| Author | Message | ||
     Puredrive |
Holy crap..I almost went down this morning  Accelerated hard on 2nd gear. Leaned a bit forward and then the handle bars just went crazy. I must admit, I thought it was going down. This was the most violent tank slap I have experienced. My wrist are bruised, But I am just glad I did not go down. I'm sure I must of looked like this guy to the cagers..lol http://www.youtube.com/watch?v=LZ1srcQMa_0 But the odd thing is that my front brakes felt spongy when I tried to apply them..This is perhaps 30 sec after my recovery. I had to use the rear brakes to come to a stop. After wards I did a few pumps on the front brake lever and all is good. Just wanted to share my scary moment this morning. Be safe out there. | ||
| Dnlink |
The tank slapper set your brake pads back in the the caliper farther than normal. Takes a few pumps to move them back out, specially with a small Master cylinder on a MC. It can happen to cars under the right circumstances, not a tank slapper just the pads moving back farther than normal  | ||
| Puredrive |
^^^ That makes sense. I guess, I need to lean more on the front tire if I'm going to be redlining on 2nd gear. On another note. All the squids liked my 1125CR specially my HPE exhaust note.  | ||
| Dannybuell |
Yes, keeping your weight forward and increase the spring preload on your rear shock. The bike will not rock back/suspension travel as far so less weight will move from the front to the rear. | ||
| Rodrob |
BTW - the guy in that video does everything wrong and exacerbates the situation to the point of disaster. Just sayin'. (Message edited by Rodrob on October 19, 2010) | ||
| Bigblock |
steering damper. | ||
| Puredrive |
^^ I thought that no Steering Damper was made for the CR models. | ||
| Rodrob |
"Accelerated hard on 2nd gear. Leaned a bit forward and then the handle bars just went crazy" I would propose that when you accelerated and leaned forward, you held tight to the bars and pulled to keep yourself on the bike, thus turning a small, necessary shake, into a near crash. Be light, loose on the bars, hold on with you knees and feet. Do not try to stop small shakes with your arms. You will turn them into big shakes. | ||
| Andymnelson |
If truly a tank slapper, it is not from the front end coming up....it's from the wheels becoming mis-aligned. Bring the front end up straight, and keep the front wheel straight upon landing. For someone inexperienced with wheelies, this is harder to accomplish that it sounds. Keep you feet firmly planted and squeeze the frame with your knees (or as an alternative, stand on the pegs....but that's a better posture for stunts rather than acceleration), this way you will rely less on you arms/hands for positioning your body, and can instead keep them more relaxed and keeping the bars straight. If you ever actually do get into a tank slapper, LOTS of throttle is the solution, not the instinctive braking- you ned to unload the front tire as much as possible to allow the bike to correct the mis alignment as easily as possible. Glad you kept it upright! | ||
| Puredrive |
Rodrob, Yep..I just held the handle bars lightly. This is about the 5th time I have experienced tank slap. All others have been child's play compared to this last episode. But thanks for the tips. I'll definitely look into the rear spring adjustment. Dunno if it matters..but I only weigh about 156lbs and with gear..maybe 165 LBS  | ||
| Xl1200r |
If this is the 5th time there is either something wrong with your suspension or something wrong with your technique. I've only ever had the slightest bit of head shake on my CR, and it's always when the front end lofts a bit and I'm hanging onto the bars to hold on from the acceleration. | ||
| Duphuckincati |
FWIW, the factory race 1125's have one degree more rake (from 21 to 22 degrees) and a couple of inches added to the wheelbase. There's a reason. I really enjoy my CR, but these bikes are on the twitchy side for sure. My old 900SS Ducati feels very stable compared to these. | ||
| Littlebutquick |
same thing happened to me but front was strapped down doing a dragrace got steering damper now breaks did same thing | ||
| Azxb9r |
If you crank the throttle hard, it is easy to pull on the bar a bit while you are applying the throttle. If the front wheel floats, and you get the bar turned with the wheel in the air, when the wheel comes back down the bike will shake its head. the more you get the wheel turned, the harder it will shake its head. | ||
| Puredrive |
Xl1200r If this is the 5th time there is either something wrong with your suspension or something wrong with your technique. I've only ever had the slightest bit of head shake on my CR, and it's always when the front end lofts a bit and I'm hanging onto the bars to hold on from the acceleration. I'm not opposing the idea of bad technique. This Dec it will be my 3rd year riding and I got the CR back on July of 09. The first 4 times tank slap happened, it barely shake. Never got scared that's for sure. But this time around, it was darn scary. I'm replaying the incident in my head. I just don't think I leaned as much as I should have. And my overall weight I am sure it does not help on the CRs short wheelbase. | ||
| 1125rcya |
I have only experienced the tank slapper with new tires. Test: While riding your bike stand on the pegs and lean forward while recreating a tank slapper. Now imagine hitting your front break throwing all your body weight forward, and that my friend spells disaster! The throttle is your friend, but not MC Hammer Happy in a slappy moment! | ||
| Court |
>>>> I only weigh about 156lbs and with gear..maybe 165 LBS If you are only wearing 9# of gear you need to evaluate your kit. | ||
| Lemonchili_x1 |
If you haven't already, just to be sure check your tire pressures (cold) and steering head bearings, and check suspension settings are set for the lightest settings in the book (170lbs or less). "...the factory race 1125's have one degree more rake (from 21 to 22 degrees)..." I vaguely remember reading somewhere that the race bikes also run a different rear ride height so that the rake is still 21°. I could be remembering things incorrectly though. | ||
| Puredrive |
If you are only wearing 9# of gear you need to evaluate your kit. I miscalculated..lol leather jacket, helmet. gloves. No riding boots tho  I'll definitely look into the suspension settings. I had it professionally set by a shop. I'm sure it would be easy to look into it. | ||
| Rodrob |
There is only one cause for a tank slapper. That is when the front tire is heavily side loaded by not being parallel to the direction of travel. This creates excessive castering forces do to trail and tire flex, which causes the forks to snap back perpendicular to the line of travel. The momentum of this movement causes the forks to overshoot, and the same thing happens on the other side, setting up the resonant oscillation known as head shake. The only way to stop it once it begins is to remove the energy that feeds the oscillating system. Once head shake starts, leaning forward will only make things worse as you will be increasing the energy in the system by increasing the flexing force of the front tire. Your new body position will transfer the shake to the rest of the bike, which will wobble and shake your feet off the pegs and you WILL be that guy in the video. Better to let the bike wheelly, there by removing all the energy from the system, then set it down with the correct steering angle. Remember that under hard acceleration, the rear tire is doing most of the steering, not the front. Many riders unconsciously stop counter steering when the front gets light, which is the initial trigger when the front tire starts to plow. The throttle is your only way out. A steering damper can help prevent the initial overshoot in mild situations, and increase the margin of error the system will tolerate. But if the error is severe, it won't help. BTW, what is your front free and rider sag? (Message edited by Rodrob on October 19, 2010) | ||
| Puredrive |
^^ Rodrob I don't know off the top of my hand. I got measured and weighted at the bike shop. Motorcycles Unlimited www.motorcycles-unlimited.com I got asked what my riding style was, tons of question about how I would like the bike to feel. etc. They are known for their bike suspension work. Not sure if it matters.. But I lost about 6lbs since the suspension adjustment. | ||
| Xl1200r |
I got asked what my riding style was, tons of question about how I would like the bike to feel. etc. What exactly did you tell them? What are your settings at now? That could answer some questions. I'm not sure how much fine tuning they'd be able to do without them making a change, having you ride it, then adjusting again and repeating until it's where you like it, but I'm not a suspension pro. | ||
| Puredrive |
^^^ That I was a noob.lol I tell everyone that actually. I ride within my limits. I ride to work,in the city and your typical outing out in the country. I have improved dramatically from a yr ago IMO The shop basically dialed down the settings. From what a typical 10yr rider would be looking for. Before the suspension adjustment, the bike felt loose. After the adjustment, it felt much better. gave me confidence. | ||
| Rodrob |
You should have at least 30 mm of front sag when you are on the bike. If not, the front fork will top out under hard acceleration and the tire will be searching for pavement. At your weight, you might have to back the preload all the way out, or lower the fluid level in the forks from 100mm to 120mm. Knowing your sag is step one to good handling. Lots of posts here about measuring sag. Get a couple of buddies and do it. (Message edited by Rodrob on October 20, 2010) | ||
| Iamarchangel |
Better re-evaluate something. This is 2010, not 1960, 15 tank-slappers indicates a real problem. One that will hurt really soon. I haven't had a tank-slapper, well, ever, on my Buell. Maybe once when I took a very fast inside line on an uphill corner and hit a bunch of potholes. Tires: check pressure (what type are you running?) Suspension: think you should scrap the shop's recommendation and go with the manual. Start with your weight settings. Find a bit rough road and take several runs. Keep adjusting until you find the right settings for you and your style. It only takes three tools, two really, and a copy of the settings and pen. Save yourself some pain. | ||
| Bigblock |
My rear shock went bad and I had a bad tankslapper. Buell replaced the shock, and I got a GPR damper. I have an R, I think the Erik Buell Racing ohlins damper might work on your bike? I had a fair number of headshake incidents with the suspension in good shape and adjusted well, so I think these bikes may not be as stable under certain conditions as some. It never happened with pirellis on the bike, come to think of it. I have tried various brands in search of mileage while keeping good grip, I may have had bridgestones on at the time. Won't run those again. The bad one happened on a real poor quality piece of road, and really getting on it in 3rd. My brake pads backed off the disc, too. SCARY! I like my GPR damper, peace of mind. | ||
| Tpoppa |
http://www.sportrider.com/tech/146_0006_susp_handl e/index.html TANKSLAPPER Problem: Terry's bike feels unstable, especially when entering turns. The bars seem to "twitch" excessively whenever a midcorner bump is encountered. The bars often whip back and forth violently several times (or more) when Terry is accelerating aggressively over bumps while coming out of a turn--in other words, a "tankslapper." The bike steers very easily, although a lack of traction is sometimes noticeable in the rear whenever he tries to accelerate at moderate lean angles. The bike also seems to have a dropped-down, "nose low, rear-end-high" attitude while riding. Solution: The biggest distinguishing factor in this case is the "nose-low/rear-end-high" chassis attitude feeling. If Terry's bike definitely feels this way, then probably he has too much front end weight bias. This not only hinders traction at the rear, but also affects the steering geometry (steeper rake/less trail) and can cause the instability problems. As long as Terry has his suspension static sag levels set correctly, the first step is to try less rear spring preload and/or more front preload, to the point just before they begin to affect handling negatively; Terry should remember to adjust his rebound damping if necessary (in fact, he should check to see if decreasing the front rebound damping in small increments helps; the forks may be too stiff, hindering traction). If only partially successful, a more drastic step would be changing chassis ride height; this would involve raising the front end by dropping the fork tubes in the triple clamps (if there's enough material protruding above the top clamp, to ensure front fork structural integrity), and/or dropping the rear by shortening the rear shock (if possible). | ||
| Anonymous |
Duphuckincati Posted on Tuesday, October 19, 2010 - 01:47 pm: FWIW, the factory race 1125's have one degree more rake (from 21 to 22 degrees) and a couple of inches added to the wheelbase. There's a reason. I really enjoy my CR, but these bikes are on the twitchy side for sure. My old 900SS Ducati feels very stable compared to these. That is actually incorrect, Dphcti. Race bikes have more angle in the headcups, but that is to correct for the fact that the back end is raised up for more anti-squat bite with all the HP. So the actual rake angle is the same as stock. Also, the Erik Buell Racing race bikes are run as short as we can possibly make them with clearance for slicks, and as gearing and chain slack requires. The bike handles much better short. | ||
| Thefleshrocket |
Tpoppa, I've got my fork dropped so that there's only the cap visible above the top of the triple and the front end still feels like it wants to get twitchy under hard acceleration in 2nd through 4th. Raising the front end apparently isn't a cure all, at least on the 1125s. I've never had an outright tank slapped but the front end has gotten really twitchy a few times. | ||
| Puredrive |
my tire pressure is 36psi front & back. I'll definitely look into the sag measurement. |
