Road Bike VS Time Trial Bike

The Test

At the final round of the Spires Trilogy series I decided to take along both my Time Trial bike and Road bike with a view to post a winning time in both categories. With 37 riders signed on it would be a challenge to finish the first run and get changed and onto the road bike for the second run.

Bike Set-ups

TT Bike Configuration

TT Bike: Planet X Exocet 2 with Fast Forward Disc and Tri spoke.

Rider attire: Skinsuit, time trial aero helmet and overshoes

The set-up shown above was used with the addition of a fast forward tri-spoke over the 80mm Planet-X rim shown above.

Road Bike Configuration

Road Bike: Dolan Ares with Von2 Raptor wheelset 38mm aluminium clinchers.

Rider attire: Bib shorts and top + road helmet and no overshoes.

A very similar set-up was used to what is shown here. Water bottles and overshoes were removed for the test.

Course and Conditions

The event was ran on the Toome out and back course. Weather conditions saw a strong headwind out with a strong tailwind on the return leg.

Results:

Outward Leg (Head Wind)

TT Bike -12.21 @ 362 watts

Road bike - 13.38 @ 319 watts

With the headwind one is going slower so it takes a bit longer to cover the 5 miles. We can see here that around 80 seconds was lost to the time trial bike.

Return Leg (Tail Wind)

TT Bike 8.27 @ 351w tt return leg

Road Bike 9.24 @ 327 road bike return leg

Faster speeds attributed to the tail wind shows the 5 miles was covered in much faster times on both bikes. Just under 60 seconds of difference in the road vs time trial bike with the road bike. My legs felt a bit better on the return leg on the road bike and was able to lift the power a bit.

Overall Results

TT Bike - 21.17 @ 360 watts

Road Bike - 23.20 @ 323 watts

In percentage terms the road bike was 9% slower with an 11% drop in power shown. One might question if the road bike power was the same as the TT bike i.e 11% more power would that not have yielded the 9% back in time? The answer to this is definitely not. Wind resistance is exponential in proportion to speed, i.e the faster you go the more power you need to put out to go a little bit faster again. In real terms that means a stronger rider actually benefits more from the aerodynamic equipment than a weaker rider.

Conclusions

I hadn't any rest between outings and this would account for most of the drop in performance in terms of power output., As soon as I finished on the time trial bike I got changed and put TT bike in car and pulled out road bike. By that time I had ridden over to the start line it was time to go again.

It would have been a little more scientific if the power outputs could have been the same. but I think one might take a rough guess that 40w could have yielded up to 60 seconds of time so ultimately the full road set-up perhaps being only around 60 seconds slower over a 10 mile time trial.

The rider accounts for up to 90% of the aerodynamic resistance so it would be fair to say that the time trial helmet, skinsuit and overshoes and also the more aerodynamic position would have yielded much of the time gain regardless of the bikes in test. We must also not overlook the fact that the geometry of the time trial bike and handlebars allow for the aerodynamic position. A good bike fit can sometimes be a better investment than the same money spent on equipment/clothing if your position is not aerodynamic you certainly won’t yield as much free time as you might otherwise do with a good position on the bike.

To anybody thinking of getting into time trials the should not feel they require the latest and greatest equipment. To compete at the front of the field where every second counts getting as much free time through equipment is important in order to level the playing field. Ultimately it can be an evolutionary process as it was for me and starting out on a road bike with some clip on tri bars would be the obvious first step followed by a TT helmet, deep section wheels then a skinsuit. A more expensive skinsuit vs a decent club one is a very very marginal gain.  

A few more bits and pieces

Just recently specialized has come out with its new venge claiming it to be up to 5 minutes faster than other "high end" road bikes. I can hear by tell you that is total nonsense and in the real world if its actually so much as 1/4 of that its as much as I would expect.

Case in point,I have a few...

Last year Colm Cassidy one of Ireland's top testers was at woodgreen on his Cervelo P5. This is a quote from Cervelo "Cervélo says the P5 is 6-11 watts quicker than the other so-called superbikes, saving roughly 24-44 seconds over 40km". Where does a planet X TT bike fall then? One wouldn't put it in the super bike bracket with the Shiv or the Trinity etc? 

I rode pretty well that night and posted a 19.09 with Colm posting a 19.08 he was kind of on the wind down after his brilliant national achievements etc but was still in very good shape. Talking Watts etc after its clear to see that the bike doesn't make that much difference and certainly there are not the free watts that we are led to believe. That night I put out 5.25w/kg for the 10 miles. Colm would have been close to that also.

Michael Hutchinson has a very good book called "Faster" which has a nice chapter on equipment. A great read for anyone interested in the topic. He sums it up pretty well with a passage that goes something like "I sat down and added up all the free speed I had gained over the last ten years. Bikes, skin-suits, wheels, wind tunnel testing etc. The problem was that when I added it all up, I should have gained about ten minutes over a 40km time trial. In reality it was more like two."