First look: Giant Propel Advanced SL & Envie aero road bikes +video

David Arthur wrote:

Just in, the Propel Advanced SL 3 will cost £4,499. Seems like Giant only offering one bike (in the UK at least) for starters

Plus, they've told us a women's version, the Envie, has been developed too. The first women's specific aero road bike?

David, whats the spec changes for that version? Mainly, what are the wheels on it please?

tony_farrelly wrote:

Would there be a link to those wind tunnel protocols MinardiM189 cos it'd be useful to have?

Do a search for wind tunnel blockage effects.

In general it is considered bad practice to have a frontal area of the test object that is 10% or more of the wind tunnel working section area. As the test object is yawed the frontal area increases and makes things worse.

This originated in aerospace testing where test objects are reasonably aerodynamic and have a small 'wake'. With less aerodynamic objects the 'wake' is larger and in some cases can have an area greater than the test object. In these cases the cross sectional area of the wake should be considered. Bicycles probably fall into this latter category.

An F1 car has a huge wake mainly from the rear wing, this can be up to 10 times the height of the car (vertically). So the blockage effect is much greater.

Many bicycles are tested in F1 wind tunnels or varying size, I believe the McLaren & Mercedes F1 wind tunnels have been used for aero testing of bikes. These are much larger (and of a different design) than the 'old' Ligier/Prost tunnel used by Giant. Results from these tunnels would be more believable.

Attached is a pic of another bicycle in the Magny Cours tunnel. With a rider on the bike would this give realistic results?

MinardiM189 wrote:

Another manufacturer testing in a wind tunnel which is too small.

More meaningless aero figures.

Everyone's figures say their own bike is the most aerodynamically efficient. There's no such thing as a standard aero testing protocol. Everyone tests in different ways and says that their protocol is the most realistic – and, invariably, their product rates best according to their system of measurement. Hence, lots of numbers that mean very little.

Mat Brett wrote:

MinardiM189 wrote:

Another manufacturer testing in a wind tunnel which is too small.

More meaningless aero figures.

Everyone's figures say their own bike is the most aerodynamically efficient. There's no such thing as a standard aero testing protocol. Everyone tests in different ways and says that their protocol is the most realistic – and, invariably, their product rates best according to their system of measurement. Hence, lots of numbers that mean very little.

There are also basic rules for what size wind tunnel should be used for testing to give believable results. I believe the ex Ligier/Prost F1 wind tunnel at Magny Cours is too small for a full size bike/rider combination.

Amongst other things this will change the size of the wake & the rider's wake influences the whole flow around the frame. The situation will become even worse when they test at yaw, the whole flow field around the bike/rider will be distorted.

In this case I believe the results of any tests will be pretty much meaningless.

MinardiM189 wrote:

There are also basic rules...

That's the point, MinardiM189. There aren't any agreed rules. Giant clearly think their test results are valid.

They say, "Eschewing current industry testing standards, which typically utilize either static dummies or human riders to measure aerodynamic performance of rider and bike, Giant developed a dynamic mannequin for its wind-tunnel development sessions at the ACE wind tunnel in Magny-Cours, France. Unlike a static mannequin, a dynamic mannequin accurately replicates the aerodynamic effects of a cyclist pedaling a bicycle."

Other designers/engineers will doubtless disagree with Giant's protocol. There are no standard rules to which everyone has signed up, so everyone will continue to publish their own figures which demonstrate that their product is undoubtedly more aerodynamically efficient than everyone else's.

Mat Brett wrote:

MinardiM189 wrote:

There are also basic rules...

That's the point, MinardiM189. There aren't any agreed rules. Giant clearly think their test results are valid.

They say, "Eschewing current industry testing standards, which typically utilize either static dummies or human riders to measure aerodynamic performance of rider and bike, Giant developed a dynamic mannequin for its wind-tunnel development sessions at the ACE wind tunnel in Magny-Cours, France. Unlike a static mannequin, a dynamic mannequin accurately replicates the aerodynamic effects of a cyclist pedaling a bicycle."

Other designers/engineers will doubtless disagree with Giant's protocol. There are no standard rules to which everyone has signed up, so everyone will continue to publish their own figures which demonstrate that their product is undoubtedly more aerodynamically efficient than everyone else's.

There are standard rules for wind tunnels testing accepted across aerospace and automotive sectors.

The fact that Giant and some other bicycle manufactures don't follow these shows a fundamental lack of aerodynamic training. Or they are testing purely for marketing reasons.

To get any meaningful results (particularly at yaw) they need to use a bigger wind tunnel.

It isn't about any protocols it is about the basics of wind tunnel testing.

MinardiM189 wrote:

Mat Brett wrote:

MinardiM189 wrote:

There are also basic rules...

That's the point, MinardiM189. There aren't any agreed rules. Giant clearly think their test results are valid.

They say, "Eschewing current industry testing standards, which typically utilize either static dummies or human riders to measure aerodynamic performance of rider and bike, Giant developed a dynamic mannequin for its wind-tunnel development sessions at the ACE wind tunnel in Magny-Cours, France. Unlike a static mannequin, a dynamic mannequin accurately replicates the aerodynamic effects of a cyclist pedaling a bicycle."

Other designers/engineers will doubtless disagree with Giant's protocol. There are no standard rules to which everyone has signed up, so everyone will continue to publish their own figures which demonstrate that their product is undoubtedly more aerodynamically efficient than everyone else's.

There are standard rules for wind tunnels testing accepted across aerospace and automotive sectors.

The fact that Giant and some other bicycle manufactures don't follow these shows a fundamental lack of aerodynamic training. Or they are testing purely for marketing reasons.

To get any meaningful results (particularly at yaw) they need to use a bigger wind tunnel.

It isn't about any protocols it is about the basics of wind tunnel testing.

I think it's purely for marketing point - sure some might be genuinely more aero than others but on the whole it's hard to trust anyone. It's funny that drag coefficients of cars are not told in the same way.

MinardiM189 wrote:

Another manufacturer testing in a wind tunnel which is too small.

More meaningless aero figures.

Ha! I thought I was the only one that noticed that. Car/scale model wind tunnels are not designed for vertically tall structures.

Besides, and here is a shocker, wind tunnels are just about useless for reliably establishing real world aerodynamic performance of small structures traveling at low speeds due to the very low ratio of forward motion versus incident wind speeds. In other words, air around us is not a perfectly laminar, stable, uniform density mass as in a wind tunnel, but a swirling random mess. At car or airplane speeds, this does not matter much as the forward motion vector is orders of magnitude higher than any local vectors, but at bike speeds it matters a great deal...I'd like to see field testing become the norm for establishing aerodynamic superiority of bikes.

Lastly, Giant admitted that the setup of their bike was different to the setup of other bikes, thus how they can then combine the data and present their bike as being superior is beyond me.

I wonder when bike brands will start suing each other for misrepresentation with intent to cause commercial damage to competitors...

mythbuster wrote:

MinardiM189 wrote:

Another manufacturer testing in a wind tunnel which is too small.

More meaningless aero figures.

Ha! I thought I was the only one that noticed that. Car/scale model wind tunnels are not designed for vertically tall structures.

Besides, and here is a shocker, wind tunnels are just about useless for reliably establishing real world aerodynamic performance of small structures traveling at low speeds due to the very low ratio of forward motion versus incident wind speeds. In other words, air around us is not a perfectly laminar, stable, uniform density mass as in a wind tunnel, but a swirling random mess. At car or airplane speeds, this does not matter much as the forward motion vector is orders of magnitude higher than any local vectors, but at bike speeds it matters a great deal...I'd like to see field testing become the norm for establishing aerodynamic superiority of bikes.

Lastly, Giant admitted that the setup of their bike was different to the setup of other bikes, thus how they can then combine the data and present their bike as being superior is beyond me.

I wonder when bike brands will start suing each other for misrepresentation with intent to cause commercial damage to competitors...

Field testing is extremely difficult to do accurately and far more expensive than wind tunnel testing.

Wind tunnel testing can be done accurately, even for a bicycle.

David Arthur wrote:

What Giant says is that in riding the Propel you can expect to be 12 to 36 seconds AHEAD of other aero bikes

So if it takes 60 minutes to cover the 40km time trial on their Propel, the other aero bikes are going to be between 12 and 36 seconds slower and behind the Propel. Make sense?

Problem with aero claims, is there is no real standard of measurement. Time saved over a 40km TT is emerging as one, but as Giant shows, they don't all really follow it

Remember to factor in who's riding the bike. Horses for courses.

David Arthur wrote:

What Giant says is that in riding the Propel you can expect to be 12 to 36 seconds AHEAD of other aero bikes

So if it takes 60 minutes to cover the 40km time trial on their Propel, the other aero bikes are going to be between 12 and 36 seconds slower and behind the Propel. Make sense?

I'm sure Matthew knows exactly what Giant's spin doctors mean. He's just pointing out that what they actually said makes no sense.

If you're riding at 40kph for 60 minutes then it doesn't matter if you're riding a Propel, a Venge or your kid's tricycle - 40km will take exactly 3600 seconds. Not one second more or less.

mattheww385 wrote:

Well this manages to make absolutely no mathematical sense

Yeah, Giant say, "At a speed of 40 kilometers per hour over a distance of 40 kilometers, the Propel Advanced SL was 12 to 36 seconds faster than the other bikes tested."

Presumably, they mean that if you go 40kph for an hour on the Propel, at the same power output you'd cover the 40km 12-36secs slower on the other bikes tested.

That would be my interpretation.