Will a wheelset that is 300g lighter make a big difference in avg. mph. when climbing and/or in flats?

Question

I'm 5-8, 145lbs. and don't have much more body fat I can loose. I'm now starting to look at my ride to see if there is any weight I can loose there. My Specialized Roubaix weighs about 18.5lbs.

Answer 1

Yes, absolutely. a 300g weight savings (150g per wheel) is a similar jump in performance to saving almost 4000g (4kg!) of any other part of the bike.

However, don't mistake riding technique with performance of the bike. Many riders try to save-save-save on bike weight but have kinda lousy riding techniques, so I think that before you spend the extra bucks on wheels that you reassess your riding.

Answer 2

Firstly I'll do the flat bit

Typically a rider doing 32km/h (20 mph) will devote 80% of their output to overcoming wind resistance. The other 20% is devoted to rolling resistance.

The formula for wind resistance does not include weight.

The simplified formula for rolling resistance is
power = mass x gravity(9.81) x speed x Crr (coefficient of rolling resistance)

300 grams out of 163 lbs (love mixing metric and imperial) is not going to count for much at a constant speed.( About half a percent of 20%)

If you are climbing say a 10% grade. The same power will only give you a speed of about 10km/h wind resistance accounts for only 35% of your effort. The same formula for rolling resistance applies. But you also need to overcome gravity simplified formula


Power = mass x gravity x invtan of slope

If your technique is not smooth then will you are climbing you will be constantly accelerating and decelerating.
The formula Force = mass x acceleration comes into play.
During changes in speed rotating mass is roughly equivalent to 2 times.( it has to accelerate rotationally as well as laterally)

All in all 300 g is still a quite small percentage generally less than 2%. Even if it is only 0.5 % that means that you pick up half a yard every 100 yards. Even over a shortish 4000 yard climb that adds up.

When you take into account that most of the moves in cycling occur on the hills and even small differences can mean the difference between staying with the group or being "dropped off" 300gram lighter wheels start looking like a good investment.

In summary if your competing definitely, If your not competing the extra weight usually equates to more reliable service.

Answer 3

wheels are the best place to save weight, since the rims/spokes (outer part of the wheel) is what you have to move in order to accelerate the bike.

but who knows if this will make a difference for you, it's hard to say.

you can always get faster without losing weight from the bike/yourself.... at some point there are no more 'tricks' to do, you've just got to ride harder.

if you really want to shave pounds from the bike, get a carbon frame that will weigh in closer to 15 pounds when built - but then again, is it worth it, especially monetarily? are you being paid to race, or just out having fun?

Answer 4

300g means about 1/2lb weight loss at the wheels. thats a decent amount. saving weight on the wheels is better than most things because thats where all the momentum is. the lighter the rims, the less rolling resistance you have meaning you can accelerate and slow down faster. its kind of a physics thing, but think about it, is it easier to spin a heavy wheel or a light one?

Answer 5

It will make very little difference. There is a very cool web page for cycling geeks to find this kind of thing out. http://www.analyticcycling.com/

I plugged in your numbers to their wheel weight/climb calculator, and for a steady, 5KM climb, your 300g lighter wheelset nets you about 3s over your old wheelset if you're putting out a nice 275W.

If your riding by yourself (ie, not in a pack or paceline), the number one thing you can do - besides improving your 'engine' - is to improve your aerodynamics.

Answer 6

Anything lighter makes a difference. A BIG difference, no.