[Rhino]

I just watched this from Dave moss the most interesting point was when he measures the front and winds the preload all the way in. It changes his start measurement from 0mm to 6mm. not that it maters in the end when you have reached your SAG numbers and re check but interesting to see how it makes the difference. Dave is the Man... he knows his stuff:grin2:

 

[Motoaudiodoc]

Just bought the Slacker device to set sag, but haven’t had time to use it. Lucky here in Sacramento: Dave Moss will be setting up bikes at our local Cycle Gear on May 9th and our Sport Bike Night the next night. Best $40 you can spend! I’ll report on the results...

 

[Ed K]

Just bought the Slacker device to set sag, but haven’t had time to use it. Lucky here in Sacramento: Dave Moss will be setting up bikes at our local Cycle Gear on May 9th and our Sport Bike Night the next night. Best $40 you can spend! I’ll report on the results...

This will be great! If poss, plz take copious notes regarding clicks, etc.

 

[JStrube]

Just bought the Slacker device to set sag, but haven’t had time to use it. Lucky here in Sacramento: Dave Moss will be setting up bikes at our local Cycle Gear on May 9th and our Sport Bike Night the next night. Best $40 you can spend! I’ll report on the results...

I've been wanting to attend a Dave Moss session for some time. Sac mid week is just a bit far. I would love to see him in Fresno!

 

[Dino de Laurentiis]

So, regarding static sag. In the rear, I get absolutely no static sag. Measurement is the same when bike is on both two wheels and when rear wheel is off the ground. I know the shock spring is massive at 105N/mm and the SS tail is really tiny/light, but I haven’t seen such behaviour on other bikes. I bought the bike second hand, so probably previous owner has fiddled a bit with suspension settings, just trying to find out what’s normal. At this heavy preload, I still got 30 mm of rider sag (measured from forward edge of rear indicator to the inside top of the wheel axle).

I did unload the preload ring on the shock a bit, and still got the same rider sag (30 mm), but a few mm:s of static sag. Seemed a bit funky, but maybe that’s how it is with this massive spring? To get to the Öhlins app suggested sag of 28 mm, i should in fact have increased, rather than decreased preload but then it’d have been superstiff?

Front rider sag was 55 mm when I got it (30 mm static sag), but I set it to 45(ish) mm rider sag, per the Öhlins app. Just to be clear, the figure for rider sag includes the static sag, correct? That is, I shouldn’t add the suggested 46 mm to the 30 mm of static sag, that’d be way to much (half the suspension travel), correct?

 

[John]

Just to be clear, the figure for rider sag includes the static sag, correct? That is, I shouldn’t add the suggested 46 mm to the 30 mm of static sag, that’d be way to much (half the suspension travel), correct?

Correct.

 

[John]

So, regarding static sag. In the rear, I get absolutely no static sag. Measurement is the same when bike is on both two wheels and when rear wheel is off the ground. I know the shock spring is massive at 105N/mm and the SS tail is really tiny/light, but I haven’t seen such behaviour on other bikes. I bought the bike second hand, so probably previous owner has fiddled a bit with suspension settings, just trying to find out what’s normal. At this heavy preload, I still got 30 mm of rider sag (measured from forward edge of rear indicator to the inside top of the wheel axle).

I did unload the preload ring on the shock a bit, and still got the same rider sag (30 mm), but a few mm:s of static sag. Seemed a bit funky, but maybe that’s how it is with this massive spring? To get to the Öhlins app suggested sag of 28 mm, i should in fact have increased, rather than decreased preload but then it’d have been superstiff?

Based upon what you've explained, the rear spring is too soft.

If you have a correct rider sag, and inadequate free sag, the spring is too soft. To help get you head around this non obvious concept, imagine fitting the ultimate firm spring, a solid piece of pipe. You could set you rider sag to 30mm, and when you get off the bike the free sag would be exactly the same, excessive still at 30mm. An excessively strong spring gives excessive free sag because it doesn't need to compress much to change from free sag to rider sag.

A soft spring is the opposite and has to compress a lot, hence it expands a lot when the rider gets off after the rider sag is set, pushing the bike way up to give inadequate or even zero free sag.

Keep the pipe 'spring' example in your head to easily remember the relationships, works for me.

 

[Miweber929]

Based upon what you've explained, the rear spring is too soft.

If you have a correct rider sag, and inadequate free sag, the spring is too soft. To help get you head around this non obvious concept, imagine fitting the ultimate firm spring, a solid piece of pipe. You could set you rider sag to 30mm, and when you get off the bike the free sag would be exactly the same, excessive still at 30mm. An excessively strong spring gives excessive free sag because it doesn't need to compress much to change from free sag to rider sag.

A soft spring is the opposite and has to compress a lot, hence it expands a lot when the rider gets off after the rider sag is set, pushing the bike way up to give inadequate or even zero free sag.

Keep the pipe 'spring' example in your head to easily remember the relationships, works for me.

I’m not understanding this.

In my experience, if you have NO free (static) sag, the spring is too stiff because the spring is holding the bike up too much and not allowing the spring to compress. If you have too much free sag, the spring is too light; regardless of rider sag numbers on both situations. Using the pipe spring example, in my mind at least, proves this.

I ran into this on my last bike when Ohlins resprung the shock with a WAY too light spring and the bike sank down like it had a blown shock.

I’ve also run some bikes with little to no free sag in the rear without issue. That sometimes happens on bikes that will see two up or heavy loads, not ideal but it happens.

 

[John]

I’m not understanding this.

In my experience, if you have NO free (static) sag, the spring is too stiff because the spring is holding the bike up too much and not allowing the spring to compress. If you have too much free sag, the spring is too light; regardless of rider sag numbers on both situations. Using the pipe spring example, in my mind at least, proves this.

I ran into this on my last bike when Ohlins resprung the shock with a WAY too light spring and the bike sank down like it had a blown shock.

I’ve also run some bikes with little to no free sag in the rear without issue. That sometimes happens on bikes that will see two up or heavy loads, not ideal but it happens.

The basic error your making is not setting rider sag first.

The first thing you do in suspension set up is set rider sag. As long as you have sufficient adjustment range on the shock or fork you can set a correct rider sag with ANY weight springs no matter how hard or soft. You can even set a correct rider sag with my extreme example of an appropriate length of pipe substituted for the spring. For purposes of this discussion lets say we set the rider sag to 30mm.

Next you get off the bike and check the amount of free sag. What will it be with the piece of solid pipe substituted for the spring? Answer: 30mm (exactly the same as the rider sag you set, because obviously the pipe doesn't expand in response to now just supporting the lighter weight of the bike).

An excessive free sag after a correct rider sag has been set reflects that the spring hasn't needed to expand much (push the bike up) to support just the weight of the bike. The stronger the spring the less it needs to expand to equal the weight of just the bike when the rider dismounts (result: excessive free sag). A near solid spring will hardly move at all.

On the other hand a soft spring will have been compressed a lot to give a correct rider sag (rider and bike). When the rider gets off all this compression wants to expand a lot in response to the now much lighter weight of just the bike. So the expanding spring pushes the relatively light bike up a lot, resulting in inadequate or zero free sag.

P.S. If all the above still seems confusing, think of it this way. A light spring compresses a lot more in response to weight put on it than a heavy spring. So with both set to the same rider sag measurement, when you get off the bike the light spring will expand more, result: less free sag.

 

[Dino de Laurentiis]

The basic error your making is not setting rider sag first.

The first thing you do in suspension set up is set rider sag. As long as you have sufficient adjustment range on the shock or fork you can set a correct rider sag with ANY weight springs no matter how hard or soft. You can even set a correct rider sag with my extreme example of an appropriate length of pipe substituted for the spring. For purposes of this discussion lets say we set the rider sag to 30mm.

Next you get off the bike and check the amount of free sag. What will it be with the piece of solid pipe substituted for the spring? Answer: 30mm (exactly the same as the rider sag you set, because obviously the pipe doesn't expand in response to now just supporting the lighter weight of the bike).

An excessive free sag after a correct rider sag has been set reflects that the spring hasn't needed to expand much (push the bike up) to support just the weight of the bike. The stronger the spring the less it needs to expand to equal the weight of just the bike when the rider dismounts (result: excessive free sag). A near solid spring will hardly move at all.

On the other hand a soft spring will have been compressed a lot to give a correct rider sag (rider and bike). When the rider gets off all this compression wants to expand a lot in response to the now much lighter weight of just the bike. So the expanding spring pushes the relatively light bike up a lot, resulting in inadequate or zero free sag.

P.S. If all the above still seems confusing, think of it this way. A light spring compresses a lot more in response to weight put on it than a heavy spring. So with both set to the same rider sag measurement, when you get off the bike the light spring will expand more, result: less free sag.

I have to say I’m a bit confused by this, stil trying to wrap my head around it. While I’m doing that, figured I’d ask you what your weight with gear is, what sag numbers you have and if you’re running the stock spring? I’m about 88-90 kg with all gear on, and as far as I know am still running the stock spring.

What I’m getting at is, would it be possible to have the same effects by the previous owner winding up the preload to much? I mean, I didn’t notice any difference in rider sag after I decreased preload a couple of turns.

 

[Miweber929]

The basic error your making is not setting rider sag first.

The first thing you do in suspension set up is set rider sag. As long as you have sufficient adjustment range on the shock or fork you can set a correct rider sag with ANY weight springs no matter how hard or soft. You can even set a correct rider sag with my extreme example of an appropriate length of pipe substituted for the spring. For purposes of this discussion lets say we set the rider sag to 30mm.

Next you get off the bike and check the amount of free sag. What will it be with the piece of solid pipe substituted for the spring? Answer: 30mm (exactly the same as the rider sag you set, because obviously the pipe doesn't expand in response to now just supporting the lighter weight of the bike).

An excessive free sag after a correct rider sag has been set reflects that the spring hasn't needed to expand much (push the bike up) to support just the weight of the bike. The stronger the spring the less it needs to expand to equal the weight of just the bike when the rider dismounts (result: excessive free sag). A near solid spring will hardly move at all.

On the other hand a soft spring will have been compressed a lot to give a correct rider sag (rider and bike). When the rider gets off all this compression wants to expand a lot in response to the now much lighter weight of just the bike. So the expanding spring pushes the relatively light bike up a lot, resulting in inadequate or zero free sag.

P.S. If all the above still seems confusing, think of it this way. A light spring compresses a lot more in response to weight put on it than a heavy spring. So with both set to the same rider sag measurement, when you get off the bike the light spring will expand more, result: less free sag.

I'm not out to debate you, but this information just doesn't sound right and I want to be sure someone is not sent down the opposite road due to differences in terminology or concepts

Based on Dino's description, his shock spring is too heavy or the previous owner set the bike up to more preload than Dino needs.

SETTING free sag is something else. I would argue the amount you need to be a personal preference and not something that you HAVE to have but you should be setting that along with rider sag, not after.

Watch the video by Dave Moss that was linked above, it's VERY much what is the "common" way of doing things and is how most tuners go. I can also say by my experience of the WAY too soft spring that was sent with my Ohlins for the CBR650F I had, there was exactly zero way I can set rider sag when the bikes weight itself sank the spring to 3/4 of it's travel just statically sitting there. Once Ohlins sent me the correct spring that would support me and the bike, I was able to setup my rider sag and I had at least "some" static sag. Based on how I am reading what you wrote above, you'd have said my spring was too light.

 

[John]

I'm not out to debate you, but this information just doesn't sound right and I want to be sure someone is not sent down the opposite road due to differences in terminology or concepts

Based on Dino's description, his shock spring is too heavy or the previous owner set the bike up to more preload than Dino needs.

SETTING free sag is something else. I would argue the amount you need to be a personal preference and not something that you HAVE to have but you should be setting that along with rider sag, not after.

Watch the video by Dave Moss that was linked above, it's VERY much what is the "common" way of doing things and is how most tuners go. I can also say by my experience of the WAY too soft spring that was sent with my Ohlins for the CBR650F I had, there was exactly zero way I can set rider sag when the bikes weight itself sank the spring to 3/4 of it's travel just statically sitting there. Once Ohlins sent me the correct spring that would support me and the bike, I was able to setup my rider sag and I had at least "some" static sag. Based on how I am reading what you wrote above, you'd have said my spring was too light.

I'm not debating anything either. I'm just explaining the facts (and why) a spring with a correctly set rider sag which results in an inadequate free sag is indicative of a spring rate that is too light for the rider. Excessive free sag - spring to heavy.

In nothing you've written have you said you set a correct rider sag, then checked the free sag. Had you been able to set a correct rider sag with your spring that 'sank 3/4 of the suspension travel under just the bikes weight' then you would have found you had ZERO free sag.

The OP of this bit of the thread said he set (or has) 30mm rider sag, was worried about reducing it to 28mm by increasing preload, because a 30mm rider sag is already giving him zero free sag. Indicative of a spring that is too light. In all of this I'm assuming the OP's methods and measurements are correct.

P.S. Increase the preload on the current spring to 28mm will not make it 'superstiff'. Doing so will just make the bike sit 2mm higher in the rear. Preload/sag has no effect on spring rate, it just changes the ride height. But ride height on a bike with a progressive link rear suspension does affect the 'effective' spring rate at the wheel. Increasing preload (reducing sag) actually makes the 'effective' spring rate at the wheel decrease (because of the progressive linkage and the bike sitting higher in its suspension travel), the complete opposite of what most people think. But this change would be unnoticeable over such a small amount as 2mm.

 

[John]

The OP of this bit of the thread said he set (or has) 30mm rider sag, was worried about reducing it to 28mm by increasing preload, because a 30mm rider sag is already giving him zero free sag. Indicative of a spring that is too light. In all of this I'm assuming the OP's methods and measurements are correct.

Reflecting on this as I was walking down to get a coffee and newspaper (life is tough :grin2 I perhaps should have questioned the measurements.

A rider sag of 28mm is pretty small. I'd only ever consider something as small as this on a pure track bike on VERY good surface tracks. The reason track bikes can run smaller sag numbers is mainly because you don't expect potholes in a race track (and so you want to max upward travel).

Race Tech's generic rear sag recommendations for a 'road bike' are 28-37mm. The SS has a 144mm rear suspension travel. With an acceptable rider sag percentage of travel being 28-35% that gives a range of 40 - 50 mm. So putting those two rules together, I'd be shooting for a rear rider sag of 35mm.

My recommendation would be to increase the current 30mm rear rider sag to 35mm and then see what the free sag is. If there's say 5mm (or more) free sag then just go with the current spring and evaluate its suitability on the road.

In my book you want the heaviest spring rate that will do the job. And to me, that's exactly the same thing as saying you want the lightest spring rate that will do the job. I'll let people reflect on that one.

My idea of the heaviest/lightest spring rate that will do the job for a road bike, is the heaviest one possible that will not unduly upset the chassis going hard around a fast rutted corner cranked hard over. This assumes correctly set (even loose) rebound/compression damping settings. An excessively heavy spring (if damping is back off) will have the bike 'skipping' through the bumps when hard over (suspension working at extreme angle to the road) rather than absorbing the bumps.

 

[John]

One thing I noticed reading thought this thread is conflicting meaning given to terminology. And that can be found in just about any discussion on 'sag'. The same term being used to describe different things, especially the term 'static sag'.

To me the terms are ...

Suspension travel .... its just called that.
Free Sag ..... the amount just the weight of the bike alone compresses the suspension
Race, Rider, Static Sag ........ all mean the exact same thing. The amount the combined weight of the bike and rider compress the suspension

Now I'm sure the above is not going to straighten out the whole world's use of the terms, so just be aware of this problem when reading any article on the topic. Some 'interpretation' of terms being used is often necessary.

 

[Miweber929]

I'm not debating anything either. I'm just explaining the facts (and why) a spring with a correctly set rider sag which results in an inadequate free sag is indicative of a spring rate that is too light for the rider. Excessive free sag - spring to heavy.

When you say “inadequate free sag” are you stating too much (bike sinks under sits own weight too much) or too little free sag (zero sag)?

In nothing you've written have you said you set a correct rider sag, then checked the free sag. Had you been able to set a correct rider sag with your spring that 'sank 3/4 of the suspension travel under just the bikes weight' then you would have found you had ZERO free sag.

No, I had 300mm of free sag, or 3/4 of the shocks travel. I couldn’t even sit on the bike or it would bottom out, I could do that with my hand.

You’re right I didn’t say anything about rechecking free sag because in my experience free sag can be personal preference and you dont have to have certain amount for the suspension to work properly. I’ve ridden under sprung bikes with plenty of sag and those without any that were over sprung and both rode as you’d expect, just fine. If your rider sag is fine, free sag isn’t a huge deal.

The OP of this bit of the thread said he set (or has) 30mm rider sag, was worried about reducing it to 28mm by increasing preload, because a 30mm rider sag is already giving him zero free sag. Indicative of a spring that is too light. In all of this I'm assuming the OP's methods and measurements are correct.

I guess that’s not been my experience and according to others I’ve talked to, worked with in setup and videos I’ve seen I’m not seeing what you’re seeing. I agree I’d rather have a heavier spring than light one, the bike rides better that way in my experience.

I’m out, it’s not worth going back and forth over. I believe if Dino decreases his preload, he’ll gain some free sag and still have a rider sag in the area he should be, even though his spring may be a bit stiff.

 

[Miweber929]

One thing I noticed reading thought this thread is conflicting meaning given to terminology. And that can be found in just about any discussion on 'sag'. The same term being used to describe different things, especially the term 'static sag'.

To me the terms are ...

Suspension travel .... its just called that.
Free Sag ..... the amount just the weight of the bike alone compresses the suspension
Race, Rider, Static Sag ........ all mean the exact same thing. The amount the combined weight of the bike and rider compress the suspension

Now I'm sure the above is not going to straighten out the whole world's use of the terms, so just be aware of this problem when reading any article on the topic. Some 'interpretation' of terms being used is often necessary.

I’m going to leave my last response, though this clears some things up. Where some of my confusion sits is in my experience, free sag and static sage are interchangeable, rider sag is the rider sag plus free sag.

 

[John]

When you say “inadequate free sag” are you stating too much (bike sinks under sits own weight too much) or too little free sag (zero sag)?

I believe if Dino decreases his preload, he’ll gain some free sag and still have a rider sag in the area he should be, even though his spring may be a bit stiff.

Common meaning of 'inadequate' - insufficient, too little

Yes we agree that decreasing the pre-load to increase rider sag may gain some free sag .... even thought the spring rate may be a bit soft.

If you don't believe me, try this authoritative and extensive discussion of the subject ...... https://www.peterverdone.com/archive/springs.htm

SPRING RATE -
Spring Rate OK - Both free and rider sag within acceptable range.
Spring Rate too soft - Rider Sag OK, but too little or no Free Sag
Spring Rate too firm - Rider Sag OK, but too much Free Sag


See I think it is worth endlessly going over so people who want to understand and adjust their suspension just beyond the basics correctly understand these very useful 'rule of thumb' to establish if their current spring/s are in the ball-park . Nothing will improve the performance of a motorcycle more than a correct set up and adjusted suspension. As the linked article says, next to tires (tyres) springs are the next most important part of the suspension system.

 

[Rhino]

So, regarding static sag. In the rear, I get absolutely no static sag. Measurement is the same when bike is on both two wheels and when rear wheel is off the ground. I know the shock spring is massive at 105N/mm and the SS tail is really tiny/light, but I haven’t seen such behaviour on other bikes. I bought the bike second hand, so probably previous owner has fiddled a bit with suspension settings, just trying to find out what’s normal. At this heavy preload, I still got 30 mm of rider sag (measured from forward edge of rear indicator to the inside top of the wheel axle).

I did unload the preload ring on the shock a bit, and still got the same rider sag (30 mm), but a few mm:s of static sag. Seemed a bit funky, but maybe that’s how it is with this massive spring? To get to the Öhlins app suggested sag of 28 mm, i should in fact have increased, rather than decreased preload but then it’d have been superstiff?

Front rider sag was 55 mm when I got it (30 mm static sag), but I set it to 45(ish) mm rider sag, per the Öhlins app. Just to be clear, the figure for rider sag includes the static sag, correct? That is, I shouldn’t add the suggested 46 mm to the 30 mm of static sag, that’d be way to much (half the suspension travel), correct?

I thought I would give my 2 cents worth to try and help I have set my Rear spring at 25%of travel (36mm) and my front at 30% of travel(39mm with upgraded springs as im too heavy for the standard oem) this is my personal setting that gives me as much ride Hight as possible through hard cornering where the suspension is fully compressed. With regards to yours it does sound like the rear has too much preload for reference the difference between my Extended / top out SAG (bike lifted with no weight) and my Free/Static SAG Bike under its own weight) is 5mm at the rear and that's at the 25% of travel so once you had yours set at 30% of 144mm = 43.2mm then I would expect you to have about 10mm of extended travel. If so then the spring is fine and ideal.

 

[Derek]

...
On the other hand a soft spring will have been compressed a lot to give a correct rider sag (rider and bike). When the rider gets off all this compression wants to expand a lot in response to the now much lighter weight of just the bike. So the expanding spring pushes the relatively light bike up a lot, resulting in inadequate or zero free sag...

I get the gist of what you're saying but this description seems to ignore the extension limits of the shock. The spring can only expand as far as the shock allows it.

 

[John]

I get the gist of what you're saying but this description seems to ignore the extension limits of the shock. The spring can only expand as far as the shock allows it.

No, it doesn't ignore the extension limits of the shock. That's the very reason you end up with zero (or near enough) free sag with a significantly underweight spring, when the preload has been cranked up to get a reasonable rider sag.

When the rider gets off, the highly compressed spring will push the bike up till it hits the extension limit of the shock. That's exactly what has happened when you have zero free sag. It may want to push the bike up much higher, but the shock is at full extension and preventing it going up further.