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post #1 of 20 Old May 16th, 2010, 3:05 am Thread Starter
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k1200lt oversteer/understeer

I stumbled upon this,, good reading...matthew

BMW Motorcycle neutral steering

by Duane Ausherman


Neutral steering is very important for stress free long distance riding. Just what is it and why is it important? Neutral steering is what makes some motorcycles so easy to ride, so effortless to go through turns and allows the rider to go for long distances. It is the tire profile and geometry of the forks and frame that determine it.

Test for neutral steering
First you must test for straight tracking. With your hands off in the 30-50 mph range, it must go in a straight line. If it does not, then maybe the frame is bent.

It is very easy to test for neutral steering. Make sure that your tires are in good condition and are properly inflated. It is an absolute must to have the throttle lock to keep it at one speed. If you can't hold a steady speed, you can't perform this test. The steering bearings should be correctly adjusted. Remove any steering damper friction. You should also know that your bike has little or no tendency to have a low speed wobble. If you have any question about that, go to my page on wobbles.

Find a curvy road where a fast rider could easily go through the curves at 50 mph, but 30 mph is easy and "normal" for the average rider. Find a time when you have little traffic with which to be concerned. As you go through a turn, sort of lighten up on your hand pressure on the bars. As you lighten up, the bike should stay in the same line as before. If you feel that the bike wants to "fall over" or "go straight" then maybe you don't have neutral steering. As you feel your bike want to stay in the same curve, lighten up even more. If you can get to the point of having your hands completely off of the bars and the bike still stays in the same curve, then you definitely have neutral steering. It may take several "runs" though the curves to do all of this. You should discover that your airhead BMW will go through the turn without your hands even on the bars. One can even put it into the turn and pull it out without even touching the bars. It won't be done as quickly as with your hands on the bars, but it certainly can be done. I have ridden miles through many curves without even touching the bars, just by using my body to steer.

Oversteer
This is where the bike seems to want to fall over into the turn, or turn tighter as you relax your pressure on the bars. If you had a remote throttle, you could accelerate and that would tend to "pick" the bike up. As it is, you have to "grip the bars" in a curve and that is a most unsettling feeling to have. You sort of have to "hold the bike up" to feel confident. Many of the older Japanese bikes were designed this way and it was "normal" for them.

This will cause a change in geometry, basically too short of a wheel base and too little trail. If the front end sits too low, this will be the result. One of the reasons for this to occur on a BMW is to have sacked out (collapsed) fork springs. A common reason is when the Earles fork was bent back from an accident. We saw a few telescopic fork models do this too, but usually they bind up so badly that the owner can't/won't ride it.

Low air pressure will allow the front end to sit low too. A tire that is too small for the front will do it too. One of the most common reasons is that the owner mounted a too large tire on the rear. This sets the front lower by comparison and it will oversteer.

The /2 Earles fork series used the same sized tire front and rear, a 3.50 X 18" and that worked very well. The US models with the "new" telescopic forks used a 4.00 X 18" on the rear and it had neutral steering when all was in top condition. Don't confuse the two types of forks and get some wild hair to use a 4.00 on the rear of your Earles forks BMW if you value neutral steering.

On the /5, and later bikes, it was common for owners to overload the bike with accessories and ruin otherwise good handling. I have no experience with BMWs after 1981, but geometry and human nature probably haven't changed very much.

Understeer
This is where the bike doesn't even want to lean. It will try to stand up in the curve if you reduce pressure on the bars. This is far rarer than oversteer on a BMW. It makes you really work to go into a curve and stay there. I have seen it from a variety of situations on a BMW. Once a /2 came in with a 4.00 on the front and it was a real bear to ride. Once I found a 3.00 or 3.25 Metzler C on the rear. I didn't even know that they made them that small.

Tire profiles
The shape of the tire profile greatly alters how a bike goes into corners. The old Dunlop K81 had a triangular profile and that caused it to give one a scare as it transitioned from straight ahead to medium cornering. After it was in the corner it really held well. Take a look at the profile and see if it has any irregular shape to it. I have seen some new (meaning in the last 10 years) tire profiles that would really mess up an old airhead. The cafe racer could easily give up some smoothness in transition for some other advantage, such as greater traction while in the corner.

The Metzler and Continental tires recommended by BMW really had a profile that felt good. I well know that better compounds exist today, but I would like to keep a regular profile and keep the neutral steering.

The result of neutral motorcycle steering
Neutral steering makes it easier to ride long distances, go through curves with confidence and save your shoulder and back muscles. When a rider becomes really comfortable with a bike like this, the rider only needs to "see a curve" and the bike seems to just "go through the curve." I have often tried to do nothing consciously when approaching a curve and the bike just seems to have a mind of its own and do the right thing. It is this characteristic that causes some bikes to be very easy to ride and others seem to be a wrestling match. On the older stuff, the European bikes tended to be neutral steering and the Japanese were often guilty of oversteer.

Stay with the tire sizes suggested by the manufacturer. I do not know the size conversion to the newer modern metric tire sizes.
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post #2 of 20 Old May 16th, 2010, 5:06 am
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Re: k1200lt oversteer/understeer

Nice article. Looking back at the amazement I felt negotiating my first sweeper with my LT neutral steering might be the reason. I remember thinking how little control input, and how no changes were required to keep the bike tracking in the constant radius curve.

Ya gotta be careful around these parts even suggesting one take ones hands off the bars for even a second. Including the furtherance of science. Apparently this might cause an immediate and drastic disturbance in the "force" which causes your bike to hunt down and hit other motorcycles, or to become a circus star! This information is based on a previous thread. Do a search for some amusing reading.

Loren

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post #3 of 20 Old May 16th, 2010, 7:16 am
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Re: k1200lt oversteer/understeer

My background, before the LT, had been cruisers. When you get your start and history from there everything else is based on that experience. The statement "that's a good handling bike" was RELATIVE to the other bikes you've experienced. Now that I have a year and a half of the LT under my belt, while still being the owner of a "cruiser, I laugh at what I once thought was a "good handling bike". I'm sure there are "better handling bikes" out there, but, the LT is very neutral and it pays off in how I feel at the end of a long ride. It's what makes me feel "not tired" and makes me feel like I could go another couple of hours easily. I love the handling, smoothness and effortless feel I get with the LT.
A year and a half into it and I STILL like my LT.....excuse me....LOVE my LT !

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post #4 of 20 Old May 16th, 2010, 11:19 am
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Re: k1200lt oversteer/understeer

If you try this test on an LT and take your hands off the bars, make sure you're wearing diapers that day.

Life happens...you control your reaction.

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post #5 of 20 Old May 17th, 2010, 2:08 am
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Re: k1200lt oversteer/understeer

Quote:
Originally Posted by pickerbiker
If you try this test on an LT and take your hands off the bars, make sure you're wearing diapers that day.
Larry, It sounds to me like you may have had a bad experience (shimmy, tank slap, gross steering instability) with your LT in the past. With or without the sidecar mine will cruise straight as an arrow down the interstate. On Iong straight stretches of backroad have set the cruise control, and then turned it off and let it decelerate to 35 mph while holding my hands just above the hand grips with no change in its ability to track straight and true. Straight and true with the sidecar is a no-brainer because it has hydraulic camber adjustment.

Am I just really freakin' lucky that that the steering on my ride doesn't shake, rattle, and roll as it seems others do?

Loren

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post #6 of 20 Old May 17th, 2010, 11:05 am
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Re: k1200lt oversteer/understeer

Quote:
Originally Posted by wa1200lt
Am I just really freakin' lucky that that the steering on my ride doesn't shake, rattle, and roll as it seems others do?

Loren
Count me in on the 'lucky' too I guess.

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post #7 of 20 Old May 17th, 2010, 8:40 pm
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Re: k1200lt oversteer/understeer

Quote:
Originally Posted by pickerbiker
If you try this test on an LT and take your hands off the bars, make sure you're wearing diapers that day.
You might check: front wheel shimmy
The big "fix" for my 09 was to revert back to a pre-05 rake.

Kaw ZX12R Ninja
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post #8 of 20 Old May 17th, 2010, 10:40 pm
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Re: k1200lt oversteer/understeer

Quote:
Originally Posted by IronButtOpie
You might check: front wheel shimmy
The big "fix" for my 09 was to revert back to a pre-05 rake.
Jack, this may well be the difference. Mine is an '01, the other respondent to this thread who has experienced no handling issues is also a pre '05. The low speed handling changes made in '05 and later bikes may have affected the high speed stability. At least the "hands off" stability.

I think I like the way mine is set up!

Loren

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post #9 of 20 Old May 18th, 2010, 12:19 am
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Re: k1200lt oversteer/understeer

Quote:
Originally Posted by wa1200lt
Larry, It sounds to me like you may have had a bad experience (shimmy, tank slap, gross steering instability) with your LT in the past. With or without the sidecar mine will cruise straight as an arrow down the interstate. On Iong straight stretches of backroad have set the cruise control, and then turned it off and let it decelerate to 35 mph while holding my hands just above the hand grips with no change in its ability to track straight and true. Straight and true with the sidecar is a no-brainer because it has hydraulic camber adjustment.

Am I just really freakin' lucky that that the steering on my ride doesn't shake, rattle, and roll as it seems others do?

Loren
Loren,
I experienced the dreaded LT tank slap while decelerating from about 45 mph. I had taken both hands from the bars to make a quick adjustment to my helmet. With my hand off the throttle, the bike naturally started to slow down and at around 40 mph, the handlebars just started going crazy. I quickly grabbed them, but it scared the sh^^& out of me and in 40 years of riding various motorcycles, I've never had that happen. I've very careful about keeping proper tire inflation, replacing tires before they're too worn, etc. Didn't matter. What's strange, is it's not like I feel any vibration in the bars or any tendency towards tank slapper during normal deceleration. Needless to say, that's the last time I EVER took my hands off the bars of the LT.

Larry

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2015 R1200 RT (holy cow…what a bike)
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post #10 of 20 Old May 18th, 2010, 9:08 am
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Re: k1200lt oversteer/understeer

I have to say no matter what I do to a tire I have a 40 MPH deceleration wobble.

I know conventional wisdom is it is a balance problem. I can not get it balanced out nor does Dyna Beads remove the wobble.

I just don't take both hands off the bars. I can lock the cruise at any speed above 45-50 and it will track all day no hands.

I never had a bike that acted this way.

I have checked all pivot points including the steering head and can find nothing wrong. I have checked and rechecked torque settings on the FD/Swing arm.

I just don't take both hands off.

Lee
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post #11 of 20 Old May 18th, 2010, 2:03 pm
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Re: k1200lt oversteer/understeer

I feel ALL your pain with regard to "tank slap, shimmy, wobble."
For me, after replacing the lower steering arm with a pre-05 arm, I checked for wobble again. I still had wobble but it had GREATLY changed for the better. Keep in mind, I had a fresh set of tires, fresh balance, and pressurized the tyres to 42 & 48 psi BEFORE the lower steering arm replacement and had a great amount of wobble (20- 60mph all the time). The replacement to a pre-05 is what made a huge difference.
After the replacement, I got enough guts to allow the wobble to build to its' most extreme condition. I found it would not progress to a point that would throw me from the bike. But was one scary ride.
Now, my 09 only wobbles between 40-43 mph. I havn't allowed that to hamper my enjoyment of "hands off" riding.
FYI
Good luck!

Kaw ZX12R Ninja
05 GS ADV
07 GS ADV- Iron Butt, Copper Canyon
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post #12 of 20 Old May 18th, 2010, 3:12 pm
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Re: k1200lt oversteer/understeer

Quote:
Originally Posted by LAF
I have to say no matter what I do to a tire I have a 40 MPH deceleration wobble.

I know conventional wisdom is it is a balance problem. I can not get it balanced out nor does Dyna Beads remove the wobble.

I just don't take both hands off the bars. I can lock the cruise at any speed above 45-50 and it will track all day no hands.

I never had a bike that acted this way.

I have checked all pivot points including the steering head and can find nothing wrong. I have checked and rechecked torque settings on the FD/Swing arm.

I just don't take both hands off.
+1 What he said...

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post #13 of 20 Old May 19th, 2010, 2:36 pm Thread Starter
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Re: k1200lt oversteer/understeer

These k12000lt just have allot of mass in the front end, sitting on your bike in nuetral just quickly shake rapidly the front handlegrips back and forth then let go, notice the front mass flexing in opposite - opposing action, quit interesting indeed...matthew
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post #14 of 20 Old May 19th, 2010, 3:42 pm
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Re: k1200lt oversteer/understeer

Quote:
Originally Posted by roadcrave
These k12000lt just have allot of mass in the front end, sitting on your bike in nuetral just quickly shake rapidly the front handlegrips back and forth then let go, notice the front mass flexing in opposite - opposing action, quit interesting indeed...matthew
Yeah matthew, it does have a lot of mass. But interesting, my 05 and my 07 GS ADV do the same thing.

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post #15 of 20 Old May 20th, 2010, 2:01 pm Thread Starter
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Re: k1200lt oversteer/understeer

I would have never guessed that to be on those bikes...matthew
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post #16 of 20 Old May 21st, 2010, 11:07 am
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Re: k1200lt oversteer/understeer

Matthew,
I think it's an issue of harmonics. If you get the frequency of handlebar occilation correct, the handlebars oppose the weight (force)- which is lagging reaction to the induced force. It happens- to some degree- on all bikes. Most are probably not noticeable. My 05 GS ADV is more noticeable than my 07 GS ADV, (I'm a GREAT fan of the 07 & newer).

Kaw ZX12R Ninja
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09 LT

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post #17 of 20 Old Jul 13th, 2010, 4:51 pm
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Re: k1200lt oversteer/understeer

I had the dreaded wobble on my front end last week while riding twisties in the hills of North Georgia. I must say that it scared the Sh** out of me when I was avoiding a truck coming into my lane while going through a curve. The wobble occurred while braking, is this the same thing?

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post #18 of 20 Old Jul 13th, 2010, 7:07 pm
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Re: k1200lt oversteer/understeer

No. The wobble he is talking about at a stable straight line speed. If you hit the brakes, then you are upsetting the ability of the bike to corner. When you hit the brakes in a corner, the bike wants to stand straight up to stop. You trying to keep it forced over in the curve without much pressure on the handle bars will make the bike wobble. At least that is how I understand it.

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post #19 of 20 Old Jul 13th, 2010, 7:39 pm
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Re: k1200lt oversteer/understeer

wtevritks,

Steve nailed it. The WORST thing you can do in a curve is hit the brakes.

Always better to stuff it deeper into the corner. I realise the instinct when faced with a truck coming into your lane is to brake but that actually puts you closer to the threat. May want to practice an outside line transitioning quickly into and inside line (I am talking a right hander here). This is "stuffing it deeper" and the LT will do it. That way you will be ready the next time. Happy riding.

John
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post #20 of 20 Old Jul 13th, 2010, 8:50 pm
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Re: k1200lt oversteer/understeer

My bike always tracks to the right when I let go of the bars. I have gone so far as to put 40 lbs. in the left case & nothing in the right case & it still tracks to the right. As far as braking in a corner the LT is the most forgiving bike I have ever owned. I think it is because of the overall weight & the fact that it is top heavy. One time while I was adjusting the zoom in on my center GPS I way over rode in to a corner hit the brakes hard halfway thru & it hardly stood up. One bad ass bike in my opinion.

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