Blipping the throttle on downshifts?

[Badjelly]

It does, it's not just the crank that you're syncronising revs with re the back wheel, it's the complete drivetrain. The most relevant bit of which is the dogs on the side of the "target" gear which ideally need to be spinning at the same revs as the gates they're about to engage with.

The "CLUNK" you hear when you don't match revs is exactly that, the dogs taking a hammering when they engage. That, and the shifter drum, which is under far more load.

So, bearing in mind that the clutch is disengaged when you blip the throttle (n'est ce pas?) do you agree that clutch drag is required to communicate the "blip" to the drive train?

[Warr]

So, bearing in mind that the clutch is disengaged when you blip the throttle (n'est ce pas?) do you agree that clutch drag is required to communicate the "blip" to the drive train?

A disengaged clutch will still follow the input drive changing RPM when the cogs do disengage. Remember there is a neutral between every gear.
So it is definitely possible to make smooth changes with a bit of practice

[Ocean1]

So, bearing in mind that the clutch is disengaged when you blip the throttle (n'est ce pas?) do you agree that clutch drag is required to communicate the "blip" to the drive train?

Yes. I dont't know how a bike would behave if the clutch had zero drag, not aware of any clutch designs that would have none, be interesting...

[Badjelly]

Yes. I dont't know how a bike would behave if the clutch had zero drag, not aware of any clutch designs that would have none, be interesting...

I've found that car clutches have very little drag (with the exception of my current Mazda Familia, but my mechanic told me the clutch on that car was on its last legs five years ago). Once you've disengaged the clutch, revving the engine does not affect the gearbox at all, or such is my impression.

All the bikes I've ridden (all of them Japanese) have had perceptible clutch drag. Eg, they jolt forward slightly when you put them in gear. I'd assumed this was a result of the clutch running in an oil bath (ie a wet clutch). Ducatis have dry clutches, don't they? Do they have as much drag as Jap bikes?

[jrandom]

All the bikes I've ridden (all of them Japanese) have had perceptible clutch drag.

Yes; when I put Betty up on the centerstand with the gearbox in neutral, start the engine running, pull the clutch in and whack her into first while holding the clutch in, the rear wheel kicks around as the gear engages and spins down for a few seconds before coming to a stop again.

I'd love to hear about precisely how all of that works with a sequential gearbox and a clutch, and the relevant design considerations for a motorcycle's transmission.

[Ocean1]

I've found that car clutches have very little drag (with the exception of my current Mazda Familia, but my mechanic told me the clutch on that car was on its last legs five years ago). Once you've disengaged the clutch, revving the engine does not affect the gearbox at all, or such is my impression.

All the bikes I've ridden (all of them Japanese) have had perceptible clutch drag. Eg, they jolt forward slightly when you put them in gear. I'd assumed this was a result of the clutch running in an oil bath (ie a wet clutch). Ducatis have dry clutches, don't they? Do they have as much drag as Jap bikes?

Any clutch running in oil needs shitloads more surface area than a dry one. When engaged the spring pressure forces oil from between the faces, so while there's some lubrication going on the plates aren't actually floating on an oil film. When you disengage the clutch in neutral there's not much load forcing the inner and outer plates to part company, it's only when you kick it into gear that significant load forces them to "unstick".

If you think Japanese bike clutches are "sticky" you need to ride some of the older European stuff. You can pick it at the lights, the stiff kick off the mark with the left foot before selecting gear, the desperate fumbling for neutral before coming to a complete stop. Most Jap transmissions are pure mech-art by comparison, wonders of modern engineering.

As for dry clutches? Duno, never had one, must listen carefully to the next new Ducatti I encounter to see if the same solid clunk is there. Might have trouble hearing it over the rattle though...

[dipshit]

And for those that doesn't know what it is... this is what it sounds like...

[PrincessBandit]

Essential and necessary.

DB

I do it most of the time; always on the ginny, usually on the bandit.

[Motu]

1) Momentum. Change down but don't blip the throttle, let the clutch out and you'll feel "drag" on the bike while the engine spins up. Do this on a big engine, or an engine with high torque and it'll possibly cause a loss of traction on the back wheel due to so much load being placed on the back wheel by the engine (i.e. it wants to go from 3,000 rpm in the higher gear... to 5,000rpm in the lower gear, and if you just pop the clutch out it the rear wheel has to supply all that energy in the space of 1/10th of a second).

More the effect of flywheel weight than engine size....it's just a coincidence that bigger engines have more rotating mass.Try a big single....and then compare to an even bigger multi - the single has more flywheel effect and so has much more pronounced "Oh fuck,I got that wrong!'' Works in the opposite direction too - try thrashing an old Britsh single through the gears,say a B31....each up change gives you a huge kick in the back from the flywheel energy,it has more stored power than the engine is actually putting out.

[ManDownUnder]

More the effect of flywheel weight than engine size....

Worth knowing - cheers

[HenryDorsetCase]

do people who have slipper clutches need to do this? I know MotoGP people have slipper clutches AND their electronics either blip the throttle or up the idle speed so the rear wheel doesnt hop.

I do it because it sounds cool, and chicks dig it.

[madandy]

I do it out of simple mechanical sympathy. Trucks, tractors (with a double de-clutch), bikes, cars - all things with a gear box - even an auto trans if done right
With my open Yoshi it also sounds really cool.

[HornetBoy]

I blip the throttle cause that was how i was told to do it when i first started riding .

plus it sounds good

[rufusdion]

.............. and blipping just sounds cool

[onearmedbandit]

And this rider is blipping on the downshift with no clutch. And to think they said it couldn't be done...