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Compression Braking
Posted: Tue Oct 30, 2007 8:11 pm
by Longcat
From what I gather, compression braking is simply downshifting through all the gears so that it slows the engine while applying the brakes. I know that if you're just downshifting and not going to be coming to a complete stop anytime soon you close the throttle, pull clutch in completely, downshift, release clutch and then throttle up in a fluid motion. I've got no problem with this.
My question is when you're coming to a complete stop, can you just close the throttle, pull in clutch, downshift, and release clutch, and keep downshifting while the throttle is closed, or do you have to give it a little gas after each shift? I would think you need a little gas to complete the shift but I have no real idea.
Also when you're in 2nd gear coming to a complete stop and you downshift to 1st, do you need to release the clutch in 1st gear even though you're going to have it held in for the duration of the stop? It would seem somewhat redundant to hold in the clutch, shift from 2nd to 1st, then release clutch only to pull it in all the way again for the stop. I don't know what that would do to the bike mechanically though.
Posted: Tue Oct 30, 2007 8:42 pm
by Shorts
Re: Compression Braking
Posted: Wed Oct 31, 2007 5:12 am
by jonnythan
Longcat wrote:From what I gather, compression braking is simply downshifting through all the gears so that it slows the engine while applying the brakes. I know that if you're just downshifting and not going to be coming to a complete stop anytime soon you close the throttle, pull clutch in completely, downshift, release clutch and then throttle up in a fluid motion. I've got no problem with this.
My question is when you're coming to a complete stop, can you just close the throttle, pull in clutch, downshift, and release clutch, and keep downshifting while the throttle is closed, or do you have to give it a little gas after each shift? I would think you need a little gas to complete the shift but I have no real idea.
Also when you're in 2nd gear coming to a complete stop and you downshift to 1st, do you need to release the clutch in 1st gear even though you're going to have it held in for the duration of the stop? It would seem somewhat redundant to hold in the clutch, shift from 2nd to 1st, then release clutch only to pull it in all the way again for the stop. I don't know what that would do to the bike mechanically though.
Downshifting and releasing the clutch without blipping the throttle puts a little bit more wear on the clutch plates than really necessary. I don't think it's a big deal, and I blip the throttle just to smooth out the shifts, but I usually only downshift through no more 2 gears before just pulling the clutch and braking (ie, riding in 5th, downshift to 4th, downshift to 3rd, clutch and brake).
Posted: Wed Oct 31, 2007 6:07 am
by Sev
It won't affect clutch plate wear.
What it will do is have a large difference between engine speed and tire speed. If you don't have a slipper clutch this can result in the rear wheel locking up, and a fun little skid. It's advisable to attempt to rev-match.
Personally given enough time I'll work my way down through the gears until I hit first. Otherwise it's full on emergency braking, or switching to braking as I realize engine braking isn't fast enough. There is not hard and fast rule as to what to do or when.
Re: Compression Braking
Posted: Wed Oct 31, 2007 6:17 am
by Nibblet99
Longcat wrote:From what I gather, compression braking is simply downshifting through all the gears so that it slows the engine while applying the brakes. I know that if you're just downshifting and not going to be coming to a complete stop anytime soon you close the throttle, pull clutch in completely, downshift, release clutch and then throttle up in a fluid motion. I've got no problem with this.
Sounds about right, but the wording makes it sound like you almost always have the clutch pulled in... the clearer version is let off the throttle, but don't pull the clutch, so you utilise the engines braking effect. Before the revs drop too low though to make the engine stall, you have to pull the clutch and drop a gear or 3, to then let the clutch out and continue the effect.
Longcat wrote:My question is when you're coming to a complete stop, can you just close the throttle, pull in clutch, downshift, and release clutch, and keep downshifting while the throttle is closed, or do you have to give it a little gas after each shift? I would think you need a little gas to complete the shift but I have no real idea.
You don't have to give it some gas, but most advise to, as it just makes things a lot smoother when easing the clutch out, if the engine and gearbox are running at a similar speed when letting out the clutch. Any wear from not blipping the throttle is likely to be minimal, most motorcycle clutches are "wet" (meaning they have oil running between the plates)
Longcat wrote:Also when you're in 2nd gear coming to a complete stop and you downshift to 1st, do you need to release the clutch in 1st gear even though you're going to have it held in for the duration of the stop? It would seem somewhat redundant to hold in the clutch, shift from 2nd to 1st, then release clutch only to pull it in all the way again for the stop. I don't know what that would do to the bike mechanically though.
Yep just keep the clutch pulled in and change as many gears as you like, the gear box doesn't care whether you pause to let the clutch out for a sec between gears or not.