| Author | Message | ||
     Blake |
Another off topic thread given its own forum... | ||
| Blake |
Originally posted by XB9 Sunday, March 02, 2003 - 12:57 am . -------------------------------------------------------------------------------- Somethin's wrong if your EB'n instead of using the real brakes on a modern motorcycle ........ isn't the engine for goin and the brakes for stoppin? Only thing ya should be doing with the gearbox under braking is getting it in the right friggin gear for when your ready to give it somemore. | ||
| Rick_A |
Xb9...I agree with you there. I think it's best to keep the engine spinnin' in relation to your road speed while down shifting...but who doesn't use a little engine braking when you only have to slow up a tad? I do it all the time | ||
| Blake |
originally posted by Blake... Sunday, March 02, 2003 - 09:36 am XB9, So when coming into turn 2 at the local track, having to slow from 100 mph to 40 mph, how would you propose I keep the engine from exerting braking forces on the rear tire? Whether you intend it or not, the engine will act as a rear brake, albeit a poor one. The only time I consciously use the engine as a brake is when negotiating a long downhill run. What I think is more common is that in aggressively attacking a set of twisties like Deal's Gap or any other world class sport biking road, we leave the bike in a lower gear. Rather than upshift then immediately downshift to get good drive upon apexing the corner, we just leave the bike in 2nd or third gear. How do you keep the engine from acting as a brake in that scenario? Answer... you don't. | ||
| Xb9 |
Blake, Quote:"So when coming into turn 2 at the local track, having to slow from 100 mph to 40 mph, how would you propose I keep the engine from exerting braking forces on the rear tire?" Short answer: pull in the clutch as soon as you start apply the brake. Long answer: Obviously, under racing conditions while on the brakes, at some point you will be downshifting, the key to doing this smoothly is matching three things: 1. The gear you downshifted to. 2. Speed (MPH). 3. Engine RPM. If you do it correctly and match these three things precisely, it will be very smooth and non-abusive to the engine. Smooth is faster. On the track, there is little advantage to engine braking. It's just spinning up the engine. If the Frt. brake is being used optimally, there is so little weight on the rear wheel it is not helping to slow the bike. In fact it will mess you up more than it helps. Most of my racing experience was on two-strokes, RD/RZ's back in the '80's. Since a 2-stroke engine gives very little engine braking affect, my braking/downshifting habits are probably a little different than most people without that type of racing experience. In agreement with Rick_A, on the street I do use moderate engine braking in certian situations. Nothing wrong with that, and it’s fun at times. Good habits – Bad habits It's been a long time since I've studied "A Twist of the Wrist" by Keith Code, but I recall a chapter addressing the detriments of engine braking and using the rear brake in racing. Mr. Code teaches that neither should be used in a racing environment, it is an unnecessary distraction to the rider, and causes unnecessary wear and tear on the engine. Based on my experience and experimentation on the track, I totally agree with Mr. Code. The front brake as the single mode of deceleration will give you the best lap times. I proved it to myself with the stopwatch. Easiest way to decrease your lap times. See what happens to your lap times if you try this: Immediately after hitting your brake point and applying only the front brake, pull in the clutch and keep it applied, concentrating on just the application of the front brake. As you reach the point where you start easing off the brake, downshift X times (you should have memorized how many times X is for each turn) and ease out the clutch, matching the three items listed above. This should be done prior to reaching the apex, and done smoothly. Then you will be on moderate throttle as you reach the apex, and rolling it on as you exit. First thing you will notice as you practice this is that you will start extending your braking point, going in deeper because you deceleration efficiency is increasing. You’re concentrating on one thing, the feedback from the front brake. The lap times will drop. It worked for me, and many others I raced with. Everyone has their own techniques, some of which are habits we developed from however we started out riding. Street riding “habits” that are carried over to the race track can be less than optimal for best lap times. ************************** Quote: "The only time I consciously use the engine as a brake is when negotiating a long downhill run. What I think is more common is that in aggressively attacking a set of twisties like Deal's Gap or any other world class sport biking road, we leave the bike in a lower gear. Rather than upshift then immediately downshift to get good drive upon apexing the corner, we just leave the bike in 2nd or third gear. How do you keep the engine from acting as a brake in that scenario? Answer... you don't. " I agree with you here, Blake. Successive tight turns this is true. Applicable to street riding more than the track. Most tracks have only one or two sequence of turns where this may apply though. | ||
| Xb9 |
Sorry for the lengthy post, guess I took it to the nth degree Got carried away again.... | ||
| Blake |
XB9, I don't know of any racers, other than you, that hold the clutch in while braking to the apex. I rarely use the rear brake, hardly ever on the track. I cannot imagine dropping down two or more gears and then letting the clutch out at the apex. Nope, that is not going to work. If by chance you miscount and go one too low, you are going down. At/near the apex, I am hanging off trying to maintain optimum corner speed. I wonder what all the top racers of today who make prodigious use of slipper clutches and engine braking would say to your recommendations. One thing I have tried... Instead of blipping the throttle to synchronize engine and tranny, I've tried instead to carefully/gently engage the clutch letting tranny gently spin up the engine to synchronous speed. That can allow one to maintain better control/feel of the front brake. When the rear end starts to waggle, I know I'm pushing the limit. If I'm going for best lap time, six out of eight turns on my local track do not involve downshifting, one is a 2nd gear turn, the others are 3rd gear.  Oak Hill Raceway (1.8 mile circuit) My best average speed... 67.5 mph Track record avg. speed... 77.7 mph (set last year by now AMA Pro Racer, John Haner) I just cannot imagine how engine braking is such a terrible thing. Someone needs to explain how a backdriven engine under closed throttle (-14 psig combustion chamber pressure, minimal exhaust temperature) is more severely stressed than one putting out max power near the rev limit at WOT (>1000 psi combustion chamber pressure, 1000oF exhaust temperature). I don't buy it. Makes absolutely no sense to me. | ||
| Xb9 |
Blake, Respectfully, Quote: "I don't know of any racers, other than you, that hold the clutch in while braking to the apex". That is not what I said. Please reread my post. It's pretty specific. Just curious, did you read Keith Code's book(s)? He explains it a little better than I. At the time I was racing and using this technique (all things being equal), I was turning times -5 sec. off the lap record at Nelson Ledges on a 350. Look, I don't see anything productive with going back and forth arguing with this, it's all about different styles anyway. I'm just stating what worked for me. If your technique works for you, great. Use it. Were all human, no two alike. BTW, I was reading some article recently about a factory racing team that had a special clutch on a factory ride that eliminates the engine braking effect on the drivetrain. Wish I could dig that article up. If I find it I'll let you know where i saw it. | ||
| Xb9 |
Feb. 2003 Cycle Word article on Rossi's RC211V and his interview. | ||
| Notsip |
Looks like some of you have been reviewing your riding styles and how it could possibly affect the engine. I see that some of you have different riding styles. Not everyone rides the same. There was one comment by someone that said they pull the clutch in and brake until they reach the apex of the turn. As a former racer and Crew Chief for many AMA Professional Racers, I would have to ask if you have your insurance policy up to date because I think you might be needing it. The last thing that you want to do is run it off into a corner, pull the clutch in and then brake with both front and rear brakes. Let's think about this. It is simple physics. When you tie a ball on the end of a string and swing it around in a circle it takes power to keep it moving in a circular motion, correct? Now if the string breaks and you lose the power to make the ball go around in a circle what happens? Centrifical force send the ball in a straight line. This is what is happening when you pull in the clutch and take the power away from the rear wheel. The motorcycle wants to stand up and go in a straight line. Not only does it cause you problem in that aspect it also unloads the chassis and suspension needlessly and then you have to try to figure what gear you should be in and at what rpm the engine should be at when you release the clutch. Then when you get all of that figured out then you have to reload the chassis and suspension again. If you have time to figure all of this out you are not going very fast or you are a super fast thinker. Because if you are hauling it off into the corner like you ought to you definately don't have time to do all of that. Whew....Wears me out just thinking about it. Here is the fastest way through a turn. The next time you go riding keep the clutch engaged at all times except for upshifting and downshifting. Run the bike into the corner and gradually roll off the throttle while you are applying the rear brake. This will keep you from unloading the chassis and drivetrain and make the bike more managable to handle. If you have to downshift make your down shift and gradually release the clutch, but keep the throttle open and the bike under power. As you reach the apex of the turn gradually increase the throttle with the rear brake still applied. As you exit the turn gradually release the rear brake and apply the throttle as necessary. This is called power braking. By doing this you will not be upsetting the chassis and suspension as severally and you can control the tire spin and lift-off of the front wheel. Now you will have complete control and feel of the motorcycle and know what it is doing at all times. If you practice this I guarantee that your corner speeds will pick up drastically. The faster you get through and off a corner the faster you are going to accelerate down the straight away. Proven time and time again by all professional racers. Ask any of them. | ||
| Blake |
Notsip, As a former racer and Crew Chief for many AMA Professional Racers..." Hold one there! You were a crew chief for "many AMA Professional Racers?!"} Too cool! Please do tell more... who, when, what, where... ! "The last thing that you want to do is run it off into a corner, pull the clutch in and then brake with both front and rear brakes. Let's think about this. It is simple physics. When you tie a ball on the end of a string and swing it around in a circle it takes power to keep it moving in a circular motion, correct? Yes and no. Lacking air resistance (aerodynamic drag) and frictional effects, only a force is needed to support constant angular motion. "Now if the string breaks and you lose the power to make the ball go around in a circle what happens? Centrifical force send the ball in a straight line.' Actually the lack of centripetal force (the force that the string exerts on the ball) allows the ball to fly straight away. "This is what is happening when you pull in the clutch and take the power away from the rear wheel. The motorcycle wants to stand up and go in a straight line." No, that is incorrect. The broken string would be analogous to the motorcycle losing traction, like when hitting a patch of ice. "Not only does it cause you problem in that aspect it also unloads the chassis and suspension needlessly and then you have to try to figure what gear you should be in and at what rpm the engine should be at when you release the clutch. Then when you get all of that figured out then you have to reload the chassis and suspension again." When transitioning from hard braking to hard acceleration (from on the brakes to off the brakes to on the throttle) passing through a point where the suspension "unloads" is unavoidable. Unless I misunderstand what you mean by "unloads the chassis and suspension." "If you have time to figure all of this out you are not going very fast or you are a super fast thinker. Because if you are hauling it off into the corner like you ought to you definately don't have time to do all of that. Whew....Wears me out just thinking about it." I think you started this by contending that under a panic stop, most riders would be downshifting to slow the bike. Now we find ourselves talking about how to best approach a turn on a racetrack. Let's save that for another topic. Yeah, I'm guilty of adding to the off topic banter too.  BTW, you omitted any mention of using the front brake in your description of the "fastest way through a turn." | ||
| Blake |
Originally posted by Rick_A... Monday, March 03, 2003 - 01:09 am . -------------------------------------------------------------------------------- I've tried the technique of pulling in the clutch and downshifting X# of times while decelerating...half the time X wasn't what it shoulda been. So, I continue to blip as I go. When downshifting from a slightly reduced speed I like to keep the throttle constant and quickly work the clutch while I shift. It takes a lot less time and concentration then slowly letting the clutch out and waiting for the engine/tranny to synchronize. I like letting the front end dive into corners...and to raise coming out. Feels to me like the weight is transferring where you'd want it. Everyone has their style I use the rear brake only in the dirt/wet, any time the front tire is nearing the limit of adhesion...or when doing tight parking lot maneuvers...I've been through two front rotors and my rear still has many years of life left on it. I've tried some of the other techniques above, but I feel most comfortable with mine. | ||
| Xb9 |
Under hard braking, what is the percentage of weight (and available adhesion) on the front wheel vs. the rear? Hint: I was watching a race on Speedvision a couple of Tuesdays ago, and I noticed one rider's rear wheel came off the ground slightly just before he started pitching it in. (he was also running in the top three) | ||
| Blake |
XB9, You are right, I did not correctly read your statement. Sorry about that. You said... I can see how that might work. I'd rather have the clutch already engaged at full lean though. As to the "special clutch that eliminates the engine braking effect on the drivetrain"... It's called a "slipper clutch." A slipper clutch does not "eliminate" engine braking, nor is its intent to spare the drivetrain. A slipper clutch's intended purpose is to limit the severity of engine braking to prevent loss of optimum control of the bike. When properly set, the racer can simply dump the clutch on downshifts, the clutch partially disengages and slips thus gradually letting the engine come up to synchronous speed just like if the racer had slowly/carefully re-engaged the clutch himself. There is still plenty of engine braking going on, just no uncontrollable sliding of the rear wheel in the process. It's no different than the way all of us SHOULD be operating the clutch when downshifting without throttle blipping. A slipper clutch simply does for the racer what he used to have to do himself. The desired result is that he can concentrate more on braking and steering without worrying about a smooth clutch engagement upon downshifting. I'm still waiting for someone to explain to me how engine braking could possibly subject the engine/drivetrain to more severe stresses than WOT acceleration.  | ||
| Blake |
Notsip, No need to use the front brake?  I know you are right, but that level of finesse and control is beyond my expertise. I'm not sliding the rear tire exiting turns, on purpose anyway. My best approach is the following... 1. Identify braking marker (this could be a spot on the track, or a clump of grass nearby, whatever you can find on/near the racing line that marks where you want to commence braking). 2. Approaching the marker, roll off the throttle, not too quickly, not to slowly (don't want to upset the chassis), then begin to smoothly apply front brake. 3. Smoothly increase braking effort to maximum upon reaching braking marker. The bike is now just shy of lifting the rear tire, it may waggle a little as it starts to lift and slide. 4. Maintain braking. Identify turn-in marker. Again, this is any conspicuously visible feature on or near the racing line that coincides with the point where we want to initiate the turn. 5. As the engine slows downshift and synchronize, usually by throttle blipping or controlled release of clutch lever or if you are lucky enough to have one, by simply dropping the lever and letting the slipper clutch handle the job, as you prefer. Complete downshifting to desired gear prior to reaching turn in marker. Initiate hanging off as desired. 6. Upon reaching turn-in marker begin to ease of front brake and smoothly initiate turn through countersteering and hanging off (body steering). 7. Identify apex marker. 8. Continue trail braking approaching apex with gradual reduction in braking effort to zero one full lean is achieved. 9. Once speed is appropriately scrubbed, release brake while smoothly commencing slight throttle input. 10. Pass apex marker, identify turn exit marker. 11. Initiate turn recovery through smooth application of throttle and steering to get bike stood up. 12. Continue rolling on throttle withing the envelope of traction and track boundaries. 13. Get bike pointed downtrack, tuck in, let her rip WOT, hold on - upshift (no clutch) as required, identify next turn braking marker, repeat above... I have not touched the rear brake. Did I miss anything? | ||
| Blake |
Xb9, I've read Keith Code's A Twist of the Wrist. The only thing new that I took from it was the analytical approach to improving lap times and to rigorously identify and learn appropriate markers. Those concepts alone were worth price of the book. | ||
| Crusty |
"When you get to the end of the straight, turn left" - Jay Springsteen (He knows a little bit about engine braking) | ||
| Nevco1 |
Gosh Blake...I think you finally have it. That is the most condensed and accurate description of the process that I have ever read. | ||
| Reepicheep |
Blake... I'll bite. Blake wrote:
I'm talking transients here, not steady states. The following argument may hold for steady state though. I would think BOTH forces are limited by the co-efficient of friction for the tires. Oh. I think I see what you are getting at. I was going to say that I know if I am going, say, 75mph, and drop into first, and just dump the clutch, in the instant before my transmission grinds itself to little pieces and my pistons get fired through my heads, the back wheel sees a far greater acceleration force (deceleration force in this case, but same deal) then my stock cyclone could ever hope to produce. But I think the coefficient of friction, combined with the weight transfer, is what you are getting at, and I guess I agree now. Dumping the clutch to decelerate does indeed drop a lot of "power" through the drivetrain, but as soon as it starts, all the weight of the bike transfers forward, and dramatically reduces the frictional force at the rear wheel. So the forces can never be that great, the rear just locks up and slides. On hard acceleration however, you still get a lot of power to the rear, but you also get a significant weight transfer to the rear, which combined with the constant coefficient of friction, results in increasing traction forces, rather then decreasing traction forces, thus acceleration forces will always be greater then deceleration. So the potential forces of both are great, but the limitation of each is the coefficient of friction of the rear tire combined with the weight transfer during the activity. Acceleration will always have more weight towards the back, and therefore always have higher resulting forces. So none of you racers touch the rear brake, huh? On my street riding (I am no expert, and not super aggressive) I always feel more comfortable dragging the rear brake as I set up for my turn. It seems to settle the suspension down, and I feel like I have a little more control. I leave it in whatever gear I set up for before entering the turn, and roll on the throttle coming out. If I need to shift coming out, I wait until I am pretty straightened out. Of course, my goal is to have as much fun as possible while keeping the best margin, not making the best possible lap times, so I doubt that applies to the discussion we are having here... Bill "easy game for Blakes bait" | ||
| Blake |
Bill, You nailed it. XB9, The front brake provides 100% of total available maximum braking force available to a sport bike, at least on dry pavement. | ||
| Blake |
Notsip said (back on the catch can thread...
Let me get this straight... if too hot into a turn and running wide, you advocate "gassing it" to tighten up the turning radius? | ||
| Buelliedan |
You only have one option if you go too hot into a turn and start running wide... Lean more!! | ||
| Blake |
What if you are already scraping hard parts? | ||
| Buelliedan |
Kiss your ass goodbye?? | ||
| Hootowl |
I've always found that a little more throttle, within reason, does help to tighten up the turn. But then, I'm never at the limit of adhesion. I don't ride like that on the street, and I've never been to the track. | ||
| Xb9 |
"What if you are already scraping hard parts?" Hang off more if your not already draggin your shoulder on the curbing  | ||
| Blake |
More throttle to tighten a turn. Man, that's riding in a different universe from where I ride. XB9 got it right, plus, if you are on the throttle, smoothly roll off the throttle and/or lightly engage the brake(s). The main thing is to slow down without upsetting chassis/suspension or exceeding limits of traction. I guess there is one other answer for those foolish enough to attempt it... get the rear tire spinning and kicked out dirt track style? Not me, no thank you! | ||
| Hootowl |
I'm not talking about WOT. Just a little. Again, I'm not talking about being at the limit and about to run out in the gravel pit. Obviously at that point you'd want to bleed off some speed. And since you brought it up, sliding the rear a little does help the front end track better. Whether that will make you turn sharper is another question. | ||
| Imonabuss |
Reepicheep, A violent downshift is one of the most damaging things you can do to a drivetrain. Although you maintain a load under max acceleration, it is not nearly as high as the instant downshift. The killer is the inertia, which gives a huge spike into the system. It is about the most damaging thing you can do to your final drive and transmission. Back to the original topic, there are many ways to ride and what amazes me is the difference in styles that can work for riders at the top level who are competing with one another. For example, Garry McCoy literally backs the bike in on pavement with the power on, just like a flattracker or speedway bike, and smoke pouring off the tire. When he gets it pointed where he wants to go he lets off the throttle slightly which gets the rear tire to bite, and the bike explodes out of the turn. One of the bravest styles of riding I have ever seen, unbelievably fast, but probably the reason why he spends so much time in casts! Kenny Roberts Jr. rides like his dad, with the rear tire broken loose and sliding well before the apex, but never to the extreme of McCoy. Max Biaggi on the other hand uses the Euro style of very late braking, extreme lean angle and corner speed, but late on the throttle. Which is best? Whatever works for you and feels right. I think a lot of it boils down to the type of riding you learned on. If you learned on a dirt bike, you are probably most comfortable with throttle on before the apex and the bike in oversteer. If you learned on a small streetbike/scooter with little power, you probably will choose high corner speed and late braking. | ||
| Blake |
Imonabus, Am I wrong in thinking that the shock load resulting from dropping the clutch under acceleration, like in an overzealous wheelie attempt, would be worse than the errant downshift scenario? Since the shock loading would be mitigated as it travels up/down the drivetrain, I guess it may depend on which end of the drivetrain is considered. I'm thinking more of the engine itself than the output side of the tranny. |
