Lightweight Cassettes - do they make a difference?

[Bigbananabike]

My Singlespeed has heavier wheels than my other bikes but it only has one sprocket on the freehub body. It maybe my imagination but the wheels fee faster. Its not that I go faster - its a one speed after all.

So, it got me thinking. Could a lightweight or super lightweight cassette make much difference to rotational mass speed?
It should but then it shouldn't make much because its in near the axle.

I'd like to know if its worth me replacing my perfectly good 105 series cassette for races this coming season with something that'll cost me two days wages!
Is it worth having a closer ratio - say 12-21 instead of 12-26 to save some weight and hope to be able to grunt it out in the hills more?

Cheers, Paul

 

[Peter@vecchios]

My Singlespeed has heavier wheels than my other bikes but it only has one sprocket on the freehub body. It maybe my imagination but the wheels fee faster. Its not that I go faster - its a one speed after all.

So, it got me thinking. Could a lightweight or super lightweight cassette make much difference to rotational mass speed?
It should but then it shouldn't make much because its in near the axle.

I'd like to know if its worth me replacing my perfectly good 105 series cassette for races this coming season with something that'll cost me two days wages!
Is it worth having a closer ratio - say 12-21 instead of 12-26 to save some weight and hope to be able to grunt it out in the hills more?

Cheers, Paul

'Feel' is an amazing thing!! Rotational mass differences as it effects ride performance, even at the rim, are teeny tiny. Weight differences at the sprockets would reduce the mass of the rider and bike package but not by much..not enough to notice. Could be the stiffness of the wheels make them seem 'fast' but there is so many variables in bike to bike, it could be anything. Also, remember to make cogsets light they gotta be of an exotic material, aluminum or ti, both of which are expensive and don't wear as well as steel.

 

[Felt_Rider]

Just a note that the new SRAM Red cassette (166 grams - 11/26) is formed from a single piece of steel and weighs less than most cassettes, but for the cost is high at around $230 US.

As usual I think it will be less expensive for me to lose 5 pounds rather than a few grams on a bike component.

 

[Peter@vecchios]

Just a note that the new SRAM Red cassette (166 grams - 11/26) is formed from a single piece of steel and weighs less than most cassettes, but for the cost is high at around $230 US.

As usual I think it will be less expensive for me to lose 5 pounds rather than a few grams on a bike component.

"Reality, what a concept!!"
-anon

 

[Felt_Rider]

"Reality, what a concept!!"
-anon

Once in a LBS a clerk was trying to talk me into a couple of carbon bottle cages and he kept saying in a serious tone, "these are the fastest bottle cages." If it were not so humorous I would have felt really insulted as he must have expected my intellect to be really low.

 

[rudycyclist]

As far as getting a smaller cassette (11-23 compared to 12-26) will not do much at all. Basically you are reducing your cassette by several teeth. These teeth weigh close to nothing at all and will not make a noticeable difference. Only switch cassettes if you need a different combo for the race course.

 

[alienator]

No, it doesn't make any perceptible difference at all. The moment of inertia for a 900g 700x23 wheel/tire modeled as a hoop is 155 times greater than the moment of inertia of a 220g, 12-25 cassette modeled as a cylinder (a model that would estimate the cassettes moment of inertia to be higher than it actually is). That means at any given speed, the wheel will have 155 times more energy stored than the cassette. Given that differences in moments of inertia between wheels matters about diddly, cassette weight matters about 155 times less than diddly.

 

[rudycyclist]

No, it doesn't make any perceptible difference at all. The moment of inertia for a 900g 700x23 wheel/tire modeled as a hoop is 155 times greater than the moment of inertia of a 220g, 12-25 cassette modeled as a cylinder (a model that would estimate the cassettes moment of inertia to be higher than it actually is). That means at any given speed, the wheel will have 155 times more energy stored than the cassette. Given that differences in moments of inertia between wheels matters about diddly, cassette weight matters about 155 times less than diddly.

I wish I could talk like that ^^^

 

[Frank D.]

IMHO lightening up your wheels will make a noticable difference in how your bike feels and in how you ride. I changed cassettes from Veloce to Chorus both 13-25 and felt a difference in performance. I think if your wheels "feel" fast it helps give you a push to go faster.

 

[TheDarkLord]

IMHO lightening up your wheels will make a noticable difference in how your bike feels and in how you ride. I changed cassettes from Veloce to Chorus both 13-25 and felt a difference in performance. I think if your wheels "feel" fast it helps give you a push to go faster.

But this is probably more psychological than real. Alienator pointed out the physics behind this. There shouldn't be any appreciable difference. If you "felt" that your wheels were fast, maybe your performance difference was also a "feeling" rather than real? Or do you have real numbers to verify that your performance improved?

 

[Falcodore]

I always feel faster when my wallet has taken a hit!

 

[Peter@vecchios]

IMHO lightening up your wheels will make a noticable difference in how your bike feels and in how you ride. I changed cassettes from Veloce to Chorus both 13-25 and felt a difference in performance. I think if your wheels "feel" fast it helps give you a push to go faster.

30 gram, one ounce difference between the 2 12-25 cogsets(no 13-25..13-26 only). Not sure what you felt but..........

 

[alienator]

IMHO lightening up your wheels will make a noticable difference in how your bike feels and in how you ride. I changed cassettes from Veloce to Chorus both 13-25 and felt a difference in performance. I think if your wheels "feel" fast it helps give you a push to go faster.

Hmmm. I have one set of wheels that weighs 1380g. My other set is a high profile rimmed set that weighs 880g. Guess how different they feel on the bike? The answer is that they don't.

 

[Frank D.]

Hmmm. I have one set of wheels that weighs 1380g. My other set is a high profile rimmed set that weighs 880g. Guess how different they feel on the bike? The answer is that they don't.

Then whats the point of owning the "high profile" wheelset? And why would anyone even need a set of wheels as light weight as 1380g? Why would anyone ever need to Lighten Up !

 

[alienator]

Then whats the point of owning the "high profile" wheelset? And why would anyone even need a set of wheels as light weight as 1380g? Why would anyone ever need to Lighten Up !

Anyone that says they can feel the aerodynamic benefit of a high profile wheelset is a liar. The BEST aero wheels provide a 0.3-0.5 mph benefit at 25mph. Whether that's insignificant or not depends on the rider's needs. Light wheels are fine. Just don't expect to feel any benefit. The only time that anyone is likely to feel the difference in wheelset weights is when they are throwing the bike back and forth on a climb...maybe in a sprint. You won't, however, feel the difference in how a wheel accelerates. Do the math.

Just because the performance benefits are marginal, small, or possibly even non existent doesn't mean that someone shouldn't buy said bits. If it gets you excited about riding, they're good bits to buy. Also, if durability is still good, having a lighter, more aero wheelset doesn't hurt anything.

Besides, there are other reasons for buying lightweight stuff. It's an entertaining technical exercise to build a bike that is as light as possible while still having the durability and function that a given rider demands.

As for "needing to lighten up" their bike(s), no one "needs" to do that.

 

[TheDarkLord]

Then whats the point of owning the "high profile" wheelset? And why would anyone even need a set of wheels as light weight as 1380g? Why would anyone ever need to Lighten Up !

At the pro level, every small difference counts. However, the difference between light and "heavy" wheels is much smaller than you think. I suggest that you read the wikipedia entry on the subject: http://en.wikipedia.org/wiki/Bicycle_performance. Pay attention to the section marked "Advantages".

 

[Peter@vecchios]

Anyone that says they can feel the aerodynamic benefit of a high profile wheelset is a liar. The BEST aero wheels provide a 0.3-0.5 mph benefit at 25mph. Whether that's insignificant or not depends on the rider's needs. Light wheels are fine. Just don't expect to feel any benefit. The only time that anyone is likely to feel the difference in wheelset weights is when they are throwing the bike back and forth on a climb...maybe in a sprint. You won't, however, feel the difference in how a wheel accelerates. Do the math.

Just because the performance benefits are marginal, small, or possibly even non existent doesn't mean that someone shouldn't buy said bits. If it gets you excited about riding, they're good bits to buy. Also, if durability is still good, having a lighter, more aero wheelset doesn't hurt anything.

Besides, there are other reasons for buying lightweight stuff. It's an entertaining technical exercise to build a bike that is as light as possible while still having the durability and function that a given rider demands.

As for "needing to lighten up" their bike(s), no one "needs" to do that.

Well said and once more, "reality, what a concept".