Current road bike/commuter is about 24lbs with 28mm tyres. I weigh 180 lbs. If I ride in moderately hilly terrain at an average speed of, say, 17 mph between 137 and 157 beat per minute.

If I buy a new road bike with 25mm tyres and weighing 17 lbs, how much faster could I expect my average speed to be.

probably not much, but it would feel faster 😀

You probably wouldn’t really notice an increase in speed, perhaps in comfort/quality of components IMO. I’ve lost 9 lbs this month from my belly and I haven’t noticed my average speed inscrease!

You might feel a marginal benefit over the fact that the new bike would likley have lighter wheels. You will feel greater benefit shedding rotational mass than non-rotational.

Harry.

You’d be a lot faster up the hills, I’m willing to wager.

It is about the bike a bit.

I changed from a 11kg cyclocross bike to a 7.5kg carbon bike, tyres on both were 25cc conti gatorskins. On a standard 60-80 mile hilly ride it increased my overall average by about 1.5mph. Big increase in pace uphill, unfortunately a decrease in pace downhill!

But most of all you get ‘new bike faster’ 🙂

The answer is 4.

Upon completion of ‘Project: May’ My bike wil have gone from 17.5lbs ish with 23s and std rims to around 15lbs with 25s and aero rims. I weigh 160lbs.

Might be a (little) bit faster, but will both look nicer and be nicer to ride.

Rule #4

If that’s true, how can I justify 4 figures on a new bike?

there’s been some actual science done on this.

Objective: To determine whether the author’s 20.9 lb (9.5 kg) carbon frame bicycle reduced commuting time compared with his 29.75 lb (13.5 kg) steel frame bicycle.

Design: Randomised trial.

Setting: Sheffield and Chesterfield, United Kingdom, between mid-January 2010 and mid-July 2010.

Participants: One consultant in anaesthesia and intensive care.

Main outcome: measure Total time to complete the 27 mile (43.5 kilometre) journey from Sheffield to Chesterfield Royal Hospital and back.

Results: The total distance travelled on the steel frame bicycle during the study period was 809 miles (1302 km) and on the carbon frame bicycle was 711 miles (1144 km). The difference in the mean journey time between the steel and carbon bicycles was 00:00:32 (hr:min:sec; 95% CI –00:03:34 to 00:02:30; P=0.72).

Conclusions: A lighter bicycle did not lead to a detectable difference in commuting time. Cyclists may find it more cost effective to reduce their own weight rather than to purchase a lighter bicycle.

source

if i read it right: the biggest factor was weather. Windy andor rainy days lead to slower times.

It’s the combined mass innit, Bike plus Skin bag on top of it:

180+24 = 204lbs
180+17 = 197lbs

The answer is 4.

…Close he’s reduce the all up weight by 3.43%… that’s something…

As with every thread about saving weight on bikes requires I now have to tell you to Have a pre-ride Poo/eat less/do some sit ups/take less water/MTFU/etc…

But don’t buy and use a light weight sexy bike now, the weather will bollox it by spring and you’ll be well annoyed, ride the “nag” till the weather improves…

If that’s true, how can I justify 4 figures on a new bike?

Because it’s shiny, obviously. 🙄 🙄 🙄

If that’s true, how can I justify 4 figures on a new bike?

Can you afford it? Do you want it? Problem solved.

On my regular hilly 25 mile loop I am about 1.5mph faster on average on carbon defy with 23c rubber over Croix de fer with 35mm

Actually, it’s the square root of 4 isn’t it! Ke = 1/2mv squared.

Once you get nearer 20mph aerodynamics is more useful than weight. Try getting into a bit lower position if you want to go quicker.

1.8kg of extra weight on bike = 1 minute 54 seconds up Alp D’huez at around 275 watts.

But stick the 1.8kg on the wheels and it adds on about 2 minutes 20.

science

or you could just make sure you pump up your tyres…

That said does anyone really buy a bike to go faster. My next purchase is soley based on vanity.

I’m with ahwiles on this. Can’t believe there’ll be much difference. I found the difference in speed on the road between my road bike (10 kg, 23 mm tyres at 90 psi) and my MTB (11 kg, 2″ knobblies – Specialized Fast Trak at 28 psi)is 3 km/h. That’s over quite a few long, steady, not-too-hilly rides with the same average heartrate. Probably 15 hrs on each bike. This doesn’t account for the automatic ‘new bike’ speed boost though.

I went out with a bunch of triathletes in their road bikes on my 26lb Fargo with 2.2 mountain bike tyres the other week end.

Generally I kept up fine surprisingly, but I did drop back a bit on a long gradual climb (2 to 3 miles) except for the 4 people who had punctures

Probably largely due to the tyres though – sure it would climb better on slicks. Generally I don’t notice much difference until speeds where a road bike gets into it’s stride (17 ish mpg upwards)

unfortunately a decrease in pace downhill!

I found that too.

Shorter rear end partly to blame I think, feels like it’s skipping about more at speed and my new frame is stiffer so I feel more of the bumps.

How much does the feel good factor effect how you feel about the ride though? Training more is the best way to go faster, but buying anew bike might well give you much greater enjoyment from your cycling.

it is generally accepted that downhill, a heavier vehicle will be faster than a lightweight vehicle (if cd is equal) so it stands to reason that uphill the opposite will be true, a lighter vehicle will be faster for a given power output.
on the flat, weight is less of a factor, compared to power output vs aero effiency.
so a lighter bike will be quicker uphill, may not be quite as fast downhill, and wont be any faster on the flat if it has the same riding position. (although it will accelerate more quickly)
however, TTIPWP.

Difference in speed = **** all, difference in feel/enjoyment = significant (and thus speed to a slight extent)

tonyg2003 – Member
Once you get nearer 20mph aerodynamics is more useful than weight. Try getting into a bit lower position if you want to go quicker.

No, remember the rules – n+1, buy an aero road bike. Foil, Venge, etc… There you go – shiny new bike and faster!

My winter bike weighs in around 23lb. When I switch to one of my summer bikes the av-mph will go up about 1.5-2mph for same route/effort.

According to Lance its not about the bike – he should know! 🙂

I can’t believe that no one has asked the key question here….

Will the new bike be red?

I’m generally 2-3mph faster on my good bike vs. the commuter. I think the difference comes from:

less weight
more aggressive geometry (lower/aero)
harder gears
just wanting to go fast on the good bike all the time!

The difference is most pronounced on long climbs or rolling fast roads, short steep stuff is less of an issue

I’d love to try an aero bike and see if that makes as much difference as is claimed

1.5-2mph average increase is quite a bit when you’re averaging 16-17mph.

You will be faster up hills for the same effort .I have dropped my weight by 15kg over the winter and riding up hills is now fun again.

As has been said, how fast you go doesn’t matter as much as how fast you feel (Although the former will obviously impact the latter).

You might only find that your average speed is 1-1.5 mph faster on the shiny bike but it’ll probably feel like more of a difference. Which is important. Very important.

I very unscientifically reckon my 28mm tyred hybrid is about 2mph slower than my racer. It also owns the hybrid downhill but I think that’s as much down to aero as anything else.

mooman – Member

My winter bike weighs in around 23lb. When I switch to one of my summer bikes the av-mph will go up about 1.5-2mph for same route/effort.

how is the ‘switching’ decision made?

a) random chance – flipping a coin before every ride regardless of weather/season.
b) weather/season related

if it’s ‘a’ – good stuff, your science is off to a good start.

if it’s ‘b’ – your data is invalid.

Buy some Veloflex Records, now they will make you faster.

Might get a lot of punctures though.

Definitely more to do with position. My TT bike is on average 2 – 2.5mph quicker than my road bike, and it’s old and about 3lbs heavier too.

1.8kg of extra weight on bike = 1 minute 54 seconds up Alp D’huez at around 275 watts.

But stick the 1.8kg on the wheels and it adds on about 2 minutes 20.

science

That’s not science. The figures don’t back up the the claim that weight in the wheels is more important that weight on the frame. The figures:

52:01 275W – 1.8kg added to tyres
51:34 277w – 1.8kg added to frame

So that’s 26 seconds slower or 0.84%.
But the average power was lower on that run by 2W or… 0.72%.

So basically they’re exactly the same, which is what the Physics tells you:

http://en.wikipedia.org/wiki/Bicycle_performance#Advantages_of_light_wheels

Buy a posh bike which you’d feel stupid riding if you were only fit enough to bimble on it and let your pride take over and get you fitter so you can ride it fast…
Or a bike so nice that you want to ride it all the time.

Several months later your new bike will be a lot faster than the old one 🙂

The lighter bike will allow you to ride faster, for longer, should you wish to push yourself. It’ll still hurt though. It’ll also accelerate faster and be nippier on the hills. As already mentioned above, if you really want to go faster the best upgrades are wheels and tyres, though really fast tyres = lots of punctures.

However, as also mentioned above, the best way to reduce weight is to lose weight yourself. of course, riding a nice fast bike will help in this respect. Particularly if it’s red 😉

ahwiles – Member

mooman – Member

My winter bike weighs in around 23lb. When I switch to one of my summer bikes the av-mph will go up about 1.5-2mph for same route/effort.

how is the ‘switching’ decision made?

a) random chance – flipping a coin before every ride regardless of weather/season.
b) weather/season related

if it’s ‘a’ – good stuff, your science is off to a good start.

if it’s ‘b’ – your data is invalid.

ummmm? same route and effort please you Mr Logic?

mooman – Member
ummmm? same route and effort please you Mr Logic?

If the conditions were the same, and your effort the same with a power meter, perhaps.