On the difference in speed between road and TT bike
This is something that I’ve often wondered, but never gathered any data to test. I did one club TT on my road bike last year, but it was a 2UP, so I can’t count the time, since for more than half of it, I was being dragged round by Ben Price of Kinetic Velo.
I’ve not written any updates recently, because I haven’t been racing. I was supposed to race the fast 25 course at Etwall, near Uttoxeter, earlier this month. I went all the way there and then chickened out due to the weather. About half the field didn’t start. I wasn’t happy with the side wind and the amount of spray coming off the road. So I drove home again. This means I am still to do a 25 in 2014! I’d resolved to focus more on 25s this season, and yet I still haven’t managed to ride one. After that I went to Mumbai with work for a week, which messed up two weekends, and so the open racing has ground to a halt.
Anyway, onto the subject of this post. St. Ives CC – until very recently – ran it’s club TTs on the venerable N1/10 course at Sawtry. I’ve written loads about racing on this course. This season, the local district has ruled that the course requires more marshals to hold events, and this has been deemed unrealistic for club events. So a new course was sought. Terry and Chris, who run the club race, worked out a new course in the vicinity of the old one. It’s what you would call a ‘sporting’ course. The old course was pretty sporting (this means slow!) in my opinion, and the new one is even more so. What makes a course sporting is hills, bumps and twisty bits. The things that slow you down. The new course has a big uphill section after a mile or two, and then snakes through a wood on a very bumpy, twisty road, before a downhill section back towards the start. To make it up to 10 miles, you then do a loop round a couple of roundabouts before finishing outside the HQ. It’s quite complex to get your head around (which I think also contributes to the lack of speed). It’s not a traditional out and back, more of a loop. But I prefer it. It’s more interesting than the old course, and time seems to pass quicker. No doubt I will grow to detest it over time.
Since the course is slower, last week I thought I’d turn up and ride it on my road bike, because I thought it wouldn’t be too much slower than on the TT bike, and it’d be a bit of a novelty. It’d also put down a marker so I could compare my speed on the TT bike at some point. So I rolled up on my trusty Planet-X and shallow section wheels, wearing regular cycling gear (no skinsuit) and non-aero helmet. To cut a long story short, I trundled round in a disappointing 25:48. Power was low, too, just 280w, which I think is because I have trained for TT efforts almost exclusively in the TT position, and so I am not optimised for road bike riding, even on the drops. What also affected power, I think, is the nature of the course. There are plenty of places where you have to slow down. Not brake, necessarily, but freewheel. In a short race like a 10, this really hurts average power. Just a few seconds without pedalling takes a few watts off your average power. Anyway, excuses, excuses. We all have our expectations of the times we should do, and for me that was pretty dire.
So this week I decided to roll out the heavy artillery. Full lycra jacket. TT bike, aero wheels, skinsuit, aero helmet. I chatted to Mike Hoy at the line who thought the course wasn’t any faster on a TT bike. “It’d better be!” I thought to myself. The weather wasn’t good today, raining almost all day. By the time 7pm came around, the rain had gone, but the surface was damp and the air was full of water. The wind was quite light. Overall, the conditions were a little poorer than the week before, which was comparatively warm and sunny. Only 6 people turned out to race tonight, testament to the weather, but also the numbers have been poor so far this year. Since the early TTs were cancelled due to the old course being unsuitable, the attendance hasn’t really got going yet.
Off I went, number 3 at 19:03. Last week I think I went a little too hard up the hill, so I watched the power this time and tried to keep it below 320w. This is quite hard to do when you want to cycle fast uphill. It’s very easy to get over 400w, which for me would be pretty terminal (for a good time, at least). At the top of the hill there’s a sharp left turn which is tricky when it’s damp, and then almost immediately another sharp left. By this time I had passed numbers 2 and 1, and so there was nobody in front of me. I set off into the twisty wooded section and by now my visor had started to mist up quite badly. At the end of the woods there is a VERY sharp left bend, a sharp right which marks the half way point and then you go down a steep hill. I was feeling ok. I could see that power was down but I felt I was going reasonably well, and put the slightly lower power down to the 2 junctions and 2 sharp bends where I’d been freewheeling, sitting up.
By now my visor was completely misted up. There are a couple of tiny vent holes on the top edge. I was peering through those to be able to see anything. A bit precarious when you’re hitting speeds of up to 40mph on the downhill, but in the moment you just shrug it off.
I don’t think I rode the next couple of miles brilliantly, time to be made up there, and then you go into the last section where you have to loop back on yourself. I saw a couple of riders here, since it takes a good 3-4 minutes to complete the loop. I didn’t ride very well over the last mile, because the line was approaching before I even realised, and I should have been pasting myself much earlier. The garmin bleeped 10 miles as I crossed the line, but I couldn’t see the time because of the visor. I was reasonably happy with the ride, although there is definitely time to be made up on several parts of the course.
So, the time. I went round in 23:25 at 25.7mph, which is 2:23 faster than the week before. Average power was 287w, up 7w on the week before. But conditions were poorer, which I suspect would more than make up for the power difference. So all in all, I think I am around 2 minutes 30 seconds, or just over 2.5mph faster on my TT bike than my road bike on this course. When you consider that it isn’t a course that really favours aerodynamics (compared to a flatter, less technical course), I find that quite interesting. On a dual carriageway course, I suspect the gap would be considerably wider. Well over 3 minutes.
The last race of the first half of my season is this Saturday, on the fast E2/10 course near Cambridge. Alex Dowsett has entered! Hopefully he won’t catch and pass me, since I’m starting over an hour before him 🙂 After that, I will be training for La Marmotte in June, before hopefully returning to TTing in July.
Thanks for reading 🙂 A link to tonight’s ride on Strava: http://www.strava.com/activities/146633506