merlinextraligh

I think that oversimplifies it, because you do have the aero component that doesn't change. Thus the difference is less on shallower climbs, its also less with higher watts.

For example at 3% grade with a rider putting out 350 watts, 6 pounds is going to make a smaller percentage difference, than it will with a 10% grade, with 175 watts.

Example 1 its 2 seconds per mile; Example 2 it's 32 seconds per mile.

So rider strength, and steepness of the terrain definitely affects the answer.

Drew Eckhardt 

As a 150 pound rider that will make you about 3% faster up the steepest hills (165.5/171 pounds) which is two minutes off a one-hour hill climb.

wphamilton

Just specify going up a hill that's too steep to climb fast. That might be 5% for the 175 watt guy, 10% for the 350 watt guy, but both of them are getting the same percentage gain.

Both guys are also getting the same gain in power saved when they go up at the same speed. Regardless of how powerful they are. It's not oversimplifying it so much as clarifying the situation.

FLvector

Some on this forum are simply obsessed with making their bike as light as possible, with little focus on their power and performance. Seems odd to me, but I guess it makes them happy. Different strokes.

Bunyanderman

Have you tried doing the calculations with pen and paper? I tried to do them with only google's calculator so there might be one error throwing it all off. But the results I got still made logical sense, so I would believe they are accurate.

Bunyanderman

I think that it is a coincidence that the calculations and weight drop both came out to be a 3% difference. If I have more energy later, or if others care I can try and calculate the time differences on different grades.

wphamilton

No coincidence. power is mgh/t, ie, proportional to mass.

* ignoring aerodynamic drag as merlinextralight pointed out, and a tiny impact on rolling resistance

merlinextraligh

you're taking aerodynamics out of the equation. Depending on grade and power, it makes a difference as shown in the illustrations I gave.

ColaJacket

Why not just upgrade to 105's? They're a lot less expensive than a Di2 set. And they'll be a lot better at shifting than the Sora's.

By the way, when you start the climb, I guess you're already shifting into the small ring on the FD. No bike shifts well from the big ring to the small ring when under climbing load.

And on the Sora's, when was the last time that you had the RD adjusted? It could be that adjusting the RD will do wonders for you.

GH

Bunyanderman

True, but Sin theta is not a linear function.

kbarch

Technically speaking, a figure is significant if it's within the range of what you can measure precisely.
Which brings me to this whole thing about whether one will notice the difference. I'm convinced that our bodies are capable of noticing very fine differences in anything that matters to us, and if it matters enough, the degree of difference we notice will exceed that suggested by instrumental measurement, e.g., a five second improvement over the course of two miles may not seem like much, but to someone attuned to the effects of weight, every bit of that may be felt, noticed and greatly appreciated at the time.

3/1081 on a little local hill by this old beanpole earlier today. In your face, normal-sized folks!

wphamilton

I thought it was understood, it's the maximum amount of gain, with respect to power. There are situations where it's zero, or when it's negative.

Overcoming gravity, aerodynamic drag, rolling resistance. Decreased weight affects the first in linear proportion. It doesn't affect the other two in any meaningful fashion. plug in any parameters to get the total - you'll get different total power or speed, and different ratios, but that's not really helpful for someone trying to understand the impact of +/- 6 pounds.

The first term is proportional to weight, simple, easily understood. In situations where it predominates and the other two terms are not important, such as climbing a steep hill*, it is a very simple situation that mainly depends on weight, and it's the simple ratio. It just needs to be understood that there are other factors involved in other situations.

*actually if you want to be precise about it, and I have a feeling that someone will, rolling resistance is not completely negligible for the weaker rider, going uphill or otherwise.

It's a ratio, it cancels out. Why does everyone want to complicate the simple concept (and correct physics)?

Sy Reene

Of course this won't mean you're any better of a cyclist, just that your lighter weight bicycle makes you think you are.

Carbon Unit

Robert Kahler, who runs the torture clinic, told me not to concern myself with a bike's weight until I had stripped all of the unnecessary fat from my body. So far I haven't lost all of my body fat so I haven't upgraded my bike.

Kahler Cycling Development & Torture Clinics

macca33

Just let the bloke buy a new rig!!!

I reckon it is a good buy and it WILL provide benefit to him, even if it is all psychological.

Although, in saying that, it will be a more dynamic handling bike and the pleasure of riding it will encourage more riding, which, in turn, will manifest into higher cyclist performance...

cheers

bruce19

Bike Weight - Smart Cycles - Norwalk, CT

redfooj

because Houston

f4rrest

I have both of those bikes. Started with an Allez triple with Sora, then upgraded to Ultegra 6600 road double ($200), which helped shifting noticeably. Also upgraded wheels to Easton 90 SLX ($500), which made the bike feel like a totally different bike, since the original Alex wheels weighed over 2100 grams. Was doing 150 to 200 miles/week on this bike.

Then I bought the SuperSix Evo with Ultegra Di2 last year, and it's about 4 lb lighter than the upgraded Allez with the pedals and such attached. I enjoy it even more than the Allez and still ride similar mileage, but the difference in speed is not noticeable. The shifting is beautiful, especially on the chainring going uphill. I can hang with the same fast groups on either bike and have beat some PRs / KOMs on the newer bike while there are others that I set on the Allez and haven't beaten.

For reference, 320 watt FTP 185lb.

If I were 21, I'd spend a few hundred upgrading the Allez, race it, and put the extra in savings for when it's crashed.

Jarrett2