Shifting without using clutch?

[soto]

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How do you change your rpms without changing your speed and not using any clutch?

you're right, it's impossible. by backing off the throttle a bit you're just unloading the transmission so that there is enough slack for the shifter to move. if you back off too much then the engine braking loads the transmission again.

 

[cola_fiend2003]

you're right, it's impossible. by backing off the throttle a bit you're just unloading the transmission so that there is enough slack for the shifter to move. if you back off too much then the engine braking loads the transmission again.

Zactly. That's why the shifter has to be 'loaded'. Just enough pressure until the pedal can't move anymore and the gears will mesh as soon as the engine unloads.

 

[bear22099]

To figure out your rpm difference, I was referring to driving your bike normally, using the clutch to do a proper gear change and looking at your tach to see your rpm difference.

If you follow the order of how I explained it, it tells you to figure out your rpm difference, and then use that info to attempt clutchless upshifts.

You are not answering the question. The question is, how do you get the engine rpm to drop the 800rpm you gave in your example, without either slowing down, or using the clutch. Given that the engine is physically attached to the rear wheel when the clutch is engaged, you cannot slow the engine down 800 rpm and NOT slow the bike down. Now, since you have slowed the bike down, you have new numbers. The difference between the two gears is approx 13% (using your numbers), so that means if you have dropped the engine rpm by 800, the speed has to be reduced by approx 10km/h, now the rpm in 4th is about 6200, but the rpm in 5th is now about 5400, damn, still not matched by about 800 rpm (actually closer to 700rpm). Time to let off the throttle to get the engine to slow down another 800rpm, and circle continues.

You do not let off to match rpm, you let off enough to just unload the drivetrain. You do not completely release the throttle, you release enough to maintain your speed, without acelerating, or decelerating. Just unload the drivetrain. I may have understood what you meant, but obviously some don't.

 

[V-Tom]

You are not answering the question. The question is, how do you get the engine rpm to drop the 800rpm you gave in your example, without either slowing down, or using the clutch.
...

Chain slack, and the space between the dogs in the transmission take care of that.

Unlike a manual in a car that has Syncronizers to make the gears match speed before engaging (these are essentially little clutches), the gears in a bike tranny are constant mesh. They are always engaged. The shift mechanism within the transmission moves the gear sideways on the shaft so that the large, course "gears" (called "dogs") engage, and this transfers the power. The clutch does nothing (while moving) to ease the engagement of gears apart from removing drive load; it just takes drive load off the gears.

If you shift properly with a clutch (quickly back off throttle while pulling in the clutch lever, shifting and releasing the clutch while applying power), then the exact same motions - but not using the clutch - will engage the gears. The clutch is not really needed once you are moving. There is no reason to use the clutch if you shift perfectly. Of course, we rarely shift perfectly so using the clutch lessans potential damage by removing the drive load.

Downshifting is a little trickier as you need to give throttle but the exact same priciple applies.

..Tom

 

[jeero]

lol bear22099, you don't have to explain it to me. If you and I are having a misunderstanding in how we are explaining things, I can live with that.
Preload shifter, unload transmission by quickly letting go of the throttle a tiny bit, shifter slides in, open throttle again.
This all happens in way less than a second.

In the end I know how to do it quite well and I understand how it works (read post about how I have been power shifting nearly all my vehicles).

The rpm difference is more important when you are power shifting in a car/truck because the gear will only engage into the next shift when the engine is at the right rpm for the transmission to engage.
Still it's a concept that anyone who power shifts, or has interest in power shifting should understand.

 

[bear22099]

Chain slack, and the space between the dogs in the transmission take care of that.

Unlike a manual in a car that has Syncronizers to make the gears match speed before engaging (these are essentially little clutches), the gears in a bike tranny are constant mesh. They are always engaged. The shift mechanism within the transmission moves the gear sideways on the shaft so that the large, course "gears" (called "dogs") engage, and this transfers the power. The clutch does nothing (while moving) to ease the engagement of gears apart from removing drive load; it just takes drive load off the gears.

If you shift properly with a clutch (quickly back off throttle while pulling in the clutch lever, shifting and releasing the clutch while applying power), then the exact same motions - but not using the clutch - will engage the gears. The clutch is not really needed once you are moving. There is no reason to use the clutch if you shift perfectly. Of course, we rarely shift perfectly so using the clutch lessans potential damage by removing the drive load.

Downshifting is a little trickier as you need to give throttle but the exact same priciple applies.

..Tom

If all the gears are "engaged" that would be called "park". You cannot have more than one gear "engaged" at a time with a single clutch transmission, regardless of being a bike or a car. Just because the gears are in mesh does not mean that they are engaged. Car transmissions also have gears in mesh at all times, but never more than one engaged at a time.

A bike transmission is a sequential transmission, meaning you can only go up one gear or down one gear at a time, you cannot go from 6th to 2nd in one motion like you can in a car. This does not preclude the engine from not having to instantly change rpm on clutchless shifts. You cannot match rpm on shift with a sequential type transmission without using the clutch. The best you can accomplish is to unload the driveline when changing gears. You are not matching speeds, you are simply unloading the driveline. The engine will instantly change rpms on gear change when no clutch is used. If you "speed" shift a car, generally the driven wheels will be the part to cushion the rpm change by spinning. On a bike, that is not always a good thing to happen.
I think we are saying essentially the same thing in the end, except you are missing the part where something has to absorb the energy change. Something has to absorb the instant rpm change that the engine goes through. Engine rpm changes that fast take their toll on cam chains, crankshafts, and connecting rods. May be a small toll, but it has to create issues somewhere, eventually.
I am not saying don't do it, hell I do it, just saying that it does not come without a cost. And if you understand what is really happening, you may find that you cut back on the WOT clutchless gear changes.

 

[Baggsy]

All my friends with scooters use clutchless shifting all the time.
What are the benefits of clutchless shifting on bikes with a clutch?

 

[Zaneris]

All my friends with scooters use clutchless shifting all the time.
What are the benefits of clutchless shifting on bikes with a clutch?

Save a fraction of a second on your shift? 100% useless for street riding.

That being said, I find it smoother to shift without the clutch on more aggressive acceleration than slow acceleration

 

[V-Tom]

If all the gears are "engaged" that would be called "park". You cannot have more than one gear "engaged" at a time with a single clutch transmission, regardless of being a bike or a car. Just because the gears are in mesh does not mean that they are engaged. Car transmissions also have gears in mesh at all times, but never more than one engaged at a time.
...

We may very well be saying the same thing but from different points of view.

The gears are always meshed with their partner gears. This is always the case in a (traditional) bike transmission. Using the clutch does not allow you to match the speeds in the transmission as the gears are always connected to each other. It's why we don't have syncros in our gearboxes. The only thing the clutch does is unload the driveline from the engine, and the driveline lash and the lash built into the "dogs" allows the shifts to proceed. You can rev the engine all you want to match the engine speed with the needed speed of the transmission but there is no real effect on the gearbox from a shifting point of view. The dog gear and matching cutouts allow about a third of turn (iirc) in the transmission shafts and the time involved in that third of a turn is all there is to match speeds of the next higher or lower gear.

..Tom

 

[V-Tom]

If all the gears are "engaged" that would be called "park". You cannot have more than one gear "engaged" at a time with a single clutch transmission, regardless of being a bike or a car..
...

A little footnote: the transmissions in Formula One use essentially the same principal as a bike transmission. The latest versions (Seamless shift) *do* engage more than one gear at a time but when engaging the next higher gear the lower gear is kicked out of engagement the moment the upper gear starts turning.

..Tom

 

[El Zilcho]

Unlike a manual in a car that has Syncronizers to make the gears match speed before engaging (these are essentially little clutches), the gears in a bike tranny are constant mesh. They are always engaged.

Not "unlike". Gears in a car transmission are also always engaged.

 

[onecartel]

I only use the clutch to shift up when crawling around in traffic.

And all my downshifts are clutchless and rev-matched.

Learn to ride on a monkey bike, ride the same way forever.

 

[fastar1]

It puts additional, unnecessary stress on the engine and the drivetrain.

What exactly do you gain in terms of convenience?

Even if you do it wrong it doesn't add much stress the engine or drivetrain. Nothing they can't handle compare to say, a botched shift with clutch. And if you do it right it saves clutch wear.

http://www.sportrider.com/ride/146_0704_clutchless_upshifting/index.html

So you gain is a faster shift, less wear, less distraction, and greater satisfaction. It's particularly usefull when riding in a high performance mode.

 

[Baggsy]

Save a fraction of a second on your shift? 100% useless for street riding.

That being said, I find it smoother to shift without the clutch on more aggressive acceleration than slow acceleration

So then race bikes don't have clutches in order to save on weight?

 

[V-Tom]

Not "unlike". Gears in a car transmission are also always engaged.

Yes I mis-spoke and had a brain fart. Gear pairs are always engaged in either transmission.

..Tom

 

[knowledge]

done it in 2 of my 3 standard cars (for some reason my 5.0 was a picky ***** and wouldn't let me do it properly) and I use the same concept on my bike.

Slightly off topic...but do you have any pointers for doing it on cars? I've got it down pat on my bike, but it always grinds in my car; so I've been too scared to practice it. Or is it the car?(2000 civic si)

 

[bear22099]

Slightly off topic...but do you have any pointers for doing it on cars? I've got it down pat on my bike, but it always grinds in my car; so I've been too scared to practice it. Or is it the car?(2000 civic si)

As you pass through neutral, change engine rpm to match trans rpm. Start off by moving the shifter to neutral, and as you lean on the shifter towards the gear you want, slowly raise and lower the engine rpm, once they match it will fall into gear. With lots of practice you will be able to match rpm a lot faster. It is not that hard to do in a car.

 

[bear22099]

A little footnote: the transmissions in Formula One use essentially the same principal as a bike transmission. The latest versions (Seamless shift) *do* engage more than one gear at a time but when engaging the next higher gear the lower gear is kicked out of engagement the moment the upper gear starts turning.

..Tom

The new VFR also has that option, it is called a dual clutch transmission.

 

[V-Tom]

The new VFR also has that option, it is called a dual clutch transmission.

No, a dual clutch transmission a fundamentally different setup. Basically the transmission is two separate transmissions which each have their own clutch. One tranny is the odd gears, the other the even gears. When starting both first and second can be engaged in their respective transmissions but the clutch is only released for first gear. When time to shift the other clutch is released and the first clutch is disengaged. Then third is selected in the odd gear tranny (and so on.) The concept was first used by Porsche in Endurance racing about 25 years ago.

..Tom

 

[fastar1]

Slightly off topic...but do you have any pointers for doing it on cars? I've got it down pat on my bike, but it always grinds in my car; so I've been too scared to practice it. Or is it the car?(2000 civic si)

It's harder on cars because the synchros slow things down. You can't just slap it into each gear like on a bike, it takes timing and familiarity with the car and even then it'll probably grind a few times.

The advantage is that you have neutral between each gear so you can pause and play with the throttle mid-shift until you get the RPM you need. Works the same for downshifts too.

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