the valve up with the tire decal
to have a reference
point when checking for problems. Cheechee