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:

  • Schwalbethe 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.


Time for some high-geekery.   Whilst climbing big hills, I noticed an occasional crunchy-slippiness coming from somewhere on the bike.  A quick application of the magic chain gauge showed that the chain was indeed pretty worn, and the sprockets had gone a bit shark-tooth shaped.  Since I’d already planned to get a new 22 tooth rear sprocket (for the hills), I augmented my shopping list with a new 20 tooth rear sprocket and a new chain and then set about trying to understand what the heck all these different kinds of chainrings were for, and which one I needed.  Several hours later, and I think I now have a Clue – which I’m going to preserve here for Google and posterity.

I’ll use this chainring as an example, because it’s the one I’m going to buy.  It’s a “Thorn 104mm PCD 4 arm reversible single chainring 3/32 inch 46teeth”.  Which all meant nothing to me when I first read it.  But now I can explain!

  • Thorn is a product range made by SJS cycles.
  • 104mm PCD means that if you draw a circle which passes through all of the mounting bolts, it’ll have a diameter of 104mm.  PCD stands for ‘pitch circle diameter’.  Some people say ‘BCD’, which means ‘bolt circle diameter’, but it means exactly the same thing.  It can be kinda fiddly to measure this directly on your bike, so you can measure it indirectly by measuring the distance between the bolts and looking up a table like this one.
  • 4 arm means that the chainring will have 4 mounting bolt, to connect to the four arm ‘spider’.  The spider itself is part of the cranks.  As a bonus, you can infer this from the PCD size.  All 104mm PCD chainrings have 4 bolts, and all 110mm PCD chainrings have 5 bolts, etc.
  • single means that this chainring has been specifically designed for bikes with a single chainring.  If you have a derailleur bike with multiple chainrings, the chainrings will have ramps and pins to help lift the chain up onto the next sprocket when you are changing gears.  Additionally, a few of the teeth will be short and stubby – again, to help shifting.  Also, the teeth might be shaped specially to help shifting.   When your bike only has one chainring, you don’t all this magic.  The teeth can be much simpler (possibly stronger for it?).  So that’s what a single chainring is promising – straightforward teeth with no fuss.  As a bonus, they can be …
  • reversible, which means that when the teeth get worn out, you can just take the chainring off, flip it over, and have a go at the other side of the teeth.  Twice the lifetime!
  • 3/32″ is the width of the chain it was designed for.  On a derailleur bike, a narrower chain is desirable because the sprockets on the rear cassette can be closer together.  But on a hub-geared bike, you don’t have that constraint.  So typically you run a wider 1/8″ chain (= 4/32″) (presumably inspired by a belief that a wider chain means more contact area, therefore lower pressure on the links, therefore less friction and longer life).  However, a 1/8″ chain will happily ride on a 3/32″ sprocket (it’s just a wee bit wider after all).
  • 46 teeth is pretty obvious.  More teeth on the front == harder to pedal.

Phew, the mystery of chainrings revealed!  The only other dimension I came across was the kind of metal.  Aluminium alloy is lighter than steel, but will probably wear out faster.  From what I saw, large chainrings are often made of alloy and smaller ones are made from steel.

Cross country training

This weekend I was up at Leanachan Forest (Fort William) checking out the route for 10 Under the Ben which is at the end of May.  Much to my surprise, all my LEJOG training has put me in pretty good stead for this.  The course largely consists of long energy-sapping climbs on big wide roads!  Hurrah, that’s the course for me!  Having said that, there’s plenty of weaving through trees (yay!) and the odd heartstopping (potentially literally) rockstrewn descent.

The drive up to Fort William took us across Rannoch Moor and through Glencoe, which is the route I’ll be cycling during LEJOG.  Awesome scenery, but nowhere to shelter from the wind.  So, as an experiment I’ve borrowed a set of aero bars for my bike (thanks Tim!) which I’m going to try out over the next few weeks.  It’s 600g extra weight to carry, but the reduction in drag is significant (when you can use them).  I’m not too sure whether the posture will give me a sore back, so I’ll try them out for a while and see.

I have now ordered a 22 tooth sprocket for my road bike.  The internet suggests that you can switch them over just using a screwdriver, so my plan is to take a 20t and a 22t sprocket and switch between them as required.

A huge thankyou to all the people who have sponsored me.  I got an email from the Sick Kids hospital the other week saying thanks for the fundraising, and so I wanted to pass that thanks onto all of you who’ve donated money!

ObRandom:  Whilst scouring flickr today, I found this.  It’s not a staged photo.  This guy really did cycle Lands End to John O’Groats on a unicycle – read about it in his blog.

– Sponsor me at http://www.justgiving.com/andrewbirkett_lejog

Changing gear

I was excitedly looking forward to getting my shiny new touring bike this week.  Unfortunately, when all the new bikes got delivered to BikeTrax (the bike shop), my bike was missing.  Ridgeback, the company who make the bike, now say they can’t built it until June because of supply problems.  I spent a lot of this week on the phone, but didn’t get anywhere.  I’ve now had to cancel the whole order.  Google take note:  Ridgeback == bad.

All of which means … plan B is needed!  I’ll do the ride on my existing bike, which is a 8-speed hub geared Courier Nexus which I use for commuting to work.  Whilst undeniably the touring bike would’ve been a bit nicer, I’m reminded of the title of Lance Armstrong’s book – “It’s Not About The Bike”.  The challenge is a mental and physical one at heart, and the bike itself is a relatively minor factor.  On the plus side, I’ve done all my training on this bike and I know that I can do long days in the saddle fairly comfortably.

I’m doing some maths to figure out if it’d be worth tweaking the gear ratios for the hilly sections at the start and end of the LEJOG route.  Even though the hub gears are all fixed, there’s still a sprocket on the back wheel which you can replace with something other than the default 20 teeth job that came with the bike.

Training: I’ve just got over a fortnight of colds + stomach bugs so the training has been a bit light recently.  I cycled to work a couple of times, including a mammoth 18 mile off-road route coming home on Thursday which looped around next to the airport (passing just under the planes as they departed!).

If I’m feeling up to it, I’ll cycle to/from Kirkcaldy this weekend (~50miles).  Next week, I’m heading down for an evening blast around the red route Glentress and then I’m cycling  to Ayrshire and back at the weekend (~130 miles over 2 days).

Logistic-wise, I need to:

  1. finalise my gear list and try fitting it into my panniers.
  2. Buy a handlebar mount for the GPS
  3. Finalise the route, get it onto GPS and figure out where I’m staying each night
  4. Err, that’s about it.

Five weeks to go …

– Sponsor me at http://www.justgiving.com/andrewbirkett_lejog

Route planning

Planning a LE-JOG route is quite good fun in the internet age.  You can fly around the country on Google Earth, and use tools like bikehike.co.uk to design routes which you can copy onto a GPS system.  You can experiment with routes and check how bad the hills are!   Quite a few people have done this ride before and put up GPX trails of where they went.

One problem is that my GPS system (ok, actually my brother’s!) can only store 50 points per route, and 20 routes overall.  I’ve found that you need about 250 points to accurately track all the roads on each day of the LEJOG route.  Apps like gpsbabel can simplify routes down so they use fewer points, but you also lose accuracy.  This isn’t much of a problem in the highlands of Scotland where there are only two roads.  But trying to pick your way through a city with waypoints that are a mile apart won’t work.

I don’t really want to buy a new shiny GPS system just for this trip, so I’ve decided to stick with a combination of lower-resolution GPS routes plus pages torn from a roadmap.

On my training rides, I keep having to stop and get my map (or food) out of my panniers.  This is a pain, so I’m definitely going to invest in a handlebar bag so I can check the map or grab something to eat without stopping.  A waterproof map cover is a must in the Scottish weather!

By using the bikehike site, I’ve been able to scope out what kind of hills I’ll be hitting.  Day 2 through Dartmoor looks one of the worst, with 400m climbs.  In constrast, Arthur’s Seat in the centre of Edinburgh is only 100m high.  I’ve been hunting for good hill-training routes, and have settled on the road from Sanquhar up to Wanlockhead as being pretty representative of the Devon hills.

– Sponsor me at http://www.justgiving.com/andrewbirkett_lejog

The Story

At some point last year, I decided that cycling from Lands End to John O’Groats was something that I could attempt.   Since then I’ve been doing lots of training rides, cycling to work as much as possible, deciding on gear and tech and plotting potential routes on maps.  I intend to keep this blog updated as I complete the buildup and will also send updates whilst en-route.

I’m raising money for the Sick Kids hospital, and you can visit my sponsorship page at http://www.justgiving.com/andrewbirkett_lejog.

I’ll be getting the train down to Penzance and then starting the ride from Lands End on May 11th.  I’ll be doing the ride solo and unsupported (ie. carrying all my own stuff) and will be staying in B&B’s along the way.  The total distance is over 1000 miles, passing up the west coast of England, through Glasgow and then heading north along Loch Ness towards the highlands.  I picked the start date to avoid busy school holidays and to try to get decent cycling weather (neither too hot or too cold, fingers crossed).

I originally intended to do the ride on my hub-geared Courier Nexus bike because I love hub gears, but after doing lots of longer rides I found that wind resistance is a big deal.  So now I’ll be doing the ride on a Ridgeback Horizon touring bike with drop handlebars.  For navigation, I’ll have pages torn out of a road atlas, plus a GPS system to keep me going in the right direction.

For training, I’ve been gradually doing longer rides.  Last summer, I cycled to my parents place and back (~50miles).  Then in September I cycled to my inlaws place (60miles) and then back the next day (another 60 miles).  I try to cycle to work when life allows it (10 miles there, 10 miles back).  I got back into training in January with a freezing cold 25 mile loop through Musselburgh, Dalkeith and Loanhead – made the mistake of not taking enough food, and underestimated the effect of getting chilled.  Then, a few weekends later, I did a 20 ride out to Gullane with the wind behind me, followed by a painful return home against a gale.  Last weekend, I did a 55 mile loop around via the Kincardine bridge – it was even warm and sunny at one point!  And this weekend I’m planning a 65 mile ride.  I seem to be averaging about 14mph over a typical 4 hour ride.

Training also involves getting used to eating more food than I normally do.  Last weekend’s ride burned something like 2,500 calories and I need to keep myself fueled during the big ride.  So I’m trying to get used to loading up with extra food.

– Sponsor me at http://www.justgiving.com/andrewbirkett_lejog