How much time difference does aero really make?

I'm still new at this myself, but Iwould think that once you start talking about 15+ mile and longer rides that the time savings would really start to add up.

I think I've read that that single biggest factor in slowing people up on the bike (or ways to increase speed) is to reduce air drag.

The body's resistance to the wind or air flow is the single biggest thing that slows you down, so the more you can get into and the longer you can stay in an aero position ... I would say would add significant time savings.

Depends on you, your position and the overall coefficient of drag that the complete package (you and bike) make.  The lower the CD, the better you will go through the wind.

I just tried to find the real world testing that Cyclingnews did with a road bike, TT bike and adding parts to quantify the benefits, but I can't find it ... grrrrrrr.  Need to bookmark it when I do!

If you go from a normal upright position on a road bike to a completely aero position with all the aero goodies (and a proper fit to that position) you could see anywhere from a 3 - 5 mph difference in your speed as a very broad and general number.  A lot of factors go into that which could move that number up or down.

this might be the link you are thinking off... interesting stuff

http://www.cyclingnews.com/tech.php?id=tech/2008/features/jeffs_need_for_speed08

Bingo!!

I had it linked in another thread last year but just couldn't find it.

x2. Aero position on a properly fitted TT frame, after that your biggest savings are an aero helmet, and a wheel cover. (You get pretty much the same savings out of a wheel cover as you do a disc, and a fraction of the cost.)

John 

So, not to Hijack but to add to the OP's question, would that mean you would expend less energy holding the same average speed on a properly fitted Aero setup Vs a Traditional road setup??

All other things being equal, theoretically yes.

One of the analogies I use is that you have a certain amounts of endurance credits to spend in a race. You spend X to do the swim, Y to do the bike, and Z to do the run. Ideally, you want to get to zero credits and the finish line at the same time.

Now, if doing a 40k TT normally costs you 70 credits at 20mph on a non aero/non fitted setup, theoretically you could then do the 40k TT at 20mph and only need to spend say, 60 credits. That gives you another 10 credits to spend on the swim or the run. 

 John

There a lot of people here that can speak to this with more knowledge than I, but I bought a tri-bike in December and have been trying to get a feel for exactly what you are asking.  I have made a couple of observations over the 10-12 rides I have made so far.

* I don't climb hills as well on the tri-bike as on the road bike.  People say this will get better as I get more used to the tri-bike and I think I am getting a bit faster.  However, I can still climb better on the roadie after about 350 miles on the tri bike.

* I can't tell any difference running off of the tri bike as compared to the road bike even though people told me it would be easier.  My legs feel the same either way.  My back feels better coming off of the tri bike, though, just doesn't really translate into more speed on the run.

* Obviously, the aero position provides more benefit the faster you are going.  So, stronger riders that can average higher speeds will derive more benefit than riders that typically average 15-16mph.  My anecdotal observations (very unscientific) are that the tri bike benefit at speeds below 15-16mph is negligible, 17-19mph is modest, and 20 and higher is pretty significant.  I have come to these conclusions from observing the differences between rides I have done with another fairly equal rider that I have also ridden a lot of miles with on my road bike.

* I think some of the aero benefits are diminished somewhat on a hilly course.  Sure, you can pick up a lot of distance on the downhills, but the time you spend going downhill is less than the time spent climbing hills since you are going probably double the climbing speed.  The tri bike is still beneficial, but I think it is even better on a flattish course where you are cruising at a higher speed continuously than a course where your speed is going up and down.  I discovered this from comparing Garmin 305 data (you know, one of those 'toys') on identical rides on the tri bike and road bike.

* Drafting in the aero position behind my partner (he trusts me) is a pretty big deal.  After about a minute drafting, my heart rate drops 25-30 bpm, just to give you an idea of the drop in workload.   Sure wish we could draft in triathlons!  When we are going downhill and I am aero, I have to keep hitting the brakes while my riding partner is still pedaling.

Of course, YMMV.  I just started cycling a year ago, 52 years old, and probably average cycling fitness for my AG but significantly below what the typical, younger triathlete could do with my bike.  I now prefer riding the tri bike over the roadie since getting used to the aero position.  To me, it is more relaxed and when I lean over and drop my arms in the cups it is almost like chilling out.  I know that I can ride at least 50% farther comfortably on the tri bike than the roadie because my back, shoulders, and arms don't get as tired.

FWIW,

Greg