Wobly back-end when in 3 figures - K-Bikes.com - Excellence in Motion
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post #1 of 26 (permalink) Old Oct 8th, 2007, 4:51 am Thread Starter
JIS
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Wobly back-end when in 3 figures

Hello chaps ! We've all discussed the value of replacement shocks at or around 20k miles (mine has 21k miles). I am convinced that Ohlins is the right option but cannot do that yet. Meanwhile, I have a concern that, each time the bike gets about 105mph (in Germany of course) the bike's normal stability disappears and it feels "nervous" with a less than solid rear end. Tyres are Michelin Pilot Road 2s with masses of tread and propery inflated. The rear damping is set just over "half way".

Any thoughts please?

John I. Stephen - Tunbridge Wells, Kent, UK
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post #2 of 26 (permalink) Old Oct 8th, 2007, 12:36 pm
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I doubt its the shocks that's causing this high-speed instability. I waited until 64k miles to replace my stockers, and never had a problem doing 130+MPH with them. Cornering with the worn shocks was a different issue, however.


Quote:
Originally Posted by JIS
Hello chaps ! We've all discussed the value of replacement shocks at or around 20k miles (mine has 21k miles). I am convinced that Ohlins is the right option but cannot do that yet. Meanwhile, I have a concern that, each time the bike gets about 105mph (in Germany of course) the bike's normal stability disappears and it feels "nervous" with a less than solid rear end. Tyres are Michelin Pilot Road 2s with masses of tread and propery inflated. The rear damping is set just over "half way".

Any thoughts please?

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post #3 of 26 (permalink) Old Oct 8th, 2007, 1:30 pm
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Quote:
Originally Posted by JIS
Hello chaps ! We've all discussed the value of replacement shocks at or around 20k miles (mine has 21k miles). I am convinced that Ohlins is the right option but cannot do that yet. Meanwhile, I have a concern that, each time the bike gets about 105mph (in Germany of course) the bike's normal stability disappears and it feels "nervous" with a less than solid rear end. Tyres are Michelin Pilot Road 2s with masses of tread and propery inflated. The rear damping is set just over "half way".

Any thoughts please?
My '97KRS 36K has done more than yours for looong stretches with side cases and top case (In Germany) with stock (some would say worn out) oem suspension on tires nobody else probably buys (Avon ST's) and some wind. The bike was absolutely stable. Without the side cases I'm even more confident.

As rhhall says, on the Autobahns (!) at high speed you're pretty well riding a straight line with some gentle sweepers so I wouldn't look at suspension first to cure a stability issue. Assuming you're not expecting the same rock solid stability with full luggage or have added a high screen/lamina lip, I'd first make sure you've got no wear in the rear swingarm bushes, rear drive bearing, front telelever and fork head bearings which might put the bike out of track. Forget the damper, it doesn't do anything in straight lines. You could also slacken the front wheel axle pinch bolts and do the bounce thing. Also check your wheels for any runout on the rims and balance.

These bikes are amazingly stable. Now I have to go find out why my motor exhaust sounds a bit low, agricultural and I got 55 mpg over a 300 mile sustained cruise. Something's up, I was getting around 35mpg with a sooty exhaust before I did lots of things. I've done the same motorway route before and at my usual gas stop the guage was reading 3/4 and a 1/4 is what I put in.



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post #4 of 26 (permalink) Old Oct 8th, 2007, 3:24 pm Thread Starter
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Quote:
Originally Posted by voxmagna
....Assuming you're not expecting the same rock solid stability with full luggage or have added a high screen/lamina lip....
... Well Mr Vox.. no luggage at all but, yes I do have a Laminar Lip; set as high at possible. Do you think that it is this that causes the high spped instability? Suppose I lower the screen at 100+?

John I. Stephen - Tunbridge Wells, Kent, UK
K1300 GT (quite superb ! )
Triumph Tiger 1050 (2008)
K1200 GT (2003)
R1150R (2002)
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post #5 of 26 (permalink) Old Oct 8th, 2007, 5:29 pm
 
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Quote:
Originally Posted by JIS
... Well Mr Vox.. no luggage at all but, yes I do have a Laminar Lip; set as high at possible. Do you think that it is this that causes the high spped instability? Suppose I lower the screen at 100+?


Are you an "elbows in" or an "elbows out" rider?

Riders who stick their elbows out instead of tucked in at high speed can experience a weave due to uneven air flow pulling on their arms and it can make the rear feel loose.

Try raising and lowering the screen at speed and moving your body position around.



Testing this could be taken as an excuse to travel at high speed in the interest of science.



Ride safe.
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post #6 of 26 (permalink) Old Oct 8th, 2007, 6:24 pm
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Quote:
Originally Posted by JIS
... Well Mr Vox.. no luggage at all but, yes I do have a Laminar Lip; set as high at possible. Do you think that it is this that causes the high spped instability? Suppose I lower the screen at 100+?
When in der deutche land I had no lip, screen low, side and top bags. Laminar lip is bad news at speed with strong cross winds on open roads, luggage doesn't help either. Most faired bikes will give you a big surprise when on a sheltered or enclosed road and you meet an open stretch with a cross wind. As well as looking out for all the usual fast rider hazards, you need to be watching ahead for the giveaways of crosswinds. Checkout trees, trucks with sheeting, anything moving from wind and be ready. Twisting the throttle is the easy part, staying alive needs practice.

Keep safe - Vox



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post #7 of 26 (permalink) Old Oct 9th, 2007, 12:51 am Thread Starter
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I have some things to try

Thanks Mr Vox and Coach; I suspect that I keep my elbows "out" and try to duck behind the Laminar Lip. Your point about safety are 100% understood but I do enjoy the odd burst of speed when in "der deutsche lande"; but we'll take it easy. as you say, twisting the throttle is the easy part. (And boy does she find it easy to "point east" on the speedo. However, going east south east is probably not for me)!

Thanks!

John I. Stephen - Tunbridge Wells, Kent, UK
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Triumph Tiger 1050 (2008)
K1200 GT (2003)
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post #8 of 26 (permalink) Old Oct 9th, 2007, 5:20 am
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Quote:
Originally Posted by JIS
Thanks Mr Vox and Coach; I suspect that I keep my elbows "out" and try to duck behind the Laminar Lip. Your point about safety are 100% understood but I do enjoy the odd burst of speed when in "der deutsche lande"; but we'll take it easy. as you say, twisting the throttle is the easy part. (And boy does she find it easy to "point east" on the speedo. However, going east south east is probably not for me)!

Thanks!
Hi guys,

From a racing perspective if I had my elbows out......then not only was there substantial wind noise but an evident weave and a certain amount of instability caused by the streamlining effect being disstorted.

I ride my K1200rs of 98 vintage with relaxed tucked in arms, light grip on the bars (as this can also cause weaving due to excessive grip issues with your hands) and just relax zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz, the more relaxed one is the faster you go, plain and simple.
Tyre pressures, fuel, worn wheel bearings, warped discs, worn rear shock, camber conscious riding, squared off tyres, weather conditions, uneven fueling, moving pillion, full monty brekky and uneven loading of luggage can all add to weaving woes.............now if you have got all this lot together there is some serious problem...

Andy
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post #9 of 26 (permalink) Old Oct 9th, 2007, 7:19 am
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Gandy, I came across something on the brain/body co-ordination thing:

If I'm in a UK outside lane with only the curb/gravel and steel crash barriers on my right the bike is fine when I'm looking a long ways out in front and concentrating. But if I'm looking into my right hand rearview, any slight loss of concentration tends to put the bike to the right where you don't want it, but glancing down at the left mirror does the opposite. That can't be a bike issue, so either my brain is too old and worn out, or something is happening when I'm seeing the rear perspective, then switch attention back to the front.

There are only a few opportunities to go to a track in UK, and I think it's a good idea to get some experience of triple digits on a track first. I don't think straight lines are so difficult, but setting up even gentle curves can bring surprises compared to slower speed twisties. I've already experienced the side wind problem half way into a high speed curve and it's scary. If you bottle out and slow, you've then lost the setup to make the rest of the curve.

JIS is probably like me and isn't going to be comfortable shifting his weight about too much at autobahn speeds, but I don't have any problems tucking in arms, slightly bent, relaxed and sometimes head well down. I keep my screen low and that makes the wind balance body weight wanting to move forwards, whilst taking pressure off the arms. Big wide screens seem fine at lower speeds when the bike has a true upright cruiser riding position. I now only use my Laminar lip in Winter around town, mainly to keep the rain off.

I've had my throttle springs slacked off for a couple of years now and that helps stay more relaxed. Sometimes I excercise my hands and give them a rest by straightening the fingers and just holding the palms against the grips. I find excercises and stops help keep me relaxed on long cruises at sustained high speeds. I notice more now that most of the naked bikes and cruisers I come across are riding at about 60-70 mph with occasional bursts, so I appreciate the bodywork we have on the K-bikes to sustain high cruising speeds with stability - but mine needs a bit more in the comfort department!



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post #10 of 26 (permalink) Old Oct 9th, 2007, 12:24 pm
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Quote:
Originally Posted by JIS
Hello chaps ! We've all discussed the value of replacement shocks at or around 20k miles (mine has 21k miles). I am convinced that Ohlins is the right option but cannot do that yet. Meanwhile, I have a concern that, each time the bike gets about 105mph (in Germany of course) the bike's normal stability disappears and it feels "nervous" with a less than solid rear end. Tyres are Michelin Pilot Road 2s with masses of tread and propery inflated. The rear damping is set just over "half way".

Any thoughts please?
My general understanding and belief is that the K bikes becomes more stable as speed increases without luggage on the bike. That's been the case for me on my 2003 GT. Contrary to that statement..........My GT IS nervous above 100 mph with the bags installed.

You may have something wrong with the rear end differential pivot adjustment. Make sure there is no play in the adjustment. Is there any perceivable side to side play of the rear wheel?

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