Time for a motorbike list
- Thread starter Rasher
- Start date
Well, no guarantee that it will stay on a motorbike chain, at speed it will get thrown off, on my bike not likely. But I'd just lash it on, it won't hurt it. Slap some more on next time out if it's been washed or thrown off.^ That's even better - made my day hearing that. Thanks Steve
richardg
Admonishtrator
I've ridden a 675 Street. No way it needed a damper. I have never owned a bike with a damper. I rode a 2014 Fireblade with an electronic one. It was amazing in that I did not notice it was there and the bike never twitched when being properly spanked. I can't stand hydraulic dampers. On low powered bikes like a 675, I don't get it. Please enlighten me.
-alan-
pfm Member
It's not really down to the power Richard, the stability (or otherwise) is a function of the steering geometry - things like the steering head angle/rake/trail, and indeed things like weight distribution all play a part. There's a fair body of engineering maths that has been developed around vehicle stability, based on the work of pioneers like Tony Foales and one of my old college lecturers - Robin Sharp - who worked with Percy Tait and Yamaha to resolve problems on the early 650 Yamaha, which was notorious for throwing head-shakes. (Helped explain why there was a brand new front end of an XS650 bolted into a test rig in one of the ground-floor engineering labs in Leeds when I was there )
In simple terms, a bike designed to turn-in quickly and be more manoeuvrable will have a different set of design parameters than one designed more for stability with the resulting slower turning/less responsive chassis. Its like with fighter aircraft - there's invariably a tradeoff between stability and manoeuvrability. The less stable they are, the quicker they turn, but the harder they become to manage, and less likely they are to 'self-stabilise' when there's a change to some of the inputs - on bikes, things like a bump in the road, change in weight distribution, sudden steering input at the bars.
A real life case in point. Many moons ago I had a low mileage, fresh GPZ600, the one with the 'hot off the race-track' 16" front wheel. I was accelerating hard out of a junction one morning when the bike/I ran into a 30-40 yard long, 2-3"wide groove where there was a strip of tarmac missing. The b@stard thing went into a huge wobble as the front wheel ran along the edge of the ridge. I froze, rolled off the throttle, and the thing then went into a frenzy that a bull rider in a rodeo would have been proud to ride out. The chassis was bucking so violently from full lock one side to full lock the other that I banged one of my knees against the tank and ended up with a bruise the size of your hand, that lasted at least a week. I later rationalised what happened as me rolling off the throttle changed what was a mild enough shimmy with the front-wheel / fork oscillating largely independently from the chassis into a shimmy into a full-on lock-to-lock whole chassis thing as the extra weight pitched forwards onto the forks. I really wouldn't wish it on anybody - it was fuggin' terrifying.
Turns out the GPZ was notorious for the tank-slapper thing - hence why they moved back to a 17" the following year. I parked the bike when I got home and didn't set a foot on the thing again until the steering damper hastily ordered out of the back pages of MCN turned up a week later
)In simple terms, a bike designed to turn-in quickly and be more manoeuvrable will have a different set of design parameters than one designed more for stability with the resulting slower turning/less responsive chassis. Its like with fighter aircraft - there's invariably a tradeoff between stability and manoeuvrability. The less stable they are, the quicker they turn, but the harder they become to manage, and less likely they are to 'self-stabilise' when there's a change to some of the inputs - on bikes, things like a bump in the road, change in weight distribution, sudden steering input at the bars.
A real life case in point. Many moons ago I had a low mileage, fresh GPZ600, the one with the 'hot off the race-track' 16" front wheel. I was accelerating hard out of a junction one morning when the bike/I ran into a 30-40 yard long, 2-3"wide groove where there was a strip of tarmac missing. The b@stard thing went into a huge wobble as the front wheel ran along the edge of the ridge. I froze, rolled off the throttle, and the thing then went into a frenzy that a bull rider in a rodeo would have been proud to ride out. The chassis was bucking so violently from full lock one side to full lock the other that I banged one of my knees against the tank and ended up with a bruise the size of your hand, that lasted at least a week. I later rationalised what happened as me rolling off the throttle changed what was a mild enough shimmy with the front-wheel / fork oscillating largely independently from the chassis into a shimmy into a full-on lock-to-lock whole chassis thing as the extra weight pitched forwards onto the forks. I really wouldn't wish it on anybody - it was fuggin' terrifying.
Turns out the GPZ was notorious for the tank-slapper thing - hence why they moved back to a 17" the following year. I parked the bike when I got home and didn't set a foot on the thing again until the steering damper hastily ordered out of the back pages of MCN turned up a week later
richardg
Admonishtrator
Come on, Alan. I know this stuff. I had a 90s blade with a 16" front wheel until May this yea. It steered quickly and had much more power than the GPZ600. The reason these dampers went on bikes of yesteryear is because they were not designed and built well. Now is a different story with 200bhp and a thirst for super fast steering.
Most of my bikes have been track bikes with quick steering. It includes
TZR250
RGV250
NSR400
R6
Fireblade
None of them tankslapped, it's about choosing a good handling machine for the road. My mate had an NSR250 when I had a TZR250. The NSR tankslapped. Mine did not
I had a Ducati 900 Supersport that did not tank slap until I put an 1100 Monster engine in it. Then it did. My fault.
Remember the Suzuki twin TL1000S? Nicknamed the widowmaker because it tankslapped and even cracked the frame in the process I recall. That's a bad motorbike. Not just a motorbike with a steep steering angle.
I have a Vitpilen 701 now that is an apex monster, amazing track tool. Light at 150kg, big torque as it is a 75 bhp single. Not one tank slap yet, yet the front wheel is always wanting to come up. That because it is a good bike.
Right? That said I am still not aware of the 675 having a reputation for this. And wonder if there is something else on your bike not right?
Most of my bikes have been track bikes with quick steering. It includes
TZR250
RGV250
NSR400
R6
Fireblade
None of them tankslapped, it's about choosing a good handling machine for the road. My mate had an NSR250 when I had a TZR250. The NSR tankslapped. Mine did not
I had a Ducati 900 Supersport that did not tank slap until I put an 1100 Monster engine in it. Then it did. My fault.
Remember the Suzuki twin TL1000S? Nicknamed the widowmaker because it tankslapped and even cracked the frame in the process I recall. That's a bad motorbike. Not just a motorbike with a steep steering angle.
I have a Vitpilen 701 now that is an apex monster, amazing track tool. Light at 150kg, big torque as it is a 75 bhp single. Not one tank slap yet, yet the front wheel is always wanting to come up. That because it is a good bike.
Right? That said I am still not aware of the 675 having a reputation for this. And wonder if there is something else on your bike not right?
-alan-
pfm Member
I'm not sure I get your point on steering dampers ? With the right (or wrong..) combination of geometry, weight and control inputs, a bike can and will throw a tank-slapper. There are plenty of other bikes with designs which are more prone to it, not because they are bad bikes, but because of the choices the designers made in the hunt for a quicker turning, more manoeuvrable chassis. If the Vitpilen doesn't do it - happy days
As you say, I haven't heard of the issue arising on the Street triple 675 either - but the Daytona will throw the head-staggers if you get the front end of it light and then roll the weight forward at speed with the wheel not fully straight ahead. There's plenty of vids across the web. Mine never has - most likely because I don't ride it like that these days. The reason I was focusing on the damper was to see if I can cure a vagueness in the steering once the thing is banked over - which I only noticed after a spin back-to-back with a mate's 748. I suspect my issues were down to they tyre pressures being off - but having a sticky steering damper can't have helped much either.
As you say, I haven't heard of the issue arising on the Street triple 675 either - but the Daytona will throw the head-staggers if you get the front end of it light and then roll the weight forward at speed with the wheel not fully straight ahead. There's plenty of vids across the web. Mine never has - most likely because I don't ride it like that these days. The reason I was focusing on the damper was to see if I can cure a vagueness in the steering once the thing is banked over - which I only noticed after a spin back-to-back with a mate's 748. I suspect my issues were down to they tyre pressures being off - but having a sticky steering damper can't have helped much either.
richardg
Admonishtrator
Is the geometry on the Daytona 675 different to the Street 675?I'm not sure I get your point on steering dampers ? With the right (or wrong..) combination of geometry, weight and control inputs, a bike can and will throw a tank-slapper. There are plenty of other bikes with designs which are more prone to it, not because they are bad bikes, but because of the choices the designers made in the hunt for a quicker turning, more manoeuvrable chassis. If the Vitpilen doesn't do it - happy days
As you say, I haven't heard of the issue arising on the Street triple 675 either - but the Daytona will throw the head-staggers if you get the front end of it light and then roll the weight forward at speed with the wheel not fully straight ahead. There's plenty of vids across the web. Mine never has - most likely because I don't ride it like that these days. The reason I was focusing on the damper was to see if I can cure a vagueness in the steering once the thing is banked over - which I only noticed after a spin back-to-back with a mate's 748. I suspect my issues were down to they tyre pressures being off - but having a sticky steering damper can't have helped much either.
My point stands. A quick steering bike for the street should not tank slap. If it does, it is not a good street bike.
-alan-
pfm Member
Most don't - but in the case of many that's down to the assistance provided by a steering damper. Are you saying manufacturers shouldn't sell street bikes that need dampers ?
Just checked - the Street has 1/2 degree more rake and 6mm more trail than the Daytona btw, so yes, the steering will be slower on it.
Just checked - the Street has 1/2 degree more rake and 6mm more trail than the Daytona btw, so yes, the steering will be slower on it.
richardg
Admonishtrator
Not saying that they should or should not sell them.,..but if a bike gets a reputation for tank slapping on the street, then it tends to not sell so well, methinks? Certainly I will avoid it and find a quick steering bike elsewhere.
My grandfather's 1932 Sunbeam had a steering damper and it only did 55mph. It was a massive screw on the fork that basically just shut the steering down altogether. Lol. It didn't slap, it just wobbled and weaved and shook. It was horrible.
Itzs funny that the Daytona has even more...the Street already steers really quickly.
When an ignorant overconfident youngster I bought a second hand LC250 that had been used for racing and the road. It seemed fine on the road but the first time on the track I was thrown off by a tank slapper at the end of the straight on the first lap. The laughing elder that picked me up after I had managed to both bollock and wind myself pointed out that a steering damper was required for racing and showed me where it used to be mounted. He also pointed out that a cricket box was pretty useful as well.
-alan-
pfm Member
^ Ouch
I remember those friction steering dampers well Richard - some 70s Jap bikes had them. The messers round our way used to take pleasure winding them on full on parked bikes, much to the entertainment of the rider and neighbouring bystanders when it came to moving off up the road
I do find the whole thing about bike dynamics really interesting. I know the early H2 750 Kwacks had a reputation for being an evil b@stard that would throw the head and spit you off at the slightest provocation. I read an article in later years written by one of the first UK journalist to ride one, who said that the demo model he had definitely weaved under very little provocation, but when he asked the dealer to get rid of the high US spec bars and fit some proper lower European ones, it killed the weaving and removed the skittishness entirely.
I remember those friction steering dampers well Richard - some 70s Jap bikes had them. The messers round our way used to take pleasure winding them on full on parked bikes, much to the entertainment of the rider and neighbouring bystanders when it came to moving off up the road
I do find the whole thing about bike dynamics really interesting. I know the early H2 750 Kwacks had a reputation for being an evil b@stard that would throw the head and spit you off at the slightest provocation. I read an article in later years written by one of the first UK journalist to ride one, who said that the demo model he had definitely weaved under very little provocation, but when he asked the dealer to get rid of the high US spec bars and fit some proper lower European ones, it killed the weaving and removed the skittishness entirely.
richardg
Admonishtrator
Well we are all aware of the handling issues surrounding the LC...
Enfield boy
pfm Member
For it's time the LC was an extraordinarily good bike for budget conscious loonies. My cousin had a 350, I rode it occasionally and loved it. It's the only bike I've ever experienced "chatter" on, he was riding and I was pillion on that occasion.
Arkless Electronics
Trade: Amp design and repairs.
...simply power through a tank slapper...
richardg
Admonishtrator
The same bike is now called a KTM 790 Duke.
Enfield boy
pfm Member
If it came with a 2 stroke motor I'd buy one!
Yes Jez, I've powered through a few tank slappers, my last on a 2001 Bonnie. I unsettled it clipping a cats eye on a bend while overtaking a Porsche.
Yes Jez, I've powered through a few tank slappers, my last on a 2001 Bonnie. I unsettled it clipping a cats eye on a bend while overtaking a Porsche.
I can imagine that, I remember a documentary from years ago that showed a bike wea ving and the expert rider on it demonstrating that he could make it worse by leaning back and better by leaning forward. All no-hands at considerable speed on a banked track, the throttle having been set to stay put when released. He was impressively calm throughout, including when the shakes became increasingly violent as he sat up, no hands, at (ahem) motorway speeds.
