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Wheel weight(31 posts)

Wheel weightTimePedal
Dec 9, 2003 4:06 PM
Will there be a noticeable difference in performance (going uphill) between the Reynolds Cirro wheelset and the Ksyrium SL's? Roughly a 400g difference.
Define significantKerry Irons
Dec 9, 2003 4:39 PM
A quick calculation shows that on a 6% grade with the power output needed to move a 150 lb (68 kg) rider at 20 mph (32 kph) on the flats, 400 gm weight savings/increase is good for 0.04 mph. That's 200 feet (65 meter) every hour of riding.
Your math is right but...torquecal
Dec 9, 2003 5:27 PM
What's significant to one person might not be to another. Personally, I'm slow enough, and weak enough, that I can't feel 0.04mph difference.
"Wheel weight"ngl
Dec 9, 2003 6:04 PM
Climb your favorite hill a few times alternating between carrying two full water bottles and carrying no water bottles (one pound static is worth about two pounds rotational). IMO this should give you a pretty good comparison of the difference in wheels. For me it is the difference between hanging with the slightly faster riders on a climb or being dropped ( all else being equal). Some may argue. I am very happy I made the change. I hope this helps.
"Wheel weight"altidude
Dec 9, 2003 7:08 PM
You have an overactive imagination like many in here. If a rider can drop you while you are on SL's he can certainly ride you off his wheel while you are on Cirros. If he can drop you with both your water bottles filled, he can drop you if you're riding without your bottles, bare naked with no helmet, and any other accessory weight you choose to shed.

My Cirros make me hang with the faster riders, LOL, sounds almost as dumbarse as Russw19 and his moronic theory about Wheels Manufacturing cassettes, shamino cog ramps and better shifting than Campy cassettes. This place is good for comedy though.
Why act so smug?The Human G-Nome
Dec 9, 2003 11:02 PM
Is it impossible for you to just disagree with someone and move on without throwing out insults in the process? If your theory is so golden, why would you even bother to ride "light" wheels. Why not buy 2500 grams wheels? Not EVERYTHING is a marketing gimmick. Sure, carbon tubulars are WAY overpriced, but light AND stiff wheels make more then a psychological advantage. No, wait, what am I thinking? I'm disagreeing with you which obviously makes me a moron. Nevermind, carry on.
hey!colker1
Dec 10, 2003 3:30 AM
i know russ... he knows bikes and raced bikes. what about you? why don't you give us some resumee of your brilliance? acid remarks mean nothing. what are your results? it's what you do, not what you talk that earns points...
if you back off this, then get away from here as well.
So what you're saying is...Dwayne Barry
Dec 10, 2003 3:51 AM
that there is never a situation in which an equipment advantage could allow a rider to keep up or even drop another rider? Even in a race, where there's been a selection for riders of somewhat similar ability?
I have acheived greatness... I have my own personal troll....russw19
Dec 10, 2003 7:25 AM
Have you riden ANY of the products you talk about???? Have you ever raced a race???? Have you ever won any of them??? Are you really just mad at me because I am faster than you will ever be? Or is it because my bike is nicer than yours? Or do you just have a small penis?

Tell me, what is the source of your pent up anger? At least you are mad at me now and not the guy who wanted to buy a pair of Zipps. God forbid somebody who makes more money than you actually spends it on something that makes him happy. It may not make him any faster, but it makes him happy.... something you obviously are not.

You should go out to a bar, get really drunk and leave with any girl willing to touch you....get some booty, be happy, and then come back here with a different attitude.... maybe, just maybe you would actually help someone for once instead of trying to be the biggest baddest troll on your block.

Russ
Can we focus on the word TROLL?Kerry Irons
Dec 10, 2003 5:49 PM
Do not reply to this guy. It only gives him the attention he so obviously craves. The only cure to trolls is to ignore them.
"Wheel weight"ngl
Dec 10, 2003 6:01 PM
I would really like to be a fly-on-the-wall when you enter your bike shop.
Very bad analogyjhr
Dec 10, 2003 6:05 AM
The question related to a 400g diffference between wheels. Your analogy used two full water bottles. I will assume you ment two small standard H2O bottles. They hold about 24 oz each. So in your example you are doing the hill with a difference of 48 oz of H2O each time. H20 weighs 8lbs per gallon (gallon = 128 oz). So 48 oz = .375 gall or 3lbs of H2O (or 1362 grams). Thats almost 3.5 times more than the original comparison.

Your assumption that "one pound static is worth two pounds rotational" (aside from being backwards) is also dead wrong. If you review Craig Willett's article on wheels at Bike.com you will see that aerodynamics are more important than weight by almost a factor of ten.

What no one has factored into the equation is aerodynamics. Kysriums are like great big fan blades (ie not very aero). I assume the Reynolds wheels are a deep section rim and therefore far more aero than the Mavic wheel. At 20mph the time savings should be in minutes over 40k.

jhr
Very bad analogyTimePedal
Dec 10, 2003 7:48 AM
Thanks for all the advice. I was comparing the ksyrium SL's vs. the Reynolds Cirro (climbing, non-deep dish) wheelset.
Very bad analogyngl
Dec 10, 2003 5:29 PM
My apology. One pound rotational roughly equals 2 pounds static.

I really don't know this new math, but, my large water bottle holds 26 oz and my small bottle holds 16 oz = 450 grams = 1 pound.

As I said earlier: 2 water bottles ( each with 14 oz in it ( roughly 400 grams) for a total of 800 grams static should roughly simulate 400 grams rotational.

I wish someone would just strap the damn things on their bike and find out the difference ( IF ANY).

I NEVER SAID THIS WOULD BE NIGHT AND DAY. I SAID THIS GIVES ME THOSE FEW SECONDS SAVED ON THE CLIMB TO HANG WITH THE GUYS THAT ARE A FEW SECONDS FASTER THAN ME GOING UP THAT HILL. I NEVER EVER SAID THIS WILL TURN ANY ONE INTO A SUPER HERO.
BUT THEN YOU ALREADY KNEW THIS.
Here's your answer...Dwayne Barry
Dec 11, 2003 6:46 AM
go to analyticcycling.com and figure it out for yourself, assuming similar drag for the two wheels you can plug the numbers in and find out what a 400g difference makes on a climb.
significance depends on terrain...C-40
Dec 11, 2003 7:06 AM
If you're only riding moderately rolling terrain, then the difference may be truly insignificant, since hills may only constitute 25% of your riding time. Anything gained on the uphill through weight reduction is also LOST on the downhill run. A fact that is generally overlooked. If the route you are riding is a loop that starts and ends at the same point, then all uphill gains are lost on the downhill and there is no net gain or loss.

The idea that rotating weight has twice the effect of dead weight is also a myth. It's only has some truth when the ride or race involves many large speed changes (like a criterium). A heavy wheel will require more power to accelerate to a higher speed. If speeds are relatively constant, the additional wheel weight will have little more impact than dead weight (body, frame or components).
Is that right?Dwayne Barry
Dec 11, 2003 10:44 AM
Assuming power is constant, seems like to me going slow uphill, weight would be more of a factor slowing you down than it would be in speeding you up going downhill when going fast and air resistance becomes the primary factor that is slowing you down?

So assume two riders with the exact same power output and even frontal area (although in reality a bigger guy would naturally create more drag) but one weighs 50 lbs more than the other, you're saying whatever time the 50 lbs heavier rider lost going up a climb he would regain going down the hill (assuming no corners or anything) and at the bottom the two riders would be together again? Even if it took 30 minutes to go 10K uphill (20 kph) and only 10 minutes to go the 10K back downhill (60 kph) for the smaller rider?
Is that right?asgelle
Dec 11, 2003 2:34 PM
Dwayne Barry wrote: " Assuming power is constant, seems like to me going slow uphill, weight would be more of a factor slowing you down than it would be in speeding you up going downhill when going fast and air resistance becomes the primary factor that is slowing you down?"

That is correct. To use your example take a 130 lb rider +25 lb bike&equipment on a 6% grade for 6 mi. At 250 W it takes 31 minutes to go up and 9 minutes to go back down for a 40 minute round trip. Under the same conditions a 180 lb rider with a 25 lb bike takes 39 minutes to go up and 8 minutes back down. Total time is 47 minutes, 7 minutes longer than the light rider.

This illustrates the effect of weight on time for a fixed power. As you say, in reality, the larger rider would most likely have greater frontal area. On the other hand the larger rider would also be expected to produce higher power at the same fitness level. Nevertheless, this calculation does show that the time lost due to more weight on the uphill is not regained on the downhill.
Is that right?russw19
Dec 11, 2003 11:20 PM
Maybe I am missing something, but you guys took one analogy and twisted it from what I can see. You took the thought that saving 400 grams going up a hill may save you a minute, but coming back down you may gain that minute back.... If I understood right, that was C40's thought. But then you guys took the example and twisted it to 50 pounds of rider difference to show a 7 minute difference. That would be true, but not what C40 was claiming.

But what is the round trip difference on the same hill for equal riders with equal frontal area (let's be simple.. same rider changing wheels) and see what the 400 gram difference makes. Also, consider the other side of the coin when you do this stuff... the K's have a metal braking surface... many light carbon wheels don't. That makes a HUGE difference on the other side of the mountain when you have to break for a corner. Look at the Tour a few years ago when Ullrich lost minutes going down the side of the mountain because he was on those ADA carbon wheels. Also, what about wheel stiffness when going downhill? I wouldn't set up for a 180 turn at 45 mph on a set of ultra light carbon wheels... and not even the pros tend to change wheels at the top of climbs.

All these analogies forget one factor... the real world. In the real world outside of a mountain top finish (doesn't happen here in US races) or an uphill time trial, you are going back down that hill you climbed. Ultralight wheels aren't the best for that. I would suggest that anyone who would ride these wheels in a race make sure you know your stopping distance long before you set up for the corners in that race...

I am not knocking nice light wheels, but they are limited in their real world applications and that must be considered by people who would buy them. Think about that before you decide to strap them on your bike. There are times I would trust them, and times that a 32 hole Open Pro is going on my bike.

Russ
Well, Russ...Dwayne Barry
Dec 12, 2003 5:02 AM
we were both addressing C-40's assertion that any time lost by a heavier rider going up hill will be regained going downhill assuming two equal riders that only differ in weight. Whether the difference in weight is 1 gram or 100 kg, it's either true or it's not, only the magnitude of the difference would change!

It's obvious the more I think about it that C-40's assertion can't be true even in a vacuum, afterall, as my example demonstrates the acceleration due to gravity would be resisting you going uphill for 30 minutes but only helping you going downhill for 10 minutes. In the real world, the acceleration due to gravity would affect your speed all the way up a hill because it is the primary factor in limiting your speed. But the accelerating effect going downhill would be balanced out by drag as you reached high speeds. Everyone knows this, if you stop pedaling going uphill you come to a stop, if you stop pedaling going downhill you don't accelerate to infinity, you reach a terminal speed that can be increased by adopting a more aero position.

You're point about the real world is valid but confuses the issue by introducing a ton of variables. The original question was about a 400 g difference, not necessarily the performance of 2 different wheels.

And here's an answer calculated from the analyticcyling site. For a 6%, 10K climb shaving 400g gets you to the top 8.75 seconds faster. I would assume slightly faster if you take that 400g off of the rotational weight of the wheel.

And as for the real world, losing 10 kg (which alot of cyclists could afford to do!) would get you to the top of that hill over 3 & 1/2 minutes faster.
Thanks Dwayne!russw19
Dec 12, 2003 5:50 AM
I think that what C40 was trying to get across is that the difference to the top of the hill only being 9 seconds if a rider changes to a 400 gram less wheelset, and everything else being equal, was that on the other side of the hill, that 9 seconds could maybe be made to more like 4. Which is really nothing once you add the other factors of braking performance of aluminium rims vs. carbon rims.

Other than that, I now see both sides of the issue, but I think it is now a case of glass half empty or half full. The people in favor of the lighter wheels will see the advantage going up, or the half full glass... but those who think the difference is minimal will see that as simply 9 seconds saved going up, who knows what they lose going down, but either way, it's not a significant advantage, so the glass is half empty.

The thing that was getting to me was that people were taking a 400 gram wheel difference and using a 50 pound rider difference to skew the numbers to their favor.

Thanks again for taking the time to do the calculations.

Russ
YES!, I was wrong...C-40
Dec 12, 2003 6:31 AM
I went to analytic cycling and ran a quick comparison that is truly relevant to the topic. If you plug in a 400 gram weight reduction for a 80Kg rider over a 300 meter hill, you save .27 seconds over the length of the hill and LOSE only .03 seconds on the downhill.

Similar results occur over longer distances, where the time gained is 8-10 times more than the losses on the downhill run. I was surprised that there is so little loss on the downhill.

If your typical training ride has a dozen of these hills, then you stand to gain a whopping 3 seconds on 1-2 hour ride. As I've said many times before, quit pedaling while you take a drink and all the gains from those high buck wheels (frame,saddle, bars, etc.) go down the drain. The mental part of riding fast is almost always more important than your equipment. The rider who has the most determination and concentration on his effort is most likely be the quickest.
YES!, I was wrong...ngl
Dec 12, 2003 10:08 AM
I only have a few minutes to be back, therefore, I only scanned the replies. Question, shouldn't you plug a static value of 800 grams into the model to represent 400 grams of wheel weight? ( a 2 to 1 ratio)

I am still trying to show the merits of light wheels. Lets say my freind and I can produce the same 200 watts power. I stated earlier I can beat my freind up that hill by 10 seconds. I now have that 10 seconds to ride slower and recover while he catches up. I now have the ability to produce that same 200 watts riding along the next flat section as compared to my freind still sucking wind ( for a while) and having to up his heart rate to produce his 200 watts. Do this over too many hills and he gets dropped and I don't.
Well...Dwayne Barry
Dec 12, 2003 10:57 AM
yes lighter wheels are "faster" but the diffence is relatively small. You'd be better off getting more aero wheels, getting into a good aero riding position, and finally losing bodyweight. In no particular order all three of those factors would help you drop your friend without getting any fitter to a greater extent than having a lighter set of wheels.
no....C-40
Dec 12, 2003 12:18 PM
Wheel weight savings are only an extra advantage when the riding involves repeated, large variation in speeds, where reaccelerating the lighter wheel takes less energy. A citerium race with sharp corners would be an example.

That's why less attention is paid to the weight of aero wheels used for time trialing. Most TT courses are pretty flat and the speeds are relatively constant, making the aero advantge more important than light weight.
more....C-40
Dec 12, 2003 1:12 PM
Go to www.analyticcycling.com and look at the comparison between a standard 32H wheel and a heavier tri-spoke aero wheel on a long climb.

They claim that the heavier, but more aero wheel is actually .5 second faster on a 3-mile climb. Only when the grade gets very steep does the aero wheel fall behind. Hard for me to believe at a speed of about 12mph.

If you put in all the same values, except the weight of the wheels, you get the same .27 seconds on a 300 meter hill. In reality though, the moment of interia of a lighter wheel is less. I plugged in some substantially reduced values for the moment of inertia of the a 400 gram lighter wheelset and got virtually the same result. So the bottom line is wheel weight reduction on a climb is no more important than body weight or any other form of weight reduction.
The masses will have a hard time believing this...russw19
Dec 12, 2003 3:11 PM
Because for the past 5 or 6 years we have heard that light weight "climbing wheels" were the wave of the future. Funny how marketing often gets in the way of the truth, huh?

Makes a good handbuilt wheel look better and better every day in my eyes.

Russ
The short answerKerry Irons
Dec 12, 2003 5:17 PM
It's fun to save weight, and if you're Roberto Heras & co. it's really important. For the rest of us "uhh, not so much." However, the benefits of aero wheels are pretty small too - 3 or so minutes in a 5 hour century. Again, that's huge if you're time trialling and lost in the noise otherwise. Then you have to put up with the cross wind sensitivity of truly aero wheels. Given this and the weight of most aero wheels and the associated negative feeling you get when you pick them up, it's no surprise to me that the standard, non-aero wheel is still the most popular choice.
Youve hit on it..koala
Dec 13, 2003 8:57 AM
I live where the wind howls all the time. Truly areo wheels on the front are a pain in the posterior and scary in tight traffic at speed. Im going light and shallow with my wheels cause I dont race anymore...
Can't resist an observation...peter1
Dec 14, 2003 7:44 PM
...at the end of this fray. Isn't the real benefit of lighter equipment is that it takes less work, in the physics sense, to get yo'self up the hill? That is, if you expend X amount of energy to ride a certain distance, you would expend X minus whatever with lighter gear, thus making you fresher at the end of the ride.

Seems like the downhill weight point is a red herring, especially since for many racers or those who ride in groups, the downhills are a good place to tuck into a draft and rest...sure, in a two-abreast drag race, the weight difference MIGHT be cancelled, but since we're talking about real-world conditions...

so think the answer to the original question is that the difference may not be noticeable on a given hill, but over a typical race or group ride, it will be.
Can't resist an observation...russw19
Dec 14, 2003 8:13 PM
I think the better observation is that it doesn't make any difference in your scenario. If you and I both do exactly the same amount of work to go up a hill in a race, and we both are the same body type and size riding identical equipment with the one exception of your wheels are 400 grams lighter than mine, here's what happens. You got to the top of the climb 4 or 5 seconds faster.... I draft someone on the downhill until we catch you. You have carbon rims and I have aluminium rims... I outbreak you by a much more significant factor than you outclimb me... I beat you down the hill with the other guys I am drafting with and you either can't keep up because you lose time on the corners, or you spend way more energy going down the hill than I do because you have to catch up what you lost in braking and cornering.

Going downhill is not a red herring. Paolo Salvodelli's Giro 2002 win is proof that going down the mountain is just as important as going up it. He won the Giro on the descents... on the ascents he put himself in a position to win, but he never was the first to crest a final climb... he put the time into his closest competitors on the descents.

Russ