More high-geekery, this time related to tyres. By way of explanation, once I’ve finished the ride I’ll turn this blog into a set of ‘real’ web pages and hence I’m dumping random technical content here too.
When I bought my Courier Nexus bicycle from Edinburgh Bicycle Coop, it came with a set of tyres composed largely of soft cheese. The web says they were probably ‘Continental Sport Contact’. They barely survived a few weeks of the ‘ned diamonds’ (broken glass) on my work commute, whereas the tyres I had on my previous bike (Schwalbe Marathons) had lasted ages without problem. So I switched them over to the Nexus and they’ve lasted 1.5 years so far. Awesomely reliable tyres, and I’d totally recommend them.
So, coming up towards LEJOG I thought it might be a plan to put on a fresh set of tyres (as some kind of puncture insurance). But now that’s a whole new world of tech and numbers to grok. Once again, I’ll use the tyres I bought as an example – they were Schwalbe Marathon 40-559 26×1.5 HS 368 kevlar guard 50EPI with reflex side walls. Which all translates to:
- Schwalbe – the company who make them.
- Marathon – their range which is designed for long life (rather than saving weight)
- 40-559 – the ETRTO (European Tyre & Rim Technical Organizations) standard designation for a tyre which has width 40mm and inner diameter of 559mm. All very precise and well defined (ish).
- 26×1.5″ – the classic albeit fuzzy way of giving the size. 26″ is the tyre outer diameter and 1.5″ is the width.
- HS368 is a particular tread pattern which Schwalbe do. You can find the same HS368 tread pattern on 28″ tyres too, so they’d also be HS368’s.
- Kevlar guard – underneath the rubber tread, there’s a layer of kevlar material – the same stuff they use in bullet-proof vests. This is insurance against punctures.
- 50EPI describes the weave of the tyre carcass – the inside bit that looks kinda like canvas. EPI is ‘ends per inch’, a measure of the density of the weave. There’s a tradeoff between strength, weight, puncture protection etc. Everyday tyres seem to be around 50, whereas race tyres (ie. weight-saving at all cost) are around 120.
- Finally, reflex sidewalls just mean that the sides of the tyre are kinda reflective, so that you’re more visible at night.
Schwalbe do an excrutiating detailed technical document about all this stuff if you’re into that kinda thing.