Will I notice .5kG off Wheels and Lightening a Madone

Jeff Jones

Haynes wrote:

On a 7km climb of 10-12% I was roughly 200m behind a chap weighing 7kg lighter than me + 1kg lighter bike. So the question is how much weight would i have to lose to claw back that 200m? (And yes im already cutting the calories and have lost over 2kgs so far)

http://www.kreuzotter.de/english/espeed.htm

Estimates that at 5'6 and 70kg, riding a 9.5kg bike up a 7km climb averaging 10% at 270W, it'll take you roughly 38'00. Knock 2kg off, and you'll be a minute quicker at that power output. That's about the same as 200m at 11.5km/h.

So you're already there :-)

andrewgturnbull

jjones wrote:

Of course. Aero + light is better than aero + heavy. Although I do remember the misguided theory that heavy discs were so good because once you got them up to speed they would just carry you along ...

Hi there.

Ondřej Sosenka may disagree with you!

Despite what his wheel sponsors say in their adverts he apparently used a spoked rear wheel which weighted a whopping 3.2kg when he broke Boardman's hour record.

For a reference see this link:

http://www.cyclingnews.com/news/?id=200 ... jul19news6

The editor of the article was a certain Jeff Jones...

Cheers, Andy

aracer

Depends how much you weigh now, but assuming all the work is being done against gravity and that you weigh 75kg, then (75+8.5) * 0.2 / 7 = 2.4kg. Or in other words 500g less would put you ~40m further up the road. In reality since you are also working against other forces, a bit more weight than that.

allaction

I'm sure the frame is perfectly fine. You could sell the frame on ebay for about £400 and put the money towards a De Rosa if thats your dream bike. Use the components you have and upgrade when the urge or finances allow. My father in law just got a 2006 Madone and he's in love, it's his dream bike. Follow your heart.

nce21

Of course if you are in a pack climbing a hill then the aero advantage won't be so big, more of you work will be against gravity, even on a long gradual hill.

Jeff Jones

andrewgturnbull wrote:

Ondřej Sosenka may disagree with you!

Despite what his wheel sponsors say in their adverts he apparently used a spoked rear wheel which weighted a whopping 3.2kg when he broke Boardman's hour record.

For a reference see this link:

http://www.cyclingnews.com/news/?id=200 ... jul19news6

The editor of the article was a certain Jeff Jones...

Don't believe anything that he writes. It's all rubbish :-)

From what I've read, the energy required to get the wheel up to speed in the beginning and to keep it going is always going to be greater than the benefit of the 'flywheel effect'. So Sosenka might have broken the record by even more with a light wheel!

aracer

As I keep trying to point out, Jeff, the energy required to keep it going is zero, no matter how heavy it is. Hence you are just left with the energy required to get it up to speed. Working on the same calculation as before, assuming 2.5kg extra at the rim (which we double), the extra KE at 30mph is: KE = 1/2 * (2.5*2) * 13.3^2 = 444J. Now the KE of the whole system assuming a 70kg rider, 10kg bike is KE = 1/2 * 80 * 13.3^2 = 14.2kJ. Therefore if it takes him ~30s to get up to speed without the heavy wheel it's only going to take him ~31s with it, so even in worst case scenario it only lost him ~13m.

That's of course if you ignore the benefits of keeping his speed more constant since you should in theory on a track go faster on the curves than on the straights (since on the curves for a given ground speed the speed of your body and hence the aero drag is less). The heavier wheel helps to decrease the variation in speed, and since aero drag power goes as the cube of the speed decreases the average power requirement for a given average speed. Given he has almost 400 curves in 49.7km on a 250m track, he only needs to gain 3cm on each one to make up for the loss at the start. I'd suggest the thinking was correct.

Jeff Jones

aracer wrote:

As I keep trying to point out, Jeff, the energy required to keep it going is zero, no matter how heavy it is. Hence you are just left with the energy required to get it up to speed. Working on the same calculation as before, assuming 2.5kg extra at the rim (which we double), the extra KE at 30mph is: KE = 1/2 * (2.5*2) * 13.3^2 = 444J. Now the KE of the whole system assuming a 70kg rider, 10kg bike is KE = 1/2 * 80 * 13.3^2 = 14.2kJ. Therefore if it takes him ~30s to get up to speed without the heavy wheel it's only going to take him ~31s with it, so even in worst case scenario it only lost him ~13m.

Ah, someone with equations to the rescue I didn't think the effect would be that great, either way.

That's of course if you ignore the benefits of keeping his speed more constant since you should in theory on a track go faster on the curves than on the straights (since on the curves for a given ground speed the speed of your body and hence the aero drag is less). The heavier wheel helps to decrease the variation in speed, and since aero drag power goes as the cube of the speed decreases the average power requirement for a given average speed. Given he has almost 400 curves in 49.7km on a 250m track, he only needs to gain 3cm on each one to make up for the loss at the start. I'd suggest the thinking was correct.

I hadn't considered the effect of a lower body speed in the curves... I'm just thinking there might be another offset because of the rotational inertia of the heavier wheels. Because the faster you go on the curves, the more you lean. And if you're leaning more then you have to overcome more of the wheels' rotational inertia.

This will do my head in.

Anonymous

Haynes wrote:

05pro wrote:

Just buy the De Rosa cos it's what you want. Once you've spent that sort of money you'll want to spend every waking minute riding it.

You get the bike of your dreams and you'll lose weight into the bargin.

If you're married and buy the De Rosa chances are the wife won't speak to you for weeks afterwards either (or she kicks you out meaning more time to ride)

You win on so many levels that the De Rosa looks like the only sensible option IMO

Of all the above arguments, this one appeals to me the most. Physics aside, aesthetically the madone which is the 05 model with the fin on the seat tube, coupled with the aero wheels just doesnt look like a svelte climber and a change of wheels wouldnt resolve that. I suppose because i'm only 5'6 climbing's my thing i now want a bike that reflects that.

On a 7km climb of 10-12% I was roughly 200m behind a chap weighing 7kg lighter than me + 1kg lighter bike. So the question is how much weight would i have to lose to claw back that 200m? (And yes im already cutting the calories and have lost over 2kgs so far)

Perhaps he was just fitter/stronger than you and he'd have beaten you whatever the weight differences.
I really think a lot of peoples priorities are somewhat misplaced.

Jeff Jones

andrewgturnbull wrote:

Ondřej Sosenka may disagree with you!

Despite what his wheel sponsors say in their adverts he apparently used a spoked rear wheel which weighted a whopping 3.2kg when he broke Boardman's hour record.

I've been doing some digging on this.

Apparently, although it was reported at the time he used a 3.2kg wheel for his hour record, several months later the story was changed to say that he only used that wheel in training and used a light wheel for the actual attempt.

Here's a pic (hard to tell, but the wheel doesn't look that heavy):



Whether this was reverse engineering to keep his wheel sponsors (Vuelta) happy for some reason, or whether it was the real story, I'm not sure.

Interestingly, Francesco Moser's 1984 hour record (51.151km) was done on an 11kg bike! Whereas Eddy Merckx's 1972 record (49.431km) was done on a 5.75kg bike. Funnily enough, that's below the current UCI limit, despite the UCI's insistence that this was the benchmark for the athlete's hour![/img]

aracer

jjones wrote:

Whereas Eddy Merckx's 1972 record (49.431km) was done on a 5.75kg bike. Funnily enough, that's below the current UCI limit, despite the UCI's insistence that this was the benchmark for the athlete's hour

Does 6.8 apply to track bikes?

John Stevenson

gkerr4 wrote:

so in summary then.......


if I had a budget, say of £600

Buy some high-quality coaching advice, and follow it.

John Stevenson

aracer wrote:

Does 6.8 apply to track bikes?

Yes.

Lack of brakes, gears etc means that it's not hard to build a sub-6.8kg bike for a small rider.

This leads to the insane situation where mechanics for diminutive female trackies end up dropping bits of chain down the seat tube to get the bike up to UCI weight.

<Insert usual rant about stupid UCI equipment rules here.>

You probably do want everything as light as you're allowed for an hour record attempt. If nothing else, heavier gear will increase the rolling friction of your tyres, which increases with the total weight of the system.

Down the Road

Take 500g of you. Will make you a much better climber than taking 500g off your wheels.

You'll need the Aero wheels for crits as they are a high speed race and that's why you win on Aero wheels.

Yes you can always lose more weight.

dennisn

How about something heavier to make things feel lighter. Maybe a set of barbells to
put across your shoulders and do deep knee bends. To me getting stronger is a
much better way to go faster. There is an old saying that you can't buy performance.
When you are in great shape and lean and mean, that's when the high end stuff may help.

Dennis Noward

aracer

John Stevenson wrote:

Lack of brakes, gears etc means that it's not hard to build a sub-6.8kg bike for a small rider.

It's not even that hard to build a normal size road bike <6.8kg. Applying that rule to a track bike with over 1kg less of bits needed is crazy!