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Offline genie

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Head shake
« on: September 28, 2014, 06:25:04 pm »
I have covered just over 10000 km with my late 2013 model (OE steering damper fitted) I have TKCs on the front and Karoo 3s on the rear- pressures on gravel 2.0 front 2.4 bar rear. I have experienced head shake twice. On my 2004 GS I never ever experienced it in 25000 km. In both cases I was traveling between 80 and 90 km/h on a reasonable gravel road with no passenger or baggage. I encountered a short stretch of corrugation and this set up the violent head shake. In my opinion if I did not have a steering damper I would have lost control. Luckily my wife was not on the back. It is of short duration and possibly a function of the corrugations's wave length as I have covered many kms.  of corrugated gravel roads and not experienced it. Your weight distribution on the bike also plays a role.
 

Offline 1190

Re: Head shake
« Reply #1 on: September 28, 2014, 07:02:10 pm »
It's happened to me twice before on my 2014 lc and a few times on my 990. I just slow down and then when it goes away I either stay at that speed or go faster than when it happened. It happens when you encounter a certain type of corrugation on a gravel road? I found it worse when the suspension is set to soft but could just be a coincidence? I rode in enduro mode on hard in the TK for 500km last week and it only happened once but I react as above alot quicker because i know when to expect it.
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Offline Sandban(g)k

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Re: Head shake
« Reply #2 on: September 28, 2014, 07:58:20 pm »
Tyre pressure of 2.4 on gravel is not a good idea. Was your suspension set up correctly? And were you standing i find that when sitting down on corrugation the headshakes are less. This is because of the weight ditribution a bit backwards.
 

Offline genie

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Re: Head shake
« Reply #3 on: September 28, 2014, 08:12:32 pm »
Set to single no baggage and soft.  Enduro mode. Sitting down in both cases.
 

Offline Garfield

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Re: Head shake
« Reply #4 on: September 28, 2014, 08:18:47 pm »
Tyre pressure of 2.4 on gravel is not a good idea.

Why?
What is?
 

Offline Sandban(g)k

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Re: Head shake
« Reply #5 on: September 28, 2014, 08:34:00 pm »
On gravel I go down to 1.8 usually. Even 1.6 if needed. But Im lazy when it comes to tyre pressure, so leave front and rear at 2 bar except when I know where Im going.

Hard tyre pressures on gravel on bike or car lets the vehicle do strange things. If you dont believe me, inflate your bakkie to 2.8 and try a bad gravel road. Especially with no extra weight.
 

Offline Garfield

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Re: Head shake
« Reply #6 on: September 28, 2014, 08:38:37 pm »
Did serious corrugations last bit home today, 2.4 and 2.8, no issues.
Also did corrugations yesterday, same speeds, same load, 2.0 and 2.0, also no issues.

This head shake sounds like a combination of things, not just pressure.
 

Offline Sandban(g)k

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Re: Head shake
« Reply #7 on: September 28, 2014, 08:49:06 pm »
Sure, tyre pressure alone is not the problem, but Ill definately not do gravel at 2.8 on a BMW  :biggrin:
 

Offline Garfield

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Re: Head shake
« Reply #8 on: September 28, 2014, 08:54:18 pm »
Used to do 2.8 back on GSA on gravel often when I was lazy to deflate, never an issue, but I did change suspension settings though.

Can't speak for the new 1200 though.
 

Offline SGB

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Re: Head shake
« Reply #9 on: September 28, 2014, 10:21:31 pm »
Head shake will happen (or the slight movement that initiates the head shake).  I have experienced it many many times.  On old and new GS's.  And KTM's.  And Honda's.
Conditions dictate when it happens.  And bike set-up and the way you ride also come into play - obviously.  There is unfortunately no scientific cure.  When it happens, you have to ride it out.  If you are going to panic - chances are you will close the throttle or brake and that makes it worse.  Experience is the best weapon here.

Just a few things:
- I have never pumped a tyre to 2.8 bar ever.  I think it will only be needed if my pillion is heavier than me and we load all our furniture.
- 2.0 bar to 2.2 works - OK traction, and you don't easily bend rims.  I used to be at 1.8, but with the rims going softer, I have now standardized on 2.0.
- Why pump the rear harder than the front?  That is where you need traction.  I can see the front being a little harder - smaller tyre profile and at the leading edge for impact.  I use the same pressure for both, if one has to be slightly harder, it would be the front.
- Confidence is what drives you through a dodgy situation.  Hesitation, panic, closing the throttle and stuff like that are the biggest contributors to changing a slight lateral movement into a proper oscillating shake.  Ride it out.  With confidence.
- I often encounter people who have seen one or two shakes, and then fear causes initiation of more violent future shakes.
- Make sure that you fully understand the fundamentals of riding the bike.  Suspension settings, tyres, body posture, cornering technique, acceleration, deceleration, (hard) braking and the like.  The better the understanding, the more fun the ride.
- "It is like dancing.  It sadly lacks power if you have not mastered the fundamentals."  Bruce Lee

I am not trying to solve the problem raised in the first post.  I am just sharing some personal perceptions formed over time by looking carefully at many riders from the side-line. Including myself..... ;)
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Offline Lord Knormoer

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Re: Head shake
« Reply #10 on: October 02, 2014, 10:50:12 am »
Sure, tyre pressure alone is not the problem, but Ill definately not do gravel at 2.8 on a BMW  :biggrin:

My rear is 2.8 and front 2.4. Tar or gravel, I do not change pressure. I also struggle to understand why this is bad.

Ps: I ride a GS
 

Offline eberhard

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Re: Head shake
« Reply #11 on: October 02, 2014, 11:08:54 am »
I have always kept my tyre pressure consistently at around 2.2 (the suggested pressure for my bike), whether on or off tar. Never had handling problems (or punctures for that matter). Only times I deflated my tyres were when driving extended stretches on a beach or thick sand only road where you know it is going on and on for 50km or more. It dumb folds me when I see the pack stopping before they go onto a gravel road and ceremoniously deflate their tyres. Often that particular gravel road is harder than the tar road. Why TF deflate?! 
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Offline Koet

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Re: Head shake
« Reply #12 on: October 02, 2014, 11:10:26 am »
http://www.wilddog.za.net/forum/index.php?topic=159582.0;topicseen

Buy it, make a new bracket to fit it to your bike and never worry about it again.  I had head shake on my 2008 1200GS on BAD corrugated dirt road once.  Was damn scary.  Fitted mine not long afterwards and been happy ever since.
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Offline genie

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Re: Head shake
« Reply #13 on: October 02, 2014, 11:32:00 am »
My bike has a factory fitted steering damper. The original LCs did not have factory fitted steering dampers.
 

Offline lecap

Re: Head shake
« Reply #14 on: October 03, 2014, 07:45:44 am »
...
- Why pump the rear harder than the front? ...

Because the rear is carrying more weight than the front, maybe ???
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Offline Sandban(g)k

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Re: Head shake
« Reply #15 on: October 03, 2014, 03:39:28 pm »
I have always kept my tyre pressure consistently at around 2.2 (the suggested pressure for my bike), whether on or off tar. Never had handling problems (or punctures for that matter). Only times I deflated my tyres were when driving extended stretches on a beach or thick sand only road where you know it is going on and on for 50km or more. It dumb folds me when I see the pack stopping before they go onto a gravel road and ceremoniously deflate their tyres. Often that particular gravel road is harder than the tar road. Why TF deflate?! 

Many a guy also didnt flip his Fortuner with higher tyre pressures, but a lower tyre pressure surely is better. The science of a larger footprint.
 

Offline eberhard

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Re: Head shake
« Reply #16 on: October 03, 2014, 04:22:18 pm »
Yes, I understand the larger footprint concept, i.e. why I deflate when in consistently thick sand. The not thick sand part I do not understand. I have ridden a lot of the roads outside of S.A.'s borders that are written about in the ride reports, except I have never ever even had a flat tyre on any of those roads. Some of those guys had multiple flat tyres, damaged tyres or damaged rims. I know they deflated, because they wrote such. Which leaves me with two causations :a) the riding style; b) the deflate tyres. Or both. I grew up in South West Africa before there was electricity on the farms. There was only one tarred road, the one that went from south to north. We drove more non tarred road than we drove tarred road. We never deflated, except as stated above. You ran a higher risk of getting a flat or damaging your wheels with deflated tyres on those dirt roads. The deflating of tyres strikes me as a concept that appeared with organised off road motorcycling. And back to the head shake on the water cooled BMW, I have thus difficulty in ascribing it to the tyre pressure. Incorrect tyre pressure can most surely cause an accident (I have lived too long in South West not to know that), but head shake? Should the head shake then not be blamed on: a) design flaw in the bike itself; b) style of riding?
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Offline K-9

Re: Head shake
« Reply #17 on: October 03, 2014, 04:36:16 pm »
the so called headshake: I experienced a small shake on the way back from the eco on tar, above 175.  It happened twice after a dip, more than a bump in the road.

I had a well used TKC on the front and brand new Karoo 3 on the rear.  

after it happened I started watching, above 165 I noticed the bar moving slightly side to side.  I have done 16 000kms on this bike and have not seen it before.

Back in Durban I borrowed a complete wheel from Ryder and perfect no movement.  so I put on a new K3 on the front, PROBLEM SOLVED.

the front was uneven and worn badly on the one side, possibly from riding from Rhodes to bloem in a near gale with soft tyres.

like SGB said- ride it out.  SGB thanks for the confidence to do so.

the worn tyre was at fault, not the bike and I like to think not the rider.
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Offline Vintage_Mania

Re: Head shake
« Reply #18 on: October 03, 2014, 05:05:39 pm »
I'm no GS buff, but even if dirt roads are as hard as tar, I would think that deflating helps with the unevenness on hard dirt more than bigger foot print. It is a very different surface than a tarred road, even if it is hard. It helps absorb and soak in the uneven surface, taking in some of the pressure.

Just my 2c.

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Offline PieterV

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Re: Head shake
« Reply #19 on: October 03, 2014, 09:34:09 pm »
I experienced head shake several times with my 2014 GSA LC on the corrugated dirt sections at Eco.  Was between 80 and 100 km/h at the time.  New Karoo 3s front and back, pressure on 2 bar front and back.  Was in Enduro mode, single rider, no luggage, suspension setting at the time.  Cannot remember the hardness setting.
« Last Edit: October 03, 2014, 09:35:59 pm by PieterV »