"Lightness" vs "Aeroness" UPDATED 10/2023

[iflyadesk]

Hi everyone. Been out with a back injury that ultimately led to surgery and then in recovery I fell in love with MTB and haven't ridden road in years. Anyway, I'm back! Just bought a Tarmac SL7 Pro. Did Tour Mag test any new bikes that are good enough they need to be added to the graphs on page one of this thread?

[maxim809]

dude, yo, welcome back. hoping that you being back means recovery has gone well?

[calleking]

Welcome back! I'm recovering from a broken tibia with an Ilizarov frame. I could use an updated graph/chart for my next bike build. Need to stay sane and have something to look forward to

These are the bikes that have been updated lately:
Cervelo S5 (updated)
Cervelo R5
Aurum Magma (Contador/Basso brand)
Bianchi Specialissima
Merida Scultura Team
Pinarello Dogma F

https://www.tour-magazin.de/rennraeder/ ... vergleich/

Btw, did anyone find the aero testing of the Cube Litening C:68x? Lots of bike for the money if you go for the UDi2 version.

[cajer]

Welcome back! I'm recovering from a broken tibia with an Ilizarov frame. I could use an updated graph/chart for my next bike build. Need to stay sane and have something to look forward to

These are the bikes that have been updated lately:
Cervelo S5 (updated)
Cervelo R5
Aurum Magma (Contador/Basso brand)
Bianchi Specialissima
Merida Scultura Team
Pinarello Dogma F

https://www.tour-magazin.de/rennraeder/ ... vergleich/

Btw, did anyone find the aero testing of the Cube Litening C:68x? Lots of bike for the money if you go for the UDi2 version.

The issue with all the new Tour bike testing, is unless otherwise specificed (only happens for 1-2 of the frames in the test) they don't test the bikes with the same zipp 404 wheelset. Instead they test them with whatever comes on the bike. So all the new comparisons are rubbish.

[rudye9mr]

It'll be a test of the system so people can compare systems from one manufacturer to the next.

Should still do that and the 404 wheelset imo.

[cajer]

It'll be a test of the system so people can compare systems from one manufacturer to the next.

Should still do that and the 404 wheelset imo.

However it's not useful for us, as most of us build up framesets or replace wheels on complete bikes.

There's also no point in comparing them with random stock wheels as then you can't tell if its the wheels or the bike that's slow.

[happydogww]

For aero's sake, I think more attention needs to be paid to BB Drop. With the recent push for larger tyres, for example 28mm vs 25mm, the bike and rider are ~3mm higher and creating more drag.

While new frames now have more tyre clearance, it seems that not many are adding BB Drop to compensate for the increased ride height. With the trend for shorter cranks, it would also make sense to increase BB Drop.

I think BB Drop should be near 80mm, at least for smaller sizes.

[Hexsense]

28mm vs 25mm is not often is 3mm increase in height thought. More like 2.4mm due to extra sag because user run softer tire pressure on wider tire.
I don't know but maybe we don't need to compensate for it all. I enjoy corner clearance provided by 74mm bbdrop, 165mm crank and speedplay pedal.
80mm drop with road tire would be usable too but not sure if I want it any lower. The more lateral grip of wider tires make corner feel less sketchy and we also pedal through sharper corners at higher speed.

Maybe Cannondale was ahead of the low bb game with SystemSix size 47 at 79mm drop.

[SixThirteen]

For aero's sake, I think more attention needs to be paid to BB Drop. With the recent push for larger tyres, for example 28mm vs 25mm, the bike and rider are ~3mm higher and creating more drag.

While new frames now have more tyre clearance, it seems that not many are adding BB Drop to compensate for the increased ride height. With the trend for shorter cranks, it would also make sense to increase BB Drop.

I think BB Drop should be near 80mm, at least for smaller sizes.

Assuming a tyre is round in cross section, wouldn't going from 25mm to 28mm give an increase in height of 6mm ie 3 at both top and bottom?

IIUC the "best" tyre pressure gives a height reduction when on the bike of about 25% so actually about 4.5mm increase?

[alanyu]

For aero's sake, I think more attention needs to be paid to BB Drop. With the recent push for larger tyres, for example 28mm vs 25mm, the bike and rider are ~3mm higher and creating more drag.

While new frames now have more tyre clearance, it seems that not many are adding BB Drop to compensate for the increased ride height. With the trend for shorter cranks, it would also make sense to increase BB Drop.

I think BB Drop should be near 80mm, at least for smaller sizes.

Assuming a tyre is round in cross section, wouldn't going from 25mm to 28mm give an increase in height of 6mm ie 3 at both top and bottom?

IIUC the "best" tyre pressure gives a height reduction when on the bike of about 25% so actually about 4.5mm increase?

Based on BRR's test, the height of GP5000 S TR is 22.1, 25.4, 27.2, and 28.8 mm for 25, 28, 30 and 32 c. Roughly 1 c wider = 1 mm heigher.

[Luften]

Hi, question on the aero data for the Giant TCRs and also the Propel:

Giant's marketing materials state that the new (2021) TCR would save 34 seconds over the old one at 200w for 25 miles. Does this match up with the chart above? The chart only shows a 2 watt difference between the two frames.

Are the data points on here for rim brake or disc brake models? Also is the Propel which is on the chart a rim brake model?

Bonus question: Where would the RIM brake Look 795 Blade RS fit into this chart?

[Roadbiker10]

What is it with so many comments about riding in the drops being faster? The hoods are faster in the right position. Also a slammed stem for many will lead to them not being able to bend their arms on the hoods but ride with straight arms, which is not very aero. I've seen many people with this kind of position.

[TobinHatesYou]

Neither the hoods nor the drops are a faster position...it depends on how your bike is set up.

However 1) aero matters more the faster you are going and 2) for me this is during sprints/attacks and descents, where I am almost guaranteed to be in the drops.

[C36]

What is it with so many comments about riding in the drops being faster? The hoods are faster in the right position. Also a slammed stem for many will lead to them not being able to bend their arms on the hoods but ride with straight arms, which is not very aero. I've seen many people with this kind of position.

Here you don’t consider how you put power down to the pedals. In the drops you can accelerate stronger (attach, out of a curve, sprinting…).

[maxim809]

I enjoy corner clearance provided by 74mm bbdrop, 165mm crank and speedplay pedal.
80mm drop with road tire would be usable too but not sure if I want it any lower.
Maybe Cannondale was ahead of the low bb game with SystemSix size 47 at 79mm drop.

For aero's sake, I think more attention needs to be paid to BB Drop.
I think BB Drop should be near 80mm, at least for smaller sizes.

Re: BB drop, since we are talking about small bikes...

Hold up are you guys advocating for MORE clearance from the ground or LESS with respect to the bottom of the BB shell?

Larger BB drop = lower to ground = more likely to strike/clip.
Smaller BB drop = higher from ground = less likely to strike/clip.

So I think for very tight, fast, banked incorrectly corners, I really need a 60~65mm BB drop in order to be able to pedal thru. Many race bikes in small size (48cm~52cm frame) are at BB drop 70~74mm. Tho I just looked at the extra small 47cm SystemSix and wow at that 79mm drop. Crazy low, I would strike all day on that.

I run 165mm cranks and really think I need to go even lower if I want to take advantage of pedaling one or two rotations through inverted crowned corners.

I've struck hard on all my +72mm BBdrop frames. Speedplay pedals, while the best theoretically at clearing, wouldn't help because I'm hitting the bottom of the crank arm before even scraping the bottom of my pedals. I've struck on my Allez Sprint which is supposed to be a crit bike made for cornering at 69mm drop.

Meanwhile, my ~60mm drop frames have yet to strike on exactly the same corners with same crank lengths. So that 1cm or 10mm-ish really makes the difference.

You're right tho, the trade-off is sitting higher which impacts cornering and drafting. But unless you are riding in a group with riders predominantly your size, that extra 1cm does not impact drafting as as much as it does for taking away your ability to pedal thru corners. In my area, most people in the field are showing up with +54cm and over so everybody becomes a good draft for a small rider. So in a trade-off situation like that, I find the option to be able to thru corners with confidence more valuable.

Emphasis on "option", because just because you can doesn't mean you should or will.

That said, I can see the argument for lower if you are riding against everyone with similar sized bikes. Then that 1cm difference will be amplified, and the trade-off discussion becomes more interesting and I'd be inclined to swing it towards the lower overall measurement (higher BB drop).

Anyway... measuring from floor to the middle of crank....

58mm BB drop = 28.8cm
70mm BB drop = 27.9cm
72mm BB drop = 27.5cm

They all have different wheels with different internal widths, which will add to the overall difference in stack height. But all running the same 25mm tires at their optimal pressures.