Comment by bartread | Hacker News Reader

Comment by bartread | Hacker News Reader

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I ride bikes and from a practical standpoint, along with small size and manoeuvrability, the acceleration (a result of torque) is one of the most useful attributes. Much moreso than top speed, or even speeds significantly in excess of the posted limits.

Bikes don't tend to have high torque in general, but their light weight and gearing are designed to maximise what torque they do produce. This means there are quite a few that will do sub 3 seconds to 60, and sub 5 seconds is practically the norm.

What this means is that you can more easily get past, and through, traffic because you can safely take advantage of gaps that no car can. Also, that sense of having your arms ripped out of their sockets and hanging on for dear life is fun.

Still, there's something to be said for going really fast as well: the feeling of the world blurring past you, and the road or track flowing and snaking underneath you like mercury, is hard to beat (if sometimes a little terrifying).

Bikes like Harleys and BMW twins have plenty of torque, where bikes like Kawasaki Ninja's major on power (peak torque at high revs). Hence Harleys and BMW's are first off the line at the lights (no need to build revs) but the Ninja's will come steaming past seconds later.

There are some fun youtube videos demoing bike performance, e.g. Ninja H2's doing 0-250MPH in 26s [0], outdragging a Bugatti [1] and outpacing an F1 car and an F16 fighter at the same time.

[0] https://www.youtube.com/watch?v=6_n7ru1e-rg [1] https://www.youtube.com/watch?v=gi5_GQ78wM8 [2] https://www.youtube.com/watch?v=_ESq00zi7bU

You cannot compare just engine torque numbers, without adjusting for gear ratios, wheel size and sprockets.

As another commenter said, you rev a Ninja (just like a sports car) and launch it using the clutch.

I believe I did point out that on Ninja's (I have one) you need to build the revs; you can't just dump the clutch and go like you can on a BMW Boxer or a Harley (which I also have). Hence the Ninja is generally slowest away when the lights change (but is by far the quickest bike overall).

In fact bicycles are fastest off the line, since they produce max. torque at 0rpm (just keep weight on a pedal, release the brakes to go). But acceleration is modest, so motorbikes and cars will soon go past.

And of course electrically-driven vehicles are also capable of producing torque at 0rpm, hence their acceleration advantage.

> In fact bicycles are fastest off the line, since they produce max. torque at 0rpm (just keep weight on a pedal, release the brakes to go).

I doubt a bicycle would actually cross the starting line before a high end bike or car would surpass it. A 180lb rider would produce about 90lb of torque at most (assuming 6” crank) and that’s only for the instant that the crank is parallel with the ground.

A high end car would deliver significantly more than 90lb of torque instantaneously by dumping the clutch (or using launch control).

/me commutes by bicycle, 32km each way, in traffic light hell that is Tokyo.

I can get off the line faster then automobiles, they aren't racing / clutch dumping at the lights. Traffic is so heavy and with so many intersections, it's typically pointless for automobiles to race off the line anyways.

As I filter past daily the same Pagani and Bugatti and LFA and Tesla S and NSX. :D

Yes, but the car has to accelerate around 20 times the mass. Bugatti Veyron is listed as having the highest torque [0] at 1,106lb/ft but then it weighs over 4,000 lbs. Plus there'd a delay for the engine to rev up to peak torque before the launch (i.e. it wont produce 1,100ft-lbs at idle). Be interesting to test, but I'm not too practiced at racing Veyron's off the line on my bicycle.

Having said that, I am very used to riding bicycles and (large) motorbikes around town, and from waiting for lights to change if I'm on a bicycle I'm generally first away even when motorbike riders are getting competitive (never mind cars).

The advantage of the bicycle is generally only a few feet, of course.

[0] https://en.wikipedia.org/wiki/Bugatti_Veyron

Race cars don’t launch at idle. If you’re racing cars that are idling when the light turns green, then you aren’t racing their engines. You’re racing the driver’s disinterested reaction time.

The Veyron might weight 20x as much as you and your bike, but has over 300x the power output of the best sprinters in the world.

Given equal reaction time and equal interest in racing, I am doubtful your cycling advantage would last for more than inches against a high end sports car.

I quite agree, as I've pointed out elsewhere although the bicycle is fastest away it's a short-lived advantage (I'm not discussion racing starts, so it's assumed all vehicles are starting from idle and reacting to e.g. lights changing).

In a racing start, a well-driven torquey car (like the Veyron) will also launch faster than a motorbike - at least to start with. Once the speed increases, the acceleration drops and the motorbike can then use its superior power-to-weight ratio (which it can't fully use off the line). Eventually - once speeds are well into triple digits - a fast-enough car starts to catch up with the motorbike again (due to better aerodynamics).

You can produce torque in excess of your weight by using pedals that clip in and pedaling "circles" instead of "squares". When I was in good shape I figured I could produce torque much closer to my weight than half of it.

The average rider probably cannot produce more torque than their weight that way. A quick search indicates that professional cycling sprinters can generate slightly over 100 ft-lb of torque. The average rider won’t be producing anything close to that. (Hard to find anything definitive, though.)

If you aren’t standing up sprinting, you’re definitely not going to be getting anything close to your “body weight torque”.

Did you forget to figure in the crank length? 180lbs at 6" is 90 foot-lbs of torque.

Track cycling sprinters (myself included) can produce over 300 Nm of peak torque (more than many mid range cars)

I don’t think that’s accurate. But apparently the number is higher than I would have guessed, at around 230 for an elite cyclist.

https://www.researchgate.net/publication/7528120_Torque_and_...

I race an r6. There's no difference at all between a 600cc and a 1000cc bike off the line assuming a capable rider. When I launch, I can't keep the front wheel on the ground at full throttle, until about 70mph. Yes, if we are talking rolling on the throttle, not using any technique etc the big torquey twin will win Everytime.

Once you are in third though displacement takes the lead, and my smaller engine bike is at a disadvantage!

What they're saying is, you can rev up before dropping the clutch. That way you can get peak torque off the line.

Try a ZX14 before lumping all Ninjas together :)

Fair enough, though I tend to see the 'true' Ninja's as been the original GPz900, ZX9s, ZX10s and H2's.

Of course, for touring there's now the H2 SX Ninja(!)

Just rev your engine before releasing the clutch and you’ll have as much (wheel) torque as you need (within power limits of the engine and tires).

To a close approximation, it doesn't matter.

Rev engine, slip clutch to launch, versus slip clutch and immediately begin putting on the power.. no matter what, you need to engage the clutch and add throttle. The motor has so little mass it's not like it takes a long time to get it spinning before dumping the clutch on a low-torque motorcycle, and you can rev before the green.

And regardless of what you're riding, you'll be across the intersection before most cars have even begun moving.

Harleys aren't high-performance machines. I highly doubt any Harley will beat even a ZX-6 over any distance, modulo rider reactions.

Harley: lights change, dump clutch.

ZX9: lights change, rev engine, dump clutch.

None we're talking about general around-time riding, waiting for the lights to change here. The point is big torque means less delay between seeing the signals change and starting to move.

No disagreement that if the ZX9 is sitting on the line with the revs already in hand that it's going to be away first.

I assume you're talking about electric bikes or motorcycles? This confused me a lot for a while because I don't usually see those referred to as "bikes".

> This means there are quite a few that will do sub 3 seconds to 60, and sub 5 seconds is practically the norm.

This was the give-away - pretty sure very few humans can do 60 mph on a bicycle, unless they're drafting.

Motorcycles are referred as bikes in many countries. And bikes are called as cycles.

It’s actually pretty common in general. I refer to my motorcycle as a bike in the US.

Frankly my favorite is the European “moto”

> I don't usually see those referred to as "bikes".

‘Bike’ is short for bicycle. Motorcycles are also bicycles so they’re also bikes.

Hmm, I'm not a biker but I always assumed your legs determine statistics like acceleration on a bike. Learn something new everyday...

I suspect that bike was short for motorbike - not too many humans can do 0-60 in 3 seconds. ;)

Sure you can, just jump from a building or cliff at least 50 metres high.

Sounds right!!!!

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