CSIT RTW Bulletin #11: Sep 2000

Feature: Avoiding Punctures

After distance and inclement weather, I guess that flats are the next most serious problem facing commuting cyclists. As Ole Nielsen remarked to me some time ago, Canberra bike paths tend to have lots of broken glass. One solution is to remove (some of) the cause: pick up the glass yourself (dont laugh, I've seen the occasional cyclist doing it, and even I have done so on an underpass near my home which seems to attract broken bottles), or submit a hazard report to Urban Services (I'm told they are fairly responsive to this kind of report).

On the bike side, what I have been using over the last 18 months are:

• (Mr Tuffys) Inner Tube Liners: these are strips costing about $15 that protect the outer side of the inner tube. They last indefinitely and are reasonably effective at preventing punctures coming through the outside (but not the walls) of the tyre.
• High Quality Tyres: Mr Tuffys unfortunately do not obviate these as the lower quality tyres tend to wear out faster, and, once that occurs, they tend to split open with little or no warning (this has happened to me 4 times over the last year and a half). As this is one kind of flat one cant fix on the road, I'm using high quality tyres only from now on.
  For these reasons, I dont think it overkill to use kevlar-reinforced tyres (about 2x more expensive) in conjuction with Mr Tuffys, even though they too only offer protection from punctures coming through the outside of the tyre.
• High-pressure Pump: while expensive, a high quality, high pressure pump helps prevent punctures through the tyre walls, and pressure punctures occurring on the inside of the inner tube. It has the added benefits of being easier to use, offering more protection to your wheel rims, and adding a few kms to your cruising speed.
  But beware! my experience is that it can be a double-edged weapon against punctures: the higher pressure will test the integrity of your inner tubes and tyres much more. Also, I found that I can no longer got away with the dubious practice of spoke tuning without partial tyre deflation (depending on the rim shape, you can get a `snake-bite' puncture around the spoke head, due to high friction between the head, the lining strip, and the inner tube).

• Green Tyres: these are a solid tyre of varying hardnesses, so as to imitate pneumatic tyres under various pressures. They are also claimed to be more durable than ordinary outer tyres. I've asked bike shops about them; they said they stopped stocking them as they tend to lose grip when hard cornering or braking (one of the wonders of pneumatic tyres is that even under high pressure, they can yield just enough to maintain grip when going over small bumps).
  This seems a pity, as they seem the ultimate solution. Can anyone who has had any experience with these make a comment on this claim?
• Flat-proofed Inner Tubes: this is a liquid which can be poured inside ordinary inner tubes, which will cause the tyre to be self-sealing for punctures up to 3mm (I read once that a similar technology helped save Charles De Gaulle's life when his motorcade was ambushed by OAS gunmen in August 1962 ... evidently that one could cope with considerably larger holes!). It costs about $13 (enough for 2 tubes). It can also be used to repair flats.
  Peter Lamb has told me that he has heard it to be reasonably effective, although unsuitable for racing bike inner tubes. Has anyone tried this? (I only saw it first in a bike shop 2 weeks ago).

Anyway, your comments (mail to me for next issue, or direct to the csitRTW mail alias) on this topic are welcome.

BikeShed Update

Hazard Reporting

Upcoming Pedal Power Events

There are lots of events coming up in September and October, culminating in the infamous Fitz's Challenge. The Canberra Festival of Cycling is from mid October to November. No weekly lunch-time events though. See the above web site for details.

Well thats it for these 2 months. Happy cycling! -Peter.