less weight equals more acceleration?

[BLOFLY 636]

has anybody noticed the advertisements claiming that the fancy carbon fibre wheels can reduce lap times by as much as 7 seconds on a stock Honda Fireblade? This has got me thinking lately and I am curious if weight is really worth SOOO much as it appears to be one of the most controversial topics among the major sportsbike producers. Has anybody noticed the difference between riding a bike with an almost empty tank and a full tank of fuel? what about Dieting? is losing weight really worth the extra acceleration? for example I see many different Quarter Mile tests run between the sports bikes in America Australia and The U.K. with some differencs as much as 0.75 of a second which is quite alot when it comes down to the crunch of winning and losing is the topic that a lighter rider can run a quicker time really all so true? what about a test of a small rider of Rossi's build against a more heavy rider, on the same bike running the same ways in gear changing and throttle control? I am on a diet now just to make myself more manouverable for my first trackday coming up on the 30th of October I live in Australia you see so we don't get so many trackdays as you guys so I want it to be as good as I can make it I wonder what the difference would be in Quarter Mile times if we were to run 3 times normally and then wear a backpack with 15kg in it? interesting to see the real world reults of power to weight?
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Those bloody footpegs......they ought to do away with em!

[Frost]

7 seconds on a stock fireblade on a single lap. thats possible, if the track were the full nurburgring

I would typically say every extra kg would cost you about 1/10th of a second around an average track. rip everything you can off a bike, and replace it with an ultra expensive lightweigh version and you might save 2 seconds. however this will cost many many tens of tousands.

Going ona diet before a track day is a bit pointless as track knowlege and expirence will matter for ALOT more.

Weight only becomes an issue when that 1% extra performance is worth spending thousands on.

Enjoy your track day

[BLOFLY 636]

Yeah my main reason for dieting is so I can move around a bit more on my bike.....I need all the help I can get to try and reach the tarmac with my nervous knees and if dieting can help then thats a step in the right direction for me I am 77kg now and just want to get to 72kg by the end of the month wish me luck I'm gonna need it
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Those bloody footpegs......they ought to do away with em!

[G]

You may get less trackdays, but you can do them all year round .
(Though the times I've been to Australia it always seemed cold as we'd come from Papua new Guinea .)

Wheels are about the best place you can save weight. 7 secs does seem a massive amount though. Lighter wheels means the suspension works better because they are 'unsprung' weight; they are the bits that move up and down with the surface when the suspension tried to keep the bike relatively at the same attitude.
They also allow quicker turning in when lighter because there is less centrifugal forces.

Unfortunatelt it's much cheaper to replace your footpegs with some shiny alloy ones that replaces your wheels with carbon ones .


As for drag racing, on powerfull bikes I would have though a heavier rider might be better; to hold the front down at the start where the main differences in time happen I believe.

[Ninja]

kinell - and I thought I had some work to do at 117kgs! Then again I am 6' 2" - but even although... 18st down to a more realistic 14st would see a marked difference in acceleration for me
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James
4 wheels transport the Body ... 2 wheels transport the SOUL

[BLOFLY 636]

I have also read that for every 1kg of unsprung weight it is directly proportionate to 2.5kg of sprung weight so by fitting carbon fibre wheels that weigh 7.7 kg lighter than alloy wheels to a bike that weighs 161kg it would feel like your riding a bike weighing 138.9 kg but in reality it would only weigh 153.3kg thats an interesting result!! but I think at a third of the price of the bike the carbon fibre wheels will stay on the shelf
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Those bloody footpegs......they ought to do away with em!

[Jammy-G]

I think you should just start practicing the track, get to know it like the route to work, tat will give you the extra advantage, not the weight IMO !
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RooRoo: just like the time i stuck my finger up my arse with no lube at all and she didnt talk to me for hours

[mchaggis]

[Demonic69]

Being a hefty fecker deffo slows me down on the drag strip. I've got a Fireblade, Stoo's got a YZF750 and Ste had a ZX6R and we were all running similar times, times which I should have been able to beat no problem, but my bike had to carry around a fair bit more weight.
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Back on a Blade. Just feels so right.

[mchaggis]

I think we had this discussion before, and the upshot was that weight isn't the be all and end all. There are multiple other factors mainly to do with aerodynamics. If you wear super slippery leathers, you'll be faster; if you present a smaller frontal area, you'll be faster; if you have an aerodynamic hump, you possibly might be faster too. Fit a hump on the back seat cover, and maybe that'll improve it too. What you want to do is to get the best of all worlds, and losing weight is the first and probably least expensive of them.

[Mr C]

aerodynamics and weight doesn't really make a difference over the quarter

power and technique are the most meaningful factors, with the emphasis firmly on technique - when it comes to top speed racing thebn aeros definitely play a much larger part

but to really make a meaningful comparison like Demonic is then you have to put the same rider on different bikes and vice versa

a good rider can be as much as a second or even two faster than a novice on the same bike which pretty much destroys the weight myth

also, the limiting factor is not F=ma but grip and wheelies as someone has said so indeed heavier can be better and you will often see drag bikes with dumbells through the front axle and swingarms filled with lead

another important factor is the position of the c of g which dictates wheelspin, wheelie or straightforward acceleration - again largely down to techniqure but can be seriously affected by bike build




for proof that larger riders can still be bloody quick go google Chris Hannam aka "Cannon"
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187.3bhp = 201mph

[ZRX61]

7lb = 1hp, do the math

[Born2bVile]

Power to weight ratio.

Increase the power, or reduce the weight, it'll go faster.

Chops first appeared in the USA. The American riders were proud of riding American made machines, but were pissed off by being left standing by Triumphs and Nortons.

There was little they could do to increase the power (unless they had serious money), but with Harleys being massively overdressed, they could reduce the weight.

For example, the front mudguard was shifted to the back. All non-vital items were junked. The bike became the barest of essentials needed to make it go.

Later on, chrome and flame-jobs took over, but..........

Cheers,

Byrnie.
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NABD Treasurer
National Association for Bikers with a Disability
Reg Charity No. 1040907

[Mr C]

no, not exactly

power to weight ratio is only the simplest factor, there are many others to consider when things start to get extreme

when power starts to overwhelm grip is the beginning of the problem, then you can get more acceleration by INCREASING weight

it's all a compromise and not as simple as just saying "power to weight ratio" it may work for aeroplanes but it doesn't work for bikes

powerful but light bikes don't necessarily make for good acceleration, they spin up and wheelie too easily

whereas powerful and heavy bikes tend to be more stable under extreme acceleration

and then there's aerodynamics and that little thing that makes all the difference

SKILL
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187.3bhp = 201mph