Australian Cycling Forums - Bicycles Network Australia

Hello.

General question regarding tyre sizes.. I'm new to the "road" bike world, and have acquired myself a fixie about 6 months ago (loving it, no crashes even!). Finally decided to shell for some puncture resistant tyres (Maxxis Re-Fuse). Got them fitted and within 30 seconds of the first ride today the rear had gone flat (loud hiss then flat as a pancake in a few seconds). Checked it out, no holes or anything. Then noticed the front has a 700x23c sized tyre, and the rear a 700x28c tyre, both old tyres were 700x23c. Question is, can the fact that the rear is a different size be the cause of the puncture? It wasn't over inflated (max 120psi, was 110psi when I left home) so I know its not that. Or was it just a freak flat? I read around the place and I keep coming across people mentioning "pinch flats" where the tube kind of moves around and gets kinks in it if the tyre is a too wide (from my understanding).

Any chance of some feedback on this? Plan to take it back to shop and get things sorted though.

Cheers

G'Day Expat, welcome outside.

Unless you are using a very very small tube then it will stretch to fill the available volume without too much trouble.

It's quite likely that the tube has been nickedd by a lever or was caught between the rim and tyre bead during installation. A classic pinch flat is caused by a heavy impact-like a pothole-which pinches the tube between the tyre and the rim.

It will also typically leave two holes in the tube which is why it is often called a snakebite puncture.


Hope this helps. How good is riding Fixed ?

Shaun

Most informative reply to a question on a forum ever! Thanks for that.. makes sense, as I'm pretty sure it went flat after dropping off the end of the driveway. I patched it up when I got home last night and had the same issue this morning when I took it for a quick test ride. 5mm is a lot of extra space I guess!

Riding fixed is something else, hah. Rode single speed for the first couple of months until my fitness got up. Took me a few rides to remember you can't stop in a hurry. I get a bit of s**t from some of the road cyclists around Canberra (one guy overtook me on a hill and told me to "get some gears ya homo") but otherwise alot of fun.

Thanks again for the info, really helpful.

How heavy are ya? 110psi should be plenty for most, but if you are 90 or 100kgs you may need a bit more air.

If it keeps happening then the 28s may be a better size for you.

I'm 77kg so don't think the 23s shouldn't be a problem?

Got it replaced this morning (for free which was a bonus), all good thus far. Made it to work no problem but will see how the next few days go. Seemed a little flat when I got to work, but it was a pretty warm morning here so I guess the rubber has expanded while riding a bit. Or it's paranoia..

Two different sized tyres? Did a bike shop do this? Why?

Yeah they did. One 23c on the front, one 28c on the rear. Guess they didn't check when pulling off the shelf, as only one tyre per pack. First world bike problems..

expatkiwi wrote:Yeah they did. One 23c on the front, one 28c on the rear. Guess they didn't check when pulling off the shelf, as only one tyre per pack. First world bike problems..

Astonishing...will you ask them to put it right?

Yep, went by this morning and got it sorted.

Blew out another tube on the way home in a similar fashion to that stated in my first post - rolled off the end of the driveway at work and out hissed all the air.

Any ideas on what causing this? 3 punctures in the same fashion since changing from ordinary road tyres to Maxxis Re-Fuse tyres. I got about 500m out of the first tube, perhaps 10km out of the second. Have had more punctures in 2 days with the puncture resistant tyres than I did in 6 months with ordinary tyres..

Any chance you're doing it when fitting the tyre? A good tip is to put some air in the tube so it holds its shape (i.e. away from the pinching bead) while you lever the tyre back on. Also, fit as much of the tyre by hand - all of it if you can manage it.

Both tubes have been fitted at a bike shop (as I'm currently tool-less), so unsure what the deal.

OK then...

My money is now on dodgy rim tape or an undiscovered bit of debris in the tyre...

I had a new rear tyre and tube fitted this morning. I'm actually out of reasons other than dodgy tubes (3 in a row), dodgy tyres (2 in a row), or poor fitting (pinching on the beading?). Just perplexed it happens whenever I roll off a small ledge (couple cm at most), but hitting cat's eyes, bumps in the road/cycle path does nothing. Who knows, ha!