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wendeg

Rear shock preload

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wendeg

I will be touring in September and will have approximately 35kg of extra weight on the bike (panniers etc.) I am 70kg... do you feel i should adjust the rear preload for the 35kg extra i will be carrying Whike touring?

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Derm

Your total weight is still less than if you were carrying a pillion, so no. However the suspension on the NC is possibly the poorest aspect of the bike, so trying it out may improve it.

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embee

I would say yes. Yours will have the simple cam type preload adjuster so not such a big deal, that's what it's there for. First, do you have a centre stand? This makes life very much easier for a host of reasons (bike is stable, load is off suspension so adjustment is easier, measurements are easier, plus chain maintenance etc).

 

See what your "static sag" and "laden sag" are first as it is set at the moment. Not complex, simply measure the distance from the rear wheel spindle (e.g middle of spindle head or top edge of swingarm) to a fixed point vertically above it on the frame or bodywork. Note the details are not absolutely critical, just choose somewhere convenient and repeatable, use tape and a felt pen if necessary.

Measure it when the bike is on the centre stand, suspension fully extended (you can substitute leaning the bike over onto the front wheel+sidestand to unload the suspension if no centre stand, you need an assistant).

Measure the same points when the bike is upright and on its wheels, again an assistant helps. Then measure again with you sitting on it normally with basically all your weight on the bike.

Record these measurements so you don't need to repeat stuff.

 

Ideally the "static sag" would be around 35-40mm on an X (others may advise a slightly different number).  Adjust the preload if it's far away from this. You should have a C-spanner in the toolkit (I would expect) to do this. Usually much easier to adjust when on the centre stand and minimum load on the suspension unit. A little oil/grease around the adjuster sleeve usually helps. Record what you set it to.

Sit on it and measure the "laden sag". Record it. This will be your normal default setting.

 

Load the bike with representative weight for what you intend to take, sit on the bike and measure it again. Adjust the preload so that you now get a value similar to your normal "laden sag". This will be your loaded setting. Then the bike will ride and handle more or less the way it does with just you on board and no luggage. You should be able to make a note of the notches used on the adjuster, e.g. normal on  notch 3, loaded on notch 5 or similar.

 

Alternatively you can forget all this and just ride it the way it is. :unsure:

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wendeg

Thanks to all!

 

Just to make sure I understood well...

 

Scenario 1: rear wheel off the ground

Scenario 2: both wheels on the ground

Scenario 3: both wheels on the ground with rider sitting fully on bike

Scenario 4: both wheels on the ground with rider sitting fully on bike plus luggage weight

 

A. Static sag is the difference between wheel off the ground (scenario 1) and bike with two wheels on the ground (scenario 2), unladen except for full fuel tank.

B. Laden sag is diference between bike with two wheels on the ground (scenario 2) and bike with rider on it (scenario 3), with full fuel tank. (Ideally this should be 35 to 40mm)

 

Laden sag with full weight (scenario 4) should ideally be near to the value in B above (scenario 3).

 

Correct?😊

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arengle
1 hour ago, wendeg said:

Thanks to all!

 

Just to make sure I understood well...

 

Scenario 1: rear wheel off the ground

Scenario 2: both wheels on the ground

Scenario 3: both wheels on the ground with rider sitting fully on bike

Scenario 4: both wheels on the ground with rider sitting fully on bike plus luggage weight

 

A. Static sag is the difference between wheel off the ground (scenario 1) and bike with two wheels on the ground (scenario 2), unladen except for full fuel tank.

B. Laden sag is diference between bike with two wheels on the ground (scenario 2) and bike with rider on it (scenario 3), with full fuel tank. (Ideally this should be 35 to 40mm)

 

Laden sag with full weight (scenario 4) should ideally be near to the value in B above (scenario 3).

 

Correct?😊

on point B that is way to much ...

Difference between scenario 3, or 4, and scenario 1 must be 30% of suspension travel, on X is 140mm, that means the difference must be around 42mm. setting in this way you will get the baseline, if you want a sportier ride you add one more click to preload or if you want a cruiser style ride you reduce the pre load.

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embee

The sag measurements are all taken from the suspension fully extended measurement.

 

So, purely for example purposes, you might find at the moment you get 50mm static sag, too much, so need to adjust the preload to get where it ought to be. Static sag is of itself really just a useful reference, it's laden sag which is what you really want to get about right, that's how you ride it.

 

Sit on it and see what you get. Perhaps this "laden sag" is now 60mm. You ought to be aiming, as arengle says, for around 30% of full travel when you are on the bike and ready to ride, so 30% of 140mm for an X is around 40mm round figures, so you need to raise it up 20mm (purely examples, see what your measurements actually are).

 

Adjust the preload until you get it to 40mm with just you on it. You can then make a note of what the static sag is at that preload for future reference, maybe it's 30mm for example. This will be your normal setting.

 

Put your luggage weight on the bike, sit on it, and see what new laden sag you get, maybe 50mm.

Adjust the preload until it gets back to where it was with just you on it, at 40mm. The static sag with all the luggage on should now be about the same as it was when you set it before (example was 30mm), and now when you sit on it you'll be at around 30% of the total travel i.e. 40mm, that's the target for laden sag whether it's just you or you plus luggage.

 

The preload just raises or lowers the ride height, it doesn't alter the stiffness etc., but that's another well worn thread …………….

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wendeg

Thanks to you Adrian and Murray. Think i got it now. Apologies for not undersranding first time.

 

Scenario 1: rear wheel off the ground... measure distance

Scenario 3 (commuting without luggage and without extra weight): both wheels on the ground with rider sitting fully on bike... distance measured must be around 70% of measurement in scenario 1

Scenario 4 (touring with luggage): both wheels on the ground with rider sitting fully on bike plus full luggage weight... distance measured must also be around 70% of measurement in scenario 1

 

'Unladen sag' is more correct term than 'static lag'? And 'unladen' even from weight of bike, no?

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Derm

There are some very bright and knowledgeable people on this forum, we are fortunate to have them and their motivation to help others. 

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SteveThackery
4 hours ago, embee said:

The sag measurements are all taken from the suspension fully extended measurement.

 

Murray, we clearly have a difference of opinion on the terminology.  This is not surprising as it seems everywhere on the internet has a different opinion!

 

I'll quote your post and comment - perhaps we can clarify?

 

4 hours ago, embee said:

 

So, purely for example purposes, you might find at the moment you get 50mm static sag, too much, so need to adjust the preload to get where it ought to be. Static sag is of itself really just a useful reference, it's laden sag which is what you really want to get about right, that's how you ride it.

 

You seem to be suggesting that static sag and laden sag are different (ref. your last sentence).  I don't think that's right.  I think static sag is normally used to refer to a bike in laden condition.  Here are some random references (the emphases are mine):

 

Spring sag is the amount the springs compress between fully topped out and fully loaded with the rider on board in riding position. It is also referred to as static ride height or static sag

http://racetech.com/articles/SuspensionAndSprings.htm

 

Static sag is a measure of how much your bike settles on its suspension with you on board

https://www.sportrider.com/ask-geek-set-your-static-sag

 

You can google for some more obviously, but I just wanted to check that it wasn't me!  I have also found a couple of sites that use other terms, including "race sag", "rider sag", and so on.  There is also at least one that says static sag is unladen, so it agrees with you.  :D

 

4 hours ago, embee said:

 

Sit on it and see what you get. Perhaps this "laden sag" is now 60mm. You ought to be aiming, as arengle says, for around 30% of full travel when you are on the bike and ready to ride, so 30% of 140mm for an X is around 40mm round figures, so you need to raise it up 20mm (purely examples, see what your measurements actually are).

 

Adjust the preload until you get it to 40mm with just you on it. You can then make a note of what the static sag is at that preload for future reference, maybe it's 30mm for example. This will be your normal setting.

 

Put your luggage weight on the bike, sit on it, and see what new laden sag you get, maybe 50mm.

Adjust the preload until it gets back to where it was with just you on it, at 40mm. The static sag with all the luggage on should now be about the same as it was when you set it before (example was 30mm), and now when you sit on it you'll be at around 30% of the total travel i.e. 40mm, that's the target for laden sag whether it's just you or you plus luggage.

 

The preload just raises or lowers the ride height, it doesn't alter the stiffness etc., but that's another well worn thread …………….

 

Actually, I think I'll comment in a separate reply.......

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SteveThackery

THE GRAND SIMPLIFICATION

 

I'm as guilty as anyone, but I think this thread is getting far too complicated.  A big part of the confusion is due to the terms static sag, laden sag, rider sag, race sag, etc, all being interpreted differently by every internet "expert"!  Also some of the discussion on the internet is for race bikes, which have a different set of requirements.

 

I propose this:

 

(0/ Don't waste time thinking about the difference between static, laden, rider, race, etc, sags!)

 

1/ For our purposes we should define "sag" as the amount the suspension is compressed from "topped out" (i.e. wheel in the air, no weight on it).

 

2/ The only sag that matters is the sag with you sat on the bike prior to driving off, along with whatever luggage (if any) you have.

 

3/ For road use, the best sag is around 1/3rd of the overall suspension travel (30-35%, fine tune to your preference).

 

4/ Turn the "preload" collar until you've got the right amount of sag for whatever load you are carrying (solo, with passenger, with luggage, etc).

 

There really is nothing more to it than that.  

 

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embee

Yes, I'm sure you're right.

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Bigglesaircraft

I need to adjust the Pre Load but unsure what size "C" spanner I require,  can any one offer a suggestion before I go out and purchase the wrong one?

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baben

Tis indeed a dark art practiced by the wizards of motorbikeryness.

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SteveThackery
On 11/18/2018 at 21:03, baben said:

Tis indeed a dark art practiced by the wizards of motorbikeryness.

 

I don't agree!  :-)

 

As I said above, it all boils down to one very simple rule:

 

The only sag that EVER matters is the sag when you are loaded up and about to set off.  That means when you, the passenger (if any), and the luggage (if any) are on the bike, and the bike is on its wheels.

 

When the bike is loaded like that, make sure that the suspension is compressed about one third of the way from fully topped out (30 - 35% of the total travel, fine tune to personal taste).

 

This rule applies whether you are riding solo, two-up, or with your entire belongings balanced on the luggage rack.  You always want the suspension to be compressed about 30-35% of its travel when riding along a (theoretical) perfectly smooth road.  Alter the pre-load collar to achieve this.

 

 

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baben
14 hours ago, SteveThackery said:

 

I don't agree!  :-)

 

As I said above, it all boils down to one very simple rule:

 

The only sag that EVER matters is the sag when you are loaded up and about to set off.  That means when you, the passenger (if any), and the luggage (if any) are on the bike, and the bike is on its wheels.

 

When the bike is loaded like that, make sure that the suspension is compressed about one third of the way from fully topped out (30 - 35% of the total travel, fine tune to personal taste).

 

This rule applies whether you are riding solo, two-up, or with your entire belongings balanced on the luggage rack.  You always want the suspension to be compressed about 30-35% of its travel when riding along a (theoretical) perfectly smooth road.  Alter the pre-load collar to achieve this.

 

 

Yep, I get that but the detailed descriptions etc do sound like a black art.

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Tex

BMW had a self levelling rear suspension back in 1979 (search for Nivomat) and, I think, had the first of the complex electronic types in use now. They rarely get the credit for their pioneering efforts. Sadly.

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fred_jb
20 minutes ago, Tex said:

BMW had a self levelling rear suspension back in 1979 (search for Nivomat) and, I think, had the first of the complex electronic types in use now. They rarely get the credit for their pioneering efforts. Sadly.

 

The latest generation BMW electronically adjustable bike suspension (ESA) includes the ability to auto-adjust preload based on actual measured suspension deflection.  I find this very effective, and it is completely automatic when set in AUTO mode (you can also select MAX or MIN preload options for special situations). I think this is a big improvement on the previous version which required the rider to select from three fixed preload options (if they remembered to do so) which were based on BMW's idea of average rider, pillion and luggage weights, and were not necessarily anywhere near accurate in many situations.

 

With the K1200/1300 bikes I believe the ESA version used on these could also adjust spring rate as well as preload.  This was done by the spring being in two parts - a standard metal coil augmented by an elastomer element.  The elastomer element had a metal sleeve which constrained its ability to compress, and the position of the sleeve could be varied, varying the compressibility of this element and so effectively varying the overall combined spring rate.

 

Edited by fred_jb
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Rocker66
5 minutes ago, fred_jb said:

 

The latest generation BMW electronically adjustable bike suspension (ESA) includes the ability to auto-adjust preload based on actual measured suspension deflection.  I find this very effective, and it is completely automatic when set in AUTO mode (you can also select MAX or MIN preload options for special situations). I think this is a big improvement on the previous version which required the rider to select from three fixed preload options (if they remembered to do so) which were based on BMW's idea of average rider, pillion and luggage weights, and were not necessarily anywhere near accurate in many situations.

 

With the K1200/1300 bikes I believe the ESA version used on these could also adjust spring rate as well as preload.  This was done by the spring being in two parts - a standard metal coil augmented by an elastomer element.  The elastomer element had a metal sleeve which constrained its ability to compress, and the position of the sleeve could be varied, varying the compressibility of this element and so effectively varying the overall combined spring rate.

 

How long is the course on how to work the BMW suspension?😀😀

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fred_jb
11 minutes ago, Rocker66 said:

How long is the course on how to work the BMW suspension?😀😀

 

That's the great thing about the latest version - all the preload and corresponding weight related damping adjustments are completely automatic, plus the damping settings are also continually fine tuned in response to road conditions and how the bike is being used.  The rider has to do nothing other than enjoy the magic carpet ride and the ability to take a pillion without any significant degrading of the handling!

 

Having faffed about with manual adjustments on previous bikes when changing from solo to two-up, and still not been able to get entirely satisfactory results, I am now a big fan of automatic systems, despite the potential for expensive faults.

 

Edited by fred_jb
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baben
1 hour ago, fred_jb said:

I am now a big fan of automatic systems, despite the potential for expensive faults.

I think the rear bouncy thing costs over £2000 if it goes wrong.:sick:

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Derm

I think I might want to get a BMW again, that'll be expensive.

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fred_jb

 

 

17 minutes ago, Derm said:

I think I might want to get a BMW again, that'll be expensive.

 

21 minutes ago, baben said:

I think the rear bouncy thing costs over £2000 if it goes wrong.:sick:

 

Yes, though BMW have been known to supply parts free out of warranty for low mileage failures.  The Missenden Flyer had this problem and initially got no help from BMW, though they eventually did the right thing.  The whole story here if you are interested:  

 

 

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baben

How much of that was down to his youtube profile and influence?

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fred_jb
8 minutes ago, baben said:

How much of that was down to his youtube profile and influence?

I think genuinely none.  He was at pains to not invoke his blogger status to get the dealer to help.  If I remember correctly the dealer later said that a member of staff had not dealt with it correctly and that it should have been referred to BMW in the first place, and that is what should happen for anyone in this situation.  To be fair you do see lots of examples on forums of BMW doing just that, so I'm inclined to believe that he didn't get special treatment when they did eventually help.

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