Why does bike weight make sure a difference when climbing but your weight does not?
 

My late-great CAAD 12 came in at just under 18 pounds.
My Fuji touring bike at 26 pounds.

Now if my weight had been constant over the last few years there would be no question posted. But I've lost 30+ pounds and the Fuji was a pain in the ass to climb with when I was 205 pounds and now that I'm 175 its still a pain.

In contrast the CAAD 12 was always a joy to climb with regardless of weight.

In fact it was easier to climb with my CAAD 12 at 205 pounds than it is with my Fuji touring at 175 pounds!

So why is that that 8 pounds of bike mass makes such a difference?

The geometry and material probably plays a role. Slack geometry and springy steel frame on the Fuji vs race geometry and stiff aluminum with large geometry tubing and bottom bracket on the CAAD. So you are tansfering more power to wheels on the CAAD and losing more energy on the Fuji.

I'll say that the bike is still extra weight from your norm. Carrying extra exte.rnal weight feels different from it being just part of you, IMO.

A piece of this may well be the stiffness as other have said. One factor is that we learn to tailor our riding style to the bikes re ride regularly. 40 years ago no one climbed on bikes as stiff as todays and a lot of us climbed on biked far less stiff. We learned to climb within the constraints of those flexible bikes, mostly by learning to keep our efforts smooth. If you took a racer of my day and put him on your Fuji tourer, it would set him back, yes, but probably a lot less that it does you because the adjustment he would have to make would be a lot less.

The other piece, as other said, is bike fit. That's huge. Less than optimum fit could be costing you 5-10% of your top end. (8 pounds in 190 pounds is 4.2%. 190 pound = 18 (bike) + 2 (waterbottles, tools, stuff in pockets) + 5 (clothes and helmet) + 165 (you).

Ben

From my experience, body weight makes a big difference when climbing.

If you were a riding robot, the key things would be overall weight of vehicle + rider, assuming that gearing, geometry/ergonomics/frame/fork properties are reasonably similar.

However, very few of us are riding robots. We tend to react disproportionally to fairly small changes in bike behaviour and performance. The consequence of this is that we tend to ride harder on "nice" bikes.

Spoke to a guy who'd stuck a power meter on his beater/commuter bike.
He'd "always" claimed that the bike was undeniably slower than his nice bike. Then data showed that he consistently used less effort when he used that bike. If he tried riding by the numbers instead of by feel, the difference between beater/commuter-nice bike became a lot smaller.
Wheel weight/rotating mass is something I react strongly to. Climbing gives a far more notchy or jagged speed curve than flat riding. While one could argue that heavier wheels keeps more inertia etc, my legs certainly don't agree. A wheelset/bike that reacts faster to each power stroke simply feels like a better bike uphill. Easier to motivate yourself to keep cranking.

Wheels make little difference. Tires and tubes make a bigger difference than the wheel.

In terms of "feel" when climbing, especially standing, I'd assert that a heavy saddle makes a much bigger difference on feel than wheels versus a light saddle.

Your body weight alone doesn't tell you much. Likely more imagination than reality.

Body weight matters just as much as bike weight. Gravity doesn't care if the weight is on you or on your bike. You probably don't notice because your body weight isn't changing by 8 lbs from one day to the next.

Bicycle weight changes the center of gravity of the man / machine system and a lighter bike raises the center of gravity. 8 pounds is a lot of weight to lose off the bike and would definitely change its feel.

Are your times faster with the lighter bike up your favorite climb than would be predicted by calculation with the 8 pound weight reduction?

Climbing at 175 with a crappy bike you're probably still going faster than climbing with the light bike at 200+ pounds. It just feels like crap.

Ask Peter Sagan if being heavier than Julian Alaphilippe matters on climbs.

This ^^ As I look at how much weight I've gained recently (damn you tasty tasty beer) my ability to climb had been getting slower and slower. Plus it just feels 'bad' having to move the extra weight up the hill. Good incentive to get on the weight loss program over the winter.

I would agree that body weight makes a difference. I've been building muscle mass in the gym, and climbing at 195# is harder than 180#, gravity doesn't care if it's muscle, fat or bicycle.

I do much prefer climbing with a stiff bike.

It's probably the difference in bike design and geometry that makes one feel slower.

But another possibility is that when you lose weight you lose muscle and thus the gains from less weight are lost.

I agree, suspect geometry or other aspects that affect handling. And I think that it's possible that a particular person's technique could just be more suited to one type of weight distribution than to another.

For me, 5 pounds off my body makes more difference climbing than 5 pounds off the bike. But I barely move the bike when I'm out of the saddle and it stays in a pretty straight line, so maybe that's it.

It's important to understand Weber's Law when considering a perceived difference in weight.

Two years ago I was 185-190lb and had a 15lb carbon bike with 50/34 11-28. Right now I'm 165 and have an 18lb aluminum bike (basically same geometry as lighter bike) and 52/36 11-28 . I can do same climbs that I needed 34/28 gear combo with 36/25 now . I am much lighter as I mentioned but also spent about a year in gym doing a lot of squats and strength work over that time

This reminds me of a racer who was said to to take his bottle out from its cage and put it in his jersey pocket before a climb, so his bike was lighter.

Try climbing with a 30 pound backpack on. Then try it without. I think you'll notice a pretty significant difference.

10/10 extremely pro.

Well, not exactly. Although the difference might not show up over small increments, muscle still produces work. While additional fat is just dead weight.
Makes sense. We mostly just refer to weight, but its actually a ratio of strengh to weight that matters most.