Wednesday, 15 June 2016

Theory and Practice - Part 2 - Weight

In part 1 I looked at aerodynamics in an attempt to explain how I had ridden the same 100km route 40 minutes faster this year than I did last year.
The answers I came up with accounted for 22 minutes and 36 seconds.
Of course, I was using some pretty "approximate" estimation techniques, so we shouldn't get too hung up on the exact numbers.
But it would be fair to suggest that about half of my faster time was accounted for by aerodynamic changes between the two rides.
This time I am looking at weight.
We will look at:
My weight loss
The weight difference between my old and new bike
Any weight differences in the clothes I was wearing
Any weight differences from the water, spares and kit I was carrying on the bike.
First, my weight loss.
As I keep a weight diary (I mentioned this in part 1), I can easily see that for the 2015 ride I weighed 90.6 kg, and this time round I weighed 84.3 kg.
So that is a weight saving of 6.3 kg
My new bike is a touch lighter than the old one, but I magnified the difference by removing the fenders, lights, etc. etc. The gear set I moved from my old bike was lighter than the one supplied with the new bike, too. But the tyres I am using are a bit heavier than the new bike came with - as I Mentioned in part 1, the wheels and tyres are the ones I got off the old bike. Anyway, the old bike weighed 18 kg, and the new one, without fenders etc weighs in at 14.5 kg.
So that is a weight saving of 3.5 kg
playing weight weenies.
the wheel I had on Mermaid last year weighs 1212g,
without tube and tyre

While Hoppy's dynamo hub wheel comes
in at 1666g, 454g (exactly a pound)
heavier. We know which wheel I'll be using
for the sportive!

Hoppy's steel M131 triple chainset weighs 786g for the "drive" side

The aftermarket forged ally drive crank
comes in at 239g lighter!

Moving onto clothes. Last year I wore jeans, a check shirt, and a hi-viz gilet. Being a bit obsessive, I weighed them. Jeans = 806g, shirt = 318g, and hi-viz gilet = 122g. For a total of 1246g, or 1.246 kg.
This year, I wore heavyweight cycling trousers (329g), sports vest (102g), sports T-shirt (149g) and a full-zip, long-sleeve cycling jersey (372g). And shoe covers (103g). The reason I had more layers on this year is was because it was cooler, and rain was predicted (and it did rain on me!). Total weight 1055g.
So the weight saving by wearing the cycle-specific clothing was 191g, even though the cycle trousers are full-length winter ones, and I had 3 layers on my torso including a long-sleeved, full-zip jersey.
Equipment was where I made a conscious effort to save weight. Last year I had quite a few tools, spare clothes, too much water, spare parts, etc. etc. From my notes I can see I had 4 litres of water and 9 kilos of kit, as well as two bike locks (790g combined) for a total weight of c. 13.8 kg.
This year I had three large water bottles (1044g, 835g, and 1074g), a handlebar bag (674g, including 3 bananas), a small top-up bag (747g, including dates, tomatoes, brioches and potatoes), and a rear pannier with a spare jacket, a multi-tool, pump, and some bits and bobs (1945g, all included). So this year I had 6319g of stuff with me.
the "full monty"

vs, the lightweigh set-up

That's a weight saving of about 7.5kg compared with last year, and is the biggest weight saving of the 4 areas I looked at.
Summary of weight changes 2015 to 2016 (savings shown as a minus)
Rider (me!): - 6.3 kg
Bike: - 3.5 kg
Clothes: - 0.2 kg
Food, water - 7.5 kg
Total weight saving: 17.5 kg.
Using a tool like Bike Calculator allows some ball-park estimates to be made.
Rider weight 2015 = Rider + clothes = c. 92 kg
Rider weight 2016 = c. 85.5 kg
That goes in the rider weight on Bike Calculator.
Bike weight 2015 = Bike + kit, water, etc = c. 32 kg
Bike weight 2016 = c. 21 kg.
Ride distance = 100km.
Elevation is about 100m.
Put all the 2015 data in, then slide the red "knob" at the top of the calculator so that time is as close to my actual time on the ride as possible.
Time for 2015 = 5 hrs 20, which is 320 minutes.
Then change the rider and bike weights to the 2016 numbers.
Time comes down to 310 minutes.
So the weight savings save me another 10 minutes.
But wait.
It isn't a flat route.
Even Strava, with it's rounding down methodology says I climbed 850 M on the ride.
So what if we split it into 2 part rides to simulate the hills. First ride gains 850m, the second loses the 850 meters. As the bulk of the hills are in the first half, but fatigue is in the second half, just for convenience we will split the time at 170 mins for the first half and 150 mins for the second half. After all, with all the big hills in the first half, then it probably did take longer.
So let's put the numbers in.
Well, that doesn't work. You can freewheel the second half in 104 minutes.
So let's try 100 minutes for the "downhill half", and that gives us 220 minutes for the uphill half.
1st 50k (850m uphill)
2015 = 220 mins (our starting point)
2016 = 199 mins (from Bike Calculator)
2nd 50k (850m downhill)
2015 = 100 mins (our starting point)
2016 = 107 mins (from Bike Calculator).
Note how for the "downhill" section, the heavy bike was actually quicker.
But the lighter bike(and rider) was much quicker on the first half, to give an overall saving of 14 minutes from the 17.5 kg weight saved.
So that is 22 minutes accounted for by aerodynamics, 14 minutes accounted for by weight, and now I have only to explain the other 4 minutes to make the numbers add up to the 40 minutes I saved "in the real world".
Of further interest, is that weight seems to be worth about 48 seconds per kilo saved at my current levels of performance over that particular 100km course. Time for another diet before the 2017 event, methinks.
Anyway, that's it for this post.
In part three I will look at some other factors that affect the change between my 2015 and 2016 times over this one particular 100km (62 mile) route.

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