SoFloGirl68

Hi everyone, I ride a Kona Sutra steel touring bicycle. Recently, my friend gifted me his old carbon fiber Specialized Roubaix. I pick it up tomorrow. I've never owned a road bike but I'm pretty excited to get my hands on this bike. My bike is a tank and anytime I've lifted a carbon fiber bike, it feels like I could toss them across the parking lot. I'm just curious if you think I will be faster because it's so much lighter?

ofajen

Quicker to accelerate perhaps. In (relatively flat) south Florida, the weight difference won’t matter much on sustained speeds, but if you are more aero on the bike, that could make a considerable difference. Of if it has better tires.

Otto

79pmooney

Or if it fits you differently. Fit - not talked about a lot, but the difference between really good fit and mediocre fit could be real percentage points in power which translates to speed.

I did my first ride on the true race bike easy since it was mid-season and I was changing crank lengths. That "easy" matched my season's best. Two days later, two minutes came off that. On the same training wheels I'd been riding. All-up weight was maybe two pounds different. But the fit! I never knew my old fit was poor but I felt stronger, better, more both stretched out and relaxed on that race bike. Better in every way.

Not saying you are going to see this. But that fit bit is the intangible that makes a huge difference. Always keep your eyes open. When you find it, document - seat height above bottom bracket, distance back from the bottom bracket and the same for handlebar height and distance. These are "your" numbers. The good bikes for you won't make you jump through hoops to set up to get them.

terrymorse 

The two major items that affect speed: rolling resistance and frontal area.

Rolling resistance is all about the tires.

Frontal area is (almost) all about your position on the bike. If your chest is lower, you lave less resistance.

The weight of the bike is not very important, unless you're climbing.

TLit

For high performance there is a considerable difference as in this video: Cheap Bike Vs. Super Bike | What's The Difference? - Bing video

For most uses the high quality feel of a quality higher level bike is noticeable but not time-wise much especially on flat lands.

cxwrench

How much difference? Depends on who you believe.

indyfabz

Try it out and report back.

VegasJen

I don't know if I totally agree with this. Yes, acceleration or uphill, the CF bike will always be faster than a sled. But even on flat ground, speed is relative to distance. Sure, you can pedal your sled at an 18mph pace, but surely you're getting more fatigued faster than you would be on a lighter road bike. In that regard, when you factor in distances, I don't think there's really any comparison. Will it make a difference on a 4-5 mile ride? Maybe not. Will it make a difference on a 25-30 mile ride? Almost certainly.

All the other factors, especially fit, are most certainly still relevant. I just think too many people are dismissing the weight disadvantage too quickly.

ofajen

Sorry but mass does not appear in the steady state power equation for cycling except in the gravity term, which includes the incline as a factor, so it vanishes on flat ground. I suppose there is a very small second order effect on rolling resistance due to increased mass, but really that would be trivial in terms of total of bike and rider on what is generally not that big of a term.

Bear in mind. This is a south Florida answer where getting worn out by added weight on big climbs is not an issue.

Otto

Fredo76

Riding steadily against the wind the difference will be proportional to the difference in frontal area, which may not be much if you ride drops now, although a good fit may allow a lower position without discomfort. The other difference will be in acceleration, which can be more of a difference than people assume. On a ten mile ride with ten 90 degree turns, some with stop signs, I would expect you to average 1 to 2 kph faster. Now just watch someone try to model this!

Do let us know your impressions, thanks.

70sSanO

It should feel a bit racier. Little steeper head/seat angles and a shorter wheelbase. Probably feel more nimble.

With the right tires it should be faster through the corners; no one only rides in a straight line.

I find wheel/tire weight impacts acceleration more that static frame weight.

John

genejockey 

I have 10 bikes that I have ridden on the same route, at the same time of day, under similar weather conditions. The route is about 25 miles. The difference in time between the slowest and fastest bikes is about 3 minutes. The lightest bike is the fastest, but the heaviest bike ties for second fastest. So, what's the difference? I dunno. But it's pretty consistent.

Koyote

You seem to be assuming different power outputs (and hence “fatigue” levels) on the short versus long rides, which confuses the issue. Short ride or long, the physics suggest very little difference in speed between a lighter and heavier bike on flat terrain with the same power output. There are plenty of online calculators, built by people who understand the physics far better than us, which demonstrate this.

SoFloGirl68

Thank you everyone for the replies. The answer was as clear as mud. I guess I will ride the bicycle and report back what I think!

cyclezen

LOL! Let me help...
The answer is YES !
and if you're not Faster, then I suggest figurin out what went wrong...

sean.hwy

I do a 37 mile route a lot. It's bumpy with a lot of turns. There's only a few places that you can really settle down and just get in a tuck and put the power down for top speed.

aero bike (2019) system six) / carbon wheels / fast road tires 19mph
gravel bike ( several ) with same carbon wheels and tires 18 to 18.3 mph
gravel bike with 35mm ish gravel tires 17 to 17.5 ish
mnt bike ( 2022 blur ) full suspension 29 inch tire / 2.4 inches wide 15mph



At my power level / speed I found the aero bike and gravel bike to be close enough in speed with the same wheels & tires I sold my aero bike. Riding by myself the gravel bike felt every bit as fast. When checking against the clock or when riding with my road buddies there's a difference. A much stronger/faster person
that rides more like 25mph avg would notice a much bigger difference on the aero bike vs gravel bike.

jgwilliams

That's an interesting question. When I changed from a 20 year old steel bike to a new carbon fibre bike, I noticed a lot of improvements in a number of areas but I can't really say I was any faster. The overall size and fit between the bikes was very similar. Changing my 2009 Giant XTC mountain bike for a 2022 Sonder XT seems to have made a lot of difference. But then, the bikes are very different: 29" wheels vs 26", tubless vs tubed tyres, a large frame that fits me vs a medium frame that was a tad on the small side, and some really good air sprung forks vs a lower end coil sprung fork. It's been quite fun suddenly scoring a lot of PRs on Strava.

bikingnerdy

Steel bike versus carbon bike,If you can couple with some other carbon components or light aluminum parts,you will feel like flying when you riding compare to your old steel bike

livedarklions

"Steady state" being the key term. Every ride I have of any length has traffic, crossings, bad pavement areas and/or wind gusts.

Weight matters on acceleration as well as climbing, so if there's a lot of starting and stopping, or slowing and restoring speed, there could be a time/fatigue effect.

GhostRider62

Rolling resistance increases with weight as does Crr, a double whammy albeit a small one.

noimagination

Sorry, but the answer is "as clear as mud" because this is real life, and real life is complicated. The short answer to your question, "... if you think I will be faster because it's so much lighter," is: maybe, depending on the circumstances, but probably not much. The reasons why are complex, and the posters above have tried to explain to you some of those reasons.

I changed from a touring bike to a much lighter (weight difference of ~10 lb/4.5 kg) steel "racing" bike. The lighter bike definitely felt faster: it was easier to accelerate from a stop; it was a little faster on climbs (mainly noticeable in that I could climb at the same level of effort in a higher gear); it felt much lighter and more responsive when riding out of the saddle; it was easier to corner; etc. The actual difference in speed was difficult to quantify, because speed is dependent on so many other factors as well as the weight of the bike, some of those factors others above have mentioned, but also: weather, road conditions, traffic, traffic lights; how the engine (myself) was performing that day; etc.

For a professional rider, I'm sure the difference in speed would be meaningful. However, for someone like me who tootles along at maybe 18 mph/30 kph on the flat, the actual difference in speed is not meaningful. I enjoy riding the lighter bike and I do feel much faster, which to me is not unimportant - it definitely increases the "fun" factor of a ride. However, the absolute difference in speed over a 2 hr moderately hilly ride would be less than 0.5 mph/0.8 kph, in my experience.

Koyote

The most interesting aspect of this thread is in the different approaches to the question: some posters think in terms of personal experience, and some think in terms of actual science.

Retro Grouch 

However, every bike ride starts at 0 MPH so your initial perception of the lighter bike will always be that it's faster.

pdlamb

Right answer. (It depends also is correct.)

My light bike feels more responsive or twitchier when I move over to it. And yet, the fastest I've ridden was on the Fuji Touring; but that had something to do with the long downhill with new pavement, little wind, few curves, and no traffic. How's the pavement and stop signs where you'll be riding?

BTW, make sure you add the Roubaix to your bike list if you keep it!

livedarklions

Our motors vary so much individually that general principles of science really only get you so far in predicting how things are going to work out in the real world.