From gravel to road

[vickster]

I’ve got my carbon out of the shed and having had interrupter brakes fitted, have ridden it a few times. It’s certainly quicker on its skinny 23mm tyres, and feels incredibly light compared to the rest of the stable of steel/Ti with rack/mudguards/discs.
It’s fun for lunchtime get away from desk rides on dry days, but as I often shop or meet friends for coffee during rides, the lack of lock makes it impractical.

 

[RichardB]

Lighter wheels/tyres do seem to translate to perceptibly snappier acceleration under effort however (though that too could be psychological... the placebo effect is a strong thing!).

Not at all, it's yer actual physics. Wheels and tyres are rotating mass, whereas a frame is static (relatively). It therefore takes proportionally more energy to get a wheel up to speed than it does a frame. Lighter wheels make a lot of difference. The old riders used to say an ounce off the wheels is worth a pound off the frame. It was explained to me like this: if you had to carry two kilo weights for a mile, would you rather have them together in a rucksack or one strapped to each foot?

 

[wafter]

Not at all, it's yer actual physics. Wheels and tyres are rotating mass, whereas a frame is static (relatively). It therefore takes proportionally more energy to get a wheel up to speed than it does a frame. Lighter wheels make a lot of difference. The old riders used to say an ounce off the wheels is worth a pound off the frame. It was explained to me like this: if you had to carry two kilo weights for a mile, would you rather have them together in a rucksack or one strapped to each foot?

I worked this out once and with the ballpark representative bike, wheel and rider masses I used it seemed that the enrgy required to accelerate the linear and rotating mass at the wheel was around double what it was to accelerate the linear-only mass of other components.. so the "ounce / pound" analogy is a gross exaggeration, if true in principal at least.

All that said when the mass savings to be had from lighter components are only a few percent of the total bike and rider combination they're usually marginal at best.

 

[Drago]

Not only more rotating mass accelerate, theres more to brake and a greater gyroscope effect, which greatly affects the feel of the whole plot.

 

[beastie]

Well I have a 9kg Road bike, and a c12kg steel gravel bike and I really notice the difference. It’s not the weight(although it’s just about noticeable) it’s the more aero position, the faster tyres, the sharper handling. Like for like rides it’s about 1.5mph quicker. Enough to feel a bit faster.

I ride the gravel bike about 80% of the time though, coz I love it....

 

[fossyant]

The difference is down to tyres and wheel weight, not the overall bike. If you stuck performance road tyres on the gravel bike, you'd notice an immediate difference. You can make any road bike feel like a slug with poor tyre choice.

 

[fossyant]

Well I have a 9kg Road bike, and a c12kg steel gravel bike and I really notice the difference. It’s not the weight(although it’s just about noticeable) it’s the more aero position, the faster tyres, the sharper handling. Like for like rides it’s about 1.5mph quicker. Enough to feel a bit faster.

I ride the gravel bike about 80% of the time though, coz I love it....

Where have you been buying your steel bikes. Both my 90's bikes are 9kg's ! OK gravel, so nearly 1kg per tyre

 

[beastie]

Where have you been buying your steel bikes. Both my 90's bikes are 9kg's ! OK gravel, so nearly 1kg per tyre

Genesis CDF with 38mm panaracer gravelkings and sks mudguards, with lights and pump takes it over the 12kg mark. It’s a heavy ass bike.

that’s without the guards...

 

[Ming the Merciless]

I love people calling 12kg heavy when they probably could lose more than 12kg in body weight :-)

 

[fossyant]

I love people calling 12kg heavy when they probably could lose more than 12kg in body weight :-)

My 15 kg full suspension MTB, with heavy dropper post and big tyres is terrible. I don't often throw it over fence. My wifes XC full suspension is super light, probably 12 kg

 

[BigMeatball]

I do have a dream brand in mind though: Wilier.

No particular reasons for it

Let's also add another dream bike to the list: I like A LOT the cannondale supersix evo ultegra disc. Slick looking bike

 

[CXRAndy]

So, less than 1 year ago I started cycling as part of my triathlon training. As a newbie and 100+kg rider, I was advised by pretty much everyone to opt for a gravel bike for all the obvious reasons (frame and wheels more sturdy, thick tires you can run at lower psi for a more comfortable ride, and so on). I bought a gravel bike and love it; have done almost 2000km on it already and despite being entry-level, I don't see myself selling it ever...call it sentimental value.

Despite saying I was a one bike type of person, I might be soon in a position where I have the space to put another bike and I'm considering buying a dedicated road bike. Something light, carbon frame, with aero frame and aero wheels, skinnier tires...a nice speed machine. Something I can slap a nice pair on tribars on and do my first few races.

My question is: what can I expect when I transition from a heavy 11kg gravel bike with 38mm tires to a lightweight carbon aero road bike with skinny tires?
What difference will I notice? What's the biggest changes I can expect?

Experience from anyone who'd done the same are much appreciated

The difference will be minimal. The biggest difference to speed will be riding with tribars. I used to use my cyclo-cross bike with TT bars, it was nearly as fast as my TT bike.

Just buy some nice aero wheels to give a boost in speed around 1mph ave

 

[cougie uk]

Interesting video on rotating mass on GCN the other week. Apparently it makes no difference. Once you're rolling you're good to go. If you stop started all the way then it would be different but it's the total weight of the bike that makes the difference.

I've passed plenty of super tribikes in races because the riders cany stay on the Tri bars.

I'd not bother with getting a superlight Tri bike. Just get one with Tri bars that you can ride all of the time.

From my tests when tribars came out - just slapping them on a road bike gives you an extra 1 or 2 mph for the same heart rate.

Aero frames are all very nice but by far the biggest drag on the bike is the rider on top.

 

[figbat]

Indeed - if just for a constant effort in a flat, straight line then once you have a mass up to speed you are then just working against aero and frictional losses. If you are climbing then total weight will be more important than rotational. However if you are accelerating and braking a lot, or if you are making significant steering inputs (eg technical off-road stuff), then rotational mass becomes more significant.