Kopsis

Light bikes feel fast, regardless of the measurable performance difference. And cycling is supposed to be a visceral experience -- how the bike feels MATTERS! A very light bike is a magical thing. It's ethereal -- a force without substance holding you aloft as you speed along the road. It can also be a source of frustration as it will make you acutely aware of your own limitations; taunting you with the knowledge that it could go much faster if only you were strong enough to keep up.

If you're not making money from racing, then performance can never really justify the added cost of a lighter bike. But as an investment that pays its dividends in fun, now that's worth something

therhodeo

First off congrats on the weight loss. I'm a formerly overweight person myself (235>158) and know the struggle. Just arguing the point that weight loss "always" means muscle loss. It doesn't and shouldn't if done correctly.

FlashBazbo

Good catch. (I didn't think of that . . . ) This time of year, the tires are the same (Gatorskins) except for size -- 28mm gravel bike, 25mm road bike. Plus, the road bike has aero wheels. Plus, the gravel bike has a cowchipper bar that has drops that flare out into the wind. And the gravel frameset isn't as aero -- disc brakes, plus its hindquarters are pretty massive, especially compared to the road bike.

Abe_Froman

Yea there's no way around it...4 lbs just doesnt mean much performance wise, unless you don't mind blowing $10,000 to pick up a second or 2 in a race.

I have noticed the difference from a feel standpoint though. I had a carbon fiber road bike last summer...and the feel difference between that which I'm sure was sub 20lb, and my 30+ lb touring bike was pretty massive. The one thing that stood out was how the carbon fiber bike would seem to buck underneath me when I hammered on the pedals forward and back ever so slightly because it had so little mass. Doesn't mean it really made it much faster...but it felt faster.

HTupolev

I wouldn't be surprised if posture and wheels are a majority of the difference you're seeing.

One interesting question would be whether the road bike is still considerably faster on flat rides.

FlashBazbo

I will disagree with you there. Of course, since I can't ride a mile in any direction from my home without hitting a 10% climb, I'm pretty sensitive to it. 4 pounds is huge on a climb. (And it costs a lot less than $10,000. I think my two bikes cost within a couple hundred dollars of each other.) If you don't believe me, put that 5 lb. dumbbell weight in your jersey pocket next time you go climb.

But aero? meh. Overrated.

andr0id

Well, you've pretty much hit the physics nail squarely on the head. The difference is NOT really between a 15lb bike and an 18lb bike, but between a 215lb rolling mass and a 218lb rolling mass.

218/215 is a 1.4% weight difference. Not that much for the average recreational rider.

What that means to me is that I get a reasonably light bike for MY weight (my road bike is about 19 lbs) and I don't spend another $5K to knock off that last 3 lbs.

FlashBazbo

Posture isn't an issue. Both bikes are set up to fit identically. Because of the comfort of the cowchipper drops, I probably spend more time in the drops on the gravel bike.

And wheels? Please. I bought the KoolAid, but I don't drink it. Most would say that the decreased rolling resistance of the 28mm tires on the gravel bike should give it a greater advantage than aero wheels could ever hope to provide.

noglider 

Let's start out with the assumption that on a given terrain, a heavy bike (however you define it) moves more slowly than a light bike, for a given amount of effort. That difference is pretty small. If you ride with someone whose pace is compatible with yours, you are likely to keep up with that person on a heavy bike as on a light bike.

But there is a difference for me. On my light bike, I go much faster, because it encourages me to pedal harder. My heavy bikes encourage me to take it easy, and they punish me if I pedal hard. This is why my travel times vary, not because efficiency is so different.

txags92

What most people miss is that most of the "light" bikes are also being made with stiffer frames than the heavier bikes. And most of them come with lighter wheels. Where you will feel the difference both in the frame and the wheels is when you change speeds. If you ride alone al the time, you won't notice much difference because you are rarely changing speeds very frequently in a way that you will notice if one is faster than the other. But if you go ride with a fast group, you will notice right away that the heavier mushier frame with heavier wheels is harder to accelerate quickly on and it is harder to react to changes in the speed of the group. Those extra efforts to keep up will build up over time and make you put out more effort riding the heavier bike.

Abe_Froman

Hey here is a question I don't have an answer for....

Is there a performance difference between wheels that is non weight/aero related? I know better rims will be stronger and less likely to go out of true....but has stiffness ever been shown to be faster?

cthenn

Does emperical data mean anything? If so, I'd say a lighter, stiffer bike really does matter, even if it's just a few lb's or less.

JBerman

Thank you! And fair enough. I prob "should" have had more protein intake, more time lifting weights, etc..

caloso

Wheels that rub the brakes when sprinting or cornering because they are laterally soft are definitely slower.

Seattle Forrest

Couple thoughts:

* I really don't like fenders. Won't have them on the bike when I can avoid it. Like you, I live in a dense city, which means slow going at times, congested traffic, etc. Toe overlap is only an issue at slow speeds. It gets worse with fenders. I don't like having a wet ass, but I also hate how they can get in the way.

* Get the tires first. Change one thing at a time, so you have a better idea how big a deal each thing is. I got new wheels recently, got new tires with them, the ride is excellent, but I don't know how much of that is the wheels and how much is the tires.

Abe_Froman

Heh, well a 15LB chromed steel wheel from 65 years ago shouldnt be doing that, much less yer fancy carbon we've gone to plaid speed wheels

Abe_Froman

Good suggestion...seems silly..but it never actually occured to me lol. I just got some nice, relatively fast 40mm touring tires on my bike, but I'd just get a set of Grand Prix 4000s's the day I bought a road bike anyway. Might as well get the tires first and play around with my current bike for a bit.

I will say though...I will miss the fenders. It just makes riding so much more enjoyable. On days I want to ride in, if the pavement is wet but it's not actually raining, I stay nice and bone dry on my commute. And as I have regular pedally pedals, not the clicky jobs, I just move my foot at slow speeds

Seattle Forrest

I disagree. Come out here, ride up Queen Anne hill, and you'll disagree too.

Whit51 

Abe, if you're looking for an older road bike but want to stay reasonably light, I recommend a Reynolds 853 LeMond or Jamis.

Seattle Forrest

Hey, on that note, buy them from the UK. You won't be charged any import fees, and shipping will be less than if they'd come from Ohio. But you'll pay half price for them.

Wiggle, Pro Bike Kit, Merlin, etc.

HTupolev

If aero wheels are properly configured with the right-width tire, at 20mph or so it's possible to be looking at something in the 5-10W ballpark compared with a non-aero configuration. Some won't consider that astronomical, but if we're trying to figure out what factors are contributing to a fraction of a mph difference in speed, it's relevant.

Modern carbon wheels are actually more prone to that sort of deflection. The stiffness of the rims makes it easier for torque from the contact patch to deflect the opposite side of the wheel near the brake pad. When that's combined with low-spoke-count carbon wheels that don't support good tension (some monocoque rims have this issue), things can get problematic.

It's generally assumed that vintage shallow wheels are flexier since the rims are such noodles, but in practice this isn't always how things pan out.

People don't miss it, it's just that most of us are at a loss to discern any actual performance difference relating to frame stiffness between road frames (outside of higher-order effects like shimmy characteristics). From where I'm standing, it seems like the reason manufacturers market it so hard is that it's an "intuitive" argument, it concerns something easily measured in the lab, it can be increased over time with changes in design and materials, and happens to be critical for fatigue-resistant design in a material that they're currently building many of their frames out of.

Might be fun to see how people react when poor performance is blamed on stiffness, though.
*Lose a sprint on Saturday group ride*
"Ah, dang... I'm just too good of a rider for this square taper spindle!"

Abe_Froman

Yeah, I got my Voyager Hypers for $17 a piece from Planet X

txags92

I noticed the difference right away when test riding several bikes. The two that stood out to me as the most responsive and easiest to accelerate just happened to be the two with the stiffest frames. I would be hard pressed to quantify a performance difference because that would mean riding alone to remove other variables...but riding alone would also remove the random accelerations, surges, and yo-yoing of a group, which is where I notice the difference between a stiffer frame and lighter wheels and a softer frame and heavier wheels.

JBerman

I'll have to look into those for future purchase. I'm usually a hardcore amazon user. I got mine for like $35 each which seemed decent.

Hermes1

Here is a good example of the difference