Evo 1100 rear shock - possible upgrade? - Page 6

chris.p · 14-06-2021, 08:53 AM

Suspension is a very dark art so to speak, but the parameter's set out in the Ohlins sheet is basically suspension gospel, because if your static sags do not sit between the recommended parameter's then your spring needs changing to a harder or softer spring depending on what the measurement's are.
If it is new suspension to you, then a basic static sag test is a must, otherwise the bike will never be pleasure to ride, if in doubt and you don't fancy doing it your self, look up a local suspension expert and go visit them.

Mr Gazza · 14-06-2021, 09:02 AM

Static and dynamic sag are just part of the nomenclature of suspension and simply puts everyone on the same page. Whether or not a fully loaded bike is dynamic is beside the point, it just gives that parameter a name.

Static sag is relevant in so much as the relationship to the dynamic sag will tell you a lot about the spring rate.

Get the static sag set at say 10mm and then load it and it goes to 50mm. That will tell you the springs are too soft.

In my case the static sag is alarmingly high, but then only deflects a few mm more when loaded. That tells me that my springs are way too hard and I'm using enormous static sag (and rebound damping) to stop it topping out . Even though it's working relatively low in it's stroke it never bottoms out, confirming the former hypothesis.
Fortunately the damping is rather good, so deals with the limited travel.
It actually handles fine, but the springs and set up are something I will look at next Winter.. Nearly did it last Winter, but bottled out!

Looking forward to joining the esoteric tuned suspension crowd..

Albie · 14-06-2021, 09:31 AM

Quote:

Originally Posted by Luddite

By the way, Paul, I've just remembered - when I fitted the DU737 with the factory settings, I found I had no static sag whatsoever and was getting pinged out of the saddle down bumpy roads. I wound off a couple of turns of preload and that improved matters considerably. So don't assume the shock will perform perfectly out of the box and check your static and dynamic sag before putting all your tools away!

That's what my 1100s was like. On the monster track day the guy from Wolverhampton ducati set it up better for me.

Darkness · 14-06-2021, 09:34 AM

This summarises the procedure quiet clearly, without reference to a static “Dynamic” oxymoron:

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

Luddite · 14-06-2021, 12:24 PM

Static and dynamic sag are equally important. If they were irrelevant, I don't think the likes of Öhlins would bother to give static sag figures in their installation instructions.

Yes, 'dynamic' sag might be a bit of a misnomer, but it's just to distinguish it from 'static' sag in this instance. 'Static' sag may also be called 'free' sag and 'ride height' is another name used for 'dynamic' sag. Some people call 'static' sag just 'sag' with the measurement for bike and rider called 'static' sag. Confusing!

You may be able to get within the dynamic sag range when sat on the bike but, as Chris.p said, if you can only do that with no static sag, that's an indication the spring rate is incorrect.

There are physical effects of insufficient static sag too.

Yes, the bike is always ridden loaded but the spring's are not always under compression - there are instances when much, if not all weight is removed from the suspension, for example, when the wheels are coming off bumps in the road or dropping into pot holes or during load transfer; braking for the rear or acceleration for the front.

Niall Mackenzie, who I respect as a rider, said of rear static sag: "...(if) you have no sag ... you're in trouble. Your bike will be on its nose braking, the rear end will be hopping and pattering, and if you get back on the gas hard out of a corner it'll probably highside you."
http://www.visordown.com/features/gu...kes-suspension

The effect can be measured too, these diagrams are from "Motorcycle Handling and Chassis Design" the book by Tony Foale, the suspension guru, and give a graphic illustration of the effects that Mackenzie described. You can see the rear wheel hopping under heavy braking in the top chart.

Dave Moss acknowledges the importance of 'free' sag in many of his videos.

He states: "Static sag with the bike under its own weight should be 15-25mm in the front and 10-15mm in the rear with cold suspension. Rider sag should be a totally separate number. Add both together. Static sag creates a dead space so when the shock (most important) tops out it does not ping you straight out of the seat."

There's no reference at all to the unloaded sag figure in that article Darkness linked to, which I think is a bit of an omission. The article is over 25 years old, so perhaps it wasn't considered important then.

So, my advice is, even if your 'dynamic' sag is fine, ignore 'static' sag at your peril.

As Paul is getting everything set up by JWR Suspension, he'll have no worries. It'll be interesting to find out what settings they use in due course.

chris.p · 14-06-2021, 03:17 PM

I think an easier way would be to say, "Static Sag" i.e. the sag the bike has with no rider on board, i.e. it's own weight. and "Rider Sag" i.e. the sag when a rider is sat on the bike.

I personally always set the "Static Sag" first, as this gave you the bikes ideal measurement's then I would do the "Rider Sag" and use the Ohlins sheet to work out whether I need softer springs or harder springs.

Remember that "Preload" only alters the ride height of the bike, not how far the suspension will compress.

"Compression" only slows down or speeds up the springs compression.

"Rebound" is the Opposite of Compression, it slows down or speeds up the extension (rise) of the suspension.

By sticking to those simple rules you can not go far wrong.

Once you go past those workings you enter the realm of a wizard's black art of suspension, oil thickness (Weight), Pistons, Oil shims, bypass shims, Air gaps etc the list is endless and you will fry your brain.

bigredduke · 14-06-2021, 03:34 PM

Can of worms duly opened!

Right, with the help of Mrs BRD & daughter I have the following measurements:

R1 = 571mm, R2 = 560mm, so static sag is 11mm
R3 = 530 so sag with rider onboard is 41mm which is 1mm outside of the Ohlins parameters so I conclude that the spring is just over the limit for my bulk. Do you agree?

If I reduce the preload slightly, will the R1 figure increase slightly because the rear wheel will drop or have I got that completely wrong?

slob · 14-06-2021, 03:57 PM

no adjustment should change R1, reducing preload should increase both Static Sag & Ride Height (Rider Sag)

bigredduke · 14-06-2021, 04:05 PM

Quote:

Originally Posted by slob

no adjustment should change R1, reducing preload should increase both Static Sag & Ride Height (Rider Sag)

Thanks Rob

I think I've got it the wrong way round! I backed off the preload & rider sag increased by 9 mm to 50mm, so if I increase the preload it should reduce (possibly)!

Luddite · 14-06-2021, 04:06 PM

Quote:

Originally Posted by bigredduke

Can of worms duly opened!

Right, with the help of Mrs BRD & daughter I have the following measurements:

R1 = 571mm, R2 = 560mm, so static sag is 11mm
R3 = 530 so sag with rider onboard is 41mm which is 1mm outside of the Ohlins parameters so I conclude that the spring is just over the limit for my bulk. Do you agree?

If I reduce the preload slightly, will the R1 figure increase slightly because the rear wheel will drop or have I got that completely wrong?

Adjusting the preload won't affect the length of the shock at full extension - whether you have zero preload or it's wound fully in, the R1 figure won't change.

That spring sounds just on the soft side of ideal, but it'd be perfectly safe to use on the road. Get it set up at JWR and see how it feels on the road. If you're not constantly bottoming out and it doesn't feel 'wallowy' you shouldn't need a stiffer spring. A lot depends on your riding of course - I favour compliance over bumps as I'm not a particularly aggressive rider but if you're flinging it into bends and powering out on plenty of throttle, you're probably going to want the next stiffness up on the spring (120N/mm).

Luddite · 14-06-2021, 04:15 PM

Quote:

Originally Posted by bigredduke

Thanks Rob

I think I've got it the wrong way round! I backed off the preload & rider sag increased by 9 mm to 50mm, so if I increase the preload it should reduce (possibly)!

Yes! If you increase the preload so that your rider sag is below 40mm, then your static sag will probably be just below the 10mm recommendation. But, as long as you have at least 5mm static sag, it'll still be safe to ride on the road.

bigredduke · 14-06-2021, 05:38 PM

Update!
I increased the preload by 4mm from standard. I don't know if that is considered a lot or a little?

I took it out and whereas before, I felt as though I was rather 'perched' over the front end & constantly sliding forward into the tank, now it feels a bit more 'relaxed'. Steering feels a little slower but the rear feels settled and comfortable. Interestingly, the front suspension feels a little harder and less forgiving now than when the OEM shock was fitted, I don't know why that should be. I need to check the sag on the front next to see if it is within recommended parameters.

I also need to check the rear static sag again to check that it hasn't gone AWOL as a result of the changes!

bigredduke · 14-06-2021, 05:43 PM

Quote:

Originally Posted by Luddite

I'm not a particularly aggressive rider but if you're flinging it into bends and powering out on plenty of throttle, you're probably going to want the next stiffness up on the spring (120N/mm).

Yes, that's me, power-sliding out of bends with my knee and elbow down

bigredduke · 23-06-2021, 07:52 PM

Rode the bike to James Wood @ JWR suspension yesterday in Louth, Lincolnshire.

Strangely, before I fitted the new Ohlins rear shock, the front felt less harsh on bumpy roads (with the standard Sachs shock).

Afterwards, the front felt awful. On bumpy roads, it felt like riding an unsprung bicycle over corrugated iron sheets. The rear felt good however.

So James backed the front compression damping off by 2 clicks, then 4, which improved the ride considerably. The rear is very supple and comfortable over uneven surfaces (with a couple of turns off the preload). I have taken another 2 clicks off the compression damping at the front but have yet to ride it. I'll see how it feels over the Weekender. I prefer the suspension to be accommodating rather than harsh but obviously, I don't want it soft and wallowy. Looks like the standard settings on the rear shock are not far off for me.

It feels less 'perched' over the front than it did & more like I am sitting 'in' the bike rather than 'on' it.
Work in progress!

14-06-2021, 09:02 AM	#77
Mr Gazza Lord of the Rings Join Date: May 2013 Location: Norwich Bike: M900sie Posts: 5,979	Static and dynamic sag are just part of the nomenclature of suspension and simply puts everyone on the same page. Whether or not a fully loaded bike is dynamic is beside the point, it just gives that parameter a name. Static sag is relevant in so much as the relationship to the dynamic sag will tell you a lot about the spring rate. Get the static sag set at say 10mm and then load it and it goes to 50mm. That will tell you the springs are too soft. In my case the static sag is alarmingly high, but then only deflects a few mm more when loaded. That tells me that my springs are way too hard and I'm using enormous static sag (and rebound damping) to stop it topping out . Even though it's working relatively low in it's stroke it never bottoms out, confirming the former hypothesis. Fortunately the damping is rather good, so deals with the limited travel. It actually handles fine, but the springs and set up are something I will look at next Winter.. Nearly did it last Winter, but bottled out! Looking forward to joining the esoteric tuned suspension crowd.. __________________

14-06-2021, 09:34 AM	#79
Darkness . Join Date: May 2007 Location: Stockbridge Bike: M900 Posts: 1,984	This summarises the procedure quiet clearly, without reference to a static “Dynamic” oxymoron: https://racetech.com/articles/SuspensionAndSprings.htm __________________ Original and Best since 1993

14-06-2021, 08:53 AM	#76
chris.p Gold Member Join Date: Mar 2004 Location: lincoln Bike: No Bike Yet! Posts: 876	Suspension is a very dark art so to speak, but the parameter's set out in the Ohlins sheet is basically suspension gospel, because if your static sags do not sit between the recommended parameter's then your spring needs changing to a harder or softer spring depending on what the measurement's are. If it is new suspension to you, then a basic static sag test is a must, otherwise the bike will never be pleasure to ride, if in doubt and you don't fancy doing it your self, look up a local suspension expert and go visit them.

14-06-2021, 12:24 PM	#80
Luddite Registered User Join Date: Aug 2011 Location: Southampton Bike: M1100evo Posts: 2,465	Static and dynamic sag are equally important. If they were irrelevant, I don't think the likes of Öhlins would bother to give static sag figures in their installation instructions. Yes, 'dynamic' sag might be a bit of a misnomer, but it's just to distinguish it from 'static' sag in this instance. 'Static' sag may also be called 'free' sag and 'ride height' is another name used for 'dynamic' sag. Some people call 'static' sag just 'sag' with the measurement for bike and rider called 'static' sag. Confusing! You may be able to get within the dynamic sag range when sat on the bike but, as Chris.p said, if you can only do that with no static sag, that's an indication the spring rate is incorrect. There are physical effects of insufficient static sag too. Yes, the bike is always ridden loaded but the spring's are not always under compression - there are instances when much, if not all weight is removed from the suspension, for example, when the wheels are coming off bumps in the road or dropping into pot holes or during load transfer; braking for the rear or acceleration for the front. Niall Mackenzie, who I respect as a rider, said of rear static sag: "...(if) you have no sag ... you're in trouble. Your bike will be on its nose braking, the rear end will be hopping and pattering, and if you get back on the gas hard out of a corner it'll probably highside you." http://www.visordown.com/features/gu...kes-suspension The effect can be measured too, these diagrams are from "Motorcycle Handling and Chassis Design" the book by Tony Foale, the suspension guru, and give a graphic illustration of the effects that Mackenzie described. You can see the rear wheel hopping under heavy braking in the top chart. Dave Moss acknowledges the importance of 'free' sag in many of his videos. He states: "Static sag with the bike under its own weight should be 15-25mm in the front and 10-15mm in the rear with cold suspension. Rider sag should be a totally separate number. Add both together. Static sag creates a dead space so when the shock (most important) tops out it does not ping you straight out of the seat." There's no reference at all to the unloaded sag figure in that article Darkness linked to, which I think is a bit of an omission. The article is over 25 years old, so perhaps it wasn't considered important then. So, my advice is, even if your 'dynamic' sag is fine, ignore 'static' sag at your peril. As Paul is getting everything set up by JWR Suspension, he'll have no worries. It'll be interesting to find out what settings they use in due course.

14-06-2021, 03:17 PM	#81
chris.p Gold Member Join Date: Mar 2004 Location: lincoln Bike: No Bike Yet! Posts: 876	I think an easier way would be to say, "Static Sag" i.e. the sag the bike has with no rider on board, i.e. it's own weight. and "Rider Sag" i.e. the sag when a rider is sat on the bike. I personally always set the "Static Sag" first, as this gave you the bikes ideal measurement's then I would do the "Rider Sag" and use the Ohlins sheet to work out whether I need softer springs or harder springs. Remember that "Preload" only alters the ride height of the bike, not how far the suspension will compress. "Compression" only slows down or speeds up the springs compression. "Rebound" is the Opposite of Compression, it slows down or speeds up the extension (rise) of the suspension. By sticking to those simple rules you can not go far wrong. Once you go past those workings you enter the realm of a wizard's black art of suspension, oil thickness (Weight), Pistons, Oil shims, bypass shims, Air gaps etc the list is endless and you will fry your brain.

14-06-2021, 03:34 PM	#82
bigredduke Nothing to see here Join Date: May 2005 Location: brough Bike: M1100evo Posts: 1,550	Can of worms duly opened! Right, with the help of Mrs BRD & daughter I have the following measurements: R1 = 571mm, R2 = 560mm, so static sag is 11mm R3 = 530 so sag with rider onboard is 41mm which is 1mm outside of the Ohlins parameters so I conclude that the spring is just over the limit for my bulk. Do you agree? If I reduce the preload slightly, will the R1 figure increase slightly because the rear wheel will drop or have I got that completely wrong?

14-06-2021, 03:57 PM	#83
slob . Join Date: Jul 2003 Location: East London Bike: Multiple Monsters Posts: 9,736	no adjustment should change R1, reducing preload should increase both Static Sag & Ride Height (Rider Sag)

14-06-2021, 05:38 PM	#87
bigredduke Nothing to see here Join Date: May 2005 Location: brough Bike: M1100evo Posts: 1,550	Update! I increased the preload by 4mm from standard. I don't know if that is considered a lot or a little? I took it out and whereas before, I felt as though I was rather 'perched' over the front end & constantly sliding forward into the tank, now it feels a bit more 'relaxed'. Steering feels a little slower but the rear feels settled and comfortable. Interestingly, the front suspension feels a little harder and less forgiving now than when the OEM shock was fitted, I don't know why that should be. I need to check the sag on the front next to see if it is within recommended parameters. I also need to check the rear static sag again to check that it hasn't gone AWOL as a result of the changes!

23-06-2021, 07:52 PM	#89
bigredduke Nothing to see here Join Date: May 2005 Location: brough Bike: M1100evo Posts: 1,550	Rode the bike to James Wood @ JWR suspension yesterday in Louth, Lincolnshire. Strangely, before I fitted the new Ohlins rear shock, the front felt less harsh on bumpy roads (with the standard Sachs shock). Afterwards, the front felt awful. On bumpy roads, it felt like riding an unsprung bicycle over corrugated iron sheets. The rear felt good however. So James backed the front compression damping off by 2 clicks, then 4, which improved the ride considerably. The rear is very supple and comfortable over uneven surfaces (with a couple of turns off the preload). I have taken another 2 clicks off the compression damping at the front but have yet to ride it. I'll see how it feels over the Weekender. I prefer the suspension to be accommodating rather than harsh but obviously, I don't want it soft and wallowy. Looks like the standard settings on the rear shock are not far off for me. It feels less 'perched' over the front than it did & more like I am sitting 'in' the bike rather than 'on' it. Work in progress!