kappakall

1st I'm a noob to the site and a 10 month rider.

I currently have a 2013 Fuji Altamira 2.3 with Ultergra components.

Thinking about moving up to a 2015 Cannondale Supersix evo with sram red.

Based on my research this is what I've found are positives to new bike:
1. sram red is better that ultegra and lighter
2. the carbon used on the cannondale is better that the c5 carbon on the fuji
3. it appears that the cannondale is lighter
4. better wheels on cannondale

Here is what I don't know:
1. Will the 2 or 3lbs lighter increase my overall speed?
2. I've heard that the cannondale is stiffer, what does that really mean?
3. both bikes are race bikes I'm assuming.

Any help on the difference would be appreciated.

GamblerGORD53

Try the road forum. They all have silly fiber bikes.

indyfabz

No we don't.

Maelochs

As I believe was asked in the Road forum ... since you already have an awesome carbon-fiber-frame bike, why do you want another? If you have been riding for less than a year, it is almost certain you have not gotten everything out of that Fuji. However, if you have the cash, a new bike is always a thrill (I will get rid of the old one for you ... just ship it to me and I will take care of disposal ... I will even pay for shipping.)

However, as many of us can attest, getting a new bike expecting night/day performance gains will always lead to disappointment unless the old bike came from Wal-Mart. You probably won't notice any difference between the two, and probably won't be noticeably faster. In all likelihood, you will like both bikes and perform exactly the same on both--in which case why drop the money?

For the cost of the SuperSix Evo, you could hire a trainer, which would probably do ten times as much to increase your speed.

But, again, if you have the cash, why not? Just don't expect to feel like you have moved up to a new level , because the most important part of the bike--the rider--will not have changed.

Drew Eckhardt 

Yes. You'll be 1-2% faster up-hill. On level ground the weight change won't have a measurable effect. The big difference is SRAM vs Shimano - which shifting interface do you prefer? You may really like an extra cog or not care.

Your speed increase up steep hills is inversely proportional to total weight. For example, as a 135 pound climber dropping from a 18 to 15 pound bike will make you (135 + 18) / (135 + 15) = 1.02, up to 2% faster. That's 30 seconds per hour of climbing. As a 200 pound rider the change will only make you 1.4% faster.

3 pounds is 1.4kg. 20 miles/hour is 8.9 meters/second. 9.8 m/s^2 * 1.4kg * 8.9 m/s * .004 Crr = 0.49W out of 200+, so you're saving about 0.25% of your power on level ground. Most of that is overcoming aerodynamic drag proportional to the cube of speed so you could expect speed to increase with the cube root of 1.00250 = 1.0008 and 0.08%.

Phil_gretz

Better fit. Better aerodynamics. Better wheels. These may help you.

A new bike won't likely make much of a difference unless it accomplishes one of the above 3.

Save your money and ride more.

1983

Not me.

1983

Wind resistance increases relative to velocity squared, not cubed.

WR = 1/2(rho)v^2(CD)A

In your last calculation, you've already accounted for (g1.kg) by noting 3lbs in the opening. Ie weight is (mass)(gravity) so if you know the weight then no need to include that breakdown.

Drew Eckhardt 

The force is proportional to velocity squared. Power is force multiplied by distance divided by time. You're covering more distance in the same time so power is proportional to velocity cubed.

That's why it takes me about 700W to break 30 MPH on flat ground while 200W is enough to average 20 MPH. 30 MPH is 1.5X the speed, and 1.5^3 = 3.375 suggesting 675W.

Kilograms are mass not weight. You need to multiply by gravity to get weight and therefore force normal in newtons.

1 joule = 1 kg*m^2/s^2
1 watt = 1 joule/s or 1 kg*m^2/s^3

9.8 m/s^2 * 1.4 kg * 8.9m/s * .004 Crr (dimensionless) = 0.49 kg*m^2/s^3 = 0.49 W

fietsbob

Step 1 , find a Dealer for the brand you are interested in . then test ride the bike ..
Carbon fiber is a Lot of hand labor .. thats why so much is coming from places where the labor costs Less..

1983

You lost me with "aerodynamic drag" which I recognize as drag force or wind resistance given the context.

So then, you are doing this: [1/2rho(v^2)CD(A)]*[F(V)]

to get this: [1/2rho(CD)A]*F*v^3 using communicative property, right?



Right, which is what I said. You started by mentioning weight (3lb) then converted it to kg, then multiplied it by g, which nets you the weight which you started with. Why not just take the 3lbs directly into the equation?

slimyfrog

... or you could add/remove a water bottle and actually find out.

shelbyfv

OP's other thread on this https://www.bikeforums.net/road-cycli...need-help.html

habilis

I currently have three bikes. The most expensive (which is a reasonable road bike) is my least favorite. I acquired it used, and it didn't need any work at all. I prefer to ride the fixed gear bike that I built on an old frame for about $200. My current favorite, however, is a low-end MTB that someone left out for the trash. I put $50 worth of parts into it, plus a lot of adjustment. My point: you may get more out of a possession if you put something into it besides money.

BillyD

That one's not doing too good.

smarkinson

Don't get the Cannondale whatever you do.

In the other thread you mentioned one of the reasons for returning the Fuji was because of a noise in the bottom bracket. Well, Cannondale and their use of the pressfit BB30 bottom bracket is rather notorious for creaking bottom bracket noises. Seriously, google "bb30 bottom bracket creaking".

veganbikes

Not a huge fan of the crabons but I can give you my thoughts on SRAM after some test rides most significantly on a Moots Ti Frame (but also on a fuji cross 1.3). I dig what they do and their underdog nature (or at least more in the past) but their shifting is odd. I love the fact the brake lever is purely for braking but the double tap had me unsure if I had run through my cassette or not.
Sram Red is certainly light but honestly unless you are a racing or just have ridiculous money it isn't going to give you such a huge performance boost.

If you really want to spend your money wisely get a custom made frame which can come in just about any material though my top choice would be high quality steel followed by titanium. You can still get lightweight but with steel and Ti you get durability and if you go custom you can get a frame built for you and your specs.

If not the custom route, get a nice set of wheels for the Fuji. You can either get a really nice set built by someone like Bill Mould or Peter White (two long time wheel builders with lots of experience) using high quality components, or you can buy some premade wheels (some of which are handmade some aren't) from a company like Zipp or ENVE or DT Swiss.

A stiffer bike is generally going to help transfer more power to the pedals but also be a little harsher ride. The bottom bracket is generally an area you want some stiffness but maybe not throughout the entire bike unless of course you are racing.

RPK79

It's doing alright...