road bike w/ aero bars vs. tri bike

If they are flying by you, then they are just that much stronger.  The aerobars will certainly help because you will be reducing drag, but the biggest difference is body position on the bike.  The purpose of a tri specific bike is to make it easier to run coming off the bike.  Tri bikes have a steeper seat tube angle which makes your biking motion closer to a running motion.

Impossible to quantify, depends on a whole bunch of variables particularly the rider and his position on the bike. Generally speaking, though, a tribike allows for a more aerodynamic position.

I can, however, assure you that the people on tri bikes that fly by you effortlessly would also do so on a properly fitted road bike with aerobars.

Yes, pretty sizable difference in the bikes in a non-drafting event.

Below article might help you. 

http://www.bikeradar.com/gear/article/how-aero-is-aero-19273


All else being equal a TT bike will be faster for you most likely or a road bike with clip-on aerobars.  But, you need to have the engine too.

Uh, no. This is an oft-repeated fallacy.

The biggest difference I noticed going from my road bike with aero bars to my tri bike was comfort. I had both bikes professionally fitted but there is only so much you can do with road bike geometry.  On my tri bike I'm in a more aggressive position and it still feels very comfortable.

Personally I do run better off my tri bike but that is just me.  I've seen this point argued here before and you'll get different opinions about it.  It might be specific to each individual.

Having said all that my times are faster on my tri bike but not dramatically.  You can still do very well on a well fit road bike with aero bars.  Like mentioned in many other posts, a lot of it comes down to the engine.

Maybe it's not the "purpose" of a tri bike, but it is a benefit.  I have run after riding my roadie and run after riding my tri bike.  I can assure you, it is easier to run coming off the tri bike.  At least for me.  

If you just add aerobars and don't change to end-bar shifters then you are constantly coming off the aerobars to shift.

Many road bikes will have 3 chainrings and usually a tri bike will only have 2.  I think this is becuase most triathlons are are on relatively flat courses...but don't tell that to IMLP finishers. 

There is a difference in the angle geometry....not really sure what this buy you though....make it puts you in a better position when you are on the aerobars?

One neat thing about "tri bikes" when you are out riding and come up on someone else riding and he has a tri bike, you can guess that he is a triathlete and ride up beside him/her and have a good tri-related conversation.  I've only done this once but my guess was right, the guy was a triathlete and we ended up riding together for the next 20 miles and talked shop.

~Mike

There is small differance between the Area Coefficient of Drag on a road bike (riding in clip-ons aerobars) and a tri bike (riding in integrated aero bars). This small differance means little at lower speeds, but increases exponentialy (cubicly, to be precise) as speed increases. You  can get a $2k+ tribike or get 90% of the benefit by buing a $100 set of clip-on aerobars.

IMHO, If you're averaging around 30km/hr (20mph) or less in races on your roadbike with aerobars then I would not spend the extra $2k+ on a Tribike... but if you have the power to go above 30km/hr for 1hr+, then your $2k+ may buy you a minute or two...

BUT its fun to have a sexy fast looking bike. I bought a Cervelo P2 even though my cycling abilities did not warrant it. I have to spend our money on something and my wife prefers I spend it on fast bikes instead other vices...

Maybe so for you. My favorite saying is, "If it only works in your head, well, it still works." But there's no evidence whatsoever to support this "benefit" to the run from riding a tri bike.

So much wrong here. To keep it short, let me say that the only "cycling ability" you need to warrant a nice tri bike is sufficient disposable income to meet the asking price.

I hear this repeated over and over and yet I haven't heard a clear explanation one way or the other.  Here is my theroy:

Being in the aero position allows you to ride at the same speed using less wattage compared to a road bike.  Being that as it may, you're essentially "saving" your legs compared to a road bike since you're using less wattage, I don't think it has anything to do with have a steeper seat tube angle.  I think that's where the misconception stems from.  Though I think in reality all that does is allow the rider to go faster and use the same wattage compared to a road bike.

Is this a correct assumption?

If you assume that one will indeed "ride at the same speed using less wattage" then maybe so. But that's a huge and probably erroneous assumption.

More likely the typical rider will (and the most desired outcome is to ) ride at the same wattage but at a higher speed.

Edited by the bear 2010-05-27 2:33 PM

+1 to the bear.

The steeper seat tube angle is to allow the rider to get into a more aggressive aero position with the head and shoulders lower.  That reduces the frontal area of the rider and allows the head to drop more into a position that better shields the chest from seeing air.  By steepening the seat tube the rider's position is essentially rotated forward about the bottom bracket thus keeping the hip angle more open allowing for more power.  I think this is where the fallacy developed.  When observed in profile, the rider looks to have a more open position.  Though it may be closer to a running posture than simply being "folded over" to get low, it is still far from being considered close to a running posture.  It's actually close to a normal road position when taking the angles into consideration.

Just throwing some clip-ons may help, or may not help.  Many would be better off just riding in the drops, keeping their elbows in and knees close to the top tube. 

Add a forward offset seatpost and you would be getting closer to the advantage of the position a tri/tt bike offers.  Then you still have a little aerodynamics help of the tri/tt bike.

Without knowing your average speed over say, a 20k time trial (or bike leg) on a flat course, it would be impossible to tell you.  I agree with the others though.  If they flew past you, they are stronger AND they are (or better be) more aero.  To give you an idea what a new post, clipons, and possibly a different stem can do for a road bike, I picked up 4-5 mph over a 20k TT.

To add to what mgalanter (although I think it benefits at all speeds) said you are going to get some time benefits (free speed) if you get a tri bike.  It will place you in a more aerodynamic position, and make it comfortable so you can stay in that aerodynamic position.  I won't argue about the legs, because I haven't seen anything proving it.

There's alot of research on this subject but my rough estimate would be a tri bike would save you 1 minute ever 40km (25ish miles).  You can add more to that if you add in getting out of the tri position to shift, etc.

So its not all that much, but it is more and the difference between a $2000 tri bike and a $6000 tri bike are probably not even noticeable in terms of speed.

Edited by furiousferret 2010-05-27 2:39 PM

From the Bikesport Michigan article "What Is the Difference between a Road Bike and a Triathlon Bike?"


"The secondary advantage to a triathlon bike is easier transitions from bike to run and faster running. Ian Garside and Dominic Doran published an interesting study in June of 2000 in the Journal of Sports Sciences. The study is known as “The Garside Study” and is used in triathlon bike fitting schools such as Dan Empfield’s Fit Institute of Slowtwitch (F.I.S.T.). The Garside study tested athletes in a biomechanical setting, in other words, aerodynamics on the bike were not a factor in the results: Aerodynamic benefits would be in addition to the biomechanical benefits from a triathlon bike. Test subjects performed a 40 kilometer (24.8 mile) time trial on a road geometry bike in a stationary trainer followed immediately by a 10 kilometer (6.2 mile) run on a treadmill. Later the same test subjects repeated the test protocol but used a triathlon geometry bike on the stationary trainer then transitioned immediately to the treadmill for the 10 kilometer run. Time savings for athletes running off the triathlon bike were enormous: They averaged a full 5 minutes time savings on the 10 kilometer run when they transitioned off a tri bike as opposed to transitioning off a road bike. Simply put, you’ll run faster and more comfortably off a triathlon bike than a road bike. "

Link to complete article: http://www.bikesportmichigan.com/bikes/difference.shtml


Edit to add: this study only change the seat angle to a tri geometery vs. road geometery. from what I've been able to find, it doesn't state anything about aerobars or any other geometery associated with a tri bike.


Edited by jase714 2010-05-27 2:44 PM

Exactly; you ride faster at the same wattage so therefore spend less time on the bike.  If you ride at 200W and go 1:10 on a road bike you might go 1:05 on a tribike for the same wattage.  Five minutes less at 200W should allow you start the run a little fresher than if you were on the road bike.

Shane

OK, good start. Smart and knowledgeable poster so far.



Problems here. All the equipment enhancements in the world aren't going to give you  "4-5 mph over a 20k TT" if you come from from a road bike with a decent fit.

Sorry but that BSM article is relatively ancient and that study it cites, I believe, has been refuted repeatedly. Thanks for playing though.

Agreed, I was just using the "how aero is aero" article posted earlier as my reference point.  This was the data they used:

Speedway data

Set-up	Estimated Ave CdA (m^2)	Speed (km/h)	Power (W)
Tarmac SL2 | Road Helmet | Drop bars	0.310	40.10	306.6
Tarmac SL2 | Road Helmet | Clip-on aerobars	0.267	40.27	268.6
Tarmac SL2 | TT2 Helmet | Clip-on aerobars	0.256	40.38	261.0
Transition | Road Helmet | Aerobars	0.265	40.17	262.9
Transition | TT2 Helmet | Aerobars	0.230	40.05	229.0

Obviously this is a very controlled environment and doesn't mimic real world conditions but still gives a decent 10,000ft look at how the aero stuff works.

If you can find a copy of the entire study you should give it a read; here's a link to the abstrct:

http://www.informaworld.com/smpp/content~content=a713776232&db=all

There are some major issues with the conclusions one runs better off a steep angled bike based on their study design.

Shane

I was searching around and found that too, was looking for the original study, but couldn't find it (anyone?).  No idea what's come out since (its early 2000's) but its nice to see someone back up what they say with a source and some actual evidance than just calling people wrong with no explanation or justification.

You beat me to it as I was editing my post. The purpose of my post was simply to state that there has been a study done and within the parameters of the experiment, it concluded that running off a bike with a steeper seat tube angle is better than running off of a slacker seat tube angle. I understand that there are other factors involved as well that may work for 1 person but not the other.

Amazing find, great article...that data is crazy

lol.  Funny.  I like your attitude.  I originally was going to post 2 mph, but then I actually did a little math.  My average speed in road position around a nice little flat loop was 18mph (damn tendinitis has killed my power).  I could ride that bike (aluminum frame at that) in a century no problem and have regularly done 50 mile rides with a good mix of hills and flat.  Now, I've never optimized my road position in an actual ride with a power meter, but I've had pro fits done and the bike obviously feels great.  Jump on the bike three days later with the conversion and going moderately I averaged 19.5mph.  Rode a TT on the bike a week later on that very loop and averaged 22.3 - with the same HR as my "control ride".  I'm willing to give you a couple mph for human factors...  I picked up 2-3mph.  Deal?