Setting the proper preload for the rear suspension

UK_r18_Classic said:
After reading this all the way through, I'm pretty confused.

Turning the adjuster all the way anti clockwise sets the minimum possible preload for the shock - how can that be the 'shipping' position?

In this position, the bike will move around / bounce the absolute most possible & the bike be in it's maximum softness setting.

When set at minimum preload, the ride can feel harsh & kick you out the saddle due to using up all the available travel, then hitting the stops. This transfers the impact to the seat (hence you feel the bump).

Have I fundamentally misunderstood how suspension works?

Spring preload too low (for rider weight) = wallowy, cushy, jarring when hitting a larger bump in the road. Glides over minor imperfections.
Spring preload too high (for rider weight) = firm, feel every imperfection in the road transfreed to seat.
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I believe that shipping position, is turned all the way clockwise (right)
 
UK_r18_Classic said:
After reading this all the way through, I'm pretty confused.

Turning the adjuster all the way anti clockwise sets the minimum possible preload for the shock - how can that be the 'shipping' position?

In this position, the bike will move around / bounce the absolute most possible & the bike be in it's maximum softness setting.

When set at minimum preload, the ride can feel harsh & kick you out the saddle due to using up all the available travel, then hitting the stops. This transfers the impact to the seat (hence you feel the bump).

Have I fundamentally misunderstood how suspension works?

Spring preload too low (for rider weight) = wallowy, cushy, jarring when hitting a larger bump in the road. Glides over minor imperfections.
Spring preload too high (for rider weight) = firm, feel every imperfection in the road transfreed to seat.
Click to expand...
It's easy to mistake preload for harsh vs soft, since it can appear to have that behavior. Ultimately, what you are doing is setting the amount of sag in the shock. Generally most suspension should have 25-35% sag. Imagine a shock has 100mm of travel. When you are seated on the bike you want the shock to have used 25-35mm of its travel. You adjust the preload until the sag matches that.

Why don't I want 0% sag? Because it wouldn't allow the shock to rebound at all since it is already fully extended. Why not more than 25-35% sag? Because compression will be the primary case of a shock, so you don't want to reduce the available travel excessively.

On the R18 there is a difference between minimum preload and the shipping position. When you back the adjuster all the way out you are in the shipping position. There is no pressure on the spring at all. There is a space where there is no resistance on the adjuster between the shipping position and the lowest preload setting (when you start to feel resistance). So why all the way backed out for shipping? Most bikes are tightened down against a pallet for shipping. By not having any pressure on the spring this allows the bike to compress as far down as possible without created constant pressure on the spring.

The soft vs harsh feeling you noted is because your effective shock travel is changed. If the sag is too little you have no rebound and the shock won't compress under normal conditions creating a feeling of a hard tail. When the sag is too much, the shock won't slow compression down before hitting the stops, so you have movement but then hit a jarring bump at the end. Correct preload gets you in the sweet spot between these extremes.
 
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nielsm said:
It's easy to mistake preload for harsh vs soft, since it can appear to have that behavior. Ultimately, what you are doing is setting the amount of sag in the shock. Generally most suspension should have 25-35% sag. Imagine a shock has 100mm of travel. When you are seated on the bike you want the shock to have used 25-35mm of its travel. You adjust the preload until the sag matches that.

Why don't I want 0% sag? Because it wouldn't allow the shock to rebound at all since it is already fully extended. Why not more than 25-35% sag? Because compression will be the primary case of a shock, so you don't want to reduce the available travel excessively.

On the R18 there is a difference between minimum preload and the shipping position. When you back the adjuster all the way out you are in the shipping position. There is no tension on the spring at all. There is a space where there is no resistance on the adjuster between the shipping position and the lowest preload setting (when you start to feel resistance). So why all the way backed out for shipping? Most bikes are tightened down against a pallet for shipping. By not having any tension on the spring this allows the bike to compress as far down as possible without created constant pressure on the spring.

The soft vs harsh feeling you noted is because your effective shock travel is changed. If the sag is too little you have no rebound and the shock won't compress under normal conditions creating a feeling of a hard tail. When the sag is too much, the shock won't slow compression down before hitting the stops, so you have movement but then hit a jarring bump at the end. Correct preload gets you in the sweet spot between these extremes.
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Learn something new every day! I stand corrected! 👍🏻
 
UK_r18_Classic said:
Thanks - will take another look tonight & see what can be twiddled.
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One thing when trying to adjust the preload especially with regards to shipping vs minimum preload. The 0 rotation point is when you begin to feel resistance in turning the adjuster, not when the adjuster is backed out as far as it will go. It can be a few rotations from shipping till you begin to feel this resistance so I've seen many people use shipping as the 0 rotation point. The net result is that they would end up with greater than 25-35% sag based on the number of rotations, causing a poor experience.
 
nielsm said:
It's easy to mistake preload for harsh vs soft, since it can appear to have that behavior. Ultimately, what you are doing is setting the amount of sag in the shock. Generally most suspension should have 25-35% sag. Imagine a shock has 100mm of travel. When you are seated on the bike you want the shock to have used 25-35mm of its travel. You adjust the preload until the sag matches that.

Why don't I want 0% sag? Because it wouldn't allow the shock to rebound at all since it is already fully extended. Why not more than 25-35% sag? Because compression will be the primary case of a shock, so you don't want to reduce the available travel excessively.

On the R18 there is a difference between minimum preload and the shipping position. When you back the adjuster all the way out you are in the shipping position. There is no tension on the spring at all. There is a space where there is no resistance on the adjuster between the shipping position and the lowest preload setting (when you start to feel resistance). So why all the way backed out for shipping? Most bikes are tightened down against a pallet for shipping. By not having any tension on the spring this allows the bike to compress as far down as possible without created constant pressure on the spring.

The soft vs harsh feeling you noted is because your effective shock travel is changed. If the sag is too little you have no rebound and the shock won't compress under normal conditions creating a feeling of a hard tail. When the sag is too much, the shock won't slow compression down before hitting the stops, so you have movement but then hit a jarring bump at the end. Correct preload gets you in the sweet spot between these extremes.
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Nice write up. Change no ‘tension’ in the spring to no ‘compression’ and you nailed it.
 
nielsm said:
That’s within the range of adjustment. The manual offers a base setting at 8 rotations in for 100KG and provides a couple other examples. If you are not exactly matching the examples, you simply adjust by 2 rotations for each 10KG from the base setting (Up or down).

So, we end up with this simplified chart for those weighing at or below the base setting

100KG (220lbs) 8 rotations
90KG (200lbs) 6 rotations
80KG (175lbs) 4 rotations
70 KG (154lbs) 2 rotations
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Thanks. I checked it this morning. I gathered I bought the motorcycle from a dealer that knew what they were doing. It wasn't set to "shipping" mode and had some turns. I don't know how many and don't want to check, since IMO the bike handles well as is.
 
Gr8adv said:
Guys don’t forget rear tire pressure. Softening it will ‘shock’ you as to the difference in ride quality. That tire is a giant rubber spring. Lose 3 lbs of pressure and you will be amazed.
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It's funny how BMW changes the pressure recommendations over time. Many years ago it was recommended to use 32/36 when riding solo with no luggage. 36/42 was recommended for 2 up with luggage. Then they just made it 36/42 all the time. They likely felt it was too hard for people to change pressure & preload with different loads and a lot of people don't check pressure regularly so at the 32/36 the pressure might end up low and have worse tire wear, so recommending higher pressure simplified it. I could easily see 32/36 working with the R18 for single rider and that would have the effect you describe, adding a bit more compliance to the giant rubber springs and perhaps even a bit better grip.

I'd also suggest people should realize the preload needs to change based on how much luggage you are carrying too. It's not just rider weight, but all load on the bike. So if you add an extra 20KG of packed gear, you need to add a few more rotations to the preload than when you ride normally.
 
UK_r18_Classic said:
After reading this all the way through, I'm pretty confused.

Turning the adjuster all the way anti clockwise sets the minimum possible preload for the shock - how can that be the 'shipping' position?

In this position, the bike will move around / bounce the absolute most possible & the bike be in it's maximum softness setting.

When set at minimum preload, the ride can feel harsh & kick you out the saddle due to using up all the available travel, then hitting the stops. This transfers the impact to the seat (hence you feel the bump).

Have I fundamentally misunderstood how suspension works?

Spring preload too low (for rider weight) = wallowy, cushy, jarring when hitting a larger bump in the road. Glides over minor imperfections.
Spring preload too high (for rider weight) = firm, feel every imperfection in the road transfreed to seat.
Click to expand...
very confused right !!!!
 
Svtweb said:
Many of the early reviews and many of the first customers have complained about the R18 having a very harsh ride and easily scraping the pegs. This is not indicative of a design flaw on the R18, but a procedural miss by BMW to properly document the unpacking and setup procedures for the customer. During shipping, the rear shock preload is placed in "Shipping" position. That means the adjustment of the rear shock is turned anti-clockwise until it hits the stop. In this position you are basically sitting on the rubber bump-stop on the shock with little to no spring action. During shipping it keeps the bike from bouncing around. The manual mentions setting the preload, but it appears that none of the dealers have been doing that. I have created a chart that gives a breakdown of preload from minimum adjustment (0 Turns) to Max Adjustment (26 Turns).

The process is very easy: With a 13mm 6-Point socket, turn the adjuster anti-clockwise until it stops. Slowly rotate the adjuster clockwise until you feel it engage the spring perch (you will feel slight resistance). This is position "0" Continue turning clockwise until you reach the desired preload based on the chart I created.

I hope this helps everyone out.
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Thank you for the explanation Svtweb. I have a question for my R18 classic. I have adjusted the preload before. This time when I tried to place it back to single rider setting, I rotated counter clockwise and I never reached that stop. It just felt like I completely loosened the adjuster bolt. Have you seen or experienced this?
 
I also wanted to mention that I contacted my local dealer and asked how much a valve adjustment would cost. I was given 2 prices. One was $970, which doesn’t include them having to replace the gasket. If they did however, it would be $1,300. Does that sound about right?
 
So help my pea sized brain understand this…
On our bike, well at least on the R18 base model, we get a basic rear spring and shock. In shipping mode, my thinking is the shock is compressed to prevent the bike from bouncing up and down while in transit. Using one of the charts in this thread we then turn, after finding starting point, the nut X turns clockwise as desired. This results in three things happening:

  • The compressed shock raises in height, ideally, to one that takes into account weight placed on the bike. Be it just body weight or also fuel…bags etc per the number of turns done. This helps prevent maybe a bouncing effect that might otherwise occur if a shock was fully extended maybe. Or to say another way, we are doing what thr B/TC models do in this step by preloading the shock manually to account for added weight.
  • One can then visually see the expanded shock. Example photo below, think it was a 27 turn photo someone posted, I am thinking, this makes me think our shock is an upside down setup. On a normal bike a shock is top to bottom so in photo below the photo would rotate say 160 degrees clockwise in order to reflect an old school two sided rear shock setup.
  • The spring is a constant, in that it is designed to compress the way it does, maybe including varying compression aspects as it becomes more compressed (aka say 2/3 of top part of spring compresse a certain way and last 1/3 does not compress as easily). We cannot adjust the Spring. Maybe on other bikes ability to do that is called rebound damping? Thus the combination of the spring (which I am guessing the Nut turning does not effect) and the shock (with its internal parts, fluid etc) provide the support to account for bumps we ride over.
Is above anywhere near correct? Ty
 

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OceanBreeze said:
Svtweb. You are the one who gave me hope the first time I rode the R18 and was dejected by the rear shock. For that I am grateful :). Owing to some personal issues at the time I did not pursue. revisiting now. I have a question - something that nags me a lot about the rear suspension. We have a 90 mm travel. That is a fact that we cannot escape from - its design and physics. So the question is that on another thread i was told about a new gas shock system from Touratech called the Black T system (several stages available) that makes the ride better. Now I am still wondering how a physical restriction of 90mm can be overcome by shock design ... can that be done ? Sorry for my lack of mechanical knowledge - am very curious whether one can surmount the physical limitations of the 90mm travel by design, by changing the shock which obviously has different than stock internals and working, but would also be subject to a similar physical restriction of travel is it not ? Hope I am able to communicate what I am trying to say clearly.
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A good quality after market shock can make a significant difference.... no matter what the travel is.

1st off.... BMW needs to supply a shock sprung and with fixed dampening to suit a wide load range.... whist being safe if adjusted poorly.... and to a price.... with a strong spring to take the full quoted payload.

2nd.... a quality aftermarket shock will be sprung to your weight range, with some providing a good range of dampening adjustment to suit.... so one can adjust low speed compresion dampening, high speed comp dampening and rebound damp Off course some shocks simplify this dampening. It can be a grand well spent.... same can be done for the forks with some cartridges.

In my case I do not carry a pillion.... so do not need to suffer an higher rate spring in everyday riding..... BMW also overdo the fixed dampening in my view.... as it is a safer generic position to take.... as people tend to slow down when experiencing harshness.... but a wallowing bike with 2 largish people on board is not safe.... so... an after market shock an provide a much better rider experience for people like me.
 
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