The 45 Degree Angle Rule
 

Hey Guys,

Its known that a torso angle at about 45 degrees is a good balance of aero and comfort. Good for general road cycling. I read an article that suggested your torso should be at 45 degrees to the top tube. However I always though it was to the horizon, or straight floor, which seems to make more sense since there are sloping top tubes. Maybe this article got it wrong?

Link?

For optimal aero penetration you should be at a negative 45 degree angle, leaning way back over the back wheel, and steering telekinetically.

In the future, bikes will not have top tubes ... they will be made of sheets of glass, which are stronger than steel.

More to the point .... obviously the article was assuming a flat top tube. Otherwise it would make No sense at all, as every bike has a different TT angle .... you know that, and you knew it before you posted.

I am beginning to wonder if you use the correct chain lube. Do your socks match your bar tape....

Brothers ... I fear he is not .... One of Us.

We must purify the hive.

When I looked into bike fit, I realized that the rider has three points of contact with the bike: Feet, hands, and arse. What happens in between those points is important for the structure of the bike, but not for fit. Comfort is relative to gravity, and aero is relative to the air, neither of which are affected by the top tube.

So, at least that was my conclusion, without claiming to be a bike expert.

I had no idea that was a rule. I change the fit on my bike until I'm "comfortable."

Here is the link to that article:

http://www.cyclingweekly.com/videos/bike-fit-and-maintenance/handlebar-reach-how-to-get-it-right-video

Oh, and cocaine is a hell of a drug to that one poster.

It might be a good starting point, but I think that 45° is not very aero.

Agreed, I was asking more about where one should measure that angle to... (the top tube or horizon/floor).

One does not simply "measure" the "angle" ..... said Boromir. And he died, pierced by many arrows.

Seriously ... get on the bike. get comfortable. if you cannot get comfortable, move the movable bits.

Rules of thumb are fine ... if you are a thumb.

General ideas are great, generally. Only you know what works for you.

I would tell you my "Perfect Bike Fit Secrets™" but everyone here would disagree ... with me and with each other.

The last time I heard that "45 degrees" line was in a spin class ... where nothing but aero matters.

I tend to set up my bikes so I am comfortable after as long a ride as I can ride comfortably ... and then start removing spacers 5 mm at a time. At some point my girth or my age will force me to stop ... and then, over time, likely reverse that scenario.

That is the "system" which makes sense to me.

Along the line of the effective top tube, IMO. Parallel with the wheel axles.

Not the horizon, because the position relative to the bike affects comfort (more than orientation with gravity), and the bike's motion is always relative to the bike's frame (in line with the wheels basically) so aero is not with respect to the horizon.

Right, so basically on level ground. The wheels would also then be level. Maybe I'm wrong, but isn't the horizon then level to all of that? I believe effective top tube is a horizontal/level measurement?

I've seen the film many times...I don't get the reference.:foo:


Anyhoo, OP:
The 45* rule of thumb may be for general riding with elbows slightly bent, sort of in cruising mode. If you want to get more aero you want to bend those elbows more, or get on the drops and bend those elbows to get the torso more horizontal. TT angle has little to do with either scenario.

for reals?

More Boromir, one does not simply memes

Finally I have made a positive contribution to this site.

Savor it.

:lol: Okaay!:crash:

The rule of thumb originated when just about all bikes had level top tubes. It's a decent starting position that is much more aerodynamic than sitting bolt upright, but not as tiring to the neck and hands as a more leaned-over position.

If for some silly reason we were going to go by the actual top tube angle, then I would argue for the inverse -- people on new carbon bikes typically want to be more aero, and folks still riding old steel bikes tend to be older and want to sit more upright. :lol:

Like most "rules of thumb," like "knee over pedal spindle" and "level saddle," this should be seen as a starting point to achieve best fit, not the end point. Your bike, and certainly your body are different from other peoples' bikes and bodies and may require deviation from these rules of thumb.

Until the road slopes up or down. But we're only talking about a difference of 5° or so, so it doesn't make much difference in sitting. Much more than that, I'm either too slow to care about aero or coasting down. :o

Gotcha. Thanks all.

I'm going to print this and hang it on my wall.


-Tim-

The more upright you sit the more pressure you put on your lower spine and sitbones.

I've got a bad feeling about this.