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Author Topic: Rev-matched Downshifting: what's the point?  (Read 9565 times)
GodfatherofSoul
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« on: August 03, 2009, 02:14:27 PM »

Kinda off-topic, but I wasn't sure where to post this question.  I have a couple assumptions about manual transmissions and racing that could be wrong; you always break in a straight line and the brakes are better for slowing a bike than the transmission is.  Assuming these are true, why do racers always downshift and rev match to slow a bike?  Seems like the best way to stop the bike would be to pull in the clutch, tap down to the right gear, then let out the clutch while staying on the brakes.
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« Reply #1 on: August 03, 2009, 02:20:14 PM »

Seems like the best way to stop the bike would be to pull in the clutch, tap down to the right gear, then let out the clutch while staying on the brakes.

There's a large discrepancy in how much your bike slows down when you:

pull in the clutch and use the front brake
as opposed to
using engine braking and the front brake

The racers here will probably go into more detail, but I've used both types of braking on the street, and the real problem is that pulling in the clutch and using the front brake by itself introduces a lot of nose dive, and not only this, but letting out the clutch at high RPMs is a very rough experience and requires RPM-matching anyways. So pulling in the clutch and braking and then rev matching is adding a more complicated step to the braking procedure.

edit: I'm sorry, this topic is (properly) placed into the Racers part of the forum so what I do on the street really doesn't matter. But this topic is interesting so now I'm subscribed anyways!
« Last Edit: August 03, 2009, 02:23:23 PM by Pogo » Logged
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« Reply #2 on: August 03, 2009, 04:06:08 PM »

Kinda off-topic, but I wasn't sure where to post this question.  I have a couple assumptions about manual transmissions and racing that could be wrong; you always break in a straight line and the brakes are better for slowing a bike than the transmission is.  Assuming these are true, why do racers always downshift and rev match to slow a bike?  Seems like the best way to stop the bike would be to pull in the clutch, tap down to the right gear, then let out the clutch while staying on the brakes.

It is, and at least i do. Most of my braking is done before i turn into the corner. sometimes i fade the brakes while coming into the corner (called trail braking), but undoubtedly while i am braking i am pulling the clutch, tap down a gear, feather out, pull in, tap down, feather out, pull in, tap down, feather out until i get to the desired gear before i tip in. That way when i'm ready to get on the gas I'm in the best gear for acceleration and entry into the next corner. rev matching the process by whacking the throttle at each pull in makes the back of the bike much more settled and gives you a more planted rear tire. the engine breaking helps compress the rear shock just like applying the rear brake would.
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« Reply #3 on: August 03, 2009, 04:12:09 PM »

Ahh I mistook his statements. I thought he was saying "pull in clutch, use front brake, tap down several gears without engaging the clutch each gear, revmatch, then engage clutch."

I usually do it Knight's way on the street.

edit: Actually... I think he is suggesting tapping down through the gears...
« Last Edit: August 03, 2009, 04:14:00 PM by Pogo » Logged
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« Reply #4 on: August 03, 2009, 04:12:28 PM »

makes for smoother gear engagement.
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stormcat
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« Reply #5 on: August 03, 2009, 05:32:30 PM »

http://www.sportrider.com/ride/rss/146_0402_shift_blip_throttle/index.html

Although screw all that, I'll just get a slipper clutch on my next bike.  Cheesy
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« Reply #6 on: August 03, 2009, 05:34:16 PM »

some people like 'em, some people hate 'em. i have a slipper on my magna (factory mind you) and i could live without it.
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« Reply #7 on: August 03, 2009, 05:34:34 PM »

That excellent article reminds me that I still have to get rid of the play in my throttle.
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stormcat
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« Reply #8 on: August 03, 2009, 06:10:10 PM »

some people like 'em, some people hate 'em. i have a slipper on my magna (factory mind you) and i could live without it.

The b/f's bike came with it factory, too. Maybe one day I'll take it out for a spin and try it. He still throttle blips though. I'm mastering it slowly but surely.
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SCkid23
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« Reply #9 on: August 03, 2009, 09:17:54 PM »

I'm a throttle blipper kind of guy myself.  Never had a slipper clutch, but I seem to be alright with the rev-matching, so I'll stick with that until I get some cash and a super sport.   
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« Reply #10 on: August 03, 2009, 09:35:59 PM »

- Braking on both ends is better than just the front, as stated before.

- Gets you in the proper gear for the drive out of the corner by maintaining higher revs to stay up in the power band.

- You want the bike in gear and settled before the turn if possible. No letting out the clutch while laid over.

- Having the transmission engaged allows you to apply some throttle in the turn. This helps ground clearance a little.
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GodfatherofSoul
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« Reply #11 on: August 03, 2009, 11:11:29 PM »

http://www.sportrider.com/ride/rss/146_0402_shift_blip_throttle/index.html

Although screw all that, I'll just get a slipper clutch on my next bike.  Cheesy

OK, this link does answer my question.  Racers *are* relying on engine braking to slow the bike faster.  I guess my next question would then be doesn't engine braking tax the tranny?  I just learned to drive a stick a few months ago (save my MSF course last October) and I thought you weren't supposed to use the tranny.  So, is rev matching best reserved for the track or is the engine wear question debatable?
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« Reply #12 on: August 03, 2009, 11:18:09 PM »

It's not just engine braking. You have to take into consideration the balancing of momentum between the front and rear of the bike, as it effects handling tremendously on a motorcycle. On a car the braking forces of the wheels are adjusted to work with just pressing one pedal whereas we have to deal with each wheel independently.

I don't think racers really consider the life of their engines as the high RPMs and speeds involved kill the engine faster than any amount of engine braking Smiley
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« Reply #13 on: August 03, 2009, 11:42:37 PM »

i rely on the engine braking to load the rear suspension, not to slow the bike down. engine wear is just one of those things you deal with. does it tax the transmission? a little. but when you're racing, who cares what happens to the bike, first place will get you enough money to fix it.
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« Reply #14 on: August 04, 2009, 06:56:31 PM »

to start, i dont race, so what i say may not apply to racing situations, just my personal experience..

I ALWAYS rev-match when downshifting @ higher engine speeds. the reason for this is 1.) It reduces the amount of wear on the clutch (slipping not needed, dont confuse w/ slipper clutch..totally different.), 2.) actually helps the transmission @ shift time (reduces shock-loading).

I've always done this anytime its appropriate be it a car, or bike. Its a good skill to know for many reasons. For one, if your clutch cable should ever break (not that they ever do on an ex!  Roll Eyes ) this will better enable to you to get ur butt home, as you need to speed match every downshift, just to shift. also, IF for some reason you ever get caught in a corner that you didnt properly set-up for (ie going too fast), and need to slow down, you can't just pull the clutch, kick down, and let out. you will upset the balance of the bike, and likely wipe out. lastly, if you just click down, you can lock up the rear tire (this is where the slipper clutch can help). be it on a straight or in a corner, wet or dry road, you NEVER wanna lock the rear tire on the bike.

I would recommend learning how to do this, its a valuable skill. but thats just me. im no racer.
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« Reply #15 on: August 04, 2009, 09:32:09 PM »

If you don't "rev match" you run a good chance of breaking traction on the rear wheel, usually just before a corner.
Losing traction right before dropping it into a corner is bad... 'K?

Don't worry about the tranny. The tire will break traction long before you will break anything. Trannys are pretty strong, traction isn't.
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GodfatherofSoul
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« Reply #16 on: August 04, 2009, 10:49:37 PM »

If you don't "rev match" you run a good chance of breaking traction on the rear wheel, usually just before a corner.
Losing traction right before dropping it into a corner is bad... 'K?

Don't worry about the tranny. The tire will break traction long before you will break anything. Trannys are pretty strong, traction isn't.

lol you know what's funny about what you just posted is I had my first drop Friday night in a right hand turn onto gravel while I was coasting with the clutch pulled in.
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« Reply #17 on: August 05, 2009, 04:38:56 PM »

Bummer on the drop!

One thing (in your previous post) to understand: many motorcycles (including the 500) have a WET CLUTCH. This reduces the damage caused by heat and slipping. Most cars have a DRY CLUTCH and slipping is a VERY BAD THING!

While it is possible, even preferable, to blip the throttle on downshifts in a car to speed match the shift, many people aren't good at it and will greatly shorten the life of the clutch while stressing the transmission, particularly the synchronizers. So for cars, it is better advice not to performance downshift. However, if you are racing, or just really don't care if your clutch dies in a few thousand miles, go to it! It is fun and will build good skills for biking.  Grin
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« Reply #18 on: September 13, 2009, 09:42:30 PM »

Some pretty good comments here.  I'll try to add some:

1) John Hopkins has said publicly he doesn't use the rear brake.  Fine, he's not winning any world championships, but I think it's fair to say he can beat any person on this list.

2) If you're braking hard straight up and down into a corner that doesn't require trailbraking, it pretty much doesn't matter what you do with the clutch ... if you just dump it out in between snicks to the lower gears, the rear tire might dance around on you a bit if the braking zone is bumpy, but as soon as you start coming off the brake to feed throttle back in, the front will rise, and the back will settle down and track along behind you.

3) The EX's clutch was downsized, but it's not much different than when it served in the Ninja 900. (From which came the LTD454, and eventually the EX500.) I run stock plates/springs, use the clutch/engine for braking in T1, 3, 6, 9, and 11 at Loudon, and in 13 years of racing have only had to replace set of clutch plates.  (5 club championships, and three other 2nd/3rd's in other classes.)  Most of the time people complain about slippage, they've f'ed up their clutch lever adjustment. (My estimation? 95% or more of the time.)

4) Most of the tranny problems that we find nowadays are with the shift drum getting notches and not allowing consistent downshifts.  The presumption is that it comes from the shocks that happen when the bike crashes on the shifter side.  EX racers at Loudon have replaced 3 this year that I know of, (I was one of them) and have two more (on a spare 16" bike, and in an otherwise good engine) that need it.  It's long job, but not hard.  In all three cases, putting in a drum from a boat anchor motor has fixed the problem, right as rain.  We then throw the old shift drum away so it never gets used again.

5) Street bikes will have sophisticated engine management/traction control systems soon enough that will make it very difficult to break the tire loose ... liability suits are such that companies will have to put them on.

Side note that does NOT prove my case: Did you know that there's a system that can instantly stop a table saw blade the moment you nick it with a finger?  You could be pushing a piece of wood through, about to lose the ability to count on the decimal system, when "WHAM"  ... the saw would stop, and all you'd need was a band-aid for nicked skin.

It works by passing a little electric charge through the blade, and "sensing" the meat. (The test "finger" you see is always a hotdog.)  But when they were originally shown it, EVERY major saw manufacturer balked, because they would have had to revamp their entire product lines. (AND pay rights to the brilliant guy who came up with it.)

I first heard about this technology, oh, about 10 years ago.

B.J. "Kill all the lawyers" Worsham
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« Reply #19 on: September 28, 2009, 04:02:09 PM »

some people like 'em, some people hate 'em. i have a slipper on my magna (factory mind you) and i could live without it.

The b/f's bike came with it factory, too. Maybe one day I'll take it out for a spin and try it. He still throttle blips though. I'm mastering it slowly but surely.

I think it's a good habit for him to keep.  1, if the slipper doesn't slip as much as it's supposed to, he'll still be in good shape.  2, if he someoen else's bike and forgets... 3, most of the really fast guys i know still blip their slipper.  Keeps the rear more stable.

like any tool, it's good to use, and poor to rely upon.  someone told me "your bike has a rev-limiter too.  do you use that every time you shift?" 
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« Reply #20 on: September 28, 2009, 04:04:54 PM »

I tried throttle blipping while braking, and just doesn't seem to work for me. I can't comfortably put only one or two fingers on the brake lever. I'd have to move my brake lever up a bit, I think. I rev-match while downshifting though.
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« Reply #21 on: September 28, 2009, 04:08:10 PM »

^ on an EX500, or some other bike?

rev-matching while down-shifting on a twin is MUCH harder IMO - but I do catch myself doing it on the EX when I get off the highway.
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« Reply #22 on: September 28, 2009, 04:08:54 PM »

I use two for braking, and two (plus a thumb) for bliping while downshifting and slowing, Pogo. Try it without the motor running, just for practice. hold the brake with two fingers and use more thumb than fingers to whack the throttle.

or just try riding while using two fingers for braking.
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« Reply #23 on: September 28, 2009, 04:17:53 PM »

I rev match all the time. Even slowing down at a light. I thought everyone does it ... i guess not.    I agree with redkow tho, rev matching was much more difficult with the 500. I found that if I didnt match the revs downshifting the bike would be extremly jerky compared to my sv and inline4's.
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« Reply #24 on: September 28, 2009, 06:40:20 PM »

^ on an EX500, or some other bike?

rev-matching while down-shifting on a twin is MUCH harder IMO - but I do catch myself doing it on the EX when I get off the highway.
I suppose I've gotten good at it, since it's no problem for me to intuitively apply the right amount of throttle for a good rev match without even thinking about it.

I use two for braking, and two (plus a thumb) for bliping while downshifting and slowing, Pogo. Try it without the motor running, just for practice. hold the brake with two fingers and use more thumb than fingers to whack the throttle.

or just try riding while using two fingers for braking.
So, hover the palm off the throttle to get a better grip on the brake, while blipping with the grip from the thumb and pinky/ring fingers?
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