I completely agree with you that the geometry is definitely a big factor in this as I've ridden a Tricross and have similar feelings towards that bike. But weight is certainly a factor, particularly in the front triangle.

i routinely switch between my 17lb Roubaix and my 15.4lb Caad and usually ride the same 25-35 mile hilly course. The Cannondale definitely feels easier going up. overall it's just more fun to ride.
anyway, i'd think any difference of 5lbs or more would feel markedly different.

again...let me re-phrase what i was trying to say earlier....I wasn't trying to imply rotational weight savings as being better than static weight savings...I don't like playing that game. it seems like arguing politics or religion even though it's science.

What I was trying to say is that if you change a part and that part makes the bike ride nicer - it may inspire enough confidence - let's say - in your handling to allow you to rail through corners better, etc. Making you feel as though you have noticed the difference. If this part also happens to weigh less....well....so be it. Too many confuse weight savings with actual performance differences.

Personal experience: I swapped cross frames this fall. It and the change in components dropped a pound or two. I "noticed" it. At first it was a handling difference and I noticed it when jumping off and shouldering the bike. That said I have had my worst placings in cross this season than ever before.

Personal experience 2: I was talking with a past Masters National Champ the other day and was amazed when he was talking about nailing his rig on the UCI weight limit....ad I thought to myself "you'd still kick everyone's ass if your bike was 5 pounds heavier". then I remembered what he has helped remind me of - it's all about the mind. In his mind the light bike is what he "needs".

Therefore - if you are susceptible, mentally, to "noticing a difference" in a small "weight" change to a bike then I guess that small weight change helped your performance.

Lookit, I know it will disappoint most BFers but I recently upgraded my 1980's steel bike to a new custom Ti bike....went from approx 24 pounds to 18 pounds....and there really is not an appreciable difference. Subtle at best.

It really is all about the engine, unless maybe you are talking double-digit pounds.

Since when has a scientific fact ever stopped anyone from arguing.

P.S. will I notice move from 21 pounds to about 17 pounds or so.

22 ounces of water is 1 1/4 pounds. So two full bottles will be 2 1/2 pounds. Do you notice the difference? I do, when I lift the bike, but I can't really tell when climbing.

I dropped almost a pound with my two new wheels. I noticed a quicker response to sharp steering changes, probably due to a lower gyroscopic effect.

Sure, weight matters to a degree (especially to very small riders like myself) but I don't focus on it. I have bikes that range from 30 lbs to 18lbs. I've ridden them all on 400km days. At the end of such a day, I'm noticing which is more comfortable (soaks up the bumps and fits best).

what's 300 @ 147lbs come out to be?

Lighteous is Righteous.

Why would anyone ever listen to either of us. We're professional career cat 4's....

I've heard it's one pea.

Forget the math and the physics folks. The question was "when do you notice a difference?" The answer is when you write the check for the bike .

In all seriousness, the answer is immediately. I dropped from an 18 3/4lb bike to a 15 1/2lb bike utilizing the same wheelset and the same gear ratios. I'm no faster than I was on the heavier bike on the flats, but I definitiely notice the difference in the climbing. There's a noticeable difference in exertion as evident by my heart rate in comparison to my pace during various familiar climbs. I can maintain the same pace with a noticably lower heart rate than I have in the past. My fitness peaked at the end of the September, so I know it's not just the engine getting stronger.

50.62 minutes with a 20 lb bike

50.19 minutes with an 18.3 lb bike

I'm asking because I just bought carbon pedals that were on sale and new shoes that are literally less than half the weight of my old shoes. I'm also upgrading the wheels to Forte Titans (which I'm sure are a lot lighter than my stock Alex PRD-15 wheels)...but I want to get a Brooks saddle, which is pretty heavy. Not a whole lot else I can do with an entry level bike.

A flying frack? I thought those went extinct during the Pleistocene!

Love your math Grumpy, but what if the 150 pound rider simply cut out the beer and shed five pounds? (I figure that would probably be a lot cheaper.)

6', 158 at the time. I dropped two pounds off my bike (group set, saddle, bars, skewers) and didn't notice anything. 18.5 to 16.5 lbs. However, my time on the local benchmark climb (Old La Honda) went down just like the math would lead you to expect.

/shrug

And what if they cut out "the beer" AND two pounds off their bike. That's 7 lbs and they would be even faster up the climb, as long as they didn't compromise their power output.

If you're doing hill climb races, that could be the difference between 1st and 10th place.

edit; sorry. just noticed we are in the 41, not 33. Don't mind me.

I don't carry beer on time trials. well, mostly.

No argument there, but for MOST of us it is far easier (and much cheaper) to lose five pounds off your butt/gut than lose two pounds off your bike. And if you live in a place like southern Louisiana where topographic relief is largely lacking and "climbs" are essentially limited to the occasional overpass, then hill climb races are irrelevant.

Btw - why the photo of the guy with his hand on his ass?

I hear you. I couldn't figure out how to hang the ice chest off the back of my saddle without it rubbing my rear tire.

I dropped over a pound with my wheels and have noticed a difference on sprints but the bearings make more of a difference. I like lifting it more though.

There will never be a major difference in feel between two different weights of the same bike because of swapped components. Every bike will feel roughly the same as it always had, assuming you didn't change features that mess with how it feels. With that said, a 18 lb bike vs. another 18lb bike could feel entirely different, in either a good or bad way. The weight will make a difference time wise, but if you aren't thinking about it, you probably would not notice weight differences on the bike unless they are 15lb+.

do I notice? yes. I have 5 bikes and they range from 15.25 pounds to 21 pounds. I also notice the weight of waterbottles, but on a hot day, the water is needed. I also notice the weigh of a heavy seat and seatpost, but I gotta have a comfortable seat. but I don't use a saddlebag.

for 20 minutes of climbing, the extra weight is not a big deal. in fact thats my short training ride, I want my heavy bike. but on long rides with the guys, I gotta have the 15.25 pound bike.

Right. The effects are less than linear since aerodynamic drag scales with the square of velocity.

Consider a 200 pound rider with the frontal area of a 5'11" professional cyclist riding on the brake hoods up a 3% grade. Doing a little rounding converting to metric numbers we get to 90 kg, 12 MPH, 5.3 meters per second, .400 meters^2 area, and Cd .760 per Gibertini and Grassi.

On OK clinchers and an asphalt road he'll take about 190W to maintain that pace.

An extra .9Kg (2 pounds) will drop his speed to 5.27 meters/second which is just .6%.

Of course on steeper, slower climbs the results will be closer to linear and just 1% (36 seconds in an hour) can still be more than enough to win or loose.