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Repeated punctures!
Hi guys,

I keep on getting punctures on my commute (3 in the last 2 days - 9miles each way in London). It's a specialized sirrius with 700x32, and I'm using 28x38 tubes.

I've had about 20 in 3 months now, and a week or so ago I noticed that there was a sharp piece of metal poking through the rim tape. It wasn't in line with the spokes, so I'm assuming it's a manufacturing defect as I haven't hit anything that could cause it. I peeled up the tape, knocked it flat, and lay another tape on top of the original for extra protection (I don't care about the extra weight)

After that, I've had about 4 more punctures but all of these were on the opposite side of the tube from the valve i.e. not next to the rim.

tyres were inflated fairly hard (80-90 psi) so I don't think these were pinch flats? or could they be? My normal commute is 100% road, but in London there are a lot of pot holes etc

I rode over a screw a few weeks back and it cut into the tyre (no puncture though!) and there's a 3-4mm slit that you can see from the inside. Could this be an issue - letting debris in?

I'm partially inflating the tubes when changing so they don't twist/snag, checking the tyres for any glass/thorns etc but can't find anything?

Does anyone have any thoughts or pointers?!?!??!

Thanks in advance!
If the holes are on the road side of the tube (not the rim side) then you know it is something to do with the tire. Pinch flats will typically have two similar holes right next to each other. A couple things I'd recommend.
- A 3-4mm hole is fairly small. But it could be letting debris in or it could actually be big enough to let the tube push its way out through the hole and burst. I would reinforce this hole from the inside. There are specific "tire boot" products you can get. But any tough material like heavy duty cloth tape should do the trick. Once you have a reinforcement on the inside, you can put a little rubber cement into the hole in the tread itself to help keep debris from collecting. Or just get a new tire...

- Very carefully inspect the inside of the tire (both by looking and by running your fingers over the inner surface) to see if anything sharp is lodged in the tread. Sometimes something small gets stuck in the rubber so it's not easily visible, but as you ride it slowly works its way back through the tube. The tips of thorns and little pieces of wire are notorious for this.

- If/when you get another flat, be very careful when you pull off the tire and tube so you can identify exactly where on the tire the puncture happened. If it lines up with the slice, you know that is causing it. If not, you know to look at that area of the tire for a problem.
Hi thanks for the reply. I've checked the inside of the tyre and found nothing, and then put on a new tube. I reckon in about 10 miles it'll be flat, so I'll find the puncture mark against the wheel as you suggested.

I've got the standard specialized kevlar tyres. Would it be better to upgrade to continental gators or schwalbe marathons?

Schwalbe marathon plus are the most flat resistant, though they are a bit slower tires than others. Any decent belted tire should be ok unless you're riding through tons of thorns, glass, etc. Rough pavement shouldn't normally give you flats unless they're pinch flats. I suspect your problem is that slice in the tire, but hard to say for sure. Sometimes you just hit a string of bad luck, but it seems like you're getting too many to be coincidence, especially if it's always just on one of the tires.
You may also want to try tire liners, as you are not concerned about additional weight. On my commuting bikes; I have Kevlar belted tires, tire liners and thorn resistant tubes. I do not want to deal with a flat on my commute.
Thanks for the advice - I'll invest in some marathons then. Hopefully, that will solve the problem!

re. Tire Liners. I've heard that these can rub the tube and cause punctures themselves if not installed properly. Do you have any pointers on avoiding this?

(11-18-2011, 08:49 AM)rhinatron Wrote:  Tire Liners. I've heard that these can rub the tube and cause punctures themselves if not installed properly.

I've seen this on narrow high pressure tires and I don't recommend them for that. On larger tires like you have, the only times I've seen this is at the ends of the liner where it overlaps inside the tire. Sometimes the ends have rough edges where they're cut at the factory. If the ends feel rough, use a knife or fine sandpaper to "deburr". I also usually put tape over the overlap just to give one more layer of protection.

That all said, I like the liners too, they work well.

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