Doublecheck my analytic cycling numbers....not making sense!

Hello,

Trying to decide weather to drop big coin on a light gravel rig for a race in August. The longest climb is about 21.7 miles at 4% and I weight 100kig with my current bike. It’s not light…I bet I could get 3kg…maybe 4kg…off of the weight.

OK so 4kg weight loss, 21.7 mile climb at 4%, let’s stay frontal area is the default 0.5m2 and air density is default 1.226 kg/m3. Let’s put rolling resistance at 0.01 (I’m guessing, it’s gravel of some type)

I’m figuring about 200 watts for this sucker.

Does this make sense so far? If so…are we really talking 1 minute slower for a ~2 1/2 hour climb? This doesn’t seem right but I’m having trouble making sense of this. Any comments you have would be most appreciated :slight_smile:

Joe

According to http://bikecalculator.com/, reducing weight by 3kg from 100kg to 97kg yields a time reduction from 146.5mins to 143mins, or about 3.5mins:

Original Weight

Reduced Weight

So a couple of minutes of time-savings seems reasonable to me but yeah not mind-blowing. Although in a race of that length even just 1 minute can affect your placement quite a lot. On the other hand, increasing your own fitness is always more cost-effective when you are smack in the middle of non-pro performance territory. Take a look at what happens when you increase your target power from 200W to 220W but keep the heavier bicycle:

Increased Power

Your time is reduced by 11.5 mins.

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Awesome, thanks for the info and the link. That calculator is easier for me to use and I can stay with more familiar units too.

Also…just playing around with it shows that increasing from 200 watts to 204 watts will make up for a 5# difference. A fast chain and/or fine tuning tire pressure or maybe even dialing in good chainline (2X in the low gear vs. 1X in low gear) could make that much of a difference.

I’m just surprised how small the difference is. I’m sticking with the heavy bike this time around. Thanks!!

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This is why lots of bike companies have been pushing aero and watts gains and not as much light weight as they did 10+ years ago. Weight just doesn’t make as big of a difference as people think. Especially when taken in the context of the bike/rider system.

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I went through this depressing exercise a couple of years ago. The benchmark climb on our Saturday group club ride is about 17 minutes long (for me) and 13 minutes for the skinny cat 1 record holder.

I plugged in all the numbers and wondered how much faster I’d be if I lost 20 pounds - a measly 10 seconds faster.

I actually have lost about 15 pounds since the and I’m a little faster.


One thing I’ve been noticing about gravel is that tire is everything. Among my bunch of riding buddies I have the lightest gravel bike - it’s a 2015 Spec S-Works Crux with light parts. It’s a full on cyclocross race bike.

Two of my buddies bought Salsa Cutthroats which are basically drop bar mountain bikes designed for the Tour Divide backpacking race. They are a few pounds heavier and come with 60mm tires.

On my Crux I’m maxed out with 40mm tires. When the trails get rocky, rough, or sandy my buddies simply leave me in the dust. They can just ride away from me. I get a small weight advantage on climbs which we have few of around here. Flat smooth trails are a neutral. So, when it’s most important their tires give them the biggest advantage.

So unless I move to the land of smooth, packed gravel trails my next gravel bike is going to be more along the lines of Cutthroat.

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To extend this point a little, aero frames don’t make much of a difference when taken in the context of bike/rider system. Maybe a couple of watts over a conventional frame.

Position on the bike is key, not the frame itself.

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True. But aero bikes usually come with more aero wheels, integrated cable routing, aero bars, etc. all of which can make a significant difference.

But this is changing now with the new emonda, (Rumored and Spotted) new tarmac, etc.

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Aero kit looks nice anyway!

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I hear you there, my bike is the surly cross check and it’ll fit these

https://www.renehersecycles.com/shop/components/tires/700c/700cx44-snoqualmie-pass/

For most gravel it’s fine but I agree, bigger is no penalty on smooth gravel and an asset on rougher stuff. I managed to get to the finish line in version 3 and 12 of this sucker on mtb tires and the schwalbe big one’s in the 2.3" size I ran in v12 rolled really fast all day (and night). Comfy too.

I’m curious about the aero gains gravel bikes. The 3T exploro racemax sounds really fast but I guess I’d need to see some data. I’m not entirely unfamiliar in trying to eek out aero gains, just not sure how to factor that in a long race with hills and gravel.

Totally 100% up for trying to streamline the floppy thing on top of the bike!!

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I think your biggest, easiest gains are positioning, aero bars, skin suit or non flappy, race fit kit. Fat aero frame - 5 watts?? Aero wheels on fat knobby - zero gains per Mavic. If you are doing a race where you can run smooth 32mm tires then you might get some gains from deep rims.

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