Sunday, 28 August 2011

An uphill struggle (in Cornwall)

For some reason, one of the reasons people like cycling in Cambridge is because it is flat. If you are one of those people I'll warn you now, the headwinds out here can be evil. I'll take hills over headwinds any day.

When I say flat, the climb into Cottenham from Rampton is 5m. The land is so shapeless, it does take some getting used to. I think it was a couple of years before I finally felt at home here and I have spoken with others that felt the same. It's not like I was born in the mountains, just somewhere with rolling hills.

I do like spending time in the hills when possible so when we decided it was time for a camping holiday in Cornwall I couldn't resist squeezing a bike into the back of the car. Unfortunately, the only one I could fit was my road bike, and that has Tour-de-France gearing on it. It has a double front chain ring, with 39 teeth on the smallest cog and 25T the largest at the back. This 39/25 combination in real terms means that 10mph is the lowest speed you can comfortably go at. Once any significant hill begins, I am out of the saddle and and heaving the pedals round. Lesson learned, I shall get a triple next time.

The landscape in much of the south of England is short sharp hills that over a ride add up to a lot of ascending. Cornwall's highest point is only 420m but you'll struggle to find a flat part.

One of my rides took me via Perranporth, Saint Agnes and it's beach - Trevaunance Cove.  Fabulous views and scenery, steeped in pirate history and now surfer dudes.  

Surfers at Trevaunance Cove, St. Agnes, Cornwall, surrounded by cliffs.

Trevaunance Cove slipway.  Cliffs behind.

I find myself planning a lot of rides in hilly areas. It is a difficult balance, seeing enough landscape but without inflicting an impossible amount of pain on yourself.  I last did that in Normandy, cycle camping with friends. I think we are still friends at least, we had to abort a route I had planned due to too many and too steep hills.

I have learned the hard way that online tools are not always accurate when planning a ride through a hilly area. They can cope with mountains, but the when they are short and sharp, the resolution of the elevation data is not good enough and they begin to under-estimate.

Take this ride via Perranporth, then an anti clockwise loop around St Agnes:

Trevaunance Cove is the last trough in the elevation profile:

Elevation profile of GPS trace.  399m ascent, but only 208m predicted by BikeRouteToaster.

I took a less steep descent in, and then took a steeper road out.  As it turned out, the road out was an impossible climb on my double chainset.  The damp road caused my smooth tyres to spin when I was out of the saddle heaving with all my might.  I was unable to deliver smooth spinning power with such high gearing.  The OS map has (disappointingly) only one arrow on this section of road:  14%-20% (or 1-in-5 to 1-in-7). 

Google Earth is quite a good tool for getting a feel for the landscape.  If you export a GPX file from your GPS or BikeRouteToaster, it can load a GPX file and plot it over the terrain in 3D.  This gives a general feel for the landscape, but its resolution is limited, meaning sheer rock faces will be smoothed out.  I find hills look more realistic if you set the Elevation Exaggeration value to 2.

The total ascending measured by my GPS was 399m.  BikeRouteToaster estimates 208m.  This is quite a typical difference in my experience. Which is right ?

Google Earth's view with Elevation Exaggeration x2

When we all worked from paper maps, we would calculate ascent in one of two ways:
  • The difference in height from bottom to top.  There are some minor descents and re-ascents of around 10m on my elevation profile. Adding up any ascents bigger than 10m, I get a total of 308m.  
  • The other way is to count contour lines passed.  This is tricky in steep areas, but I can do this with the elevation profile above. I count 350m. 

They all disagree, with BikeRouteToaster giving the lowest ascent value.  To be honest, I don't know which value is right. It's a bit like calculating the length of a coastline - it really depends on the resolution you want to work at.  It's what it feels like to your body that really matters. Total ascent is a nice statistic, but the steepness of your route is more likely to make or break your ride - its no fun pushing a bike uphill.

Crackin' ride and a Cream Tea well and truly earned.


  1. Cracking effort! I too prefer hills over headwind but I can barely imagine riding around Cornwall on such a high gear.

    Did you know that up until 2010 that crazy St Agnes ascent used to be a feature in a regular steam engine challenge? Evey five years steam engines climbed Engine Hill until the annual steam rally moved to Stithians Showground.

  2. Yep, that high gear was like getting a weights workout at the gym and I would not be able to last all day like that. I think my body could 'adapt' to a double if sticking to the B roads (and I saw plenty of roadies out on them) but they were hell at the weekend with August holiday makers - it was like a permanent rush hour near the coast.

    The steam engine event up Engine Hill must have been an excellent sight. The YouTube vids are fab. Which road are the Engines climbing ? The road I gave up on was Rocky Lane leading up from Trevaunance Cove.

  3. I am just watching a stage of the Spanish Vuelta. It's nice to compare. A 4km section of a climb is around 20% (1 in 5) with a maximum gradient of 23.5% (I guess on a hairpin bend?). Commentator is saying that standing up results in wheelspin - yep! Also, there is a rider struggling having chosen the wrong gear ratio 36/28. My calculator says at 80rpm he is doing 13km/h. They say that at some points they are down to 8km/h. I feel his pain :-)