Why are TT (or tri) frames different to road frames?

Jamey

Ok, I've done a bit of reading and I know most of the normal stuff. I know why you can't use aero bars in a road race that allows group riding, etc etc.

I've read that TT/Tri bikes are more concerned with being aerodynamic but what I don't understand is why road bikes aren't so concerned with being aerodynamic? Why wouldn't road racers want a bike that was equally aero? Why wouldn't road riders want the reduced wind resistance? Why would road riders actually prefer their bike to be less aerodynamic?

I don't get that. Unless it's UCI regulations, in which case fair enough.

Pokerface

Part of it is regulations (good old UCI), but it comes down to things like comfort, strength, etc.

TT bikes use different geometry to maximize aerodynamics - but it puts the rider in an uncomfortable position (it's not just down to the aero bars). Road bikes are designed to be stronger under certain conditions also.

But mostly it's a rules thing.

Anonymous

The aero effect isn't as important when riding in a group (due to slipstream effect) or when climbing (because you are going slower)....

Jamey

NapoleonD wrote:

The aero effect isn't as important when riding in a group (due to slipstream effect) or when climbing (because you are going slower)....

I know it's not as important, but my point was that you would still want to have it anyway, wouldn't you? I just couldn't imagine why you would say "nah, don't worry about making it as aerodynamic as those other bikes."

But if, as Pokerface is suggesting, it's mainly down to regulations then that answers the question, I guess.

keef66

Triathlons / TTs are generally shorter and more intense than road races so riders are more prepared to put up with an uncomfortable position for a shorter time

Jamey

That also makes sense. Cheers.

redddraggon

There are Aero road bikes.

Infamous

keef66 wrote:

Triathlons / TTs are generally shorter and more intense than road races so riders are more prepared to put up with an uncomfortable position for a shorter time

If it's uncomfortable, it's set up wrong.

Aeroness isn't really needed on a road bike, the frame+forks on a TT bike being more aero probably only counts for a 0.001% speed increase.

dennisn

If the truth be known there is NO such thing as aero. This word was invented to sell
bicycles to triathletes.

Bhima

Jamey wrote:

I know why you can't use aero bars in a road race that allows group riding, etc etc.

You are allowed them in a road race.





























...but most riders prefer gels instead.










I can see how riding in a group would make any bike's aero advantage almost useless, but if you break away from the bunch or sprint at the end, it will be an advantage. You could have the most aero bike in the world but bad body position would counter-act any gains because about 80% of the drag comes from you.

Infamous

do they do banana flavour?

emjayjay

also, tt bikes are designed to go very fast over a short(er) distance than a road bike. comfort, stability and handling are much less important than straight line speed.

compare a sports car to a family car. a family car will have to compromise on many things including speed and handling, whereas a sports car will be good for going fast. the sports car may not have the best ride, but it will be fast, which is what you want out of a sports car.

John.T

TT frames have different geometry to road frames so that they handle better with the rider in the more forward position used in TTs. A standard road frame set up for a full on TT position puts a lot more weight over the front wheel. A TT frame is also designed to be more stable as you do not have as much control on aero bars, You also do not need such responsive handling. Set up right they can be quite comfortable, people ride 24hr TTs on them.

TarmacExpert

But if we set aside geometry and aero bars, TT bikes generally look to have a more aerodynamic design, in ways that could easily be translated into road bike design. E.g.



Why can a road bike not have tubes shaped in the same way as that to make it more aerodynamic? Or would that make the frame heavier or weaker or have some other negative effect?

John.T

TT frames are usually heavier. Road frame tubes are already about as thin as is safe so increasing the size would also increase weight. Felt have made some aero shapes on their latest frames but nothing like as extreme as the TT one.

Alex_Simmons/RST

There is absolutely no reason why a road frame could/should not be more aerodynamic. Weight is not an issue as frames are already bumping the UCI lower weight limit.

Whether it makes a difference to the outcome depends on many things but in road racing it's more about the tactics and strategy than simply slicing through the air.

Still, if I were in a breakaway, or suffering like a dog to hang onto an echelon, I'd like every aero advantage I could get.

Mettan

TarmacExpert wrote:

Why can a road bike not have tubes shaped in the same way as that to make it more aerodynamic? Or would that make the frame heavier or weaker or have some other negative effect?

Some do Tarmac - Cervelo

http://www.cervelo.com/bikes.aspx?bike=S32009

http://www.parker-international.co.uk/1 ... n=pid12490

edeverett

It's probably worth noting that Menchov won the critical time trial in the Giro using a road bike with tubes shaped like bricks and almost box section rims. Which does raise question marks over the effectiveness the aero bit of aero equipment (as opposed to the benefits of putting the rider in a better position).

http://www.bikeradar.com/gallery/articl ... age-report

reppohkcor

edeverett wrote:

It's probably worth noting that Menchov won the critical time trial in the Giro using a road bike with tubes shaped like bricks and almost box section rims. Which does raise question marks over the effectiveness the aero bit of aero equipment (as opposed to the benefits of putting the rider in a better position).

http://www.bikeradar.com/gallery/articl ... age-report

Of course the cross-sectional area of a frame (perpendicular to direction of travel) is ....what..... less than 5% of the cross sectional area of the rider. So the frame will make a little difference, but the rider positioning is MUCH more important.

Jamey

Yes but positioning is a completely separate issue from the shape of the tubes.

Aero = the shape of the tube itself.
Position = what angle the tubes are placed at by the person that draws the blueprint for the frame.

Now I accept that the aerodynamicness of the frame/tubes probably makes very little difference. But if it makes any difference at all (even a minisule difference) then I don't understand why all tubes wouldn't be shaped like aerofoils or whatever the correct term for that particular shape of tube is.

Eau Rouge

edeverett wrote:

It's probably worth noting that Menchov won the critical time trial in the Giro using a road bike with tubes shaped like bricks and almost box section rims. Which does raise question marks over the effectiveness the aero bit of aero equipment (as opposed to the benefits of putting the rider in a better position).

http://www.bikeradar.com/gallery/articl ... age-report

Of course, everyone else was also on their normal road bikes, some weren't even using clip-on tri bars, so you can't draw any conclusions about the effectivness of the aerodynamics of a TT bike from that stage. The hills and technical decents outweighing any aero advantage in the riders opinions.

However, when presented with some hills and technical decents over 60-oddKm of a TT, (far closer to the sort of ride most of us actually do than a normal TT stage is.) )the fact the Giro Peleton opted for road-bikes en-mass speaks volumes about the useability of TT bikes in the real world

John.T

Probably it is more difficult to make an aero frame with the required stiffness caracteristics. The Cervelo has only really got a profiled down tube the rest is pretty standard. As the knowledge of how to work carbon tubes increases we will see more of this.